Newark City Council
September 12, 2024

Hazard/Problem Description
Storms in the Tri-City Planning Area are generally characterized by heavy rain often accompanied by strong winds and infrequent lightning and hail. Approximately 10 percent of the thunderstorms that occur each year in the United States are classified as severe. A thunderstorm is classified as severe when it contains one or more of the following phenomena: hail that is three-quarters of an inch or greater, winds in excess of 50 knots (57.5 mph), or a tornado. Heavy precipitation in the Planning Area falls mainly in the fall, winter, and spring months. Winter storms in the form of snow are very rare in in the Planning Area.

Packet Page No. 389
Tri-City 4-64
Local Hazard Mitigation Plan Update
March 2024
Heavy Rain and Storms
The NWS reports that storms and thunderstorms result from the rapid upward movement of warm, moist air. They can occur inside warm, moist air masses and at fronts. As the warm, moist air moves upward, it cools, condenses, and forms cumulonimbus clouds that can reach heights of greater than 35,000 ft. As the rising air reaches its dew point, water droplets and ice form and begin falling the long distance through the clouds towards earth's surface. As the droplets fall, they collide with other droplets and become larger.

The falling droplets create a downdraft of air that spreads out at Earth's surface and causes strong winds associated with thunderstorms.

Special Types of Heavy Rain
The Tri-City Planning Area and much of Northern California can be affected by a phenomenon known as an atmospheric river. According to the NOAA, atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow. This can be seen in Figure 4-21.

Figure 4-21 Atmospheric Rivers
Source: NOAA
Packet Page No. 390
Tri-City 4-65
Local Hazard Mitigation Plan Update
March 2024
Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding. These events can disrupt travel, induce mudslides and cause catastrophic damage to life and property. A well-known example is the “Pineapple Express,” a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.

Not all atmospheric rivers cause damage; most are weak systems that often provide beneficial rain or snow that is crucial to the water supply. Atmospheric rivers are a key feature in the global water cycle and are closely tied to both water supply and flood risks — particularly in the western United States.

While atmospheric rivers are responsible for great quantities of rain that can produce flooding, they also contribute to beneficial increases in snowpack. A series of atmospheric rivers fueled the strong winter storms that battered the U.S. West Coast from western Washington to southern California from Dec. 10– 22, 2010, producing 11 to 25 inches of rain in certain areas. These rivers also contributed to the snowpack in the Sierras, which received 75 percent of its annual snow by Dec. 22, the first full day of winter. This happened again in the winter of 2017/, as well as in the winters of 2022/2023 and 2023/2024.

Location and Extent
Heavy rain events occur on a regional basis. Rains and storms can occur in any location of the Tri-City Planning Area. All portions of the Planning Area are at risk to heavy rains. Most of these rains occur during the winter months, as discussed below. There is no scale by which heavy rain and storms are measured. Thunderstorms and hail are rare in the Planning Area. Lightning, while also somewhat rare during storm events, does occur on an infrequent basis. Magnitude of storms is measured often in rainfall and damages. The speed of onset of heavy rains can be short, but accurate weather prediction mechanisms often let the public know of upcoming events. Duration of heavy rain and storms in California is often short, ranging from minutes to hours. The WRCC maintains data on weather normal and extremes in the western United States. WRCC and NWS data for the Planning Area is summarized below. WRCC data goes further back in time (with a period of record from 1906 to 2016), while the NWS data is more recent (with a period of record from 1991 to 2022). The use of both datasets gives a more comprehensive look at weather normal and extremes.

City of Newark Weather Station, Period of Record 1906 to 2016 According to the WRCC, average annual precipitation in the Planning Area is 14.31 inches per year. The highest recorded annual precipitation is 31.52 inches in 1983; the highest recorded precipitation for a 24- hour period is 13.67 inches on March 1, 1907. The lowest recorded annual precipitation was 6.89 inches in 1959. Average monthly precipitation for the Planning Area is shown in Figure 4-22. Daily average and extreme precipitations are shown in Figure 4-23. NWS precipitation was shown on Figure 4-18.

Packet Page No. 391
Tri-City 4-66
Local Hazard Mitigation Plan Update
March 2024
Figure 4-22 Tri-City Planning Area – Monthly Average Total Precipitation Source: Western Regional Climate Center, www.wrcc.dri.edu/. Retrieved 4/26/2023.

Figure 4-23 Tri-City Planning Area – Daily Average and Extreme Precipitation Source: Western Regional Climate Center, www.wrcc.dri.edu/. Retrieved 4/26/2023.

Packet Page No. 392
Tri-City 4-67
Local Hazard Mitigation Plan Update
March 2024
Tri-City Planning Area – Oakland Museum NWS Station
According to the NWS, the Tri-City Planning Area sees 22.61 inches per year of precipitation at the Oakland Museum Station. Most rainfall occurs between October and April. Figure 4-24 shows the monthly precipitation averages for the Planning Area.

Figure 4-24 Tri-City Planning Area— Precipitation Averages 1991-2020 Source: National Weather Service XMAC site. Retrieved 4/26/2023.

The NOAA Storm Prediction Center tracks thunderstorm watches in the United States on a county basis.

Figure 4-25 shows thunderstorm watches in the Planning Area and the United States for a 20-year period between 1993 and 2012. Though dated 2012, this is the most recent version of this map.

Packet Page No. 393
Tri-City 4-68
Local Hazard Mitigation Plan Update
March 2024
Figure 4-25 Tri-City Planning Area– Average Thunderstorm Watches per Year (1993 to 2012) Source: NOAA Storm Prediction Center. Retrieved on 5/2/2023 Hail
Hail events in the Planning Area are rare; however, hail can occur throughout the Planning Area during storm events. Hail is formed when water droplets freeze and thaw as they are thrown high into the upper atmosphere by the violent internal forces of thunderstorms. Hailstones are usually less than two inches in diameter and can fall at speeds of 120 miles per hour (mph). Severe hailstorms can be quite destructive, causing damage to roofs, buildings, automobiles, vegetation, and crops.

Location and Extent of Hail
While rare, hail events can occur in any location of the Trio-City Planning Area. All portions of the Planning Area are at risk to hail. There is no scale in which to measure hail, other than hail stone size. The National Weather Service classifies hail by diameter size, and corresponding everyday objects to help relay scope and severity to the population. Table 4-23 indicates the hailstone measurements utilized by the National Weather Service.

Table 4-23 Hailstone Measurements
Average Diameter Corresponding Household Object
.25 inch Pea
.5 inch Marble/Mothball
.75 inch Dime/Penny
Packet Page No. 394
Tri-City 4-69
Local Hazard Mitigation Plan Update
March 2024
Average Diameter Corresponding Household Object
.875 inch Nickel

1.0 inch Quarter

1.5 inch Ping-pong ball

1.75 inch Golf-Ball

2.0 inch Hen Egg

2.5 inch Tennis Ball

2.75 inch Baseball

3.00 inch Teacup

4.00 inch Grapefruit

4.5 inch Softball
Source: National Weather Service
The speed of onset of hail can be short, but accurate weather prediction mechanisms often let the public know of upcoming events. Duration of thunderstorms that can cause hail in California is often short, ranging from minutes to hours. Hail events last shorter than the duration of the total thunderstorm. The National Weather Service tracks hail events. Figure 4-26 shows the average days each year where hail of greater than 1" in diameter occurred during a 20-year period from 1990 to 2009. As shown in the figure, hail is rare in the Planning Area. Though dated 2009, this is the most recent version of this map.

Figure 4-26 Tri-City Planning Area – Average Hail Days per Year (1990 to 2009) Source: National Weather Service. Retrieved 5/2/2023.

Lightning
Lightning, while somewhat rare in the Planning Area, can occur throughout the Tri-City Planning Area both during and outside of storm events. Lightning is defined by the NWS as any and all of the various forms of visible electrical discharge caused by thunderstorms. Cloud-to-ground lightning can kill or injure Packet Page No. 395
Tri-City 4-70
Local Hazard Mitigation Plan Update
March 2024
people by direct or indirect means. Objects can be struck directly, which may result in an explosion, burn, or total destruction. Or, damage may be indirect, when the current passes through or near an object, which generally results in less damage.

Intra-cloud lightning is the most common type of discharge. This occurs between oppositely charged centers within the same cloud. Usually it takes place inside the cloud and looks from the outside of the cloud like a diffuse brightening that flickers. However, the flash may exit the boundary of the cloud, and a bright channel, similar to a cloud-to-ground flash, can be visible for many miles.

Cloud-to-ground lightning is the most damaging and dangerous type of lightning, though it is also less common. Most flashes originate near the lower-negative charge center and deliver negative charge to earth.

However, a large minority of flashes carry positive charge to earth. These positive flashes often occur during the dissipating stage of a thunderstorm's life. Positive flashes are also more common as a percentage of total ground strikes during the winter months. This type of lightning is particularly dangerous for several reasons. It frequently strikes away from the rain core, either ahead or behind the thunderstorm. It can strike as far as 5 or 10 miles from the storm in areas that most people do not consider to be a threat (see Figure 4-27). Positive lightning also has a longer duration, so fires are more easily ignited. And, when positive lightning strikes, it usually carries a high peak electrical current, potentially resulting in greater damage.

Figure 4-27 Cloud to Ground Lightning
Source: National Weather Service
Location and Extent of Lightning
Lightning events can occur in any location of the Tri-City Planning Area and are often associated with thunderstorms, but also may occur outside of rain, often referred to as dry lightning events. All portions of the Planning Area are at risk to lightning. The speed of onset of thunderstorms (that cause lightning) can Packet Page No. 396
Tri-City 4-71
Local Hazard Mitigation Plan Update
March 2024
be short, and the duration is often short as well, generally ranging from minutes to hours. Vaisala maintains the National Lightning Detection Network. It tracks cloud to ground lightning incidences in the United States. Figure 4-28 shows lightning incidences in the Planning Area and the rest of the United States from 1997 to 2012. Though dated 2012, this is the most recent version of this map.

Figure 4-28 Tri-City Planning Area – Lightning Incidence Map 1997 to 2012 Source: Vaisala National Lightning Detection Network. Retrieved 5/2/2023.

Past Occurrences
Disaster Declaration History
A search of FEMA and Cal OES disaster declarations turned up multiple events. Heavy rains and storms have caused flooding in Alameda County. Events where heavy rain and storms (including the resultant flooding) resulted in a state or federal disaster declaration are shown in Table 4-24.

Table 4-24 Alameda County – Disaster Declarations from Heavy Rain and Storms 1950-2023 Disaster Type Federal Declarations State Declarations
Count Years Count Years
Flood (including heavy
rains and storms)
19 1950, 1955, 1957, 1958 (twice),
1962, 1963, 1970, 1982, 1983
(twice), 1986, 1995 (twice), 1997,
1998, 2008, 2017 (twice)
20 1955, 1958, 1962 (twice), 1970,
1982, 1983, 1986, 1995 (twice),
1997, 1998, 2005, 2006, 2017
(three), 2023 (three)
Source: FEMA, Cal OES
Packet Page No. 397
Tri-City 4-72
Local Hazard Mitigation Plan Update
March 2024
NCDC Events
The NCDC data recorded 85 coastal flood, flash flood, flood, hail, heavy rain, high surf, and lightning incidents for Alameda County since 1955, respectively. Many of these events also affected the Tri-City Planning Area. A summary of these events is shown in Table 4-25.

Table 4-25 Alameda County NCDC Heavy Rain and Storm Events 1/1/1955-12/31/2022* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Coastal Flood 3 0 0 0 0 $0 $0
Flash Flood 12 0 0 0 0 $100,000 $0
Flood 43 0 0 0 0 $44,325,500 $0
Hail 14 0 0 0 0 $0 $0
Heavy Rain 5 0 2 0 1 $60,000 $30,000
High Surf 1 0 0 0 0 $0 $0
Heavy Snow 1 0 0 0 0 $0 $0
Winter Storm 6 0 0 0 0 $0 $0
Total 85 0 2 0 1 $44,485,500 $30,000
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of the Planning Area and outside of Alameda County.

Planning Committee Events
A special type of heavy rain that can affect the Tri-City Planning Area is known as atmospheric river rains.

Atmospheric rivers can be weak to exceptional in strength. An example of this is shown in Figure 4-29.

These are from the winter of 2022/2023.

Packet Page No. 398
Tri-City 4-73
Local Hazard Mitigation Plan Update
March 2024
Figure 4-29 2022 Atmospheric Rivers by Strength and Count Source: CW3E
The Planning Committee noted that there are annual events of heavy rains and storms causing issues in the Planning Area. These are discussed in the Flood (Section 4.3.11) Localized Flood (Section 4.3.12), and Landslide (Section 4.3.13) past occurrences. In 2020, a lightning siege caused multiple fires in the area surrounding the Planning Area, which burned over 6,900 acres. During this event, the resulting smoke caused significant visibility issues. This is discussed in greater detail in the Past Occurrences section in Wildfire (under Planning Committee events in Section 4.3.17) below. More specific past occurrences can be found in each jurisdiction’s respective annex to this LHMP Update.

Likelihood of Future Occurrences
Highly Likely – Based on NCDC data and Planning Committee input, 85 coastal flood, flash flood, flood, hail, heavy rain, high surf, and lightning incidents over a 72-year period (1955-2022) equates to a severe storm event every year. As noted, this database likely doesn’t capture all heavy rain, hail, lightning, and severe storm events. Severe weather, including heavy rains and storms, is a well-documented seasonal occurrence that will continue to occur often in the Tri-City Planning Area.

Climate Change and Heavy Rains and Storms
According to the 2021 CAS, while average annual rainfall may increase or decrease slightly, the intensity of individual rainfall events is likely to increase during the 21st century. However, it is unlikely that hail will become more common in the Planning Area. The amount of lightning is not projected to change.

Cal-Adapt noted that, on average, the projections show little change in total annual precipitation in California. Furthermore, among several models, precipitation projections do not show a consistent trend Packet Page No. 399
Tri-City 4-74
Local Hazard Mitigation Plan Update
March 2024
during the next century. The Mediterranean seasonal precipitation pattern is expected to continue, with most precipitation falling during winter from North Pacific storms. One of the four climate models projects slightly wetter winters, and another projects slightly drier winters with a 10 to 20 percent decrease in total annual precipitation. However, even modest changes would have a significant impact because California ecosystems are conditioned to historical precipitation levels and water resources are nearly fully utilized.

Future precipitation estimates for the Planning Area are shown in Figure 4-30, which consists of two charts:
➢ The upper chart shows annual averages of observed and projected precipitation values for the selected area on the map under the RCP 8.5 scenario. The gray line (1950 – 2005) is observed data. The colored lines (2006 – 2100) are projections from 10 LOCA downscaled climate models selected for California.

The light gray band in the background shows the least and highest annual average values from all 32 LOCA downscaled climate models.
➢ The lower chart shows annual averages of observed and projected precipitation values for the selected area on map under the RCP 4.5 scenario. The gray line (1950 – 2005) is observed data. The colored lines (2006 – 2100) are projections from 10 LOCA downscaled climate models selected for California.

The light gray band in the background shows the least and highest annual average values from all 32 LOCA downscaled climate models.

These models have been selected by California state agencies as priority models for research contributing to California’s Fourth Climate Change Assessment.

Packet Page No. 400
Tri-City 4-75
Local Hazard Mitigation Plan Update
March 2024
Figure 4-30 Tri-City Planning Area – Future Precipitation Estimates in High and Low Emission Scenarios
Source: Cal-Adapt. Retrieved 5/2/2023.

Vulnerability Assessment
Vulnerability—Medium
According to historical hazard data, heavy rains and storms, including lightning, are an annual occurrence in the Tri-City Planning Area. Heavy rains can cause both localized flooding and flooding in the Packet Page No. 401
Tri-City 4-76
Local Hazard Mitigation Plan Update
March 2024
floodplains. Atmospheric river storms are of great concern as they can dump large amounts of water in single storms, or in back-to-back storms as seen above in 2022, in the winter storms of 2022/2023, as well as the winter storms of 2023/2024. Impacts can be felt by both the population of the Planning Area as well as the structures that have been built in the Planning Area.

The whole of the Tri-City Planning Area is at some measure of vulnerability to heavy rain and storms. An assessment of a community’s vulnerability to heavy rains and storms begins with an understanding of local exposure to heavy rain and storms. This is included in the discussion of the Assets at Risk to this hazard.

Assets at Risk
Assets at risk from heavy rain and storms include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

People and Populations
All populations in the Tri-City Planning Area have some measure of risk to heavy rains and storms. Those populations that work or recreate outside and unhoused individuals are more vulnerable to impacts from heavy storm events. Heavy rains and storms occur every year and do not generally cause significant adverse impacts to individuals; it is the secondary hazard, flooding, that poses the biggest impact to people.

Populations at risk to flooding resulting from heavy rains and storm events include those who live in floodplains (discussed in further detail in the Flood: 1%/0.2% Annual Chance in Section 4.3.11) and those who live in and near localized flooding areas floodplains (discussed in further detail in the Flood: Localized Stormwater Flooding in Section 4.3.12).

Structures
Structures in the Tri-City Planning Area have some risk to heavy rains and storms. Structures built to modern building codes are built to withstand heavy rains and storms (including thunderstorm winds and lightning). During a heavy storm, localized flooding may cause water intrusion into buildings from the outside. Trees can be downed causing impacts to structures. Older homes and buildings may be at increased risk to heavy rains and storms. Power outages during severe storm events can occur, impacting the use of structures until the power is back online.

Critical Facilities and Infrastructure, and Community Lifelines Heavy rain and storms can affect critical facilities and infrastructure, and community lifelines during large events. Power outages may occur taking facilities offline. High winds can down power lines and trees impacting facilities. Water intrusion into facilities and infrastructure can impact operations. Local roads, streets, and bridges can be impacted resulting in closures restricting traffic flow in the Planning Area. In certain areas, large storms can cause erosion and localized landslides which can impact affected facilities.

Many critical facilities are built to modern design standards that take heavy rains and storms into account Packet Page No. 402
Tri-City 4-77
Local Hazard Mitigation Plan Update
March 2024
when siting and building these structures, and others may need to be retrofitted to better withstand these events.

Community lifelines likely to have some vulnerability to heavy rains and storms include:
➢ Safety and Security – Search and rescue and swiftwater teams may be called on to perform riskier duties during times of heavy rains and flooding. Police, Fire, EMS, and Public Works personnel are often called on to respond during flood emergencies taxing these resources. ➢ Food, Hydration and Shelter – Those displaced by heavy rains and flooding and the unsheltered may have needs for food and water.
➢ Health and Medical – Injuries can occur during storm events. Patient movement from accident scenes by EMS may have to be rerouted around inundated and closed streets. Public health can be at risk from contaminated floodwaters caused by heavy rains.
➢ Energy –Significant storms can cause power outages throughout the Planning Area. Downed trees can fall on electric lines in the Planning Area, causing power outages. High winds and other lightning strikes can cause transformers and other infrastructure to be damaged. Fuel supplies can be temporarily cut off, until flooding subsides.
➢ Communications – Communication systems may be damaged during severe storm events. An influx of service calls to dispatch centers for reporting of flooding, power outages, downed trees, or other issues can occur. Messaging systems need to be deployed during these times to let the public know about road and closures, washouts, and debris or flooding on roads. ➢ Transportation – Highways, local roads, and bridges may be impacted by heavy rains and flooding causing road closures. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents.
➢ Hazardous Material – Hazardous material facilities can be affected by heavy rains and flooding.

Releases during these times can contaminate the environment, affecting drinking water and natural systems.
➢ Water Systems – Water, drainage, and wastewater systems can experience storm related impacts, including excessive water intrusion which can affect the operations of these systems.

Short-term, heavy rains and storms can cause both widespread flooding as well as extensive localized drainage issues throughout the Tri-City Planning Area. As storms continue to increase in intensity, existing drainage and stormwater systems may be overwhelmed at least temporarily contributing to an increase in flooding related impacts. While components of these lifelines may be damaged or otherwise impacted, it is unlikely that large storm events would overwhelm and take out any of these lifelines in the Tri-City Planning Area as a whole.

Natural, Historic, and Cultural Resources
Large storm events and associated flooding can affect natural, historic, and cultural resources. Silt and sediment can damage natural areas. Trees can be uprooted and downed by high winds. Extended periods of rainfall can erode natural banks along waterways and degrade soil stability for terrestrial species. While some natural systems can be adversely impacted during these large storms, heavy rain events can also provide benefits. Groundwater and wetland areas can be recharged and water supplies replenished. Historic and cultural resources may also be affected. Generally, the impacts are associated with damage to structures affected by large storm events, but other cultural resources such as those associated with Native Americans and old tribal areas can also be disturbed, damaged, and lost during extreme storm and flood events.

Packet Page No. 403
Tri-City 4-78
Local Hazard Mitigation Plan Update
March 2024
Economic Assets and Community Activities of Value
Heavy rain and storm events can cause direct damage to economic assets such as businesses and commercial centers. During extreme events, the economy may slow as people stay home or inside. Business revenue may be reduced during extended storm events. Community activities of value may see a reduction in attendance, impacting revenues associated with these events, especially those that occur outdoors. Events may be cancelled or rescheduled.

Impacts from Heavy Rains and Storms
Impacts from heavy rains and storms include damage to property, critical facilities and infrastructure, and the natural landscape. This includes: erosion, downed trees, damaged utility structures and infrastructure; power outages; road damage and blockages; and lightning strikes to critical infrastructure and people.

Lightning can also cause wildfires and urban fires to occur. Landslides occur when the soil on slopes becomes oversaturated and fails. Climate change may cause these impacts to worsen.

Actual damage associated with the primary effects of severe storms and heavy rains has been somewhat limited. It is the secondary hazards caused by these severe weather events, such as floods, landslides, and erosion that have had the greatest impact on the Planning Area. The risk and vulnerability associated with these secondary hazards are discussed in other sections of this Plan (Section 4.3.11 Flood: 1%/0.2% Annual Chance, Section 4.3.12 Flood: Localized Stormwater, Section 4.3.8 Dam Failure, Section 4.3.13Landslide, and Section 4.3.14 Levee Failure).

Future Development
Heavy rains and storms are taken into account in future development as discussed in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.5. Severe Weather: High Winds and Tornadoes
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
High Winds
High winds can cause significant property and resource damage, threaten public safety, and have adverse economic impacts from facility closures and power loss. High winds, as defined by the NWS glossary, are sustained wind speeds of 40 mph or greater lasting for 1 hour or longer, or winds of 58 mph or greater for any duration. These winds may occur as part of a seasonal climate pattern or in relation to other severe weather events such as thunderstorms.

Packet Page No. 404
Tri-City 4-79
Local Hazard Mitigation Plan Update
March 2024
Straight-line (i.e., non-tornadic) winds may also exacerbate existing weather conditions by increasing the effect on temperature and decreasing visibility due to the movement of particulate matters through the air, as in dust and snowstorms. The winds may also exacerbate fire conditions by drying out the ground cover, propelling fuel around the region, and increasing the ferocity of exiting fires, as well as contributing to fire weather conditions resulting in red flag days. Winds can push automobiles off roads, damage roofs and structures, cause power outages, and cause secondary damage due to flying debris and hazardous trees.

Location and Extent
The entire Tri-City Planning Area is subject to significant, non-tornadic (straight-line) winds. Each area of the Planning Area is at risk to high winds. Magnitude of winds is measured often in speed and damages.

The speed of onset of both thunderstorm winds and high winds outside of thunderstorm events can be short or prolonged, but accurate weather prediction mechanisms often let the public know of upcoming events.

Duration of thunderstorm winds in California is often short, ranging from minutes to hours, but can occur for longer periods. The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. Figure 4-31 shows the Beaufort wind scale.

Packet Page No. 405
Tri-City 4-80
Local Hazard Mitigation Plan Update
March 2024
Figure 4-31 Beaufort Wind Scale
Source: National Weather Service
Figure 4-32 depicts wind zones for the United States. The map denotes that the Tri-City Planning Area falls into Zone I, which is characterized by high winds of up to 130 mph (above Beaufort Number 12).

Packet Page No. 406
Tri-City 4-81
Local Hazard Mitigation Plan Update
March 2024
Figure 4-32 Wind Zones in the United States
Source: FEMA
Diablo Winds
Though not included on the map above as a special wind region, the Tri-City Planning Area did note that they are subject to diablo winds on a seasonal basis. Diablo wind is a name that is often used for the hot, dry wind from the northeast that typically occurs in the San Francisco Bay Area of Northern California, during the spring and fall. The Diablo wind is created by the combination of strong inland high pressure at the surface, strongly sinking air aloft, and lower pressure off the California coast. The air descending from aloft as well as from the Coast Ranges compresses as it sinks to sea level where it warms as much as 20°F and loses relative humidity. While the Diablo wind pattern occurs in both the spring and fall, it is most dangerous in the fall, when vegetation is at its driest such as what occurred during the devastating 1991 Tunnel Fire.

Tornadoes
Tornadoes and funnel clouds can also occur during severe storms events. Tornadoes are another severe weather hazard that, though rare in the East Bay, can affect anywhere within the Tri-City Planning Area, Packet Page No. 407
Tri-City 4-82
Local Hazard Mitigation Plan Update
March 2024
primarily during the storm season in the late fall, winter, and early spring. Tornadoes form when cool, dry air sits on top of warm, moist air. Tornadoes are rotating columns of air marked by a funnel-shaped downward extension of a cumulonimbus cloud whirling at destructive speeds of up to 300 mph, usually accompanying a thunderstorm. Tornadoes are the most powerful storms that exist. They can have the same pressure differential across a path only 300 yards wide or less as 300-mile-wide hurricanes. Figure 4-33 illustrates the potential impact and damage from a tornado.

Figure 4-33 Potential Impact and Damage from a Tornado
Source: FEMA: Building Performance Assessment: Oklahoma and Kansas Tornadoes Location and Extent
Tornadoes, while rare, can occur in any part of the Tri-City Planning Area. Prior to February 1, 2007, tornado intensity was measured by the Fujita (F) scale. This scale was revised and is now the Enhanced Fujita scale. Both scales are sets of wind estimates (not measurements) based on damage. The new scale provides more damage indicators (28) and associated degrees of damage, allowing for more detailed analysis and better correlation between damage and wind speed. It is also more precise because it considers the materials affected and the construction of structures damaged by a tornado. Table 4-26 shows the wind speeds associated with the original Fujita scale ratings and the damage that could result at different levels of intensity. Table 4-27 shows the wind speeds associated with the Enhanced Fujita Scale ratings.

Table 4-26 Original Fujita Scale
Fujita (F)
Scale
Fujita Scale Wind
Estimate (mph)
Typical Damage
F0 < 73 Light damage. Some damage to chimneys; branches broken off trees; shallowrooted trees pushed over; sign boards damaged.

F1 73-112 Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.

Packet Page No. 408
Tri-City 4-83
Local Hazard Mitigation Plan Update
March 2024
Fujita (F)
Scale
Fujita Scale Wind
Estimate (mph)
Typical Damage
F2 113-157 Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

F3 158-206 Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.

F4 207-260 Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown, and large missiles generated.

F5 261-318 Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yards); trees debarked; incredible phenomena will occur.

Source: National Oceanic and Atmospheric Administration Storm Prediction Center, www.spc.noaa.gov/faq/tornado/f-scale.html Table 4-27 Enhanced Fujita Scale
Enhanced Fujita (EF) Scale Enhanced Fujita Scale Wind Estimate (mph) EF0 65-85
EF1 86-110
EF2 111-135
EF3 136-165
EF4 166-200
EF5 Over 200
Source: National Oceanic and Atmospheric Administration Storm Prediction Center, www.spc.noaa.gov/faq/tornado/ef-scale.html It is difficult to predict a tornado or the conditions that preclude a tornado far in advance. Tornadoes can strike quickly with very little warning. In California it is rare for tornadoes to exceed an EF3 magnitude.

Most tornadoes that touch down are not long lived and cause limited damages.

Past Occurrences
Disaster Declaration History
There have been no past federal or state disaster declarations due to high winds or tornadoes, as detailed in Table 4-5.

NCDC Events
The NCDC data recorded 358 high wind incidents for Alameda County since 1955. This includes 5 (all F0) tornado events in Alameda County. A summary of these events is shown in Table 4-28.

Packet Page No. 409
Tri-City 4-84
Local Hazard Mitigation Plan Update
March 2024
Table 4-28 Alameda County NCDC High Wind and Tornado Events 1/1/1950-12/31/2022* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
High Wind 88 1 0 1 0 $3,210,000 $0
Strong Wind 263 4 0 8 0 $3,753,800 $0
Thunderstorm Wind 2 0 0 0 0 $50,000 $0
Tornado 5 0 0 0 0 $275,000 $0
Total 358 5 0 9 0 $7,288,800 $ 0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of the Planning area and outside of Alameda County.

Planning Committee Events
The Planning Committee noted that high wind events are a common occurrence throughout the Planning Area. They further indicated that some of the most severe high wind events occur outside of storms. These high winds, including the local Diablo type winds, contribute to the potential for catastrophic wildfires as seen in the 1991 Tunnel Fire. It is often high winds, in conjunction with heat and low humidity and compounded by drought conditions, that cause wildfire risk in the Planning Area to increase. These conditions can also cause red flag days and PSPS events in the Planning Area as previously described.

More specific past occurrences can be found in each jurisdiction’s respective annex to this LHMP Update.

Likelihood of Future Occurrences
Highly Likely – Based on NCDC data and Planning Committee input, 358 wind incidents over a 67-year period (1955-2022) equates to a severe wind event every year. High winds are a well-documented seasonal occurrence that will continue to occur annually in the Tri-City Planning Area.

Climate Change and High Winds
According to the 2021 CAS, while average annual rainfall may increase or decrease slightly, the intensity of individual thunderstorm events is likely to increase during the 21st century. This may bring stronger thunderstorm winds. The CAS does not discuss non-thunderstorm winds or tornadoes.

Vulnerability Assessment
Vulnerability—Medium
The Tri-City Planning Area is subject to potentially destructive high winds and tornadoes. Regional Diablo winds are a significant concern. High winds are common throughout the area and can happen during most times of the entire year and outside of a severe storm event. Tornadoes are rare. High winds and tornadoes can be a significant public safety and economic concern.

Vulnerability of the community is discussed in multiple sections that detail how this hazard can affect the Planning Area. These sections include assets at risk, impacts, and how future development can be affected by this hazard.

Packet Page No. 410
Tri-City 4-85
Local Hazard Mitigation Plan Update
March 2024
Assets at Risk
Assets at risk from winds and tornadoes include people and populations; structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

People and Populations
All populations are at some vulnerability to high winds and tornadoes. Certain vulnerable populations are at the greatest risk to the effects of high winds and tornadoes. These include:
➢ The unsheltered.
➢ Citizens who reside in mobile homes.
➢ Citizens in buildings with no tornado shelter or below ground floors. ➢ Those with access and functional needs.
➢ Those working or caught outdoors during a wind or tornado event.

Structures
All structures in the Tri-City Planning Area have some measure of risk from high wind and tornadoes.

Though most structures are built to withstand winds, Diablo wind speeds can still cause damages in the Planning Area. Though rare, a tornado could cause damage to virtually all facilities in the tornado touchdown path. This would affect homes, businesses, commercial property, as well as government and critical facilities. During a wind or tornado event, power lines in the Planning Area can be damaged by falling trees caused by wind. A tornado could also damage power lines. High winds are a cause for PSPS events to be declared, causing power outages to occur. High winds and tornadoes could cause sparks from electric wires and other sources, which could lead to wildfire ignition. Once ignited, high winds can also cause wildfires to rapidly spread and become out of control. High wind conditions can cause wildfires to move into more urban areas destroying structures and whole subdivisions, as seen in recent wildfire events in the West.

Critical Facilities and Infrastructure, and Community Lifelines Though most critical facilities are built to withstand winds, diablo and other type wind speeds can still cause damage in the Tri-City Planning Area. Though rare, a tornado could cause damage to virtually all facilities in the tornado touchdown path. Winds can cause PSPS events and lead to out of control wildfires, which can damage critical facilities and impact their abilities to perform their critical roles in the community.

Community lifelines likely to have some vulnerability from wind and tornado include:
➢ Safety and Security – Winds and tornadoes can increase fire spread and also lead to down trees and blocked roads, which causes issues for firefighters, police, dispatch, and EMS in the Planning Area.

Packet Page No. 411
Tri-City 4-86
Local Hazard Mitigation Plan Update
March 2024
➢ Food, Hydration, Shelter – Significant damage caused by tornadoes can increase the need for those who need shelter. This is true for the unsheltered populations as well as for those whose homes may be damaged or rendered unusable.
➢ Health and Medical – Winds and tornadoes can cause injuries or deaths to residents. Trees may be downed during these times, causing EMS to need to reroute ambulance or emergency services around areas where roads may be closed while tree materials are removed. ➢ Energy – Downed trees and other wind impacts may cause power grid issues. If a tornado were to strike a power station or large transmission lines, power outages may occur in the Planning Area. ➢ Communications – 911, dispatch, and emergency responder communications see marked increase during times of high winds and tornadoes.
➢ Transportation – Transportation routes may be blocked by downed trees, downed power wires, or downed poles and signs.
➢ Hazardous Materials – Hazardous materials facilities may be compromised during periods of high winds and tornadoes. Trucks carrying hazardous materials may be overturned on roads in the Planning Area during high wind and tornado events.
➢ Water Systems – Above ground water infrastructure may be damaged by high winds and tornadoes.

Backup power sources to these critical facilities that comprise the community lifelines should be in place to reduce possible impacts from these lifelines going offline. During periods of high wind and tornadoes, the electric system could be overwhelmed, causing brownouts and power outages to occur. Power outages and PSPS events can also occur during times of high winds, causing the electric grid to temporarily go offline. It is unlikely that whole lifelines would be overwhelmed by this hazard.

Natural, Historic, and Cultural Resources
Natural resources, such as trees, are vulnerable to winds. Increased levee and streambank erosion can occur during periods of high water and high winds. High wave action during significant wind events can cause coastal erosion and impact marsh lands and habitat areas. Soil erosion can also occur during high winds.

Most all natural, historic, or cultural resources are at risk to tornadoes. Tornadoes can tear apart habitats, causing fragmentation across ecosystems and can damage and destroy historic structures and cultural resources.

Economic Assets and Community Activities of Value
During periods of high winds and tornadoes, the economy may slow temporarily as people stay home or inside. Diabo strength winds can damage economic assets in the Planning Area. Should high winds or tornadoes damage businesses and commercial centers, long term economic issues may occur.

All community activities of value have some measure of vulnerability to high wind and tornado. High winds and tornadoes can cause life safety issues. Activities may be cancelled, postponed, or rescheduled due to high wind and tornado events.

Impacts from Severe Weather: High Wind and Tornado
Wind and tornadoes can cause damage to property and loss of life. While most tornado damage is caused by violent winds, the majority of injuries and deaths generally result from flying debris. Property damage can include damage to buildings, fallen trees, and power lines. Local industries may also be damaged or Packet Page No. 412
Tri-City 4-87
Local Hazard Mitigation Plan Update
March 2024
destroyed. Access roads and streets may be blocked by debris, delaying necessary emergency response.

Winds can push automobiles off roads, damage roofs and structures, cause power outages, and cause secondary damage due to flying debris and hazardous trees. High winds can also contribute to the spread and intensity of wildfires. Climate change may affect this hazard and cause winds to increase in velocity and more tornadoes to affect the Planning Area.

Future Development
High winds and tornadoes are taken into account in future development in each of the jurisdictions of the Tri-City Planning Area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.6. Climate Change
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Planning Area.

These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
Climate change is the distinct change in measures of weather patterns over a long period of time, ranging from decades to millions of years. More specifically, it may be a change in average weather conditions such as temperature, rainfall, snow, ocean and atmospheric circulation, or in the distribution of weather around the average. While the Earth’s climate has cycled over its 4.5-billion-year age, these natural cycles have taken place gradually over millennia, and the Holocene, the most recent epoch in which human civilization developed, has been characterized by a highly stable climate – until recently.

This LHMP Update is concerned with human-induced climate change that has been rapidly warming the Earth at rates unprecedented in the last 1,000 years. Since industrialization began in the 19th century, the burning of fossil fuels (coal, oil, and natural gas) at escalating quantities has released vast amounts of carbon dioxide and other greenhouse gases responsible for trapping heat in the atmosphere, increasing the average temperature of the Earth. Secondary impacts include changes in precipitation patterns, the global water cycle, melting glaciers and ice caps, and rising sea levels. According to the Intergovernmental Panel on Climate Change (IPCC), climate change will “increase the likelihood of severe, pervasive and irreversible impacts for people and ecosystems” if unchecked.

Through changes to oceanic and atmospheric circulation cycles and increasing heat, climate change affects weather systems around the world. Climate change increases the likelihood and exacerbates the severity of extreme weather – more frequent or intense storms, floods, droughts, and heat waves. Consequences for human society include loss of life and injury, damaged infrastructure, long-term health effects, loss of agricultural crops, disrupted transport and freight, and more. Climate change is not a discrete event but a long-term hazard, the effects of which communities are already experiencing.

Packet Page No. 413
Tri-City 4-88
Local Hazard Mitigation Plan Update
March 2024
Climate change adaptation is a key priority of the State of California. The 2023 State of California MultiHazard Mitigation Plan noted that climate change is already affecting California. Sea levels have risen by as much as seven inches along the California coast over the last century, increasing erosion and pressure on the state’s infrastructure, water supplies, and natural resources. The State has also seen increased average temperatures, more extreme hot days, fewer cold nights, a lengthening of the growing season, shifts in the water cycle with less winter precipitation falling as snow, and earlier runoff of both snowmelt and rainwater in the year. In addition to changes in average temperatures, sea level, and precipitation patterns, the intensity of extreme weather events is also changing.

In the Tri-City Planning Area and regionally, each year it seems to get a bit warmer. It was also noted that 2017 was one of the wettest years ever. Post 2017 saw many years of very dry weather. 2021 was noted by NASA to be one of the hottest on record. 2023 is trending to be the same. California’s Adaptation Planning Guide: Understanding Regional Characteristics has divided California into 11 different regions based on political boundaries, projected climate impacts, existing environmental setting, socioeconomic factors and regional designations. The Tri-City Planning Area falls in the Bay Area Region. The Bay Area is a heavily urbanized region (over 7 million people). The predominant feature of this region is San Francisco Bay and the miles of shoreline, both on the Pacific coast and along the bay, extending north to Sonoma County, inland to the Delta, and south to San Jose. The urbanized areas are concentrated primarily around the bay. To the north and south, the region is characterized by low coastal mountains. Sonoma and Napa counties produce wine grapes valued over $850 million in 2010 (California Farm Bureau Federation, 2012). To the east, Solano and Contra Costa counties are on the western edge of the low-lying California Delta. Table 4-29 provides a summary of Cal-Adapt Climate Projections for the Bay Area Region.

Table 4-29 Bay Area Region – Cal Adapt Climate Projections Effect Ranges
Temperature
Change,
1990-2100
January: 4°F to 5°F increase in average temperatures July: 5°F to 6°F increase in average temperatures (Modeled high temperatures – average of all models; high carbon emissions scenario) Precipitation Precipitation varies widely in this region, with annual totals over 40 inches in northern Sonoma County to roughly 15 inches in the eastern portions of Solano and Contra Costa counties. A moderate decline in annual rainfall, 1 to 3 inches by 2050 and 4 to 5 inches by 2090, is projected throughout the region. (Community Climate System Model 3 (CCSM3) climate model; high carbon emissions scenario)
Sea Level Rise By 2100, sea levels may rise up to 55 inches, posing considerable threats to coastal areas and particularly to low-lying areas adjacent to San Francisco Bay. The number of acres vulnerable to flooding is expected to increase 20 to 30 percent in most parts of the Bay Area, with some areas projected for increases of over 40 percent. Coastal areas are estimated to experience an increase of approximately 15 percent in the acreage vulnerable to flooding.

Heat wave Along the coast, particularly to the south, heat wave is defined as five days over 72°F to 77°F; in other areas the threshold is in the mid- to upper 90s. Over most of the region a limited increase in the number of heat waves is expected by 2050 with only the eastern areas expecting more than one or two more per year. By 2100, between six and 10 more heat waves can be expected per year.

Wildfire There is little change in projected fire risk in this region, save for the slight increases expected in western Marin County. (Geophysical Fluid Dynamics Laboratory (GFDL) climate model; high carbon emissions scenario)
Source: Cal-Adapt
Packet Page No. 414
Tri-City 4-89
Local Hazard Mitigation Plan Update
March 2024
Location and Extent
Climate change is a global phenomenon. It is expected to affect the whole of the Tri-City Planning Area, surrounding counties, and State of California. There is no scale to measure the extent of climate change.

Climate change exacerbates other hazards, such as drought, extreme heat, flooding, wildfire, and others.

The speed of onset of climate change is very slow. The duration of climate change is not yet known, but is feared to be tens to hundreds of years.

Past Occurrences
Disaster Declaration History
Climate change has never been directly linked to any declared disasters, as shown in Table 4-5.

NCDC Events
The NCDC does not track climate change events.

Planning Committee Events
The Planning Committee noted the following for the entire Tri-City Planning Area:
➢ Each year temperatures get hotter and extreme heat events become more taxing on the Planning Area. ➢ Tree Die back is increasing in and around the Planning Area. ➢ There has been an increase in red flag days. This is problematic as red flag days limit fuels management work. As a result of drought (as exacerbated by climate change) there is more dead biomass to process and less burn days to do so. In addition to an increase in red flag days which limits processing, recent weather patterns are providing less days with adequate air quality to allow burning. ➢ Lakes and reservoirs are seeing an increase in nutrient loading and blue green algae. ➢ The strength of storms is increasing.

Specific events recalled by Planning Committee members for each jurisdiction can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrence
Highly Likely – Climate change is virtually certain to continue without immediate and effective global action. According to NASA, 2021 was one of the hottest years on record with 2023 trending the same way.

Without significant global action to reduce greenhouse gas emissions, the IPCC concludes in its Sixth Assessment Synthesis Report (2022) that average global temperatures are likely to exceed 1.5°C by the end of the 21st century, with consequences for people, assets, economies and ecosystems, including risks from heat stress, storms and extreme precipitation, inland and coastal flooding, landslides, air pollution, drought, water scarcity, sea level rise and storm surges.

Packet Page No. 415
Tri-City 4-90
Local Hazard Mitigation Plan Update
March 2024
Climate Scenarios
The United Nations IPCC developed several greenhouse gas (GHG) emissions scenarios based on differing sets of assumptions about future economic growth, population growth, fossil fuel use, and other factors.

The emissions scenarios range from “business-as-usual” (i.e., minimal change in the current emissions trends) to more progressive (i.e., international leaders implement aggressive emissions reductions policies).

Each of these scenarios leads to a corresponding GHG concentration, which is then used in climate models to examine how the climate may react to varying levels of GHGs. Climate researchers use many global climate models to assess the potential changes in climate due to increased GHGs.

Key Uncertainties Associated with Climate Projections
➢ Climate projections and impacts, like other types of research about future conditions, are characterized by uncertainty. Climate projection uncertainties include but are not limited to:
✓ Levels of future greenhouse gas concentrations and other radiatively important gases and aerosols, ✓ Sensitivity of the climate system to greenhouse gas concentrations and other radiatively important gases and aerosols,
✓ Inherent climate variability, and
✓ Changes in local physical processes (such as afternoon sea breezes) that are not captured by global climate models.

Even though precise quantitative climate projections at the local scale are characterized by uncertainties, the information provided can help identify the potential risks associated with climate variability/climate change and support long term mitigation and adaptation planning.

Maps show projected change in average surface air temperature in the later part of this century (2071-2099) relative to the later part of the last century (1970-1999) under a scenario that assumes substantial reductions in heat trapping gases and a higher emissions scenario that assumes continued increases in global emissions.

These are shown in Figure 4-34.

Packet Page No. 416
Tri-City 4-91
Local Hazard Mitigation Plan Update
March 2024
Figure 4-34 Projected Temperature Change – Lower and Higher Emissions Scenario Source: National Climate Assessment
According to the California Natural Resource Agency (CNRA), climate change is already affecting California and is projected to continue to do so well into the foreseeable future. Current and projected changes include increased temperatures, sea level rise, a reduced winter snowpack altered precipitation patterns, and more frequent storm events. Over the long term, reducing greenhouse gases can help make these changes less severe, but the changes cannot be avoided entirely. Unavoidable climate impacts can result in a variety of secondary consequences including detrimental impacts on human health and safety, economic continuity, ecosystem integrity and provision of basic services.

The CNRA’s 2021 CAS delineated how climate change may impact and exacerbate natural hazards in the future, including wildfires, extreme heat, floods, and drought. ➢ Climate change is expected to lead to increases in the frequency, intensity, and duration of extreme heat events and heat waves in the Planning Area and the rest of California, which are likely to increase the risk of mortality and morbidity due to heat-related illness and exacerbation of existing chronic health conditions. Those most at risk and vulnerable to climate-related illness are the elderly, individuals with chronic conditions such as heart and lung disease, diabetes, and mental illnesses, infants, the socially or economically disadvantaged, and those who work outdoors. ➢ Higher temperatures will melt the Sierra snowpack earlier and drive the snowline higher, resulting in less snowpack to supply water to California users.
➢ Droughts are likely to become more frequent and persistent in the 21st century. ➢ Intense rainfall events, periodically ones with larger than historical runoff, will continue to affect California with more frequent and/or more extensive flooding. ➢ Storms and snowmelt may coincide and produce higher winter runoff from the landward side, while accelerating sea-level rise will produce higher storm surges during coastal storms. Together, these Packet Page No. 417
Tri-City 4-92
Local Hazard Mitigation Plan Update
March 2024
changes may increase the probability of floods and levee and dam failures, along with creating issues related to saltwater intrusion.
➢ Warmer weather, reduced snowpack, and earlier snowmelt can be expected to increase wildfire through fuel hazards and ignition risks. These changes can also increase plant moisture stress and insect populations, both of which affect forest health and reduce forest resilience to wildfires. An increase in wildfire intensity and extent will increase public safety risks, property damage, fire suppression and emergency response costs to government, watershed and water quality impacts, vegetation conversions and habitat fragmentation.

Vulnerability Assessment
Vulnerability—High
Climate change is the distinct change in measures of weather patterns over a long period of time, ranging from decades to millions of years. More specifically, it may be a change in average weather conditions such as temperature, rainfall, snow, ocean and atmospheric circulation, or in the distribution of weather around the average. While climate change on its own is a hazard, its effect on exacerbating other hazards is the primary concern.

Climate Change Impacts
The discussion on impacts to the Tri-City Planning Area and Alameda County come from three sources:
➢ Alameda County Climate Change and Health Profile Reports (CCHPRs) ➢ California Adaptation Planning Guide
➢ Proceedings of the National Academy of Sciences
Impacts from the Planning Committee were discussed in the Past Occurrences section above.

Note: All other vulnerability sections of this Plan discuss:
➢ People and Populations
➢ Structures
➢ Critical Facilities and Infrastructure, and Community Lifelines ➢ Natural, Historic, and Cultural Resources
➢ Economic Assets
➢ Community Activities of Value
Due to the complexity of climate change and the way the data sources handle some or all of these listed issues, rather than grouping the data in the bulleted list above, the source material is presented in the same way it is presented in their original documents. Each document addresses, part or all, of the bulleted list above. Additionally, each jurisdiction in the Tri-City Planning Area has their own climate plans, which are unique to their jurisdiction and are discussed in their respective annexes to this Base Plan.

Packet Page No. 418
Tri-City 4-93
Local Hazard Mitigation Plan Update
March 2024
Alameda County Climate Change and Health Profile Report Impacts (2017) According to the Alameda CCHPRs, all Californians are vulnerable to the health impacts of climate change.

Even if one is fortunate to live, work, study, or play in a place without direct contact with wildfires, flooding, or sea level rise, no one can entirely avoid excessive heat or the indirect effects of extreme weather events.

Based on medical reviews of individuals who died during heat waves and other extreme weather events, those who are particularly vulnerable to the direct effects of climate change include the very old and very young, individuals who have chronic medical conditions and psychiatric illness, people taking multiple medications, people without means for evacuation (no access to public transit or private cars), people who are socially isolated, medically fragile people, and people living in institutions. Acclimatization to heat may help reduce risks from heat waves in the healthy general population but may not be sufficient to protect those with underlying medical conditions.

Researchers have examined the pathways in which increased temperatures and hydrologic extremes can impact health and generally recognize three main pathways: direct exposures, indirect exposures, and socioeconomic disruption. Based on the review of weather-related natural disasters and historical patterns and scientific judgment, public health researchers have suggested the nature and direction of health harms or benefits.
➢ Extreme Weather-Related Injury, Mental Health, and Displacement Extreme weather events (storms, flooding) – These events can cause fatal and nonfatal injuries from drowning, being struck by objects, fire, explosions, electrocution, or exposure to toxic materials. A widespread weather-related natural disaster may destroy or ruin housing, schools and businesses and cause temporary or permanent displacement. Individuals and families may experience post-traumatic stress, depression, and increased risk of suicide.
➢ Vector-borne Illnesses – Climatic changes alter the range, biogeography, and growth of microbes and the vectors of food, water, and vector-borne illnesses. This includes the changes in aquatic environments that could increase harmful algal blooms and lead to increases in foodborne and waterborne illnesses.
➢ Food Insecurity – Climate change is expected to have global impacts on food production and distribution systems. This can cause food prices to increase, which makes food less affordable and increases food insecurity, obesity, and malnutrition in economically constrained households. ➢ Sea Level Rise, Mold, and Indoor Air Quality – Through sea level rise, saltwater may intrude into coastal aquifers thus reducing quality and quantity of water supply. Water intrusion into buildings can result in mold contamination leading to indoor air quality problems. ➢ Socioeconomic Disruption – Widespread social and economic disruption includes damage to the infrastructure for the delivery of health services and for general economic well-being. Health care facilities, water treatment plants, and roads for emergency responders and transportation for health care personnel can be damaged in climate-related extreme weather events. Increased burden of disease and injury will test the surge capacity of health care facilities. Economic disruption can lead to income loss, income insecurity, food insecurity, housing insecurity, and mental health problems, which in turn may increase substance abuse, suicide and other health problems. Energy production and distribution is also threatened by heat and wildfires through loss of efficiency, generating capacity, and fires disrupting transmission lines. California’s ports that provide the gateway to goods for California, national, and international markets are at risk from sea level rise and coastal storms.

Packet Page No. 419
Tri-City 4-94
Local Hazard Mitigation Plan Update
March 2024
In addition to the bulleted points above, drought, extreme heat, and wildfire are also exacerbated by climate change. This will be discussed further in Section 4.3.9 (Drought), Section 4.3.2 (Extreme Heat), and Section 4.3.17 (Wildfire). Sea level rise is a byproduct of climate change. It is discussed in Section 4.3.7.

All Californians are vulnerable to the health impacts of climate change. Even if one is fortunate to live, work, study, or play in a place without direct contact with wildfires, flooding, or sea level rise, no one can entirely avoid excessive heat or the indirect effects of extreme weather events.

California Adaptation Planning Guide Impacts (2020)
The California Adaptation Planning Guide (APG) prepared by California OES and CNRA was developed to provide guidance and support for local governments and regional collaboratives to address the unavoidable consequences of climate change. The APG: Defining Local and Regional Impacts focuses on understanding the ways in which climate change can affect a community. According to this APG, climate change impacts (temperature, precipitation, sea level rise, ocean acidification, and wind) affect a wide range of community structures, functions and populations in the Planning Area. These impacts further defined by regional and local characteristics are discussed by secondary impacts and seven sectors found in local communities: Public Health, Socioeconomic, and equity impacts; Ocean and Coastal Resources; Water Management; Forest and Rangeland; Biodiversity and Habitat; Agriculture; and Infrastructure. The APG:

Understanding Regional Characteristics identified the following impacts specific to the North Coast region in which the Tri-City Planning Area is part of:
➢ Increased temperatures
➢ Reduced precipitation
➢ Sea level rise – coastal inundation and erosion
➢ Public health – heat and air pollution
➢ Reduced agricultural productivity (e.g., wine grapes) ➢ Inland flooding
➢ Reduced tourism
California’s Adaptation Guide: Understanding Regional Characteristics provides input on adaptation considerations for the North Coast Region. As detailed in this guide, climate change has the potential to disrupt many features that characterize the region, including ecosystems health, snowpack, and the tourist economy. Specific regional impacts include the following:

Agriculture. Each of the products will be affected by climate change differently. The Planning Area should collaborate closely with local agricultural organizations to best support and prepare for changes in this economic sector.

Ecosystems and Biodiversity. Exacerbated by new development in the region, climate change can cause habitats to shift, creating conditions that stress ecosystems and endemic species. Continued changes in hydrologic flow regimes and increased temperatures will further stress these systems’ regional habitats supporting many special-status species.

Snowpack and Flooding. Climate-related decrease in snowpack can have significant consequences on the areas that depend on this water. In addition, a decrease in snowpack can increase impacts from flooding, Packet Page No. 420
Tri-City 4-95
Local Hazard Mitigation Plan Update
March 2024
landslide, and loss of economic base related to a drop in tourism. Increases in flood events can further stress the region and increase flood related impacts and damages.

Water Management. Depending on location, parts of this region are projected to experience between 6 inches and 15 inches less rainfall by 2100. Specifics for the Planning Area were not given in this report.

Reduced rainfall, combined with reductions in snowpack and existing diversions, could result in an altered flow regime in the region. This change would be particularly challenging due to its impact on fish. Reduced flow, altered timing of flows, and periodic extreme events can result in reduced water quality, habitat destruction, and/or isolation of habitats. The Planning Area will need to carefully assess local aquatic ecosystems for vulnerability to these changes.

Wildfire. The Bay Area Region is already challenged through past fire suppression combined with the large number of structures that have been built throughout the WUI areas. Climate change is projected to result in large increases in wildfire frequency and size which will further compound the wildfire problem.

In addition, potential impacts following fires, such as heavy rains causing landslide and erosion in postburn areas can have significant consequences on waterways and entire watersheds.

Proceedings of National Academy of Sciences Impacts (2017) In addition to the APG, a report from the Proceedings of the National Academy of Sciences (PNAS) stated that some of the recent fire impacts may have been attributed to climate change. The PNAS report posits that climate influences wildfire potential primarily by modulating fuel abundance in fuel-limited environments, and by modulating fuel aridity in flammability-limited environments. Increased forest fire activity across the western United States in recent decades has contributed to widespread forest mortality, carbon emissions, periods of degraded air quality, and substantial fire suppression expenditures. Those most vulnerable to high levels of ozone and particulate matter include people who work or spend a lot of time outdoors, such as residents of this region who spend a lot of time working or recreating outdoors.

Future Development
The Tri-City Planning Area could see population fluctuations as a result of climate impacts relative to those experienced in other regions, and these fluctuations are expected to affect Planning Area. While there are currently no formal studies of specific migration patterns expected to impact the Planning Area, climateinduced migration was recognized within the UNFCCC Conference of Parties Paris Agreement of 2015 and is expected to be the focus of future studies. Future development issues in the Tri-City Planning Area are expected to be as follows:
➢ Climate change will stress water resources. Water is an issue in every region, but the nature of the potential impacts varies. Drought, related to reduced precipitation, increased evaporation, and increased water loss from plants, is an important issue in many U.S. regions, especially in the West.

Floods, water quality problems, and impacts on aquatic ecosystems and species are likely to be amplified by climate change. The ability to secure and provide water for new development requires on-going monitoring and assurances. It is recommended that the ability to provide a reliable water supply from the appropriate water purveyor, continue to be in the conditions for project approval, and such assurances shall be verified and in place prior to issuing building permits.

Packet Page No. 421
Tri-City 4-96
Local Hazard Mitigation Plan Update
March 2024
➢ Similarly, protecting and enhancing water supply will also need to be addressed. California’s Sustainable Groundwater Management Act (SGMA) will contribute to addressing groundwater and aquifer recharge needs. Good groundwater management in the Planning Area and the surrounding counties will provide a buffer against drought and climate change and contribute to reliable water supplies regardless of weather patterns. California depends on groundwater for a major portion of its annual water supply, and sustainable groundwater management is essential to a reliable and resilient water system. Protection of critical recharge areas should be addressed across the Planning Area.

Further, these plans should include provisions that guide development or curtail development in areas that would harm or compromise recharge areas.
➢ Climate change will affect land uses and planning. Climate change coupled with shifting demographics and market conditions, could impact both the location of desired developments and the nature of development. The value of open space, urban greening, green infrastructure, tree canopy expansion and pressure to preserve it will likely increase, due in part to its restorative, recreational, environmental, and habitat, and physical and mental health benefits but also for its ability to sequester carbon and cool the surrounding environment.

How climate change is specifically taken into account in future development in each of the jurisdictions of the Tri-City Planning area will differ. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.7. Coastal Flooding and Sea Level Rise
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
Historically, cities, towns and villages were often settled around ports and waterways along the nation's coastlines, providing individuals and families opportunities for trade, jobs and transportation, recreation and relaxation. These areas are extremely important to our nation, with great economic, historic and cultural significance. Although the coastal areas of the United States comprise only one-fifth of the land area of the contiguous 48 states, they account for more than half of the nation’s population and housing supply. In 1990, over 133 million Americans lived in the 673 counties along the Atlantic and Pacific Oceans, the Gulf of Mexico and the Great Lakes. Since 1960, population in these areas increased by 41 percent. The continued increase in coastal population leads to increased coastal development, which places greater numbers of people and structures at risk from coastal hazards.

Coastal flooding can result from a variety of different causes including storm surges created by tidal influences; storms like hurricanes and tropical cyclones, and even strong rain and wind storm events; rising sea levels due to climate change (discussed below) and to a much lesser extent by possible tsunamis events (discussed in Section 4.3.7). Additionally, sea-level rise is also predicted to lead to rising water tables.

High water tables can lead to the infiltration of sewer systems, destabilization of structure foundation Packet Page No. 422
Tri-City 4-97
Local Hazard Mitigation Plan Update
March 2024
integrity, seepage of historical soil contaminates, water discharge into creeks and ponds causing additional flooding, and increase risk of soil liquefaction (discussed in Section 4.3.10) during earthquakes.

In the past decade, there have been groundbreaking studies and an increased public awareness on the worldwide effects of climate change associated with global warming. Studies continue to document that global warming is continuing at progressive rates, which has been demonstrated by warmer and colder seasonal temperatures and patterns of more severe seasonal storm events. Sea-level rise has accelerated in recent decades due, in part, to increasing ice loss in the world’s polar regions. Latest data from the World Meteorological Organization shows that global mean sea-level reached a new record high in 2021, rising an average of 4.5 millimeter per year over the period 2013 to 2021. It is projected that sea levels will continue to rise as precipitation continues to increase and ice caps continue to melt. There are number of areas in the Tri-City Planning Area that are at risk of coastal flooding and will be dramatically impacted by sea level rise.

King Tides
Coastal flooding and sea level rise are exacerbated during periods of extreme tides. Tides are long-period waves that roll around the planet as the ocean is "pulled" back and forth by the gravitational pull of the moon and the sun as these bodies interact with the Earth in their monthly and yearly orbits. According to NOAA, during full or new moons—which occur when the Earth, sun, and moon are nearly in alignment— average tidal ranges are slightly larger. This occurs twice each month. The moon appears new (dark) when it is directly between the Earth and the sun. The moon appears full when the Earth is between the moon and the sun. In both cases, the gravitational pull of the sun is “added” to the gravitational pull of the moon on Earth, causing the oceans to bulge a bit more than usual. This means that high tides are a little higher and low tides are a little lower than average. These are called spring tides, a common historical term that has nothing to do with the season of spring. Rather, the term is derived from the concept of the tide “springing forth.” Spring tides occur twice each lunar month all year long, without regard to the season.

Spring tides are also sometimes called (non-scientifically) king tides.

Location and Extent
The coastal areas of the Tri-City Planning Area at risk for coastal flooding will also be affected by sea level rise (especially during periods of extreme tides). These include areas with low-lying elevations (some at sea level) and areas that are now filled and were once marshland. Coastal flooding areas in FEMA DFIRM VE zones are shown on Figure 4-107. Duration of coastal flooding generally lasts as long as the storm that causes it and is relatively short, with a quick speed of onset. There is no scientific scale to measure coastal flooding, as floods are generally measured in depths, extent, and velocity of flooding. Coastal flooding and potential CoSMoS sea level rise scenarios are shown on Figure 4-35, Figure 4-36, and Figure 4-37. Extents by scenario are detailed in Table 4-30. Duration of sea level rise is thought to be long. The speed of onset is slow. There is no scientific scale for sea level rise, other than the actual physical measurement of sea level and depth.

Packet Page No. 423
Tri-City 4-98
Local Hazard Mitigation Plan Update
March 2024
Figure 4-35 Tri-City Planning Area – Sea Level Rise Existing Conditions Scenarios Packet Page No. 424
Tri-City 4-99
Local Hazard Mitigation Plan Update
March 2024
Figure 4-36 Tri-City Planning Area – Sea Level Rise 1 Meter Scenarios Packet Page No. 425
Tri-City 4-100
Local Hazard Mitigation Plan Update
March 2024
Figure 4-37 Tri-City Planning Area – Sea Level Rise 2 Meter Scenarios Packet Page No. 426
Tri-City 4-101
Local Hazard Mitigation Plan Update
March 2024
Table 4-30 Tri-City Planning Area – Sea Level Rise Scenarios Geographical Extents Jurisdiction / Sea Level Rise
Scenario/
Total
Acres
% of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
Existing Condition: 0-year (tidal)
scenario 9,278.33 11.44% 0 0.00% 9,278.33 26.92%
Existing Condition: 100-year
(storm) scenario 12,783.91 15.77% 21.73 0.05% 12,762.18 37.03% 1 Meter (3.1 feet) of Sea-level
Rise: 0-year (tidal) scenario 15,560.96 19.19% 23.58 0.05% 15,537.38 45.09% 1 Meter (3.1 feet) of Sea-level
Rise: 100-year (storm) scenario 18,617.54 22.96% 224.24 0.48% 18,393.31 53.37% 2 Meter (6.2 feet) of Sea-level
Rise: 0-year (tidal) scenario 21,830.37 26.92% 1,562.55 3.35% 20,267.82 58.81% 2 Meter (6.2 feet) of Sea-level
Rise: 100-year (storm) scenario 22,910.88 28.25% 2,312.14 4.96% 20,598.74 59.77% Newark
Existing Condition: 0-year (tidal)
scenario 58.99 0.40% 0.62 0.01% 58.38 1.13%
Existing Condition: 100-year
(storm) scenario 1,448.71 9.86% 19.9 0.21% 1,428.81 27.74% 1 Meter (3.1 feet) of Sea-level
Rise: 0-year (tidal) scenario 3,317.94 22.59% 272.87 2.86% 3,045.08 59.12% 1 Meter (3.1 feet) of Sea-level
Rise: 100-year (storm) scenario 4,167.98 28.38% 568.96 5.97% 3,599.02 69.87% 2 Meter (6.2 feet) of Sea-level
Rise: 0-year (tidal) scenario 4,612.32 31.40% 847.62 8.89% 3,764.69 73.09% 2 Meter (6.2 feet) of Sea-level
Rise: 100-year (storm) scenario 5,845.21 39.80% 1,737.72 18.22% 4,107.49 79.74% Union City
Existing Condition: 0-year (tidal)
scenario 0 0.00% 0 0.00% 0 0.00%
Existing Condition: 100-year
(storm) scenario 341.62 2.05% 1.78 0.02% 339.84 4.64%
1 Meter (3.1 feet) of Sea-level
Rise: 0-year (tidal) scenario 624.38 3.75% 161.38 1.73% 463 6.32% 1 Meter (3.1 feet) of Sea-level
Rise: 100-year (storm) scenario 3,000.58 18.00% 2,331.53 24.96% 669.04 9.13% 2 Meter (6.2 feet) of Sea-level
Rise: 0-year (tidal) scenario 3,617.15 21.70% 2,871.64 30.74% 745.51 10.17% 2 Meter (6.2 feet) of Sea-level
Rise: 100-year (storm) scenario 4,409.28 26.45% 3,484.04 37.30% 925.24 12.63% Packet Page No. 427
Tri-City 4-102
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction / Sea Level Rise
Scenario/
Total
Acres
% of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Alameda County Water District
Existing Condition: 0-year (tidal)
scenario 5,278.13 4.94% 0.62 0.00% 5,277.51 12.32%
Existing Condition: 100-year
(storm) scenario 15,410.24 14.43% 50.55 0.08% 15,359.69 35.85% 1 Meter (3.1 feet) of Sea-level
Rise: 0-year (tidal) scenario 22,176.50 20.76% 477.77 0.75% 21,698.72 50.65% 1 Meter (3.1 feet) of Sea-level
Rise: 100-year (storm) scenario 28,597.27 26.77% 3,151.28 4.93% 25,445.99 59.40% 2 Meter (6.2 feet) of Sea-level
Rise: 0-year (tidal) scenario 32,976.82 30.87% 5,374.62 8.40% 27,602.20 64.43% 2 Meter (6.2 feet) of Sea-level
Rise: 100-year (storm) scenario 36,111.20 33.81% 7,631.65 11.93% 28,479.55 66.48% Union Sanitary District
Existing Condition: 0-year (tidal)
scenario 54.17 0.07% 0 0.00% 54.17 0.38%
Existing Condition: 100-year
(storm) scenario 356.18 0.46% 2.19 0.00% 353.98 2.50%
1 Meter (3.1 feet) of Sea-level
Rise: 0-year (tidal) scenario 712.67 0.92% 164.85 0.26% 547.81 3.87% 1 Meter (3.1 feet) of Sea-level
Rise: 100-year (storm) scenario 4,093.19 5.28% 2,628.53 4.15% 1,464.66 10.34% 2 Meter (6.2 feet) of Sea-level
Rise: 0-year (tidal) scenario 7,390.77 9.54% 4,824.69 7.62% 2,566.08 18.12% 2 Meter (6.2 feet) of Sea-level
Rise: 100-year (storm) scenario 10,227.14 13.20% 7,054.70 11.14% 3,172.44 22.41% Source: CoSMoS 2021
Past Occurrences
Disaster Declaration History
There have been 19 state and 19 federal disaster declarations due to flooding and heavy rains and storms in Alameda County as shown in Table 4-31. These events are known to have caused some measures of coastal flooding, as compounded by sea level rise, affecting the Tri-City Planning Area. No disaster declarations have occurred specific to sea level rise.

Packet Page No. 428
Tri-City 4-103
Local Hazard Mitigation Plan Update
March 2024
Table 4-31 Alameda County Disaster Declarations 1950-2023 from Flood Disaster Type State Declarations Federal Declarations
Count Years Count Years
Flood (including heavy
rains and storms)
19 1950, 1955, 1957, 1958 (twice), 1962,
1963, 1970, 1982, 1983 (twice), 1986,
1995 (twice), 1997, 1998, 2008, 2017
(twice)
19 1955, 1958, 1962 (twice), 1970,
1982, 1983, 1986, 1995 (twice),
1997, 1998, 2005, 2006, 2017
(three), 2023 (twice)
Source: Cal OES, FEMA
NCDC Events
The NCDC does not track sea level rise. There are NCDC events for coastal flooding, which are shown in Table 4-32 for Alameda County.

Table 4-32 Alameda County NCDC Coastal Flood Events 1/1/1950-12/31/2022* Event Type Number of
Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Coastal Flood 3 0 0 0 0 $0 $0
High Surf 1 0 0 0 0 $0 $0
Total 4 0 0 0 0 $ 0 $ 0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of the Planning Area and outside of Alameda County.

Planning Committee Events
The Planning Committee noted that coastal flooding is an annual event, with some past damages and that sea level rise is adding to the concern of coastal flooding. The Planning Committee is concerned that sea level rise will exacerbate these damages in the future. Past events include:
2017 – Hayward Shoreline (near the Planning Area), Site 3 Marsh Levee, 2 sections of the levee were damaged. 1) Approx 30' long by 3' wide section of trail was lost. 2) Approx 25' long by 3' wide section of trail was lost. Repair with rip rap and rock fill. Trail restoration was needed.

More specific past occurrences can be found in each jurisdiction’s respective annex to this LHMP Update Likelihood of Future Occurrence (for both Coastal Flooding and Sea Level Rise) Highly Likely – Coastal flooding occurs in the Planning Area during large storm events. Studies continue to document that global warming is continuing at progressive rates, which has been demonstrated by warmer and colder seasonal temperatures and patterns of more severe seasonal storm events. It is projected that sea levels will continue to rise as precipitation continues to increase and ice caps continue to melt. This will compound the coastal flooding issues. Therefore, the Planning Committee regards the likelihood of future occurrence of coastal flooding and sea level rise as highly likely.

Packet Page No. 429
Tri-City 4-104
Local Hazard Mitigation Plan Update
March 2024
Climate Change and Coastal Flooding and Sea Level Rise
Global models indicate that California will see substantial sea level rise (and coastal flooding) during this century, with the exact magnitude depending on such factors as, global emissions, rate at which oceans absorb heat, melting rates and movement of land-based ice sheets, and local coastal land subsidence or uplift. Cal-Adapt’s “Sea Level Rise” map tool displays areas that may be vulnerable to inundation during an extreme storm event (coastal flooding) coupled with sea level rise. Information from that tool for the Tri-City Planning Area is shown in Figure 4-38. The upper map shows expected sea level rise between 2020 and 2040, while the lower map shows expected sea level rise between 2080 and 2100.

Packet Page No. 430
Tri-City 4-105
Local Hazard Mitigation Plan Update
March 2024
Figure 4-38 Tri-City Planning Area – Coastal Flooding and Sea Level Rise Threatened Areas Source: Cal Adapt Sea Leve Rise – Coast Inundation Scenarios. Retrieved 5/5/2023 Packet Page No. 431
Tri-City 4-106
Local Hazard Mitigation Plan Update
March 2024
According to the California Adaptation Planning Guide, Understanding Regional Characteristics, with all of the coastal development in the Bay Area Region, sea level rise is likely to be the greatest threat to the Bay Area from climate change significantly affecting development, infrastructure, transportation infrastructure, populations, and the environment.

Vulnerability Assessment
Vulnerability—High
Coastal flooding and global climate change, sea level rise, and the need to nurture sustainable community development have become widely recognized issues that need to be addressed by Bay Area communities.

The Tri-City Planning Area is impacted by these issues in its long-term operations and has an important role to play in contributing to the sustainability of the region. Complicating this situation is the realization that coastal flooding and sea level rise is affecting California’s and the Bay Area’s ecosystems in ways that are still too complex to fully understand.

Many coastal areas experience periodic minor-to-moderate shallow coastal flooding events typically as a result of meteorological factors that include high tides, winds, and rain. These events often affect roadways, buildings, natural resources and critical infrastructure. Properties located in low lying areas, including those in DFIRM VE flood zones, are most at risk, not just to long term inundation by the sea but more frequent coastal flooding during storm events. The Planning Area has a significant history of coastal flooding during "normal" rain events. The saying "Today's flood is tomorrow's high tide" is particularly applicable to areas that are frequently inundated due to seasonal rain events. More frequent tidal, rain events, and storm surge flooding of low-lying areas would cause more frequent flooding of the coastal shorelines. This can disrupt travel and damage roads, highways, levees, trails, natural resource areas, bridges, and other structures in coastal areas.

An assessment of a community’s vulnerability to climate change begins with an understanding of local exposure to coastal flooding and sea level rise. This is included in the discussion of the Tri-City’s Assets at Risk to this hazard.

Assets at Risk to Coastal Flooding and Sea Level Rise
Assets at risk from coastal flood and sea level rise include people and populations; structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

Methodology and Results
GIS was used to analyze Tri-City Planning Area assets potentially at risk to sea level rise (and coastal flooding). Alameda County Assessor’s data was obtained for the Planning Area and was intersected with CoSMoS v2.1 2021 sea level rise scenario data to determine Planning Area assets that fall into defined sea level rise scenario areas. Affected Planning Area assets are described below. Note, the sea level rise Packet Page No. 432
Tri-City 4-107
Local Hazard Mitigation Plan Update
March 2024
scenario data used to evaluate exposure does not account for the nearshore dynamic processes; as such, areas expected to be flooded are conservative estimates of the potential impact to these areas.

Six Sea Level Rise Scenarios for the Planning Area were analyzed for this LHMP Update. This includes three different sea level rise predictions presented under two conditions: a tidal scenario and a 100-year storm scenarios. These 6 scenarios are:
➢ Existing Condition: 0-year (tidal) scenario
➢ Existing Condition: 100-year (storm) scenario
➢ 1 Meter (3.1 feet) of Sea-level Rise: 0-year (tidal) scenario ➢ 1 Meter (3.1 feet) of Sea-level Rise: 100-year (storm) scenario ➢ 2 Meter (6.2 feet) of Sea-level Rise: 0-year (tidal) scenario ➢ 2 Meter (6.2 feet) of Sea-level Rise: 100-year (storm) scenario People and Populations
All people and populations in the Tri-City Planning Area located in areas subject to coastal flooding and sea level rise are at some risk to these hazards. This includes those that reside and recreate in coastal areas, including FEMA DFIRM VE Zones and within areas inundated by the CosMoS sea level rise scenarios.

Certain vulnerable populations located within areas prone to coastal flooding and sea level rise may be at increased risk to this hazard, especially during a large event with minimal advance notice. These vulnerable populations include: the unsheltered, those with limited mobility, and those that lack the resources to leave the area.

Planning Area residents that live in these coastal flooding and sea level rise areas are often the most vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to Fremont’s residential populations located in these hazard areas, the CoSMoS sea level rise scenarios were overlayed on the parcel layer, and linked to the Assessor Data. Those residential parcel centroids that intersect the scenario inundation areas were counted and multiplied by the 2020 Census Bureau average household factors for each jurisdiction in the Tri-City Planning Area. Analysis results are shown in Table 4-33.

Table 4-33 Tri-City Planning Area – Improved Residential Parcels and Population by Sea Level Rise Scenario by Jurisdiction
Sea Level Rise
Scenario/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
Existing Conditions –0-year (tidal) scenario
City of Fremont 0 0
City of Newark 0 0
City of Union City 0 0
Existing Conditions – 100-year (storm) Scenario
City of Fremont 0 0
City of Newark 0 0
Packet Page No. 433
Tri-City 4-108
Local Hazard Mitigation Plan Update
March 2024
Sea Level Rise
Scenario/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
City of Union City 2 6
1 Meter (3.1 feet) of Sea-level Rise: 0-year (tidal) scenario City of Fremont 0 0
City of Newark 0 0
City of Union City 569 1,918
1 Meter (3.1 feet) of Sea-level Rise: 100-year (storm) scenario City of Fremont 0 0
City of Newark 758 2,517
City of Union City 5,157 17,379
2 Meter (6.2 feet) of Sea-level Rise: 0-year (tidal) scenario City of Fremont 38 114
City of Newark 758 2,517
City of Union City 6,151 20,729
2 Meter (6.2 feet) of Sea-level Rise: 100-year (storm) scenario City of Fremont 781 2,335
City of Newark 3,067 10,182
City of Union City 7,773 26,195
Source: Cosmos 2021, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), US Census Bureau Average Household Factor – City of Fremont (2.99); City of Newark (3.32); City of Union City 3.37.

These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums as well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

For the special districts of ACWD and USD, analysis of their service territory populations in the CoSMos Sea Level Rise scenarios was also performed. This is derived from the table above. This analysis can be found in their respective annexes to this Base Plan.

Structures
Certain structures in the Tri-City Planning Area are at risk to coastal flooding and sea level rise and primarily include those structures located in areas prone to coastal flooding and sea level rise as shown in the CosMoS scenarios, (and the FEMA DFIRM VE flood zones which are discussed in more detail in the Flood: 1%/0.2% Annual Chance section below). GIS was used to determine the possible impacts of coastal flooding and sea level rise on parcels and structures within the Tri-City Planning Area. Table 4-34 is a summary table for the all jurisdictions in the Planning Area. Parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), estimated content replacement values, and total values Packet Page No. 434
Tri-City 4-109
Local Hazard Mitigation Plan Update
March 2024
in each jurisdiction are shown for each of the six sea level rise scenarios. More specific tables broken down by scenario and property use are shown in each respective jurisdictional annex to this Base Plan.

Table 4-34 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Sea Level Rise Scenarios by Jurisdiction
Sea Level
Rise
Scenario/
Jurisdiction
Total Parcel
Count
Improved
Parcel Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Existing Conditions –0-year (tidal) scenario
Fremont 77 0 $1,363,724 $0 $0 $1,363,724
Newark 2 0 $0 $0 $0 $0
Union City 0 0 $0 $0 $0 $0
Alameda
County Water
District
(Service
Territory)
64 0 $177,014 $0 $0 $177,014
Union Sanitary
District
(Service
Territory)
1 0 $146,517 $0 $0 $146,517
Existing Conditions – 100-year (storm) Scenario
Fremont 117 1 $1,373,889 $237,402 $237,402 $1,848,693
Newark 19 - $2,430,244 $0 $0 $2,430,244
Union City 17 2 $1,331,224 $799,083 $399,542 $2,529,849 Alameda
County Water
District
(Service
Territory)
202 9 $17,739,545 $5,185,859 $6,145,318 $29,070,722
Union Sanitary
District
(Service
Territory)
25 2 $2,923,290 $799,083 $399,542 $4,121,915
1 Meter (3.1 feet) of Sea Level Rise: 0-year (tidal) scenario Fremont 134 1 $1,373,889 $237,402 $237,402 $1,848,693
Newark 91 4 $72,875,566 $15,650,137 $15,650,137 $104,175,840 Union City 672 605 $112,615,579 $255,773,869 $167,287,216 $535,676,664 Alameda
County Water
District
(Service
Territory)
987 633 $222,126,910 $306,337,106 $220,590,875 $749,054,891 Packet Page No. 435
Tri-City 4-110
Local Hazard Mitigation Plan Update
March 2024
Sea Level
Rise
Scenario/
Jurisdiction
Total Parcel
Count
Improved
Parcel Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Union Sanitary
District
(Service
Territory)
718 606 $132,473,334 $267,952,722 $179,466,069 $579,892,125 1 Meter (3.1 feet) of Sea Level Rise: 100-year (storm) scenario Fremont 164 2 $3,967,433 $417,594 $507,690 $4,892,717
Newark 1,203 783 $483,575,703 $773,730,050 $512,281,394 $1,769,587,147 Union City 5,457 5,250 $905,421,320 $2,069,443,158 $1,137,764,150 $4,112,628,628 Alameda
County Water
District
6,925 6,065 $1,448,612,356 $2,937,707,735 $1,773,701,043 $6,160,021,134 Union Sanitary
District
6,608 6,022 $1,335,783,257 $2,838,257,116 $1,646,032,048 $5,820,072,421 2 Meter (6.2 feet) of Sea Level Rise: 0-year (tidal) scenario Fremont 497 205 $726,320,850 $1,085,899,930 $1,517,834,454 $3,330,055,234 Newark 1,599 1,073 $710,944,847 $1,266,914,275 $1,057,205,839 $3,035,064,961 Union City 6,523 6,279 $1,202,102,005 $2,722,377,094 $1,553,721,686 $5,478,200,785 Alameda
County Water
District
(Service
Territory)
8,754 7,615 $2,721,117,776 $5,199,726,160 $4,287,340,448 $12,208,184,384 Union Sanitary
District
(Service
Territory)
8,355 7,556 $2,596,569,500 $5,088,730,075 $4,145,403,255 $11,830,702,830 2 Meter (6.2 feet) of Sea Level Rise: 100-year (storm) scenario Fremont 1,477 1,084 $1,520,381,398 $2,865,783,635 $3,322,885,071 $7,709,050,104 Newark 3,898 3,170 $1,336,138,118 $2,497,079,905 $1,975,028,267 $5,808,246,290 Union City 8,342 7,999 $1,709,503,199 $3,811,837,203 $2,380,382,662 $7,901,723,064 Alameda
County Water
District
(Service
Territory)
13,871 12,319 $4,650,599,158 $9,303,102,200 $7,840,741,065 $21,794,442,423 Union Sanitary
District
(Service
Territory)
13,441 12,260 $4,515,796,435 $9,192,106,115 $7,698,803,872 $21,406,706,422 Source: Cosmos 2021, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Packet Page No. 436
Tri-City 4-111
Local Hazard Mitigation Plan Update
March 2024
Critical Facilities and Infrastructure, and Community Lifelines Coastal flooding and sea level rise presents a threat to critical facilities and infrastructure and community lifelines. Critical infrastructure plays an immensely important role in our communities. According to the 2021 Critical Infrastructure at Risk – Sea Level Rise Planning Guidance for California’s Coastal Zone by the California Coastal Commission, communities rely on roads, rail corridors, and related biking and pedestrian routes for transportation, and on water infrastructure for drinking water, wastewater service, and draining streets of rainwater. Damage to any one of these systems can threaten public safety, wreak havoc on daily life, impact properties far from flood zones, and result in economic impacts that cascade throughout California. The following GIS analysis identifies critical facilities and infrastructure at risk to coastal flooding and sea level rise, followed by a discussion on vulnerability of community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Coastal flooding and sea level rise present a threat to life and property, including community lifelines in the Tri-City Planning Area. Community lifelines that would be vulnerable to coastal flooding and sea level rise include:
➢ Safety and Security – Search and rescue and swiftwater teams may be called on to perform riskier duties during times of coastal flooding. Police, Fire, EMS, and Public Works personnel are often called on to respond during flood emergencies. This would be true in a coastal flood event. ➢ Health and Medical – There may be injuries and deaths from a coastal flood. Patient movement from accident scenes by EMS may also have to be rerouted.
➢ Energy – Coastal flooding and sea level rise could impact large areas of electric infrastructure, causing widespread power outages.
➢ Communications – Communication infrastructure can be inundated by a coastal flood event or sea level rise causing damage and an interruption in service. As well, an influx of service calls to dispatch centers for reporting of flooding, power outages, or other issues can occur. Messaging systems need to be deployed during these times to let the public know about road and lane closures, washouts, debris on roads, or other issues.
➢ Transportation – Highways and local roads may see extensive flooding. This can cause lane and road closures. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents and impact evacuation routes. ➢ Hazardous Material – Hazardous material facilities can be affected by flooding. Releases during these times can be comingled with flood waters, contaminate drinking water, as well as create additional exposures to the environment.
➢ Water Systems – Any water (and wastewater) system located close to the coast may be affected by coastal flooding and sea level rise. The Planning Area’s stormwater drainage system (close to the coast) and facilities may also be affected. Saltwater intrusion can cause significant impacts to these systems.

Generally, coastal flooding events are temporary events with flood waters receding back to pre-storm levels at the conclusion of the storm. Given the limited areas within the Planning Area prone to coastal flooding and the short duration of these events, community lifelines are not likely to be overwhelmed. However, Packet Page No. 437
Tri-City 4-112
Local Hazard Mitigation Plan Update
March 2024
sea level rise can create a permanent impact (or reduction) to the built environment causing many coastal areas to be uninhabitable as the water levels rise over time. Given the slow nature of sea level rise and limited areas prone to this hazard, the Tri-City Planning Area should be able to address these concerns proactively ensuring that these community lifelines are not overwhelmed and remain operational.

Natural, Historic, and Cultural Resources
According to sealevelrise.org, rising sea levels can disrupt coastal wetlands by drowning plant species, increasing salt levels in the soil and water, and outpacing wetland’s migration further inland. This puts important ecosystems in danger, threatens habitats, and leaves communities exposed to dangerous storm surge. Without wetlands and other critical ecosystems, many species could lose their homes or become extinct. A major coastal flood event could have a devastating impact on the Tri-City Planning Area. Large flood events can affect natural, historic, and cultural resources. Any of these resources that fall in the sea level rise scenarios shown on Figure 4-35, Figure 4-36, and Figure 4-37 would be vulnerable. This includes the Don Edwards San Francisco Bay National Wildlife Refuge owned by the US Fish and Wildlife Service.

Economic Assets and Community Activities of Value
Any economic asset located within areas prone to coastal flooding and sea level rise could be affected.

While impacts to these assets may be more limited or short term during a coastal flood event, sea level rise can create a permanent impact (or reduction) to the built environment causing many coastal areas to be uninhabitable as the water levels rise over time. This could cause those businesses and economic assets within these areas to temporarily shut down, close or relocate. Community activities of value located in coastal areas may also have to be canceled or rescheduled. Specific economic assets and community activities of value at risk to this hazard are discussed in the respective jurisdictional annexes to this Base Plan.

Impacts from Coastal Flooding and Sea Level Rise
All of the Tri-City Planning Area lands located in coastal areas are exposed to at least some level of inundation from coastal flooding and sea level rise. According to the 2020 Adapting to Rising Tides Short Report, coastal flooding is expected to worsen from sea level rise. It was noted that in the Tri-City Planning Area coastal flooding and sea level rise impacts include:
➢ A projected rise in sea level of between 15 and 55 inches will impact the Planning Area’s shoreline through increased sand and bank erosion as well as the loss of land, directly affecting piers, levees, boat launches, developed wetland areas, and other shoreline facilities. ➢ More frequent coastal floods: Rising sea levels will lead to more frequent flooding of existing floodprone areas, including more frequent overtopping and overbank flooding of riverine systems that already flood when rainfall coincides with high tides due to the increased backwater effect. In addition, gravity drained and pumped systems that discharge stormwater into flood control channels can have reduced performance, causing backups and flooding of streets. ➢ More extensive, longer-duration coastal flooding: As sea levels rise, storm events will flood larger areas for longer periods of time and that there will be new overtopping and overbank flooding of riverine systems that that do not currently cause flooding.

Packet Page No. 438
Tri-City 4-113
Local Hazard Mitigation Plan Update
March 2024
➢ Shoreline erosion and overtopping from coastal flooding: Sea level rise may cause shoreline protection, such as levees, berms and revetments, to be damaged or fail to due to increased tidal and wave energy.

There is also the potential that shoreline protection will be overtopped during storm events when there are extreme tide levels and wind-driven waves, flooding inland areas, including homes and community services that are currently protected.
➢ Elevated groundwater and increased salinity intrusion: As sea levels rise, groundwater and salinity levels are also predicted to rise. This may cause damage to below grade living spaces, finished basements, and electrical/mechanical equipment that is below or at-grade. In addition, increasing groundwater levels may increase liquefaction susceptibility, and require the use of pumping of stormwater for flood management, which will increase both operations and maintenance costs. ➢ Permanent inundation: Sea level rise can cause areas that are not currently exposed to regular high tide inundation to be flooded, resulting in the need to either protect or move people and infrastructure, and the loss of trails, beaches, vistas, and other shoreline recreation areas. In addition, increased tidal scour due to increased tidal prism in riverine systems can trigger changes in channel geometry and sediment transport processes.
➢ As sea level rises, so will the groundwater table and salinity levels, which can impact the vegetation and habitat in shoreline parks, increase the areas subject to liquefaction in earthquakes and require the use of pumping of stormwater for flood management, increasing both operations and maintenance costs.

The Planning Committee noted that coastal flooding and sea level rise are exacerbated during king tides.

King tides are simply the very highest tides. They are naturally occurring, predictable events. King tides of today may give an idea of future normal conditions that may occur due to sea level rise. High tides may coincide with heavy rain causing coastal flooding, coastal bluff erosion, and landslides, such as were experienced during the 1998 and 2016 El Nino storms. The 2023 California State Hazard Mitigation Plan noted that coupled with increased frequency, severity, and duration of high tide and storm events related to climate change, sea-level rise will exacerbate these extreme events along the coast. These events may expose the coast to severe flooding and erosion; damage to coastal structures, real estate, public access, and coastal habitats; and seawater intrusion into delta areas and coastal aquifers. El Niño events exacerbate storms and coastal inundation above that already occurring due to sea-level rise and normal coastal weather and tidal patterns.

Specific impacts to jurisdictions in the Tri-City Planning Area are discussed in their respective annexes to this Plan Update.

Future Development
How coastal flooding and sea level rise are taken into account in future development in each of the jurisdictions of the Tri-City Planning area will differ. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

Packet Page No. 439
Tri-City 4-114
Local Hazard Mitigation Plan Update
March 2024

4.3.8. Dam Failure
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
Dams are manmade structures built for a variety of uses including flood protection, power generation, agriculture, water supply, and recreation. When dams are constructed for flood protection, they are usually engineered to withstand a flood with a computed risk of occurrence. For example, a dam may be designed to contain a flood at a location on a stream that has a certain probability of occurring in any one year. If prolonged periods of rainfall and flooding occur that exceed the design requirements, that structure may be overtopped or fail. Overtopping is the primary cause of earthen dam failure in the United States.

Dam failures can also result from any one or a combination of the following causes:
➢ Earthquake
➢ Inadequate spillway capacity resulting in excess overtopping flows ➢ Internal erosion caused by embankment or foundation leakage, or piping or rodent activity ➢ Improper design
➢ Improper maintenance
➢ Negligent operation
➢ Failure of upstream dams on the same waterway
In general, there are three types of dams: concrete arch or hydraulic fill, earth and rockfill, and concrete gravity. Each type of dam has different failure characteristics. A concrete arch or hydraulic fill dam can fail almost instantaneously; the flood wave builds up rapidly to a peak then gradually declines. An earthrockfill dam fails gradually due to erosion of the breach; a flood wave will build gradually to a peak and then decline until the reservoir is empty. A concrete gravity dam can fail instantaneously or gradually with a corresponding buildup and decline of the flood wave.

The CA DWR Division of Safety of Dams (DSOD) has jurisdiction over impoundments that meet certain capacity and height criteria. Embankments that are less than six feet high and impoundments that can store less than 15 acre-feet are non-jurisdictional. Additionally, dams that are less than 25 feet high can impound up to 50 acre-feet without being jurisdictional. Cal DWR, DSOD assigns hazard ratings to large “jurisdictional sized” dams within the State. The following two factors are considered when assigning hazard ratings: existing land use and land use controls (zoning) downstream of the dam. Dams are classified in four categories that identify the potential hazard to life and property:
➢ Extremely High Hazard – Expected to cause considerable loss of human life or would result in an inundation area with a population of 1,000 or more.
➢ High Hazard – Expected to cause loss of at least one human life.

Packet Page No. 440
Tri-City 4-115
Local Hazard Mitigation Plan Update
March 2024
➢ Significant Hazard – No probable loss of human life but can cause economic loss, environmental damage, impacts to critical facilities, or other significant impacts. ➢ Low Hazard – No probable loss of human life and low economic and environmental losses. Losses are expected to be principally limited to the owner’s property.

Location and Extent
According to data provided by Cal DWR and Cal OES, there are 23 dams in Alameda County that were constructed for flood control, storage, treatment impoundments, electrical generation, and recreational purposes. Of the 23 dams in Alameda County, 11 were rated as Extremely High Hazard, 7 are rated as High Hazard, 3 as Significant Hazard, 2 as Low Hazard. Figure 4-39 identifies the dams in the County surrounding Tri-City, which are also detailed in Table 4-35.

Packet Page No. 441
Tri-City 4-116
Local Hazard Mitigation Plan Update
March 2024
Figure 4-39 Tri-City Planning Area Dam Inventory
Packet Page No. 442
Tri-City 4-117
Local Hazard Mitigation Plan Update
March 2024
Table 4-35 Tri-City Planning Area Dam Inventory
Name Significance Owner Dam Type Structural
Height (ft)
Maximum
Storage (acre-ft)
Almond Extremely High East Bay Municipal
Utility District
Earthen
Embankment
30 20
Bethany Forebay High CA DWR Earthen
Embankment
95 5,000
Central Extremely High East Bay Municipal
Utility District
Earthen
Embankment
55 485
Chabot Extremely High East Bay Municipal
Utility District
Hydraulic Fill 142 10,281
Coyote Extremely High Santa Clara Valley
Water District
Earthen Rockfill 140 22,451
Cull Creek High Alameda County Public
Works
Earthen
Embankment
55 140
Decoto Reservoir Extremely High Alameda County Water
District
Earthen
Embankment
33 46
Del Valle Extremely High CA DWR Earthen
Embankment
222 77,100
Dunsmuir
Reservoir
Extremely High East Bay Municipal
Utility District
Reinforced
Concrete Tank
43 197
Dyer High CA DWR Earthen
Embankment
30 525
James H Turner Extremely High City and County of San
Francisco
Earthen
Embankment
193 50,500
Lake Temescal Extremely High East Bay Regional Park
District
Earthen
Embankment
116 200
Leroy Anderson Extremely High Santa Clara Valley
Water District
Earthen
Embankment
235 91,300
Middlefield
Reservoir
High Alameda County Water
District
Earthen
Embankment
147 22
New Calaveras Extremely High City and County of San
Francisco
Earthen
Embankment
210 96,850
New Upper San
Leandro
Extremely High East Bay Municipal
Utility District
Earthen
Embankment
182 42,000
Patterson Significant Alameda County Water
District
Earthen
Embankment
100 56
Patterson 2 High CA DWR Earthen
Embankment
39 104
Piedmont Low East Bay Municipal
Utility District
Earthen
Embankment
64 60
Quarry Pits High Alameda County Water
District
Earthen
Embankment
26 3,360
Rubber Dam 3 Significant Alameda County Water
District
Earthen
Embankment
17 154
Packet Page No. 443
Tri-City 4-118
Local Hazard Mitigation Plan Update
March 2024
Name Significance Owner Dam Type Structural
Height (ft)
Maximum
Storage (acre-ft)
San Lorenzon
Creek
High Alameda County Public
Works
Inflatable 65 380
Seneca Low East Bay Municipal
Utility District
Earthen
Embankment
40 92
Shinn Significant Alameda County Water
District
Earthen
Embankment
45 390
Ward Creek Extremely High Alameda County Public
Works
Earthen
Embankment
71 13
Source: Cal OES, National Performance of Dams Program
*One acre foot equals 325,000 gallons
Once a list of dams was established, dam inundation layers were obtained from DSOD and Cal OES in GIS.

Dams with an inundation area in the Tri-City Planning Area are shown on Figure 4-40 (for extremely high hazard dams outside the Planning Area), Figure 4-41 (for extremely high hazard dams inside the Planning Area), Figure 4-42 (for high hazard dams inside the Planning Area), and Figure 4-43 (for significant hazard dams inside the Planning Area). Geographic flood extents as shown on the dam inundation maps are detailed by dam in Table 4-36 for extremely high hazard dams, in Table 4-37 for high hazard dams, and in Table 4-38 for significant hazard dams.

There is no scale with which to measure dam failure, only a scale to measure dam failure vulnerability based on size of dam and proximity to development. Dam failure may range from a small breach to a total failure. While a dam may fill slowly with runoff from winter storms, a dam break can have a very quick speed of onset. The duration of dam failure is not long – only as long as it takes to empty the reservoir of water the dam held back.

While a dam may fill slowly with runoff from winter storms, a dam break has a very quick speed of onset.

The duration of dam failure is generally not long – only as long as it takes to empty the reservoir of water the dam held back. For dam overtopping, the speed of onset is somewhat slower than that of a dam break, and the duration is longer (as evidenced in the 2017 Oroville Dam event). The Tri-City Planning Area would be affected for as long as the flood waters from the dam failure takes to drain downstream.

Packet Page No. 444
Tri-City 4-119
Local Hazard Mitigation Plan Update
March 2024
Figure 4-40 Tri-City Planning Area – Extremely High Hazard Dam Inundation Areas from Dams Originating Outside the Tri-City Planning Area
Packet Page No. 445
Tri-City 4-120
Local Hazard Mitigation Plan Update
March 2024
Figure 4-41 Tri-City Planning Area – Extremely High Hazard Dam Inundation Areas from Dams Originating Inside the Tri-City Planning Area
Packet Page No. 446
Tri-City 4-121
Local Hazard Mitigation Plan Update
March 2024
Table 4-36 Tri-City Planning Area –Geographical (Extremely High Hazard) Dam Inundation Extents
Jurisdiction
/Extremely
High Dam
Inundation
Areas
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
Coyote 647.32 0.80% 3.51 0.01% 643.81 1.87%
Decoto
Reservoir 24.45 0.03% 18.7 0.04% 5.75 0.02%
Del Valle 1,940.12 2.39% 127.89 0.27% 1,812.23 5.26%
James H
Turner 28,028.75 34.57% 17,798.17 38.17% 10,230.58 29.69% Leroy
Anderson 949.66 1.17% 10.52 0.02% 939.14 2.73%
New Calaveras 29,686.50 36.61% 16,514.82 35.42% 13,171.68 38.22% Newark
James H
Turner 1,873.37 12.75% 982.87 10.31% 890.5 17.29%
New Calaveras 6,541.84 44.54% 3,593.36 37.68% 2,948.48 57.24% Union City
Decoto
Reservoir 40.2 0.24% 23.01 0.25% 17.19 0.23%
Del Valle 442.26 2.65% 94.4 1.01% 347.86 4.75%
James H
Turner 6,403.72 38.42% 5,542.35 59.33% 861.37 11.76%
New Calaveras 5,954.92 35.73% 4,881.54 52.26% 1,073.37 14.65% Alameda County Water District
Coyote 580.47 0.54% 3.51 0.01% 576.96 1.35%
Decoto
Reservoir 61.92 0.06% 39.12 0.06% 22.8 0.05%
Del Valle 2,985.60 2.80% 210.49 0.33% 2,775.12 6.48%
James H
Turner 36,601.78 34.27% 24,309.03 38.00% 12,292.75 28.69% Leroy
Anderson 877.27 0.82% 10.52 0.02% 866.75 2.02%
New Calaveras 47,694.44 44.65% 25,041.52 39.15% 22,652.92 52.88% Ward Creek 1.45 0.00% 1.16 0.00% 0.29 0.00%
Union Sanitary District
Coyote 119.73 0.15% 3.51 0.01% 116.22 0.82%
Packet Page No. 447
Tri-City 4-122
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction
/Extremely
High Dam
Inundation
Areas
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Decoto
Reservoir 64.56 0.08% 41.71 0.07% 22.84 0.16%
Del Valle 1,416.19 1.83% 220.27 0.35% 1,195.93 8.45%
James H
Turner 29,783.26 38.43% 24,309.06 38.38% 5,474.21 38.66% Leroy
Anderson 150.75 0.19% 10.52 0.02% 140.23 0.99%
New Calaveras 31,348.54 40.45% 24,661.21 38.93% 6,687.33 47.23% Ward Creek 1.45 0.00% 1.16 0.00% 0.29 0.00%
Source: Cal OES/DSOD
Packet Page No. 448
Tri-City 4-123
Local Hazard Mitigation Plan Update
March 2024
Figure 4-42 Tri-City Planning Area – High Hazard Dam Inundation Areas from Dams Originating Inside the Tri-City Planning Area
Packet Page No. 449
Tri-City 4-124
Local Hazard Mitigation Plan Update
March 2024
Table 4-37 Tri-City Planning Area –Geographical (High Hazard) Dam Inundation Extents Jurisdiction /
High Dam
Inundation
Areas
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
Middlefield
Res 72.16 0.09% 58.66 0.13% 13.5 0.04%
Quarry Pits 7.25 0.01% 0 0.00% 7.25 0.02%
Union City
Quarry Pits 7.18 0.04% 0 0.00% 7.18 0.10%
Alameda County Water District
Middlefield
Res 72.16 0.07% 58.66 0.09% 13.5 0.03%
Quarry Pits 14.43 0.01% 0 0.00% 14.43 0.04%
Union Sanitary District
Middlefield
Res 72.16 0.09% 58.66 0.09% 13.5 0.10%
Quarry Pits 14.43 0.02% 0 0.00% 14.43 0.10%
Source: Cal OES/DSOD
Packet Page No. 450
Tri-City 4-125
Local Hazard Mitigation Plan Update
March 2024
Figure 4-43 Tri-City Planning Area – Significant Hazard Dam Inundation Areas from Dams Originating Inside the Tri-City Planning Area
Packet Page No. 451
Tri-City 4-126
Local Hazard Mitigation Plan Update
March 2024
Table 4-38 Tri-City Planning Area –Geographical (Significant Hazard) Dam Inundation Extents
Jurisdiction /
Significant
Dam
Inundation
Areas
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
Patterson 35.85 7.0% 0 0.0% 35.85 7.0%
Rubber Dam 3 185.84 36.4% 0 0.0% 185.84 36.4%
Shinn 288.97 56.6% 0 0.0% 288.97 56.6%
Union City
Rubber Dam 3 0.78 100.0% 0 0.0% 0.78 100.0%
Alameda County Water District
Patterson 35.85 6.4% 0 0.0% 35.85 6.4%
Rubber Dam 3 232.47 41.7% 0 0.0% 232.47 41.7%
Shinn 288.97 51.9% 0 0.0% 288.97 51.9%
Union Sanitary District
Rubber Dam 3 152.61 34.6% 0 0.0% 152.61 34.6%
Shinn 288.97 65.4% 0 0.0% 288.97 65.4%
Source: Cal OES, DSOD
Past Occurrences
Disaster Declaration History
There have been no disasters declarations related to dam failure in Alameda County as shown in Table 4-5.

NCDC Events
There have been no NCDC dam failure events in Alameda County.

National Performance of Dams Program Events
The National Performance of Dams Program at Stanford University tracks dam failures. A search of the National Performance of Dams Program database showed no past dam failure events affecting the Tri-City Planning Area.

Planning Committee Events
The Planning Committee noted no past dam failure events to affect the Tri-City Planning Area. However, two events that were close calls were noted:

Packet Page No. 452
Tri-City 4-127
Local Hazard Mitigation Plan Update
March 2024
➢ 1918 Calaveras Dam Failure—The San Francisco Public Utilities Commission-owned Calaveras Dam, located in Alameda County, failed during construction in 1918. A landslide damaged the upstream shell of the dam and destroyed the dam’s outlet tower. This event occurred prior to the incorporation of the cities.
➢ 2015 Rubber Dam 3 Failure—In 2015, the inflatable dam on Alameda Creek (Rubber Dam 3) failed due to vandalism, releasing nearly 50 million gallons of water from the community’s water into the San Francisco Bay. The water was supposed to go into the Niles Cone Groundwater Basin where residents and businesses from the Cities of Newark, Union City and Fremont could access drinking water. No damages occurred from the release of the water.

Likelihood of Future Occurrences
Unlikely– There have been few recorded events of dam failure or other issues of concern. Based on past occurrences and the rigorous monitoring and inspection requirements for dams, a dam failure may occur in the future that would impact the Tri-City Planning Area is unlikely. The Planning Committee noted that it could be considered to be occasional based on aging dam systems and variety of dam owners, some with limited resources to properly maintain dams.

Climate Change and Dam Failure
Increases in precipitation in areas upstream of dams could increase the potential for dam failure and uncontrolled releases on the dam that could affect the Planning Area.

Vulnerability Assessment
Vulnerability—High
Dam failure flooding can occur as the result of a partial or complete collapse of an impoundment. Dam failures often result from prolonged rainfall and flooding. An earthquake event can also contribute to a dam failure. The primary danger associated with dam failure is the high velocity flooding of those properties downstream of the dam. A dam failure can range from a small, uncontrolled release to a catastrophic failure. Vulnerability to dam failures is generally confined to the areas subject to inundation downstream of the facility. Secondary losses would include loss of the multi-use functions of the facility and associated revenues that accompany those functions. Dam failure flooding would vary by community depending on which dam fails and the nature and extent of the dam failure and associated flooding.

Vulnerability of the community is discussed in multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include assets at risk, impacts, and how future development can be affected by this hazard.

Assets at Risk from Dam Failure
Assets at risk from dam failure include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources, economic assets, and community activities of value). These are discussed in the following sections.

Packet Page No. 453
Tri-City 4-128
Local Hazard Mitigation Plan Update
March 2024
It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

Methodology and Results
In order to analyze people and populations, structures, and critical facilities at risk in dam inundation areas, GIS was used to quantify those values. The 2023 Alameda County Parcel/Assessor Data was provided by City of Fremont GIS and was used as the basis for the inventory of assessed values for both improved and unimproved parcels within the Tri-City Planning Area. The dam inundation areas, obtained from DSOD and Cal OES, were then overlaid on the parcel layer. For the purposes of this analysis, if the dam inundation layer intersected any portion of a parcel polygon, the entire parcel was considered to be in the dam inundation area. The parcels were segregated and analyzed in this fashion for the entire Planning Area.

People and Populations
All people and populations located in dam inundation areas are vulnerable to dam failure. Certain vulnerable populations may be at increased risk to dam failure, especially during a large event with minimal advance notice. These vulnerable populations may include: the unhoused, those with limited mobility, and those that lack the resources to leave the area.

Planning Area residents that live in these dam inundation areas are often the most vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To future evaluate the impact to the Tri-City’s Planning Area’s residential populations located in these hazard areas, a separate analysis was performed to determine residential populations in the dam inundation areas. The DSOD and Cal OES dam inundation areas were overlayed on the parcel layer and linked to the Assessor Data. Those residential parcel centroids that intersect the dam inundation areas were counted and multiplied by the Census Bureau average household factors for each jurisdiction. This is shown in Table 4-39. As shown, the Planning Area has high numbers of residents at risk to the James Turner and New Calaveras dams. Risk is smaller from the Del Valle, Decoto, and Middlefield dam, but is still sizable.

Table 4-39 Tri-City Planning Area – Improved Residential Parcels and Population by Dam Inundation Area and City Jurisdictions
Dam
Inundation
Area/Dams
City of Fremont City of Newark City of Union City
Improved
Residential
Parcels
Population Improved
Residential
Parcels
Population Improved
Residential
Parcels
Population
Extremely High Hazard Dams Inside Planning Area
Decoto 278 831 0 0 186 627
Extremely High Hazard Dams Outside Planning Area
New
Calaveras
50,281 150,340 12,073 40,082 13,119 44,211
Coyote 0 0 0 0 0 0
Del Valle 1,889 5,648 0 0 3,234 9,670
Packet Page No. 454
Tri-City 4-129
Local Hazard Mitigation Plan Update
March 2024
Dam
Inundation
Area/Dams
City of Fremont City of Newark City of Union City
Improved
Residential
Parcels
Population Improved
Residential
Parcels
Population Improved
Residential
Parcels
Population
James Turner 39,163 117,097 6,783 22,520 11,478 38,681
Leroy
Anderson
0 0 0 0 0 0
Ward Creek 0 0 0 0 0 0
High Hazard Dams
Middlefield 183 547 0 0 0 0
Quarry Pits 0 0 0 0 1 3
Significant Hazard Dams
Patterson 0 0 0 0 0 0
Rubber Dam
3 0 0 0 0 0 0
Shinn 0 0 0 0 0 0
Source: Cal OES, DSOD, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), 2020 US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City 3.37.

These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums as well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

For the special districts of ACWD and USD, analysis of their service territory populations in the dam failure inundation areas is performed. This is derived from the table above. This analysis can be found in their respective annexes to this Base Plan.

Structures
Most structures in the Tri-City Planning Area have some measure of risk to dam failure. Dam failure flooding can affect the built environment of the entire Tri-City Planning Area. Structures in dam inundation areas are at risk and depending on flood depths, can range from slight damage to totally inundated. Analysis by extremely high hazard dam, high hazard dam, and significant hazard dam follows.

Parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), estimated content replacement values, and total values that fall within dam inundation areas in the Planning Area are presented below by hazard class and by dam. The results are presented in tables below by:
➢ Extremely High Hazard Dams Originating Inside the Planning Area (Table 4-40) ➢ Extremely High Hazard Dams Originating Outside the Planning Area (Table 4-41, Table 4-42, Table 4-43, Table 4-44, Table 4-45, and Table 4-46)
➢ High Hazard Dams Originating Inside the Planning Area (Table 4-47 and Table 4-48) ➢ Significant Hazard Dams Originating Inside the Planning Area Packet Page No. 455
Tri-City 4-130
Local Hazard Mitigation Plan Update
March 2024
Extremely High Hazard Dams Originating Inside the Tri-City Planning Area Table 4-40 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Decoto Reservoir Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 314 281 $89,386,815 $196,156,707 $108,571,568 $394,115,090 Newark 0 0 $0 $0 $0 $0
Union City 229 187 $39,450,960 $93,979,383 $47,640,756 $181,071,099 Alameda
County Water
District
(Service
Territory)
539 467 $127,680,257 $288,114,630 $155,201,594 $570,996,481 Union
Sanitary
District
(Service
Territory)
542 468 $128,837,775 $290,136,090 $156,212,324 $575,186,189 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Extremely High Hazard Dams Originating Outside the Tri-City Planning Area Table 4-41 City of Fremont – Count and Value of Parcels (and Structures) in New Calaveras Dam Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 54,625 51,415 $12,156,391,286 $25,367,306,222 $15,246,062,650 $52,769,760,158 Newark 13,807 12,412 $3,441,935,461 $6,747,526,662 $4,676,583,742 $14,866,045,865 Union City 14,168 13,434 $2,884,960,639 $6,479,108,991 $3,877,243,193 $13,241,312,823 Alameda
County Water
District
(Service
Territory)
82,677 77,293 $18,528,197,410 $38,618,694,625 $23,829,033,000 $80,975,925,035 Union
Sanitary
District
(Service
Territory)
82,276 77,249 $18,413,592,760 $38,591,624,600 $23,801,878,725 $80,807,096,085 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Packet Page No. 456
Tri-City 4-131
Local Hazard Mitigation Plan Update
March 2024
Table 4-42 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Coyote Dam Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 62 12 $108,413,503 $165,757,548 $226,884,071 $501,055,122 Newark 0 0 $0 $0 $0 $0
Union City 0 0 $0 $0 $0 $0
Alameda
County Water
District
(Service
Territory)
60 12 $108,413,503 $165,757,548 $226,884,071 $501,055,122 Union
Sanitary
District
(Service
Territory)
26 12 $108,413,503 $165,757,548 $226,884,071 $501,055,122 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Table 4-43 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Del Valle Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 2,324 1,921 $729,556,612 $1,781,036,922 $1,333,534,362 $3,844,127,896 Newark 0 0 $0 $0 $0 $0
Union City 3,355 3,247 $545,803,250 $1,266,137,336 $640,768,228 $2,452,708,814 Alameda
County Water
District
(Service
Territory)
5,661 5,156 $1,271,298,057 $3,034,669,915 $1,961,811,676 $6,267,779,648 Union
Sanitary
District
(Service
Territory)
5,619 5,165 $1,271,044,378 $3,039,514,795 $1,966,656,556 $6,277,215,729 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Table 4-44 Tri-City Planning Area – Count and Value of Parcels (and Structures) in James Turner Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 42,416 39,798 $9,018,348,037 $19,817,271,325 $11,493,797,650 $40,329,417,012 Packet Page No. 457
Tri-City 4-132
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Newark 7,655 7,030 $2,014,035,274 $3,979,664,752 $3,109,277,591 $9,102,977,617 Union City 12,346 11,704 $2,335,996,238 $5,257,507,533 $3,002,980,600 $10,596,484,371 Alameda
County Water
District
(Service
Territory)
62,435 58,524 $13,372,199,132 $29,043,204,554 $17,594,834,950 $60,010,238,636 Union
Sanitary
District
(Service
Territory)
62,219 58,520 $13,317,690,728 $29,042,910,180 $17,595,396,046 $59,955,996,954 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Table 4-45 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Leroy Anderson Dam Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 83 22 $131,535,059 $200,908,287 $251,567,089 $584,010,435 Newark 0 0 $0 $0 $0 $0
Union City 0 0 $0 $0 $0 $0
Alameda
County Water
District
(Service
Territory)
81 22 $131,535,059 $200,908,287 $251,567,089 $584,010,435 Union
Sanitary
District
(Service
Territory)
46 22 $131,535,059 $200,908,287 $251,567,089 $584,010,435 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Table 4-46 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Ward Creek Dam Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 0 0 $0 $0 $0 $0
Newark 0 0 $0 $0 $0 $0
Union City 0 0 $0 $0 $0 $0
Packet Page No. 458
Tri-City 4-133
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Alameda
County Water
District
(Service
Territory)
5 4 $5,281,147 $1,905,723 $1,905,723 $9,092,593
Union
Sanitary
District
(Service
Territory)
5 4 $5,281,147 $1,905,723 $1,905,723 $9,092,593
Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) High Hazard Dams Originating Inside the Tri-City Planning Area Table 4-47 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Middlefield Reservoir Dam Inundation Area by Jurisdiction Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 424 335 140,553,833 251,078,397 187,491,620 579,123,850 Newark 0 0 $0 $0 $0 $0
Union City 0 0 $0 $0 $0 $0
Alameda
County Water
District
(Service
Territory)
424 335 140,553,833 251,078,397 187,491,620 579,123,850 Union
Sanitary
District
(Service
Territory)
424 335 140,553,833 251,078,397 187,491,620 579,123,850 Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Table 4-48 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Quarry Pits Dam Inundation Area by Jurisdiction
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 9 0 $0 $0 $0 $0
Newark 0 0 $0 $0 $0 $0
Union City 8 1 417,376 973,879 486,940 1,878,195
Packet Page No. 459
Tri-City 4-134
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Alameda
County Water
District
(Service
Territory)
17 1 417,376 973,879 486,940 1,878,195
Union
Sanitary
District
(Service
Territory)
17 1 417,376 973,879 486,940 1,878,195
Source: DSOD, Cal OES, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Significant Hazard Dams Originating Inside the Tri-City Planning Area After a review of significant hazard dams and their risk to the Planning Area, it was found that no improved parcels are affected by the significant hazard dam inundation areas. Only 5 unimproved parcels with no associated values (in the City of Fremont) fell in this area. Therefore, no tabular analysis was performed.

Critical Facilities and Infrastructure, and Community Lifelines Dam failure presents a threat to critical facilities and infrastructure, and community lifelines. The following GIS analysis identifies critical facilities and infrastructure at risk to dam inundation flooding, followed by a discussion on vulnerability of community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Dam failure flooding presents a threat to life and property, including community lifelines in the Tri-City Planning Area. A catastrophic dam failure could challenge local response capabilities and require evacuations to save lives. Community lifelines that would be at risk to dam failure flooding include:
➢ Safety and Security – Police, Fire, EMS, and Public Works personnel are often called on to respond during flood emergencies. This would be especially true in a dam failure event. Search and rescue and swiftwater teams may be called on to perform riskier duties during times of heavy rains and flooding. ➢ Food, Hydration, Shelter – a dam failure would displace many residents in the Planning Area. Some would need shelter, as well as food and water.
➢ Health and Medical – There is the potential for multiple injuries and deaths from a catastrophic dam failure taxing health and medical facilities. Casualty and patient movement from the inundation areas and unrelated incidents by EMS may be significantly impacted and have to be rerouted. Public health facilities can also be at risk from flooding caused by dam failures.

Packet Page No. 460
Tri-City 4-135
Local Hazard Mitigation Plan Update
March 2024
➢ Energy – Dam failure could impact large areas of above ground electric infrastructure, causing widespread power outages. Dam failure could also affect fueling stations, as well as electric car charging stations.
➢ Communications – An influx of service calls to dispatch centers for reporting of flooding, power outages, and rescues or other issues can occur resulting in communication networks going down for extended periods of time. Messaging systems need to be deployed during these events to let the public know about road closures, washouts, debris on roads, or lane closures. Calls to and from family and friends during a hazard event can further overwhelm communication systems such as cell towers and other infrastructure. Demand may exceed the capacity of these systems to remain operational during response efforts.
➢ Transportation – Highways and local roads may see extensive flooding. Bridges can be damaged or destroyed. This can cause lane closures or road closures and limit available routes altogether. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents. Evacuation efforts may be difficult and further put people at risk of death or injury. ➢ Hazardous Material – Hazardous material facilities can be affected by flooding. Releases during these events can contribute to the dangers of floodwaters and cause contamination of potable water sources, as well as additional exposure to the environment. ➢ Water Systems – Any water (or wastewater) system located in a dam inundation area may be affected by dam failure flooding. The Planning Area’s stormwater drainage system and facilities may also be affected.

A large dam failure event could overwhelm many critical facilities and infrastructure in the Tri-City Planning Area. As shown on the maps and tables above, there are multiple dams that would affect large swaths of the Planning Area. A failure of many of these dams could, at least temporarily, overwhelm the community lifelines in place in affected areas of the Planning Area.

Natural, Historic, and Cultural Resources
A major dam failure event and associated flooding could have a devastating impact on the Tri-City Planning Area. Large flood events can affect all natural, historic, and cultural resources that lie in the dam inundation areas. There are a number of ways floodwaters associated with a dam failure event can impact natural resources and the environment: Wildlife habitats can be destroyed by floodwaters. Contaminated floodwater can pollute rivers and habitats. Silt and sediment can destroy natural areas. Riverbanks and natural levées can be eliminated as rivers reach bankfull capacity. Rivers can be widened, and deposition can increase downstream. Trees can be uprooted by high-velocity water flow. Plants that survive the initial flood may die due to being inundated with water. Historic and cultural resources may also be affected.

Generally, the impacts are associated with damage to these structures within the inundated areas, but other cultural resources such as those associated with Native Americans and old tribal areas can also be disturbed, damaged, and lost during extreme flood events.

Economic Assets and Community Activities of Value
As shown on the maps and tables above, there are multiple dams that would affect large swaths of the TriCity Planning Area should they fail. Most economic assets of the Planning Area would be at least temporarily disrupted. Many of these would come back online relatively quickly after a dam failure flood event, but some would take longer to re-engage in business. Some economic assets may be damaged to the point where the business or area would no longer be economically viable to continue to operate. Depending Packet Page No. 461
Tri-City 4-136
Local Hazard Mitigation Plan Update
March 2024
on the dam that failed, most community activities of value would be affected if they occurred during a dam failure event.

Impacts from Dam Failure
Impacts to the Tri-City Planning Area from dam failure flooding could be extensive and widespread and include loss of life and injury, flooding and damage to property and structures, damage to critical facilities and infrastructure, loss of natural resources, and all other flood related impacts. Additionally, mass evacuations and associated economic losses can also be significant.

Other impacts associated with dam failure are landslides, bank erosion, and destruction of habitat. Dam failures can cause downstream flooding and can transport large volumes of sediment and debris and contaminants from the floodwaters. Other environmental impacts can include contamination from septic system failures and releases of contaminants from hazardous materials facilities, contamination of potable water supplies; changes in configurations of streams; loss of wildlife habitats; and degradation of wetlands.

A large dam failure event could have significant and catastrophic impacts.

Future Development
How dam failures are taken into account in future development in each of the jurisdictions of the Tri-City Planning area will differ. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.9. Drought and Water Shortage
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
Drought
Drought is a gradual phenomenon. Although droughts are sometimes characterized as emergencies, they differ from typical emergency events. Most natural disasters, such as floods or forest fires, occur relatively rapidly and afford little time for preparing for disaster response. Droughts occur slowly, over a multi-year period, and it is often not obvious or easy to quantify when a drought begins and ends.

Drought is a complex issue involving (see Figure 4-44) many factors—it occurs when a normal amount of precipitation and snow is not available to satisfy an area’s usual water-consuming activities. Drought can often be defined regionally based on its effects:
➢ Meteorological drought is usually defined by a period of below average water supply.

Packet Page No. 462
Tri-City 4-137
Local Hazard Mitigation Plan Update
March 2024
➢ Agricultural drought occurs when there is an inadequate water supply to meet the needs of the state’s crops and other agricultural operations such as livestock. ➢ Hydrological drought is defined as deficiencies in surface and subsurface water supplies. It is generally measured as streamflow, snowpack, and as lake, reservoir, and groundwater levels. ➢ Socioeconomic drought occurs when a drought impacts health, well-being, and quality of life, or when a drought starts to have an adverse economic impact on a region.

Figure 4-44 Causes and Impacts of Drought
Source: National Drought Mitigation Center (NDMC)
Location and Extent of Drought
Drought is a regional phenomenon that affects the entire Tri-City Planning Area. Drought in the United States is monitored by the National Integrated Drought Information System (NIDIS). A major component of this portal is the U.S. Drought Monitor. The Drought Monitor concept was developed jointly by the NOAA’s Climate Prediction Center, the NDMC, and the USDA’s Joint Agricultural Weather Facility in the late 1990s as a process that synthesizes multiple indices, outlooks and local impacts, into an assessment that best represents current drought conditions. The final outcome of each Drought Monitor is a consensus of federal, state, and academic scientists who are intimately familiar with the conditions in their respective regions. A snapshot of the current 2023 drought conditions in California and the Tri-City Planning Area Packet Page No. 463
Tri-City 4-138
Local Hazard Mitigation Plan Update
March 2024
can be found in Figure 4-45. Snapshots from 2017, 2018, 2019, 2020, 2021, 2022, and 2023 are shown in Figure 4-46. As seen in these figures and related data, the Planning Area has been in and out of drought over the past eight years since the last drought started in 2014.

Figure 4-45 Tri-City Planning Area – Current Drought Status Source: US Drought Monitor
Packet Page No. 464
Tri-City 4-139
Local Hazard Mitigation Plan Update
March 2024
Figure 4-46 Previous Drought Status in the Planning Area Source: US Drought Monitor
Cal DWR says the following about drought:

Packet Page No. 465
Tri-City 4-140
Local Hazard Mitigation Plan Update
March 2024
One dry year does not normally constitute a drought in California. California’s extensive system of water supply infrastructure—its reservoirs, groundwater basins, and inter-regional conveyance facilities—mitigates the effect of short-term dry periods for most water users. Defining when a drought begins is a function of drought impacts to water users. Hydrologic conditions constituting a drought for water users in one location may not constitute a drought for water users elsewhere, or for water users having a different water supply. Individual water suppliers may use criteria such as rainfall/runoff, amount of water in storage, or expected supply from a water wholesaler to define their water supply conditions.

The drought issue in California is further compounded by water rights. Water is a commodity possessed under a variety of legal doctrines. The prioritization of water rights between domestic uses, farming and federally protected fish habitats in California further contributes to this issue.

As shown on the previous figures, drought is tracked by the US Drought Monitor. The Drought Monitor includes a scale to measure drought intensity:
➢ None
➢ D0 (Abnormally Dry)
➢ D1 (Moderate Drought)
➢ D2 (Severe Drought)
➢ D3 (Extreme Drought)
➢ D4 (Exceptional Drought)
Drought has a slow onset and long duration. Drought is not initially recognized as a problem because it normally originates in what is considered good weather, which typically includes a dry late spring and summer in Mediterranean climates, such as in California. This is particularly true in Northern California where drought impacts are delayed for most of the population by the wealth of stored surface and ground water. The drought complications normally appear more than a year after a drought begins. The most direct and likely most difficult drought impact to quantify is to local economies, especially agricultural economies. Drought has the potential to affect the entire Tri-City Planning Area.

Water Shortage
Northern California communities, including the Tri-City Planning Area, generally have sufficient groundwater and surface water supplies to mitigate even the severest droughts of the past century. Many other areas of the State, however, also place demands on these water resources during severe drought.

ACWD noted that the supplies of water available to them (as the service provider in the Tri-City Planning Area) are quite robust.

Location and Extent of Water Shortage
Since water shortage generally happens on a regional scale, the entirety of the Tri-City Planning Area is at risk. There is no established scientific scale to measure water shortage. The speed of onset of water shortage tends to be lengthy. The duration of water shortage can vary, depending on the severity of the Packet Page No. 466
Tri-City 4-141
Local Hazard Mitigation Plan Update
March 2024
drought that accompanies it and the status of the water sources going into the drought. The extent of the drought considers several factors, including the nature, source, and reliability of water. While drought conditions persist, the Planning Area has sufficient water supply from municipal water supplies, which lessens the extent of water shortage impacts in the Planning Area.

Past Occurrences
Disaster Declaration History
There have been two state and one federal disaster declarations for Alameda County. These are shown on Table 4-49.

Table 4-49 Alameda County – State and Federal Drought Disaster Declarations 1950-2021 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Drought 2 1976, 2014 1 1976
Source: Cal OES, FEMA
NCDC Events
There have been no NCDC drought events in Alameda County. This is most likely due to a lack of reporting by NCDC spotters in the County.

CA DWR (with Hazard Mitigation Planning Team Events)
Historically, California has experienced multiple severe droughts. According to the DWR, droughts exceeding three years are relatively rare in Northern California, the source of much of the State’s developed water supply. Figure 4-47 depicts California’s Multi-Year Historical Dry Periods, 1850-2000. The 1929- 34 drought established the criteria commonly used in designing storage capacity and yield of large northern California reservoirs. Figure 4-48 compares the 1929-34 drought to the 1976-77, 1987-92, 2007-09, and 2012-2016 droughts.

Figure 4-47 California’s Multi-Year Historical Dry Periods, 1850-2000 Source: Cal DWR
Notes: Dry periods prior to 1900 estimated from limited data; covers dry periods of statewide or major regional extent Packet Page No. 467
Tri-City 4-142
Local Hazard Mitigation Plan Update
March 2024
Figure 4-48 Average Annual Runoff and Precipitation for Historic Droughts Source: CA DWR – 2012-2016 California Drought: Historical Perspective (https://ca.water.usgs.gov/california-drought/californiadrought-comparisons.html) Figure 4-49 depicts runoff for the State from 1905 to 2021. This gives a historical context for the 2014- 2021 drought to compare against past droughts.

Packet Page No. 468
Tri-City 4-143
Local Hazard Mitigation Plan Update
March 2024
Figure 4-49 Annual California Runoff –1905 to 2021
Source: Cal DWR
The 2018 and 2023 California State Hazard Mitigation Plan discussed the major droughts from 1900 to 2022. The discussion below appends to the tables and figures above.

The 1975-1977 Drought
From November 1975 through November 1977, California experienced one of its most severe droughts.

Although people in many areas of the state are accustomed to very little precipitation during the growing season (April to October), they expect it in the winter. In 1976 and 1977, the winters brought only one-half and one-third of normal precipitation, respectively. Most surface storage reservoirs were substantially drained in 1976, leading to widespread water shortages when 1977 turned out to be even drier.

The 1987-1992 Drought
From 1987 to 1992, California again experienced a serious drought due to low precipitation and run-off levels. The hardest-hit region was the Central Coast, roughly from San Jose to Ventura. In 1988, 45 California counties experienced water shortages that adversely affected about 30 percent of the state’s population, much of the dry-farmed agriculture, and over 40 percent of the irrigated agriculture. Fish and wildlife resources suffered, recreational use of lakes and rivers decreased, forestry losses and fires increased, and hydroelectric power production decreased. In February 1991, DWR and Cal OES surveyed drought conditions in all 58 California counties and found five main problems: extremely dry rangeland, Packet Page No. 469
Tri-City 4-144
Local Hazard Mitigation Plan Update
March 2024
irrigated agriculture with severe surface water shortages and falling groundwater levels, widespread rural areas where individual and community supplies were going dry, urban area water rationing at 25 to 50 percent of normal usage, and environmental impacts.

Storage in major reservoirs had dropped to 54 percent of average, the lowest since 1977. The shortages led to stringent water rationing and severe cutbacks in agricultural production, including threats to survival of permanent crops such as trees and vines. Fish and wildlife resources were in critical shape as well. Not since the 1928-1934 drought had there been such a prolonged dry period. In response to those conditions, the Governor established the Drought Action Team. This team almost immediately created an emergency drought water bank to develop a supply for four critical needs: municipal and industrial uses, agricultural uses, protection of fish and wildlife, and carryover storage for 1992. The large-scale transfer program, which involved over 800,000 acre-feet of water, was implemented in less than 100 days with the help and commitment of the entire water community and established important links between state agencies, local water interests, and local governments for future programs.

The 2007-2009 Drought
Water years 2007-2009 were collectively the 15th driest three-year period for DWR’s eight-station precipitation index, which is a rough indicator of potential water supply availability to the State Water Project (SWP) and Central Valley Project (CVP). Water year 2007 was the driest single year of that drought and fell within the top 20 percent of dry years based on computed statewide runoff. In June 2008, a state emergency proclamation was issued due to water shortage in selected Central Valley counties. In February 2009, for the first time in its history, the State of California proclaimed a statewide drought. The state placed unprecedented restrictions on CVP and SWP diversions from the Delta to protect listed fish species, a regulatory circumstance that exacerbated the impacts of the drought for water users.

The greatest impacts of the 2007–2009 drought were observed in the CVP service area on the west side of the San Joaquin Valley, where hydrologic conditions combined with reduced CVP exports resulted in substantially reduced water supplies (50 percent supplies in 2007, 40 percent in 2008, and 10 percent in 2009) for CVP south-of Delta agricultural contractors. Small communities on the west side highly dependent on agricultural employment were especially affected by land fallowing due to lack of irrigation supplies, as well as by factors associated with current economic recession. The coupling of the drought and economic recession necessitated emergency response actions related to social services, such as food banks and unemployment assistance.

The 2012-2017 Drought (and still ongoing after a pause in 2017) The statewide drought of 2012-2017, which is still ongoing, will be remembered as one of the most severe and costliest droughts of record in California. The drought that spanned water years 2012 through 2017 included the driest four-year statewide precipitation on record (2012-2015) and the smallest SierraCascades snowpack on record (2015, with 5 percent of average). It was marked by extraordinary heat:
2014, 2015, and 2016 were California’s first, second, and third warmest years in terms of statewide average temperatures. By the time the drought was declared officially over in April 2017, the state had expended $6.6 billion in drought response and mitigation programs and had been declared a federal disaster area.

Packet Page No. 470
Tri-City 4-145
Local Hazard Mitigation Plan Update
March 2024
Water Shortage
Figure 4-50 illustrates several indicators commonly used to evaluate water conditions in California. The percent of average values are determined by measurements made in each of the ten major hydrologic regions. The chart describes water conditions in California between 2007 and 2021. The chart illustrates the cyclical nature of weather patterns in California.

Figure 4-50 Water Supply Conditions, 2009 to 2021
Source: 2023 State of California Hazard Mitigation Plan Likelihood of Future Occurrence
Drought
Likely—Historical drought data for the Tri-City Planning Area indicate there have been 5 significant droughts in the last 86 years. This equates to a drought every 16.8 years on average or a 6.0 percent chance of a drought in any given year. Based on this data and given the multi-year length of droughts and future climate change affects, the Tri-City Planning Area determined that future drought occurrence continues to be likely.

Water Shortage
Occasional — Recent historical data for water shortage indicates that California and the Tri-City Planning Area may at some time be at risk to both short and prolonged periods of water shortage. Based on this it is possible that water shortages will affect the Planning Area in the future during extreme drought conditions.

New development, landscaping, and road paving put stress on water resources. The supply of water is currently sufficient, but as population grows and land use patterns shift, it will be necessary to consider the added stress that new development will put on water demand and quality.

Packet Page No. 471
Tri-City 4-146
Local Hazard Mitigation Plan Update
March 2024
Climate Change and Drought and Water Shortage
Climate scientists studying California find that drought conditions are likely to become more frequent and persistent over the 21st century due to climate change. The experiences of California during recent years underscore the need to examine more closely the state’s water storage, distribution, management, conservation, and use policies. The 2021 CAS stresses the need for public policy development addressing long term climate change impacts on water supplies. The CAS notes that climate change is likely to significantly diminish California’s future water supply, stating that: California must change its water management and uses because climate change will likely create greater competition for limited water supplies needed by the environment, agriculture, and cities.

A 2018 report from the Public Policy Institute of California noted that thousands of Californians – mostly in rural, small, disadvantaged communities – already face acute water scarcity, contaminated groundwater, or complete water loss. Climate change would make these effects worse.

Cal-Adapt has modeled future risk of drought. Recent research suggests that extended drought occurrence (“mega-drought”) could become more pervasive in future decades. This tool explores data for two 20-year drought scenarios (using the quad that contains the City of Fremont in Figure 4-51) derived from LOCA downscaled meteorological and hydrological simulations – one for the earlier part of the 21st century, and one for the latter part:
➢ The upper chart represents a mid-century dry spell from 2023-2042 identified from the HadGEM2-ES RCP 8.5 simulation. The extended drought scenario is based on the average annual precipitation over 20 years. This average value equates to 78% of historical median annual precipitation averaged over the North Coast and Sierra California Climate Tracker regions. ➢ The lower chart represents a late century dry spell from 2051–2070 identified from the HadGEM2-ES RCP 8.5 simulation. The extended drought scenario is based on the average annual precipitation over 20 years. This average value equates to 78% of historical median annual precipitation averaged over the North Coast and Sierra California Climate Tracker regions.

Packet Page No. 472
Tri-City 4-147
Local Hazard Mitigation Plan Update
March 2024
Figure 4-51 Tri-City Planning Area – Future Extended Drought Scenarios Source: Cal Adapt – Extended Drought Scenarios (retrieved 6/9/2023) Packet Page No. 473
Tri-City 4-148
Local Hazard Mitigation Plan Update
March 2024
Vulnerability Assessment
Vulnerability—Medium
Based on historical information, the occurrence of drought in California, including the Tri-City Planning Area, is cyclical, driven by weather patterns. Drought has occurred in the past and will occur in the future.

Periods of actual drought with adverse impacts can vary in duration, and the period between droughts can be extended. Although an area may be under an extended dry period, determining when it becomes a drought is based on impacts to individual water users. The vulnerability to drought may vary and include reduction in water supply, turf losses, impacts to natural resources, and an increase in dry fuels and tree dieback.

The whole of the Planning Area is at some measure of vulnerability to drought and water shortage. An assessment of a community’s vulnerability to drought and water shortage begins with an understanding of local exposure to climate change. This is included in the discussion of the Planning Area’s Assets at Risk to this hazard which follows the discussion on tree mortality.

Tree Mortality and Drought
One of the specific impacts of drought in the Tri-City Planning Area is the increased risk to trees from beetle kill and other insects, pathogens and parasites, and other tree mortality and die back issues. Drought weakens trees and makes them more susceptible to insect infestation and other pathogens. Insects, such as bark beetles and others, frequently attack trees weakened by drought, disease, injuries, or other factors that may stress the tree. These insects and other pathogens can contribute to the decline and eventual death of trees throughout the Planning Area, especially in those areas on the east where the elevations increase.

The tree mortality and dieback problem are a high priority because of the issue of hazardous trees and increased wildfire hazard in the wildland areas and the potential for worsening conditions and expansion into other forested sites in future years. Fuel loading and fire potential are greater in affected eucalyptus, acacia, and conifer stands as compared to healthy stands due to the higher proportion of dead and dying material. Removal of dead and dying trees near structures, powerlines, and roadways is also a high priority because of the immediate falling hazard.

University of California, Berkeley’s Department of Environmental Science, Policy, and Management (ESPM) was commissioned in 2021 to investigate the symptoms and possible causes of the dieback.

Preliminary results show that the dieback is driven mostly by environmental stressors, including but not limited to drought, predisposing trees to disease caused by opportunistic pathogens. The report includes best management practices to limit the spread of pathogens. It is important to continue investigating the causes of the tree mortality and dieback to help Planning Area jurisdictional staff track changes over time, recognize where other areas may potentially be susceptible to tree mortality, and apply appropriate best management practices.

Under current drought conditions, competition for resources within forested areas will likely continue to intensify with greater stress increasing tree susceptibility to insect damage and disease, and ultimately increase mortality.

Packet Page No. 474
Tri-City 4-149
Local Hazard Mitigation Plan Update
March 2024
In all vegetation types, drought extends the length of the fire season because of its effect on live and dead fuel moisture, with critical low fuel moisture levels occurring early in spring or summer and extending at least through the first significant rains that typically come in late fall.

Assets at Risk
Assets at risk from drought and water shortage include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

People and Populations
The people and populations of the Tri-City Planning Area are not directly affected by drought; although, their turfed areas, trees, and other water dependent resources can all be affected. In extreme drought conditions, however, residents and other populations within the Planning Area may be vulnerability to drought and water shortage issues. Water quality can be impacted causing health problems, especially to vulnerable populations where access to clean water supplies can be more challenging. Drought and water shortage can lead to an increase in wildfires threatening Planning Area residents. Water shortages can have an effect on all of the population in the Planning Area, but often have a greater effect on the unhoused and other vulnerable populations that may be unable to access clean drinking water during shortages. During periods of drought as the costs of water usage may increase, those who are economically disadvantaged may be unable to afford the increased costs of potable water.

Structures
Structures have a limited vulnerability to drought and water shortage. It is the secondary hazard of drought (wildfire) which causes risks to structures. Drought can also stress trees, causing die off. These trees may fall on structures adjacent to them.

Critical Facilities and Infrastructure and Community Lifelines Most critical facilities and infrastructure have a limited vulnerability to drought and water shortage. Should drought conditions be severe enough to cause water shortage reliability issues, some facilities and infrastructure may be affected. Water and wastewater systems may be impacted during times of reduced water supply and need to employ contingencies to remain functional and fully operational. Other water dependent systems may also be adversely affected. Further, the secondary hazard of drought (increased potential for spread of urban fires and wildfire) can pose a significant risk to critical facilities and infrastructure. Drought can also stress trees, causing die off. These trees may fall on critical infrastructure adjacent to them and impact power lines and other utilities.

While limited, community lifelines can have a vulnerability to drought and water shortage. This includes:
➢ Safety and Security – Agencies may need to assist in providing alternative water supplies. Agencies may also need to staff locations where water is distributed. ➢ Food, Hydration, Shelter – Drought can limit agricultural production, including timber and grazing activities. Additional water supplies may need to be procured.

Packet Page No. 475
Tri-City 4-150
Local Hazard Mitigation Plan Update
March 2024
➢ Health and Medical – Additional water supplies may be required for these facilities to remain fully operational during drought and water shortages.
➢ Energy – Sufficient water is required to generate electricity and power. Additional fuels and power may be required to move water to and from locations that need it. ➢ Communications – Most communication systems will not be affected. In extreme instances, additional messaging may be required during drought and water shortages. ➢ Water Systems – During period of drought and water shortage, additional pressure may be put on water companies to secure additional supplies. With reductions in available water, the ability of wastewater systems to effectively treat wastewater may be impacted.

It is unlikely that any of these community lifelines would be overwhelmed by drought and water shortages, especially given the current state of water supply reliability in the Tri-City Planning Area.

Natural, Historic, and Cultural Resources
Drought and water shortage can have a significant impact on natural resources. Water levels in reservoirs and lakes may be reduced and a loss of wetlands and coastal marsh areas may occur. Severe drought conditions can contribute to an increase in erosion of soils and lead to poor soil quality. Further, all of the trees in the Planning Area are at risk to drought impacts and a reduction in water supply. These trees provide a wealth of social and environmental benefits to Planning Area residents and visitors, from shade and beauty to air quality, carbon reduction and stormwater management. Drought can devastate crops and dry out pastures, dry out forests and critical habitat areas, and reduce food and water available for wildlife and livestock. Additionally, drought conditions can also cause soil to compact and not absorb water well, potentially making an area more susceptible to flooding. It is unlikely that drought and water shortage would have a significant impact on historic and cultural resources in the Planning Area.

Economic Assets and Community Activities of Value
Economic assets and community activities in the Tri-City Planning Area generally have a limited vulnerability to drought and water shortage. Drought is a problem which predominantly affects rural small business owners such as farmers and agricultural contractors who rely on water for their crops. However, supply issues can also affect businesses such as cafes and restaurants in more urban areas. Drought impacts to the agricultural industry can affect the supply chain and increase the cost of food and water, and adversely impact businesses tied to these industries. Reduction in or interruption of the water supply could also lead to lower productivity or closure of manufacturing facilities. Other economic sectors with a heavy reliance on water may also be affected. Depending upon how severe the conditions get and how long they last, drought can restrict recreational and community activities, all of which can stress businesses and local economies over time.

Impacts from Drought and Water Shortage
The vulnerability to drought is Planning Area wide, but impacts may vary and include reduction in water supply and an increase in dry fuels. The potential for a reduction in water supply during drought conditions generally leads to both mandated and voluntary conservations measures during extended droughts. During these times, the costs of water can also increase. Also of concern, the increased dry fuels and fuel loads associated with drought conditions can result in an increased fire danger. In areas of extremely dry fuels, Packet Page No. 476
Tri-City 4-151
Local Hazard Mitigation Plan Update
March 2024
the intensity and speed of fires can be significant. Water supply and flows for fire suppression can also be an issue during extended droughts.

Other qualitative impacts associated with drought in the Tri-City Planning Area are those related to water intensive activities such as municipal usage, commerce, tourism, and recreation use. With more precipitation likely falling as rain instead of snow in the Sierra’s, and warmer temperatures causing decreased snowfall to melt faster and earlier, water supply is likely to become more unreliable. In addition, drought and water shortage is predicted to become more common. This means less water available for use over the long run, and additional challenges for water supply reliability, especially during periods of extended drought.

The effects of drought are managed in the Bay Area through the importation of water and the storage of water in reservoirs. ACWD provides much of the water in the Planning Area. Historically, ACWD has been able to secure sufficient water to meet the demands of a growing population. The Planning Committee indicated the area’s water supplies are sufficient for most periods of drought. More information can be found in ACWD’s annex to this LHMP Update.

During periods of drought, vegetation can dry out which increases fire risk. Drought that occurs during periods of extreme heat and high winds can cause PSPS events to be declared in the Planning Area. More information on PSPS can be found in Section .

Additionally, the Planning Committee noted that wood tick populations have exploded during recent droughts. Increase of tick-borne diseases has occurred as a result. This is both for humans, as well as for animals that reside in the Tri-City Planning Area.

Drought Impact Reporter
Drought impacts are wide-reaching and may be economic, environmental, and/or societal. Tracking drought impacts can be difficult. The Drought Impact Reporter from the NDMC is a useful reference tool that compiles reported drought impacts nationwide. Table 4-50 show drought impacts for County from 1850 to June 2023. The data represented is skewed, with the majority of these impacts from records within the past ten years. It is anticipated that drought impacts to the Tri-City Planning Area would be similar to those experienced in Alameda County, though on a smaller scale.

Table 4-50 Alameda County Drought Impacts 1850-6/1/2023 Category Alameda County Number of Impacts
Agriculture 47
Business and Industry 15
Energy 6
Fire 19
Plants & Wildlife 43
Relief, Response, and Restrictions 132
Society and Public Health 71
Packet Page No. 477
Tri-City 4-152
Local Hazard Mitigation Plan Update
March 2024
Category Alameda County Number of Impacts
Tourism and Recreation 9
Water Supply and Quality 143
Total 485
Source: National Drought Mitigation Center
Future Development
How drought and water shortage are taken into account in future development in each of the jurisdictions of the Tri-City Planning area will differ. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.10. Earthquake
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
An earthquake is caused by a sudden slip on a fault. Stresses in the earth’s outer layer push the sides of the fault together. Stress builds up, and the rocks slip suddenly, releasing energy in waves that travel through the earth’s crust and cause the shaking that is felt during an earthquake. Earthquakes can cause structural damage, injury, and loss of life, as well as damage to infrastructure networks, such as water, power, gas, communication, and transportation. Earthquakes may also cause collateral emergencies including dam and levee failures, seiches, hazmat incidents, fires, avalanches, and landslides. The degree of damage depends on many interrelated factors. Among these are: the magnitude, focal depth, distance from the causative fault, source mechanism, duration of shaking, high rock accelerations, type of surface deposits or bedrock, degree of consolidation of surface deposits, presence of high groundwater, topography, and the design, type, and quality of building construction. This section briefly discusses issues related to types of seismic hazards.

Ground Shaking
Ground shaking is motion that occurs as a result of energy released during faulting. The damage or collapse of buildings and other structures caused by ground shaking is among the most serious seismic hazards.

Damage to structures from this vibration, or ground shaking, is caused by the transmission of earthquake vibrations from the ground to the structure. The intensity of shaking and its potential impact on buildings is determined by the physical characteristics of the underlying soil and rock, building materials and workmanship, earthquake magnitude and location of epicenter, and the character and duration of ground motion.

Packet Page No. 478
Tri-City 4-153
Local Hazard Mitigation Plan Update
March 2024
Actual ground breakage generally affects only those buildings directly over or nearby the fault. Ground shaking generally has a much greater impact over a greater geographical area than ground breakage. The amount of breakage and shaking is a function of earthquake magnitude, type of bedrock, depth and type of soil, general topography, and groundwater. As with most communities in Northern California near active faults, the Tri-City Planning Area could be susceptible to violent ground shaking, depending on the location of the event.

Seismic Structural Safety
Older buildings constructed before building codes were established, and even newer buildings constructed before earthquake-resistance provisions were included in the codes, are the most likely to be damaged during an earthquake. Buildings one or two stories high of wood-frame construction are considered to be the most structurally resistant to earthquake damage. Older masonry buildings without seismic reinforcement (unreinforced masonry) and soft story buildings are the most susceptible to the type of structural failure that causes injury or death.

The susceptibility of a structure to damage from ground shaking is also related to the underlying foundation material. A foundation of rock or very firm material can intensify short-period motions which affect lowrise buildings more than tall, flexible ones. A deep layer of water-logged soft alluvium can cushion lowrise buildings, but it can also accentuate the motion in tall buildings. The amplified motion resulting from softer alluvial soils can also severely damage older masonry buildings.

Other potentially dangerous conditions include but are not limited to: building architectural features that are not firmly anchored, such as parapets and cornices; roadways, including column and pile bents and abutments for bridges and overcrossings; and above-ground storage tanks and their mounting devices. Such features could be damaged or destroyed during strong or sustained ground shaking.

Liquefaction Potential
Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low.

However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other. When liquefaction occurs, the strength of the soil decreases and the ability of a soil deposit to support foundations for buildings and bridges is reduced. Liquefied soil also exerts higher pressure on retaining walls, which can cause them to tilt or slide. This movement can cause settlement of the retained soil and destruction of structures on the ground surface. Increased water pressure can also trigger landslides and cause the collapse of dams. Because liquefaction occurs in saturated soil, its effects are most commonly observed in low-lying areas near bodies of water such as rivers, lakes, bays, and oceans.

Liquefaction during major earthquakes has caused severe damage to structures on level ground as a result of settling, titling, or floating. Such damage occurred in San Francisco on bay-filled areas during the 1989 Loma Prieta earthquake, even though the epicenter was several miles away. If liquefaction occurs in or Packet Page No. 479
Tri-City 4-154
Local Hazard Mitigation Plan Update
March 2024
under a sloping soil mass, the entire mass may flow toward a lower elevation. Also, of particular concern in terms of developed and newly developing areas are fill areas that have been poorly compacted.

Landslide
Landslides can occur as a result of horizontal seismic inertia induced in the slopes by the ground shaking.

The most common earthquake-induced landslides include shallow, disrupted landslides such as rock falls, rockslides, and soil slides. Debris flows are created when surface soil on steep slopes becomes totally saturated with water. Once the soil liquefies, it loses the ability to hold together and can flow downhill at very high speeds, taking vegetation and/or structures with it. Slide risks increase after an earthquake during a wet winter. This is discussed in greater extent in Section 4.3.13.

Settlement
Settlement can occur in poorly consolidated soils during ground shaking. During settlement, the soil materials are physically rearranged by the shaking to result in a less stable alignment of the individual minerals. Settlement of sufficient magnitude to cause significant structural damage is normally associated with rapidly deposited alluvial soils or improperly founded or poorly compacted fill. These areas are known to undergo extensive settling with the addition of irrigation water, but evidence due to ground shaking is not available.

Fire Following Earthquake
Fire ignitions and spread in urban regions following a major earthquake can further compound the potentially catastrophic impacts of a large earthquake event. Fire following earthquake is a major hazard in earthquake-prone areas which are densely developed and have high inventories of wood frame buildings.

The Planning Area has a high inventory of wood frame residential and commercial buildings, is of relatively high density, and also has considerable industry. Earthquake ground shaking can result in damaged gas and electrical utilities, broken piping and connections, and toppled equipment when restraint or flexibility is inadequate. Open flames, friction, or other heat sources in combination with ordinary combustibles, combustible liquid releases, and flammable gas are among potential ignition sources. Wind speed and direction, along with relative humidity, can compound the damaging effects of fires following an earthquake. Scawthorn (2018), used the USGS HayWired earthquake scenario to model fire following earthquake – considering factors such as building construction and density, earthquake damage to property, water supply system damage, discovery and reporting of fires, fire department response, fire suppression, and fuel exhaustion and fire breaks. Assuming breezy conditions with moderate humidity at the time of the M7.0 earthquake, Scawthorn (2018) estimates that 352 ignitions would occur in Alameda County, resulting in 279 large fires (198 of which would involve multiple city blocks), and a loss of four percent of total residential and non-residential building square footage, or $9.7 billion (2014 dollars) in losses. A damaging seismic event in the Planning Area could result in multiple simultaneous fires, one or more of which could develop into a conflagration – a fire involving multiple city blocks.

The capability of fire departments to combat fires following an earthquake is impacted by the regional nature of an earthquake, damage to transportation and water supply systems, and the potential failure of telecommunications. A local fire department may suffer impacts to its personnel, buildings, equipment, Packet Page No. 480
Tri-City 4-155
Local Hazard Mitigation Plan Update
March 2024
and communications systems. Moreover, fewer resources are immediately available as mutual aid – due to the commitment of nearby fire departments responding to the earthquake withing their own jurisdictions.

Transportation system damage may adversely impact the mobilization of off-duty personnel and fire and rescue mutual aid resources from unaffected areas. Maneuvering fire crews within the affected areas of the earthquake may be impeded by debris or damage to roads and bridges. Additionally, the municipal water supply system which ordinarily supports firefighting operations is likely to be impacted. Like nearly all urban U. S. communities, the water distribution system in the Planning Area supplies both potable water to homes and businesses, as well as to fire hydrants used to fight fires. The extensiveness of the network, and the integration of both municipal and residential, commercial, and industrial water pipes renders the system highly exposed to damage and consequent pressure loss. Without adequate pressure, fire hydrants are rendered an ineffective water source for firefighting. According to a USGS HayWired Fact Sheet (2018), East Bay residents “could lose water service for 6 weeks (some as long as 6 months). Not only would normal water service be restricted, but the ability to suppress fires would also be reduced.” Fire following earthquake is an issue that could impact any California community that experiences an earthquake – both urban and rural. The problem is heightened for urban environments, where many simultaneous ignitions can lead to a firestorm, and single fires can more quickly and easily move structure to structure. The single most damaging fire of the twentieth century in the United States was the fire which followed the 1906 earthquake in San Francisco. Additionally, the largest peacetime fire in the twentieth century was a wind-driven firestorm following the 1923 Tokyo Kanto earthquake. In both cases, casualties and damage due to fire exceeded those caused by ground shaking. Significant fires also occurred in San Francisco following the 1989 Loma Prieta Earthquake, in Los Angeles following the 1994 Northridge Earthquake, and in Kobe, Japan following the 1995 Great Hanshin Earthquake. In each of these cases, multiple ignitions, dense built environments, a high inventory of wood frame buildings, and damage to water supply systems contributed to extensive fire spread. A gas explosion occurred following the 1994 Northridge Earthquake, when a natural gas line ruptured. Following the 1964 Great Alaskan Earthquake, major fires occurred in Wittier, AK, as well as at fuel refinery storage tanks in Valdez, AK.

According to the FM Global Insurance company, “Fires after earthquakes commonly initiate from electrical or fuel related sources because their use is widespread. In the US, natural gas is a factor 15 to 50 percent of the time, and electrical ignitions account for 40 percent or more of post-earthquake wildfires. Ignitable liquid spills, chemical reactions, and the contact of combustibles with heat sources have also initiated or contributed to many fires after earthquakes.”
Earthquake-Induced Subsidence
Regional uplift and subsidence may accompany earthquakes caused by large displacements on shallow faults. Such changes can damage coastal facilities, canals, roads, railroads, and other structures.

Subsidence can also be caused by natural events such as earthquakes, soil compaction, glacial isostatic adjustment, erosion, sinkhole formation, and adding water to fine soils deposited by wind (a natural process known as loess deposits).

Land subsidence can occur in various ways during an earthquake. Large areas of land can subside drastically during an earthquake because of offset along fault lines. Land subsidence can also occur as a result of settling and compacting of unconsolidated sediment from the shaking of an earthquake. The Packet Page No. 481
Tri-City 4-156
Local Hazard Mitigation Plan Update
March 2024
Geospatial Information Authority of Japan reported immediate subsidence caused by the 2011 Tōhoku earthquake. In Northern Japan, subsidence of 1.64 ft was observed in Miyako, while near Rikuzentakata it measured 2.75 ft. In the south at Sōma, 0.95 ft was observed. The maximum amount of subsidence was

3.93 ft, coupled with horizontal diastrophism of up to 7.3 ft on the Oshika Peninsula in Miyagi Prefecture.

Additionally, subsidence can occur due to Bay Mud. This is discussed in greater detail in Section 4.3.15.

Location and Extent
The Tri-City Planning Area is vulnerable to both a large damaging and potentially catastrophic earthquake and smaller, more frequent, earthquake events. Specific areas of the Planning Area are also susceptible to the effects of earthquake liquefaction or earthquake-induced landslide. Starting with the location of faults in the Planning Area, the areas most at risk are discussed in this section. According to the California Geological Survey (CGS) and US Geological Survey (USGS), multiple faults directly underlie or are near the Planning Area. These are detailed below.

Faults
A fault is defined as “a fracture or fracture zone in the earth’s crust along which there has been displacement of the sides relative to one another.” For the purpose of planning there are two types of faults, active and inactive. Active faults have experienced displacement in historic time, suggesting that future displacement may be expected. Inactive faults show no evidence of movement in recent geologic time, suggesting that these faults are dormant. This does not mean, however, that faults having no evidence of surface displacement within the last 11,000 years are necessarily inactive. For example, the 1975 Oroville earthquake, the 1983 Coalinga earthquake, and the 1987 Whittier Narrows earthquake occurred on faults not previously recognized as active. Potentially active faults are those that have shown displacement within the last 1.6 million years (Quaternary). An inactive fault shows no evidence of movement in historic (last 200 years) or geologic time, suggesting that these faults are dormant.

Two types of fault movement represent possible hazards to structures in the immediate vicinity of the fault:
fault creep and sudden fault displacement. Fault creep, a slow movement of one side of a fault relative to the other, can cause cracking and buckling of sidewalks and foundations even without perceptible ground shaking. Sudden fault displacement occurs during an earthquake event and may result in the collapse of buildings or other structures that are found along the fault zone when fault displacement exceeds an inch or two. The only protection against damage caused directly by fault displacement is to prohibit construction in the fault zone.

The San Francisco Bay Area is transected by a series of parallel faults that together accommodate the relative motion between the Pacific and North American plates over a width of more than 50 miles. The major fault zones that comprise this system include the San Andreas, Mission Hills, Hayward, Calaveras, Concord-Green Valley, Greenville, Rodgers Creek, and San Gregorio Faults. These major faults are near vertical and generally exhibit right-lateral strike-slip movement (which means that the movement is predominantly horizontal and when viewed from one side of the fault, the opposite side of the fault is displaced to the right).

Packet Page No. 482
Tri-City 4-157
Local Hazard Mitigation Plan Update
March 2024
Earthquakes occur not only on faults mapped as active or potentially active, but also on unknown faults.

Many significant earthquakes in the United States have occurred on previously unknown faults. Based on the historical seismicity in California and comparisons to other geologically similar areas, small to moderate crustal earthquakes up to about M5 or M5.5 are possible almost any place in the Bay Area. There is also the possibility of larger crustal earthquakes in the M6+ range on unknown faults, although the probability of such events is likely to be low.

Faults in and near the Tri-City Planning Area can be seen on Figure 4-52.

Packet Page No. 483
Tri-City 4-158
Local Hazard Mitigation Plan Update
March 2024
Figure 4-52 Tri-City Planning Area – Faults in and near the Planning Area Packet Page No. 484
Tri-City 4-159
Local Hazard Mitigation Plan Update
March 2024
The amount of energy released during an earthquake is usually expressed as a magnitude and is measured directly from the earthquake as recorded on seismographs. An earthquake’s magnitude is expressed in whole numbers and decimals (e.g., 6.8). Seismologists have developed several magnitude scales. One of the first was the Richter Scale, developed in 1932 by the late Dr. Charles F. Richter of the California Institute of Technology. The Richter Magnitude Scale is used to quantify the magnitude or strength of the seismic energy released by an earthquake. Another measure of earthquake severity is intensity. Intensity is an expression of the amount of shaking at any given location on the ground surface (see Table 4-51).

Seismic shaking is typically the greatest cause of losses to structures during earthquakes.

Table 4-51 Modified Mercalli Intensity (MMI) Scale
MMI Felt Intensity
I Not felt except by a very few people under special conditions. Detected mostly by instruments.

II Felt by a few people, especially those on upper floors of buildings. Suspended objects may swing.

III Felt noticeably indoors. Standing automobiles may rock slightly.

IV Felt by many people indoors; by a few outdoors. At night, some people are awakened. Dishes, windows, and doors rattle.

V Felt by nearly everyone. Many people are awakened. Some dishes and windows are broken. Unstable objects are overturned.

VI Felt by everyone. Many people become frightened and run outdoors. Some heavy furniture is moved. Some plaster falls.

VII Most people are alarmed and run outside. Damage is negligible in buildings of good construction, considerable in buildings of poor construction.

VIII Damage is slight in specially designed structures, considerable in ordinary buildings, and great in poorly built structures. Heavy furniture is overturned.

IX Damage is considerable in specially designed buildings. Buildings shift from their foundations and partly collapse. Underground pipes are broken.

X Some well-built wooden structures are destroyed. Most masonry structures are destroyed. The ground is badly cracked. Considerable landslides occur on steep slopes.

XI Few, if any, masonry structures remain standing. Rails are bent. Broad fissures appear in the ground.

XII Virtually total destruction. Waves are seen on the ground surface. Objects are thrown in the air.

Source: Multi-Hazard Identification and Risk Assessment, FEMA 1997 Alquist-Priolo Zones
According to the California Geological Survey, Alquist-Priolo earthquake fault zones are regulatory zones surrounding the surface traces of active faults in California. (A trace is a line on the earth's surface defining a fault.) Wherever an active fault exists, if it has the potential for surface rupture, a structure for human occupancy cannot be placed over the fault and must be a minimum distance from the fault (generally fifty feet). Surface fault rupture occurs when movement on a fault breaks through to the earth's surface. An active fault, for the purposes of the Alquist-Priolo Act, is one that has ruptured in the last 11,000 years.

Not all earthquakes result in surface rupture. The Loma Prieta Earthquake of 1989 caused major damage in the San Francisco Bay Area but the movement deep in the earth did not break through to the surface.

Surface rupture almost always follows pre-existing faults. It may occur suddenly during an earthquake or Packet Page No. 485
Tri-City 4-160
Local Hazard Mitigation Plan Update
March 2024
slowly in the form of fault creep. Fault creep is slow rupture of the earth's crust. Examples of creep are well known along the Hayward Fault where it crosses highly developed areas in Contra Costa and Alameda Counties. Although the Hayward Fault ruptured suddenly in the 1868 earthquake, it also exhibits slow surface creep which offsets and deforms curbs, streets, buildings, and other structures that lie on top of the fault.

Earthquake fault zones were conceived in the Alquist-Priolo Earthquake Fault Zoning Act (Alquist-Priolo Act). The intent of the Alquist-Priolo Act is to reduce losses from surface fault rupture. California created this law following the destructive 1971 San Fernando earthquake (magnitude 6.6), which was associated with extensive surface fault ruptures that damaged numerous structures.

Figure 4-53 shows the Alquist-Priolo zones in the Tri-City Planning Area. These areas might experience fault rupture as a result of an earthquake on the identified fault, damaging roads, pipelines, levees, dams, and buildings or facilities that cross the fault.

Packet Page No. 486
Tri-City 4-161
Local Hazard Mitigation Plan Update
March 2024
Figure 4-53 Tri-City Planning Area – Alquist-Priolo Fault Zones Packet Page No. 487
Tri-City 4-162
Local Hazard Mitigation Plan Update
March 2024
Earthquake Liquefaction
When ground liquefies in an earthquake, it behaves like a liquid and may sink, spread, or erupt in sand boils. This can cause pipes to break, roads and sidewalks to buckle, and building foundations to be damaged. Liquefaction can only occur under certain circumstances. Soil that is loose, sandy, silty, or saturated with water can result in soil liquefaction if it is shaken intensely for an extended period. More details on soils and liquefaction follows:
➢ Loose Soils – The soils must be loose, such as uncompacted or unconsolidated sand and silt without much clay. This happens most often along the Bay shoreline, near creeks or waterways, on dry creek beds, and areas of man-made fill.
➢ Soggy Soils – The sand and silt must be soggy and saturated with water due to a high water table. ➢ Ground Shaking – The ground must be shaken long and hard enough by the earthquake to trigger liquefaction.

Liquefaction accompanies an earthquake, so the speed of onset is short. Duration is similar to the length of the earthquake shake. There are mapped areas of areas susceptible to earthquake liquefaction in the Planning Area from the USGS/CGS. These areas are shown on Figure 4-54 and discussed in more detail in Table 4-52.

Packet Page No. 488
Tri-City 4-163
Local Hazard Mitigation Plan Update
March 2024
Figure 4-54 Tri-City Planning Area – Earthquake Liquefaction Susceptibility Zones Packet Page No. 489
Tri-City 4-164
Local Hazard Mitigation Plan Update
March 2024
Table 4-52 Tri-City Planning Area – Earthquake Liquefaction Susceptibility Zones Geographical Extents by Jurisdiction
Jurisdiction/
Liquefaction
Susceptibility
Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
Very High 2,578.95 3.3% 2,040.74 4.4% 538.21 1.7%
High 8,101.59 10.3% 6,711.97 14.4% 1,389.61 4.4%
Moderate 52,810.29 67.3% 34,293.89 73.6% 18,516.40 58.1% Low 975.88 1.2% 750.88 1.6% 225.00 0.7%
Very Low 13,192.15 16.8% 2,828.51 6.1% 10,363.64 32.5%
Water 837.47 1.1% 0.01 0.0% 837.46 2.6%
Fremont
Total
78,496.32 100.0% 46,626.00 100.0% 31,870.32 100.0%
Newark
High 765.53 5.2% 688.96 7.2% 76.56 1.5%
Moderate 13,773.77 93.8% 8,822.34 92.5% 4,951.43 96.2%
Very Low 23.31 0.2% 7.66 0.1% 15.64 0.3%
Water 120.51 0.8% 18.52 0.2% 101.99 2.0%
Newark Total 14,683.11 100.0% 9,537.48 100.0% 5,145.63 100.0% Union City
Very High 1,392.48 8.4% 1,037.29 11.1% 355.19 4.8%
High 2,887.45 17.3% 2,649.94 28.4% 237.51 3.2%
Moderate 6,370.48 38.2% 5,182.99 55.5% 1,187.49 16.2%
Low 9.74 0.1% 4.26 0.0% 5.48 0.1%
Very Low 5,985.67 35.9% 466.79 5.0% 5,518.87 75.3%
Water 22.33 0.1% 0.02 0.0% 22.31 0.3%
Union City
Total
16,668.15 100.0% 9,341.29 100.0% 7,326.86 100.0%
Alameda County Water District
Very High 4,043.25 3.9% 3,071.76 4.8% 971.49 2.4%
High 11,753.44 11.3% 10,049.78 15.7% 1,703.66 4.2%
Moderate 79,854.76 76.5% 48,317.48 75.5% 31,537.28 77.9% Low 981.55 0.9% 755.14 1.2% 226.42 0.6%
Very Low 6,492.45 6.2% 1,755.57 2.7% 4,736.88 11.7%
Water 1,312.64 1.3% 18.54 0.0% 1,294.10 3.2%
Alameda
County Water
District Total
104,438.09 100.0% 63,968.27 100.0% 40,469.82 100.0%
Packet Page No. 490
Tri-City 4-165
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction/
Liquefaction
Susceptibility
Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Union Sanitary District
Very High 3,906.62 5.0% 3,077.62 4.9% 829.00 5.9%
High 11,749.56 15.2% 10,050.88 15.9% 1,698.68 12.0%
Moderate 56,831.27 73.3% 47,608.16 75.2% 9,223.11 65.1% Low 981.78 1.3% 755.14 1.2% 226.64 1.6%
Very Low 3,615.32 4.7% 1,834.03 2.9% 1,781.29 12.6%
Water 415.78 0.5% 16.32 0.0% 399.46 2.8%
Union
Sanitary
District Total
77,500.33 100.0% 63,342.14 100.0% 14,158.19 100.0%
Source: USGS/CGS
Earthquake-Induced Landslide
Ground shaking can also lead to ground failure on slopes, triggering earthquake-induced landslides.

Landslides tend to occur in weak soil and rock on sloping terrain. Most sloping ground has some potential for landslides simply due to the effects of gravity. An earthquake can be one factor that will cause an unstable hillside to fail. When a landslide occurs, homes and structures within both the sloped areas and the runoff areas can be damaged or destroyed. Creeks and streams below the slide area may become dammed with debris and cause flooding. This is a significant hazard in parts of the Tri-City Planning Area as indicated by Figure 4-55. The CGS map layer has areas (a de facto scale) where earthquake-induced landslide is more likely. Speed of onset of these events is short, as is the duration. Clean up efforts can take days, weeks, or even months depending on the severity of the landslide. Geographic extent of CGS Earthquake-Induced Landslide Zones is detailed in Table 4-53.

Packet Page No. 491
Tri-City 4-166
Local Hazard Mitigation Plan Update
March 2024
Figure 4-55 Tri-City Planning Area – Earthquake-Induced Landslide Zones Packet Page No. 492
Tri-City 4-167
Local Hazard Mitigation Plan Update
March 2024
Table 4-53 Tri-City Planning Area – Earthquake-Induced Landslide Zones Geographical Extent by Jurisdiction
Jurisdiction Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont 7,741.13 9.55% 1,169.45 2.51% 6,571.68 19.07%
Newark 0.5 0.00% 0 0.00% 0.5 0.00%
Union City 3,466.76 20.80% 207.07 2.22% 3,259.69 44.49% Alameda
County Water
District
3,880.92 3.63% 562.64 0.88% 3,318.28 7.75%
Union Sanitary
District 1,752.04 2.26% 580.56 0.92% 1,171.48 8.27%
Source: CGS
Past Occurrences
Disaster Declaration History
There has been one federal disaster declaration from earthquake (magnitude 6.9 Loma Prieta) in Alameda County, as shown in Table 4-54.

Table 4-54 Alameda County Earthquake Disaster Declarations 1950-2023 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Earthquake 0 – 1 1989
Source: Cal OES, FEMA
NCDC Events
The NCDC does not track earthquakes.

USGS Events
The USGS National Earthquake Information Center database contains data on earthquakes in the Tri-City Planning Area. Table 4-55 shows the approximate distances earthquakes can be felt away from the epicenter. According to the table, a magnitude 5.0 earthquake could be felt up to 90 miles away. The USGS database was searched for magnitude 5.0 or greater on the Richter Scale within 90 miles of the Planning Area (centering on Fremont). These 35 results are detailed in Table 4-56.

Table 4-55 Approximate Relationships between Earthquake Magnitude and Intensity Richter Scale Magnitude Maximum Expected Intensity (MM)* Distance Felt (miles)

2.0 - 2.9 I – II 0
Packet Page No. 493
Tri-City 4-168
Local Hazard Mitigation Plan Update
March 2024
Richter Scale Magnitude Maximum Expected Intensity (MM)* Distance Felt (miles)

3.0 - 3.9 II – III 10

4.0 - 4.9 IV – V 50

5.0 - 5.9 VI – VII 90

6.0 - 6.9 VII – VIII 135

7.0 - 7.9 IX – X 240

8.0 - 8.9 XI – XII 365
*Modified Mercalli Intensity Scale.

Source: United State Geologic Survey, Earthquake Intensity Zonation and Quaternary Deposits, Miscellaneous Field Studies Map 9093, 1977.

Table 4-56 Magnitude 5.0 Earthquakes or greater within 90 Miles of the Tri-City Planning Area*
Date Richter Magnitude Location
12/14/2016 5.01 10 km W of Cobb, California
8/24/2014 6.02 South Napa
10/31/2007 5.45 6 km NNE of East Foothills, California
8/12/1998 5.1 10 km SW of Ridgemark, California
4/18/1990 5.1 4 km E of Interlaken, California
4/18/1990 5.4 5 km NNW of Aromas, California
10/18/1989 5.1 7 km SW of Monte Sereno, California
10/18/1989 6.9 Loma Prieta, California Earthquake
8/8/1989 5.4 4 km ESE of Lexington Hills, California
6/27/1988 5.3 8 km ESE of Lexington Hills, California
6/13/1988 5.3 6 km E of East Foothills, California
2/20/1988 5.1 1 km NE of Tres Pinos, California
3/31/1986 5.7 15 km NE of East Foothills, California
1/26/1986 5.5 3 km ENE of Tres Pinos, California
4/24/1984 6.2 14 km E of Seven Trees, California
1/27/1980 5.4 9 km NE of Livermore, California
1/24/1980 5.1 11 km E of Blackhawk, California
1/24/1980 5.8 8 km ENE of Blackhawk, California
8/6/1979 5.8 8 km ENE of San Martin, California
11/28/1974 5.2 9 km NW of Hollister, California
10/2/1969 5.3 Northern California
10/2/1969 5.26 3 km E of Bloomfield, California
12/18/1967 5.28 2 km W of Corralitos, California
11/16/1964 5.2 7 km WSW of San Martin, California
9/14/1963 5.4 4 km E of Aromas, California
1/20/1960 5 6 km WSW of Ridgemark, California
Packet Page No. 494
Tri-City 4-169
Local Hazard Mitigation Plan Update
March 2024
Date Richter Magnitude Location
3/2/1959 5.3 3 km SW of Gilroy, California
3/22/1957 5.66 18 km W of Montara, California
9/5/1955 5.81 7 km NNW of Boulder Creek, California
4/25/1954 5.3 4 km ESE of Interlaken, California
6/24/1939 5.5 7 km SW of Hollister, California
12/13/1933 5 3 km SW of Los Gatos, California
2/15/1927 5 9 km SW of Davenport, California
10/24/1926 5.5 1 km WNW of Davenport, California
10/22/1926 6.31 16 km SW of Davenport, California
10/22/1926 6.35 22 km S of Davenport, California
10/22/1926 6.1 36 km W of Del Monte Forest, California
10/5/1920 5.2 5 km SSW of Spreckels, California
8/8/1916 5 2 km ESE of Pasatiempo, California
7/1/1911 6.45 2 km SE of Morgan Hill, California
12/31/1910 5 2 km SSW of Hollister, California
3/11/1910 5.8 4 km WSW of Watsonville, California
4/18/1906 7.9 The 1906 San Francisco Earthquake
8/3/1903 5.8 3 km ENE of Seven Trees, California
6/11/1903 5.8 3 km S of Milpitas, California
5/19/1902 5.4 5 km S of Elmira, California
7/6/1899 5.8 Near Hollister, California
6/2/1899 5.6 Near San Francisco, California
4/30/1899 6 Near San Juan Bautista, California
3/31/1898 6.4 South of Sonoma, California
6/20/1897 6.3 Near Gilroy, California
8/9/1893 5.6 Near Santa Rosa, California
11/13/1892 5.9 South of Hollister, California
4/30/1892 5.6 Near Dixon, California
4/21/1892 6.4 Near Winters, California
4/19/1892 6.6 Near Vacaville, California
10/12/1891 5.8 Near Napa, California
1/2/1891 5.8 Near San Jose, California
4/24/189 6.3 East of Watsonville, California
7/31/1889 5.6 San Francisco Bay area, California
5/19/1889 6 North of Antioch, California
4/15/1889 5.5 East of Gilroy, California
3/26/1884 5.9 West of Santa Cruz, California
3/30/1883 6 Near Hollister, California
6/27/1882 5.8 Santa Cruz Mountains, California
Packet Page No. 495
Tri-City 4-170
Local Hazard Mitigation Plan Update
March 2024
Date Richter Magnitude Location
4/10/1881 6.3 Southwest of Modesto, California
4/2/1870 5.8 Near Berkeley, California
2/17/1870 5.9 North of Santa Cruz, California
10/21/1868 6.8 The 1868 Hayward Fault Earthquake, California 7/15/1866 6 Southwest of Stockton, California
3/26/1866 5.8 Near Gilroy, California
10/8/1865 6.5 South of San Jose, California
5/24/1865 5.9 South of San Jose, California
5/21/1864 5.8 Alameda County, California
3/5/1864 6 Alameda County, California
2/26/1864 6.1 Santa Clara County, California
7/4/1861 5.8 Near San Ramon, California
11/26/1858 6.2 North of San Jose, California
12/15/1856 5.9 San Mateo County, California
1/2/1856 5.7 Offshore San Mateo County, California
8/27/1855 5.5 North of San Francisco, California
5/15/1851 5 Near San Francisco, California
Source: USGS
*Search dates January 1, 1850 – April 1, 2023
Figure 4-56 shows major historical earthquakes in California from 1769 to 2017. Since 2017, California has experienced four additional 6.0 or greater earthquakes (2022 - 6.4 Ferndale, 2021 - 6.0 Antelope Valley and 2019 - 6.4 and 7.1 Ridgecrest). None of these earthquakes (over 6.0) since 2017 have affected the TriCity Planning Area.

Packet Page No. 496
Tri-City 4-171
Local Hazard Mitigation Plan Update
March 2024
Figure 4-56 Historic Earthquakes in California 1769 to 2017 Source: 2018 State of California Multi-Hazard Mitigation Plan Packet Page No. 497
Tri-City 4-172
Local Hazard Mitigation Plan Update
March 2024
Planning Committee Events
Discussions of Planning Committee events for each jurisdiction can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrences
Occasional (major earthquake); Highly Likely (minor earthquake)—Seismic activity within the past two hundred years has shown absence of any major or damaging earthquake occurring on identified fault lines that could affect the Tri-City Planning Area. However, the possibility of an earthquake is an everpresent phenomenon facing the Planning Area. The combination of plate tectonics and associated California coastal mountain range geology essentially guarantees earthquake as a result of the periodic release of tectonic stresses. There have been earthquakes as a result of this activity in the historic past, and there will continue to be earthquakes in the future of the Bay Area. It is likely that the Planning Area will be subject to minor earthquakes in the future. Major earthquakes are considered to be less likely, or Occasional, in the Tri-City Planning Area.

Mapping of Future Occurrences
Mapping of future occurrences is presented in the following sections:
➢ CGS Analysis
➢ UCERF Analysis
CGS Analysis
Maps indicating the maximum expectable intensity of ground shaking for the County and Tri-City Planning Area are available through several sources. Figure 4-57, prepared by the California Division of Mines and Geology, shows the expected relative intensity of ground shaking and damage in California from anticipated future earthquakes. The shaking potential is calculated as the level of ground motion that has a 2% chance of being exceeded in 50 years, which is the same as the level of ground-shaking with about a 2,500-year average repeat time. Although the greatest hazard is in areas of highest intensity as shown on the map, no region is immune from potential earthquake damage.

Packet Page No. 498
Tri-City 4-173
Local Hazard Mitigation Plan Update
March 2024
Figure 4-57 Maximum Expectable Earthquake Intensity – 2% Chance in 50 Years Source: California Division of Mines and Geology
UCERF Analysis
In 2014, the USGS and CGS released the time‐dependent version of the Uniform California Earthquake Rupture Forecast (UCERF III) model. The UCERF III results have helped to reduce the uncertainty in estimated 30‐year probabilities of strong ground motions in California. The UCERF map is shown in Figure 4-58 and indicates that the Planning Area has a predominantly moderate to high risk of earthquake occurrence.

Packet Page No. 499
Tri-City 4-174
Local Hazard Mitigation Plan Update
March 2024
Figure 4-58 California - Probability of Earthquake Magnitudes Occurring in 30 Year Time Frame
Source: United States Geological Survey Open File Report 2015‐3009 Climate Change and Earthquake
Climate change is unlikely to increase earthquake frequency or strength.

Vulnerability Assessment
Vulnerability—Extremely High
Earthquake vulnerability is primarily based on population and the built environment. Urban areas in high seismic hazard zones are the most vulnerable, while uninhabited areas are less vulnerable. The primary impacts of concern are life safety and property damage. Several faults are in and near the Tri-City Planning Area, and seismic hazard mapping indicates that the Planning Area has high seismic hazard potential. It is likely that the Planning Area will be subject to some moderate to severe seismic shaking. Some degree of structural damage due to stronger seismic shaking should be expected.

Packet Page No. 500
Tri-City 4-175
Local Hazard Mitigation Plan Update
March 2024
Seismic events can have particularly negative effects on older buildings constructed of URM, including materials such as brick, concrete, and stone, as well as soft story buildings and tilt-up concrete. These areas in the Planning Area were discussed above in the Seismic Structural Safety section. The Uniform Building Code (UBC) identifies four seismic zones in the United States. The zones are numbered one through four, with Zone 4 representing the highest level of seismic hazard. The UBC establishes more stringent construction standards for areas within Zones 3 and 4. All of California lies within either Zone 3 or Zone

4. The Planning Area is within the more hazardous Zone 4, which suggests that the Tri-City Planning Area is more vulnerable to potential damaging earthquake events.

The Tri-City Planning Area also has considerable concerns due to fire following earthquake. A discussion of this precedes the assets at risk discussion.

Fire Following Earthquake
Fire following earthquake has been known to exceed the total damage due to primary earthquake effects (shaking, liquefaction, and subsidence). Examples of major urban conflagrations (i.e., block-to-block fire spread, consuming large portions of major urban environments):
➢ 1923 Tokyo Kanto Earthquake,
➢ 1906 San Francisco Earthquake and Fire,
➢ 1995 Kobe Earthquake
Factors contributing to the nature and extent of fire following earthquake include:
➢ Potential ignitions (due to building damage or collapse, damage to power or gas utilities, etc.), ➢ windspeed,
➢ Prevailing building construction types (i.e., high inventory of wood frame buildings, regardless of the extent of modern fire protection systems – which are likely to fail following a major earthquake), ➢ Density and prevailing distance between buildings,
➢ Loss of water pressure in the municipal water supply system (which is almost assured, if there is extensive damage to buildings – absent mitigation measures to isolate functional from damaged water supply),
➢ Damage to the municipal water supply systems distribution infrastructure, the ability to isolate main breaks to maintain water flow in certain areas where damage to the system is minimal, and whether there alternative water supplies that can support and firefighting operations (e. g. static sources such as open water, cisterns or swimming pools which are accessible to fire apparatus – meaning secure hard stand next to the source, with generally no more than approximately ten feet of vertical distance (22.5 feet is the theoretical maximum) and limited horizontal distance on the order to tens of feet.

This Plan extrapolates estimated fire following earthquake losses by using the results of Scawthorn (2018) to estimate losses for the cities and Planning Area. The Plan also uses Hazus modelling to estimate fire following earthquake losses for the same areas.

Scawthorn (2018) used Voronoi diagrams to estimate fire following earthquake losses, based on the HayWired earthquake scenario. The study uses stochastic modeling, as actual fire losses following a given earthquake scenario cannot be well predicted. The study details number of ignitions, availability of water service, and the final burned area (in millions of 2014 U. S. dollars).

Packet Page No. 501
Tri-City 4-176
Local Hazard Mitigation Plan Update
March 2024
Each polygon in the Voronoi diagram below approximates the area in which an available fire engine responding from the nearest fire station would be first to arrive at a fire. This area is commonly known by fire departments as a “first due” area. Figure 4-59 shows the number of ignitions, by first due area, using the Haywired Scenario mainshock, and assuming breezy conditions and moderate humidity, as described above.

Figure 4-59 Estimated Number of Ignitions - Based on USGS 2017 HayWired Earthquake Scenario
Source: Scawthorn 2018
Packet Page No. 502
Tri-City 4-177
Local Hazard Mitigation Plan Update
March 2024
Using the results of Scawthorn (2018), Table 4-57 shows the estimated number of ignitions, likelihood of available water service, and estimated fire losses for the entire Tri-City area. The figures are based on identification of the fire station “first due” areas used by Scawthorn (2018) and aggregation of the reported results by city. The number of fire stations below are based on current fire protection services in 2024.

Table 4-57 Fire Following Earthquake Estimated Ignitions, Water Supply Availability, and Losses, Inflation-Adjusted (Based on USGS 2017 HayWired Earthquake Scenario) Area Fire Stations Estimated Ignitions Likelihood of
Available Water
Service
Estimated Fire Loss
(billions of 2024
dollars)
Fremont 11 42 <10% $1.6
Newark 3 8 <10% $0.2
Union City 3 15 <10% $0.9
Tri-City Area 17 65 <10% $2.7
Source: Scawthorn, C. 2018. "Fire following the Mw 7.05 HayWired earthquake scenario." Pp. 367-400 in The HayWired Earthquake Scenario --Engineering Implications, edited by Shane T. Detweiler and Anne M. Wein. Washington: U.S. Geological Survey Scientific Investigations Report 2017 -5013 -I -Q. https://pubs.er.usgs.gov/publication/sir20175013 Assets at Risk
Many assets in the Planning Area are at risk to surface fault and ground shaking (including liquefaction, landslide, subsidence, and fire following earthquake). Assets at risk from earthquake include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections for earthquake liquefaction and earthquake-induced landslides. A Hazus analysis for earthquake shaking follows.

Methodology for Earthquake Liquefaction and Earthquake-Induced Landslides The Earthquake Liquefaction and Earthquake-Induced Landslide Area data was obtained from the USGS and CGS. The 2023 Alameda County Parcel/Assessor Data was used as the basis for the inventory of all parcels within the City. GIS was used to overlay both the Earthquake Liquefaction and Earthquake-Induced Landslide hazard layers onto the parcel layer centroids, and where each intersected a parcel centroid, it was assigned with that hazard zone for the entire parcel.

Assets at risk from earthquake liquefaction and earthquake-induced landslide include people and populations; structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources, economic assets, and community activities of value). These are discussed in the following sections.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

Packet Page No. 503
Tri-City 4-178
Local Hazard Mitigation Plan Update
March 2024
People and Populations
All people and populations are at risk from earthquake shaking (including fire following earthquake) and surface fault. Those at heightened risk include:
➢ The unsheltered
➢ Infants and children under age five and their caregivers ➢ Elderly (65 and older)
➢ Individuals with disabilities
➢ Individuals dependent on medical equipment
➢ Individuals with impaired mobility
The greatest risk to people and populations from earthquake is death and injury. More information on people and populations at risk to earthquake shaking events can be seen in the Hazus scenarios developed for this LHMP and described in the Hazus Analysis section below.

Information on populations at risk to liquefaction and earthquake-induced landslides are detailed below.

Earthquake Liquefaction Susceptibility and Population Analysis To further evaluate the impact to the residential population to earthquake liquefaction within the Tri-City Planning Area, those residential parcel centroids that intersect the USGS/CGS Earthquake Liquefaction Susceptibility zones were counted and multiplied by the 2020 Census Bureau average household factors for each jurisdiction. This is shown in Table 4-58.

Table 4-58 Tri-City Planning Area – Count of Residential Parcels and Populations in Earthquake Liquefaction Susceptibility Zones by Jurisdiction Earthquake
Liquefaction
Susceptibility Zone/
Jurisdiction
Improved
Residential Parcels
Population
City of Fremont
Very High 2,834 8,744
High 18,515 55,360
Moderate 47,756 142,790
City of Newark
Very High 0 0
High 0 0
Moderate 13,877 46,072
City of Union City
Very High 3,419 11,522
High 4,475 15,081
Moderate 8,746 29,474
Packet Page No. 504
Tri-City 4-179
Local Hazard Mitigation Plan Update
March 2024
Source: Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City 3.37)
These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums as well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

For the special districts of ACWD and USD, analysis of their service territory populations in the liquefaction zones is performed. This is derived from the table above. This analysis can be found in their respective annexes to this Base Plan.

Earthquake-Induced Landslide and Population Analysis
To further evaluate the impact to the residential population from earthquake-induced landslides within the Tri-City Planning Area, those residential parcel centroids that intersect the CGS Earthquake-Induced Landslide Zones were counted and multiplied by the 2020 Census Bureau average household factors for each jurisdiction on the Planning Area. This is shown in Table 4-59.

Table 4-59 Tri-City Planning Area – Count of Residential Parcels and Populations in Earthquake-Induced Landslide Zones by Jurisdiction
Jurisdiction/Earthquake
Liquefaction
Susceptibility Zone
Improved
Residential
Parcels
Population
City of Fremont
Inside Zone 581 1,737
City of Newark
Inside Zone 0 0
City of Union City
Inside Zone 6 20
Source: Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City 3.37)
These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums as well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

For the special districts of ACWD and USD, analysis of their service territory populations in earthquakeinduced landslide zones is performed. This is derived from the table above. This analysis can be found in their respective annexes to this Base Plan.

Packet Page No. 505
Tri-City 4-180
Local Hazard Mitigation Plan Update
March 2024
Structures
All structures in the Tri-City Planning Area are vulnerable to earthquakes, depending on the severity and location of the shake. Unreinforced masonry is at a much greater risk to earthquakes. More information on structures at risk can be seen in the Hazus scenarios below.

Liquefaction and Structures Analysis
Structures in the Planning Area have a measure of risk from liquefaction. The USGS/CGS Earthquake Liquefaction Susceptibility Zone layer was overlaid with the 2023 Alameda County Parcel/Assessor Data in GIS to obtain results. Table 4-60 summarizes the potential estimated damages to the Tri-City Planning Area from properties (and structures) in the liquefaction susceptibility zones.

Table 4-60 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Earthquake Liquefaction Susceptibility Zones by Jurisdiction Jurisdiction /
Liquefaction
Susceptibility
Zones
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont
Very High 3,115 2,888 $801,749,326 $1,581,051,410 $1,109,142,200 $3,491,942,936 High 19,492 18,597 $3,539,204,064 $7,863,294,604 $4,273,571,257 $15,676,069,925 Moderate 54,057 49,894 $15,534,056,038 $30,486,358,491 $19,997,885,170 $66,018,299,699 Low 3,074 2,880 $957,964,366 $1,872,209,870 $980,777,432 $3,810,951,668 Very Low 4,391 3,872 $1,878,341,638 $3,653,728,248 $1,834,188,593 $7,366,258,479 Water 137 0 $1,186,710 $0 $0 $1,186,710
Fremont
Total
84,266 78,131 $22,712,502,142 $45,456,642,623 $28,195,564,652 $96,364,709,417 Newark
Very High 0 0 $0 $0 $0 $0
High 1,116 1,064 $260,451,673 $526,638,617 $349,672,428 $1,136,762,718 Moderate 15,916 14,264 $3,885,409,679 $7,656,138,926 $5,116,983,279 $16,658,531,884 Low 0 0 $0 $0 $0 $0
Very Low 108 42 $29,799,358 $21,703,200 $10,851,600 $62,354,158 Water 18 16 $14,243,503 $19,782,387 $15,221,792 $49,247,682 Newark
Total
17,158 15,386 $4,189,904,213 $8,224,263,130 $5,492,729,099 $17,906,896,442 Union City
Very High 3,853 3,536 $737,350,931 $1,573,121,083 $1,008,832,967 $3,319,304,981 High 4,603 4,499 $844,311,078 $1,876,401,326 $965,725,718 $3,686,438,122 Moderate 9,694 9,119 $2,312,948,733 $4,905,287,647 $3,211,082,618 $10,429,318,998 Low 6 6 $20,118,316 $129,466,412 $128,740,777 $278,325,505 Packet Page No. 506
Tri-City 4-181
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction /
Liquefaction
Susceptibility
Zones
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Very Low 444 329 $82,063,531 $177,477,988 $117,025,111 $376,566,630 Water 2 0 $0 $0 $0 $0
Union City
Total
18,602 17,489 $3,996,792,589 $8,661,754,456 $5,431,407,191 $18,089,954,236 Alameda County Water District (Service Territory)
Very High 6,971 6,424 $1,536,157,795 $3,154,172,493 $2,117,975,167 $6,808,305,455 High 25,202 24,151 $4,643,889,883 $10,261,489,667 $5,584,124,523 $20,489,504,073 Moderate 79,811 73,342 $21,805,615,757 $43,179,062,672 $28,491,170,990 $93,475,849,419 Low 3,080 2,886 $978,082,682 $2,001,676,282 $1,109,518,209 $4,089,277,173 Very Low 4,671 4,190 $1,923,183,644 $3,802,138,729 $1,926,132,356 $7,651,454,729 Water 142 16 $14,243,503 $19,782,387 $15,221,792 $49,247,682 Alameda
County Water
District
(Service
Territory)
Total
119,877 111,009 $30,901,173,264 $62,418,322,230 $39,244,143,037 $132,563,638,531 Union Sanitary District (Service Territory)
Very High 6,961 6,424 $1,536,157,795 $3,154,172,493 $2,117,975,167 $6,808,305,455 High 25,211 24,160 $4,643,966,815 $10,266,334,547 $5,588,969,403 $20,499,270,765 Moderate 79,457 73,298 $21,667,598,601 $43,073,695,296 $28,352,355,604 $93,093,649,501 Low 3,080 2,886 $978,082,682 $2,001,676,282 $1,109,518,209 $4,089,277,173 Very Low 4,593 4,175 $1,905,151,196 $3,787,263,291 $1,918,795,921 $7,611,210,408 Water 58 16 $14,243,503 $19,782,387 $15,221,792 $49,247,682 Union
Sanitary
District
(Service
Territory)
Total
119,360 110,959 $30,745,200,592 $62,302,924,296 $39,102,836,096 $132,150,960,984 Source: USGS/CGS Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Earthquake-Induced Landslide and Structures Analysis
The CGS Earthquake-Induced Landslide Zone layer was overlaid with the County parcel layer and linked to the Assessor data in GIS to obtain results. Table 4-60 summarizes the potential estimated damages to the Tri-City Planning Area from properties (and structures) in the Earthquake-Induced Landslide Zone.

Packet Page No. 507
Tri-City 4-182
Local Hazard Mitigation Plan Update
March 2024
Table 4-61 City of Fremont – Count and Value of Parcels (and Structures) in EarthquakeInduced Landslide Zone by Jurisdiction Jurisdiction Total Parcel
Count
Improved
Parcel Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont 859 601 $412,889,263 $755,619,849 $383,575,471 $1,552,084,583 Newark 0 0 $0 $0 $0 $0
Union City 44 7 $15,927,800 $3,914,209 $2,266,272 $22,108,281 Alameda
County Water
District
(Service
Territory)
778 590 $400,794,178 $740,271,262 $368,734,057 $1,509,799,497 Union Sanitary
District
(Service
Territory)
767 591 $405,652,989 $742,292,722 $369,744,787 $1,517,690,498 Source: CGS, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) More information on structures at risk can be seen in the Hazus scenarios below.

Critical Facilities and Infrastructure and Community Lifelines Earthquakes present a tremendous threat to critical facilities and infrastructure and community lifelines.

The following GIS analysis identifies critical facilities and infrastructure at risk to earthquake, followed by a discussion on vulnerability of community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Community lifelines at risk to earthquake include:
➢ Safety and Security – Many personnel from the Planning Area would be involved in response and recovery efforts. This includes police, fire, EMS, public works, and other personnel. Due to the potential for widespread and major damages citywide, these resources can be stretched and quickly overwhelmed.
➢ Food, Hydration, and Shelter – As homes are damaged, shelter needs would significantly increase.

Temporary housing would be to be established. Water supplies could be offline for an extended period.

Residents, visitors and others caught in a large event would need to find sources of food and water until the Planning Area recovers.
➢ Health and Medical – Substantial numbers of injuries and deaths can occur. This causes EMS calls and ER visits to spike. Portable morgues and refrigeration units may need to be brought in.

Packet Page No. 508
Tri-City 4-183
Local Hazard Mitigation Plan Update
March 2024
Transporting patients to medical facilities may be difficult. Depending on the extent of injuries and deaths the capacity of medical facilities could be strained and eventually overwhelmed. ➢ Energy – The power grid may be damaged from earthquake. Damages to natural gas pipelines that feed homes and businesses in the Planning Area may also be disrupted. Restoring these systems may take longer during a widespread event.
➢ Communications – Communications systems may be damaged during shaking events. Once the shaking ceases, responder communications need to be back online quickly to coordinate response efforts in the Planning Area. Messaging boards and alerts need to be then put into place to ensure public safety and order. Calls to and from family and friends during a hazard event can further overwhelm communication systems such as cell towers and other infrastructure. Demand may exceed the capacity of these systems to remain operational during response efforts. ➢ Transportation – Major damage can occur to roads and bridges in the Planning Area. Damage can also occur to rail lines and airports in and near the Planning Area. Roads may be closed due to damage, or to debris on the roads from earthquake events. These closures could be place for an extended period while debris clearing efforts are undertaken to allow repairs to be made. ➢ Hazardous Material – Hazardous materials facilities can be compromised during times of earthquake events causing releases of contaminants into the environment. Natural gas pipelines can be affected by earthquakes. This can affect not only residents, but those who are charged with responding to or resolving the spill/rupture.
➢ Water Systems – Damages to underground pipes may occur. These take time to locate and fix in normal circumstances. During periods of earthquake, this becomes even more difficult. Water and wastewater systems and their respective piping can be damaged and systems may become inoperational for extended periods of time.

All community lifelines in the Tri-City Planning Area are vulnerable to earthquakes, depending on the severity and location of the shake and impacts from associated subhazards. A major earthquake event could cause these lifelines to be overwhelmed. Some of these would be able to be restored to service quickly, while others would take more time having a prolonged impact on the people and structures within the Planning Area. More information on community lifelines at risk can be seen in the Hazus scenarios below.

Natural, Historic, and Cultural Resources
The 2023 State Hazard Mitigation Plan noted that environmental problems from earthquakes can be numerous. Earthquake-induced landslides can significantly damage surrounding habitats. It is also possible for earthquakes to reroute streams, which can change the water quality, possibly damaging habitat and feeding areas. Streams fed by groundwater and/or springs may dry up because of changes in underlying geology. Another threat to the environment from earthquakes is the potential release of hazardous materials. Historical and cultural resources are at risk, often due to their age and construction types. The Hazus scenarios below are relatively silent on the vulnerability to natural, historic, and cultural resources, but impacts to these resources could be long lasting.

Any natural, historic, or cultural resource that is in the earthquake liquefaction zone would be at potential risk. For the natural resources, this is likely to be more limited than those associated with the ground shaking but may include uprooting of trees and vegetation and disruption to habitat areas. Historic and cultural resources that are structures or housed in structures could be vulnerable to liquefaction.

Packet Page No. 509
Tri-City 4-184
Local Hazard Mitigation Plan Update
March 2024
Any natural, historic, or cultural resource that is in the earthquake-induced landslide areas would be at potential risk. Given the limited area of earthquake-induced landslide in the Planning Area, as shown on Figure 4-55, historic and cultural assets in the Planning Area are not at sizable vulnerability. The area where the earthquake-induced landslide zones occur in the Planning Area is in the foothill areas to the east.

While there are natural resources in this area that may be affected, there are limited historic and cultural resources located there (though there may be as yet unknown native cultural artifacts in this area).

Economic Assets and Community Activities of Value
All economic assets in the Tri-City Planning Area are vulnerable to earthquakes, depending on the severity and location of the shake and associated cascading hazards and impacts. This includes earthquake liquefaction, landslide events, subsidence, and fire following earthquake. All community activities of value would be affected by an earthquake if they were underway during an earthquake event and may be postponed or cancelled until the Planning Area has sufficiently recovered.

As shown on Figure 4-54, most of the Tri-City Planning Area is at moderate or higher liquefaction risk.

Almost all economic assets in the Planning Area would be vulnerable. As such, most of the community activities of value would be at risk from liquefaction if it occurred during the event.

Given the limited area of earthquake-induced landslide in the Planning Area, as shown on Figure 4-55, economic assets in the Planning Area are not thought to be at sizable vulnerability. Most of the landslide vulnerability is in the upper elevations to the east, which houses limited economic assets.

Hazus (Earthquake Shaking) Analysis
Hazus is a regional earthquake loss estimation model that was developed by FEMA and the National Institute of Building Sciences. The primary purpose of Hazus is to provide a methodology and software application to develop multi-hazard losses at a regional scale. These loss estimates can be used by local, state and regional officials to plan and stimulate efforts to reduce risks from multi-hazards and to prepare for emergency response and recovery.

Hazus 6.1 was utilized to model earthquake losses for the Tri-City Planning Area. Hazus level 2/3 analyses were run, meaning that this more advanced Hazus modelling utilized local inventory data of buildings, essential facilities, hazards, and other data, as provided by the local jurisdictions and Cal OES and FEMA.

This local data was used in conjunction with the default Hazus data within the model. This is a planning level analysis. Four primary Hazus scenarios were created for this Plan:
➢ A Calaveras Fault 7.43 magnitude event
➢ A Hayward + Rodgers Creek Fault 7.57 magnitude event
➢ A Hayward Fault (Haywired) Scenario Fault 7.0 magnitude event ➢ A San Andreas Fault 7.9 magnitude event
Details of these Hazus Scenarios are detailed in Table 4-62.

Packet Page No. 510
Tri-City 4-185
Local Hazard Mitigation Plan Update
March 2024
Table 4-62 Hazus Scenarios by Fault, Magnitude, and Epicenter Earthquake
Fault
Magnitude Epicenter Fault Name Hazus Scenario Name (user named) Calaveras 7.43 37.61, -
121.89
sc+cc+nc--cs+cc+cn-3-10 DETERM CN_CC_CS_CE 7.43M EQ
CT
Hayward +
Rodgers
Creek

7.57 37.55, -
121.95
sh+nh+rc-- hs+hn+rc DETERM SH_NH_RC 7.57M EQ CT
Hayward
(Haywired)

7.00 37.88, -
122.25
sh+nh-- hs+hn DETERM HN_HS 7.0M EQ CT
San Andreas 7.90 37.76, -
122.55
scz+pn+ncs+ncn --sas+sap+sa DETERM SAO_SAN_SAP_SAS 7.9M EQ CT
Source: USGS Hazus Specialist; Tri-City Participating Jurisdictions; Hazus Scenario Catalogs:
https://earthquake.usgs.gov/scenarios/eventpage/bssc2014calaverascncccscesha_m7p43_se https://earthquake.usgs.gov/scenarios/eventpage/bssc2014haywardrchnhsshaw09m_m7p57_se https://earthquake.usgs.gov/scenarios/eventpage/ushaywiredm7.05_se https://earthquake.usgs.gov/scenarios/eventpage/bssc2014nsanandreassansapsas_m7p88_se Methodology
Hazus Version 6.1 was released in November 2023. This natural hazard risk assessment GIS-based software updates Hazus Version 6.0 previously released in November 2022. Hazus 6.1 includes major inventory data, methodology, and software enhancements. Utilizing Hazus 6.1, Hazus deterministic scenarios were run utilizing supplemental and locally provided inventory data developed for input into Hazus’ Comprehensive Data Management System (CDMS). The deterministic approach allows for the selection of a recognized fault, epicenter, and magnitude associated with each identified scenario. The additional steps taken to prepare the Hazus model are detailed below.

Hazus Study Regions and Census Tracts
Hazus analyses for each of the four earthquake fault scenarios, were conducted for the Tri-City Planning Area (which also is the same Hazus study region, based on census tract data, as covered by ACWD and USD), and specific to each of the three cities: Fremont, Newark, and Union City. This required a Hazus study region to be developed providing coverage for the Tri-City Planning Area and the five participating jurisdictions. The study regions created in Hazus are defined by the US census tract areas encompassing each jurisdiction’s geographic boundaries. The study regions and associated census tracts comprising the various scenarios are shown in Table 4-63
Table 4-63 Census Tract Count and Region Name by Jurisdiction Jurisdiction / Hazus Study Region Census Tract Count Hazus Study Region Name (user named) Tri-City 74 TRICITY_BY_CT_D
Fremont 48 FREMONT_BY_CT_B
Newark 8 NEWARK_BY_CT_C
Union City 17 UC_BY_CT_B
Packet Page No. 511
Tri-City 4-186
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction / Hazus Study Region Census Tract Count Hazus Study Region Name (user named) ACWD 74 TRICITY_BY_CT_D
USD 74 TRICITY_BY_CT_D
Source: Hazus 6.1, City of Fremont GIS
Hazus Datasets
Hazus analyses are performed on a pre-designated statewide (California) facility dataset for Level 1 Hazus.

For a Level 2,3 Hazus analysis, the Hazus tool allows for the option to further refine the data with locally available data. In the development of the Level 2/3 Hazus analyses for this LHMP Update, additional datasets were integrated and/or overwritten into the model prior to performing the enhanced Level 2/3 analyses as discussed below.

Comprehensive Data Management System (CDMS)
CDMS is a Hazus support tool that allows users to move data to and from Hazus statewide datasets.

Utilizing Hazus’ CDMS application, 46 essential facilities located within the City of Fremont’s jurisdictional boundaries were provided by the City of Fremont and updated into Hazus’ California, statewide dataset. These included the following categories and numbers of essential services facilities that replaced the associated default (statewide) data:
➢ potable water facilities - 11
➢ natural gas – 1
➢ electric – 9
➢ police stations – 8
➢ medical care – 3
➢ fire stations – 11
➢ emergency operation centers (EOC) – 3
These CDMS updates enabled refined local data for the City of Fremont to be utilized during the Level 2/3 Hazus analyses. Essential facilities in Newark and Union City’s jurisdictions were not updated.

Advanced Engineering Building Module (AEBM)
The Advanced Engineering Building Module (AEBM) was also updated utilizing the CDMS tool. Fremont provided a 65-building supplemental datasets to be incorporated into the AEBM statewide dataset in CDMS to be utilized specifically for the Fire Following Earthquake analysis. The AEBM system allows users to be able to create building-specific damage and loss functions to better assess losses for an individual building (or group of similar buildings). The term “building-specific” distinguishes the development of damage and loss functions from the “generic” building functions of Hazus. Building-specific damage and loss functions are based on the properties of a particular building. The 65 facilities updated in the AEBM included the following categories and numbers of facilities:
➢ police stations – 8
➢ medical care – 3
➢ fire stations – 11
➢ EOC – 3
Packet Page No. 512
Tri-City 4-187
Local Hazard Mitigation Plan Update
March 2024
➢ user-defined facilities – 40
The detailed AEBM inventory of the 65 facilities utilized for the Hazus analyses, Fire Following Earthquake scenarios are detailed in Figure 4-60 and Table 4-64.

Packet Page No. 513
Tri-City 4-188
Local Hazard Mitigation Plan Update
March 2024
Figure 4-60 Tri-City Planning Area – Hazus AEBM Inventory Map Packet Page No. 514
Tri-City 4-189
Local Hazard Mitigation Plan Update
March 2024
Table 4-64 AEBM Inventory - Categories and Facilities
AEBM Category Facility Name Hazus/AEBM ID Building Count EOC
City Of Fremont Emer Oper CA000012 1
Maint Ctr Admin CA000054 1
Ohlone COLL EOC CA000013 1
EOC Total 3
Fire Station
Fremont Fire Dept Stn 1 CA000009 1
Fremont Fire Dept Stn 2 CA000001 1
Fremont Fire Dept Stn 3 CA000004 1
Fremont Fire Dept Stn 4 CA000010 1
Fremont Fire Dept Stn 5 CA000003 1
Fremont Fire Dept Stn 6 CA000002 1
Fremont Fire Dept Stn 7 CA000008 1
Fremont Fire Dept Stn 8 CA000005 1
Fremont Fire Dept Stn 9 CA000011 1
Fremont Fire Dept Stn 10 CA000006 1
Fremont Fire Dept Stn 11 CA000007 1
Fire Station Total 11
Fire Outbuild
Fremont Fire Dept Stn 10 (Stor Bldg) CA000025 1
Fremont Fire Dept Stn 6 (Stor Bldg) CA000024 1
Fremont Fire Dept Stn 7 (Stor Bldg) CA000026 1
Fremont Fire Dept Stn Tact Train CTR CA000027 1
Fremont Fire Dept Tact Train Tower CA000028 1
Fire Outbuild Total 5
Medical Care
Fremont Hospital CA000065 1
Kaiser Foundation Hospital - Fremont CA000063 1
Washington Hospital - Fremont CA000064 1
Medical Care Total 3
Police Station
BART Police Substation CA000062 1
California Highway Patrol - Nimitz In... CA000055 1
Fremont Police Department CA000057 1
Jail/Evidence WHSE CA000061 1
Ohlone College Police CA000056 1
Police Department Ancillary Building CA000058 1
Police Department Fuel Station CA000059 1
Police Motorcycle Storage CA000060 1
Police Station Total 8
Shelter
Age Well Ctr At Lake Elizabeth CA000029 1
Age Well Ctr At S. Fremont CA000030 1
Packet Page No. 515
Tri-City 4-190
Local Hazard Mitigation Plan Update
March 2024
AEBM Category Facility Name Hazus/AEBM ID Building Count American HS (CFTRA) CA000039 1
American HS (Rotunda & Gym) CA000038 1
Centerville JH (Multi-Use Rm) CA000045 1
Ctrville Park Comm Ctr CA000031 1
Fremont Main Library CA000036 1
G. M. Walters Middle (M-P RM) CA000047 1
Irvington COMM CTR CA000032 1
Irvington HS (CFTRA) CA000049 1
Irvington HS (GYM) CA000048 1
John F. Kennedy HS (CFTRA) CA000051 1
John F. Kennedy HS (Gym) CA000050 1
John M. Horner JH (M-P RM & KIT) CA000046 1
Lila Bringhurst Elem (M-P RM) CA000035 1
Los Cerritos Comm CTR CA000033 1
Mission SAN Jose HS (CFTRA) CA000041 1
Mission San Jose HS (Main GYM) CA000040 1
Ohlone Coll - Frem Camp (CFTRA) CA000053 1
Ohlone Coll - Frem Camp (Gym) CA000052 1
Thornton Junior HS (GYM) CA000037 1
Warm Springs Comm Ctr CA000034 1
Washington HS (CFTRA) CA000043 1
Washington HS (GYM & AUX GYM) CA000042 1
William Hopkins JH (M-P RM) CA000044 1
Shelter Total 25
Other
Admin CTR BLDG "B" CA000014 1
Dev Svcs Ctr CA000015 1
Downtown Event Ctr CA000023 1
Fremont Hall Of Justice CA000021 1
Fremont Unified School Dist CA000016 1
CA000017 1
Maint Ctr Shops CA000018 1
Maint Ctr Vehicle Mtce CA000019 1
Maint Ctr Warehouse CA000020 1
Tri-City Animal Shelter CA000022 1
Other Total 10
Grand Total 65
Source: City of Fremont
Packet Page No. 516
Tri-City 4-191
Local Hazard Mitigation Plan Update
March 2024
Additional Datasets
Three additional hazard based data sets were integrated into the Hazus model. These include USGS shake maps and liquefaction and landslide susceptibility layers. These are discussed in the following paragraphs.

Within the Hazus application and for each of the study regions, the USGS ShakeMap was integrated into the Hazus model. The ShakeMap is a product of the USGS Earthquake Hazards Program in conjunction with the regional seismic networks. ShakeMaps provide near-real-time maps of ground motion and shaking intensity following significant earthquakes. The ShakeMaps used for each of the four primary scenarios are shown in Table 4-65.

Table 4-65 USGS ShakeMap Dataset
Earthquake
Fault
Selected USGS
ShakeMap
(PGA)
USGS Website (scenario information)
Calaveras M74-Calaveras:

CN+CC+
CS+CE v14
https://earthquake.usgs.gov/scenarios/eventpage/bssc2014calaverascncccscesha_m7p43_se Hayward +
Rodgers
Creek
M7.6-Hayward:

RC+HN+ HS
v13
https://earthquake.usgs.gov/scenarios/eventpage/bssc2014haywardrchnhsshaw09m_m7p57_se Hayward
(Haywired)
M 7.1 Scenario
Earthquake -
Haywired M7.05
Scenario v33
https://earthquake.usgs.gov/scenarios/eventpage/ushaywiredm7.05_se San Andreas M 7.9 Scenario
Earthquake - N.

San Andreas:

SAN+SAP+SAS
https://earthquake.usgs.gov/scenarios/eventpage/bssc2014nsanandreassansapsas_m7p88_se Source: Hazus 6.1
Two additional hazard-based datasets, were included to further enhance the model. The FEMA Hazus team provided the latest California liquefaction susceptibility dataset, and the California landslide susceptibility dataset was obtained from the California Geological Survey. Both datasets were uploaded into the Hazus application and are shown in Table 4-66
Table 4-66 Additional Hazard (Liquefaction and Landslide Susceptibility) Datasets Type Dataset
Liquefaction Susceptibility BayAreaLiquefaction.mdb
Landslide Susceptibility CGS_Earthquake_Hazard_Zones_SHP_Landslide_Zones Source: Hazus 6.1
Packet Page No. 517
Tri-City 4-192
Local Hazard Mitigation Plan Update
March 2024
Running the Hazus Analyses
Running the four primary Hazus scenarios on each of the four study regions, as previously described, provides coverage and results for the Tri-City Planning Area and specific to each of the five participating jurisdictions to this LHMP Update.

Each of the four primary earthquake scenarios generated an Earthquake Hazus Global Summary Risk Report for each Hazus defined study region. The report provides an estimate of seismic risk and assesses current and future potential seismic-related losses. For each study region, the report provides information on loss estimates based on that study region’s earthquake risk and general building stock value, which includes building and lifeline related losses on the study region’s available inventory. The loss estimates provide Annualized Earthquake Loss (AEL) that detail long-term losses measured in U.S. dollars per one year. It also provides estimates of debris, displaced households, shelter requirements and casualties. The total economic loss includes:
➢ Building-Related Losses. The building losses are broken into two categories: direct building losses and business interruption losses.
➢ Transportation and Utility Lifeline Losses. For the transportation and utility lifeline systems, Hazus computes the direct repair cost for each component only. There are no losses computed by Hazus for business interruption due to lifeline outages.

To support the results presented in the Hazus Global Summary Risk Reports for each primary scenario (and by each jurisdiction’s study region), three maps each were developed to further illustrate seismic risk and losses. These include:
➢ Peak Ground Acceleration Shake Map
➢ Liquefaction Probability Map
➢ Total Loss Map
Fire Following Earthquake
The Hazus analysis for each of the primary Hazus runs also includes two scenarios or iterations of Fire Following Earthquake. The Fire Following Earthquake component to the Hazus tool allows for parameters to be adjusted to obtain varying output results based on factors such as fire engine response times and weather-related parameters such as wind speed and direction. For each of the four Hazus primary scenarios run for each of the four study regions (i.e., The Tri-City Planning Area/ACWD/USD, Fremont, Newark, and Union City), two Fire Following Earthquake iterations were run. The two Fire Following Earthquake parameters modified for this analysis included Wind Speed and Direction:
➢ Fire Following Earthquake Baseline Parameters. Utilizes a wind speed of 10 mph, with a default direction of 0, which is a north wind.
➢ Fire Following Earthquake Adjusted Parameters. Utilizes a wind speed of 50 mph, with a northeast direction. Note: this is based on the presence of the Diablo Winds in the study region which generally flow at a northeasterly direction and can reach speeds (or gusts) of up to 70-80 mph. The 50 mph wind speed was utilized as this was the reported wind speed that occurred during the 1991 Tunnel Fire.

These are shown in Table 4-67.

Packet Page No. 518
Tri-City 4-193
Local Hazard Mitigation Plan Update
March 2024
Table 4-67 Fire Following Earthquake – Wind Speed and Direction Scenarios Jurisdiction / Hazus
Study Region
Scenario 1 Scenario 2
Tri-City Wind: 10 MPH, Wind Direction: 0 Wind: 50 MPH, Wind Direction: 45 degrees Fremont Wind: 10 MPH, Wind Direction: 0 Wind: 50 MPH, Wind Direction: 45 degrees Newark Wind: 10 MPH, Wind Direction: 0 Wind: 50 MPH, Wind Direction: 45 degrees Union City Wind: 10 MPH, Wind Direction: 0 Wind: 50 MPH, Wind Direction: 45 degrees ACWD Wind: 10 MPH, Wind Direction: 0 Wind: 50 MPH, Wind Direction: 45 degrees USD Wind: 10 MPH, Wind Direction: 0 Wind: 50 MPH, Wind Direction: 45 degrees Source: Hazus 6.1
To support the Fire Following Earthquake results for each primary scenario (and by each study region), four maps were developed to further illustrate Fire Following Earthquake risk and exposure. These include:
➢ Number of Ignitions Map
➢ Population Exposure Map
➢ Value Exposure Map
➢ Fire Water Demand (gpm) Map
Hazus Results by Scenario
The Hazus results by scenario are summarized below. Of the four primary earthquake scenarios run for the Tri-City Planning Area, the Hayward Rodgers Creek Scenario is the one likeliest to cause the greatest damage.

Calaveras Fault Hazus Scenario (Epicenter: Fremont; Magnitude: 7.43) The Hazus results for the Calaveras Fault Hazus Scenario is summarized below in Table 4-68. Appendix H includes the Earthquake Hazus Global Summary Risk Report for each Hazus defined study region where more detailed information can be obtained.

Table 4-68 Tri-City Planning Area– Calaveras Fault HAZUS Earthquake Deterministic Results for 7.43 M Event
Type of Impact Impacts to City from 7.43 Deterministic Earthquake Total Buildings Damaged
(based on 102,000 buildings)
Slight: 34,485
Moderate: 10,737
Extensive: 3,324
Complete: 802
Building and Income Related Losses $6,072,200,000
Total Economic Losses
(Includes building, income and lifeline losses)
$6,694,910,000
Casualties
(Based on 2 a.m. time of occurrence)
Without requiring hospitalization: 410
Requiring hospitalization: 64
Life threatening: 4
Fatalities: 7
Packet Page No. 519
Tri-City 4-194
Local Hazard Mitigation Plan Update
March 2024
Type of Impact Impacts to City from 7.43 Deterministic Earthquake Casualties
(Based on 2 p.m. time of occurrence)
Without requiring hospitalization: 655
Requiring hospitalization: 134
Life threatening: 20
Fatalities: 32
Casualties
(Based on 5 p.m. time of occurrence)
Without requiring hospitalization: 534
Requiring hospitalization: 138
Life threatening: 74
Fatalities: 34
Damage to Transportation Systems 1 bridge with at least moderate damage Damage to Essential Facilities 4 schools and 1 EOC with at least moderate damage. 0 facilities with complete damage.

Damage to Utility Systems 1 wastewater facility, 1 electrical power facility, and 2 communication facilities with at least moderate damage. 0 facilities with complete damage.
1,018 potable water line breaks, 511 wastewater line breaks, and 8 natural gas line breaks.

Households without Power/Water Service
(Based on 113,685 total households)
Power loss, Day 1: 113,685
Power loss, Day 3: 113,685
Power loss, Day 7:

Power loss, Day 30: 113,685
Power loss, Day 90: 113,685
Water loss, Day 1: 110,435
Water loss, Day 3: 109,958
Water loss, Day 7: 108,722
Water loss, Day 30: 72,925
Water loss, Day 90: 0
Displaced Households 2,703 displaced households
Shelter Requirements 1,328 persons
Debris Generation 624,000 tons
Hazus 6.1
Loss Estimates Highlights
Hazus estimates that about 14,862 buildings will be at least moderately damaged. This is over 14.00 % of the buildings in the region. There are an estimated 801 buildings that will be damaged beyond repair.

Before the earthquake, the region had 556 hospital beds available for use. On the day of the earthquake, the model estimates that only 310 hospital beds (56.00%) are available for use by patients already in the hospital and those injured by the earthquake. After one week, 79.00% of the beds will be back in service.

By 30 days, 93.00% will be operational.

The total building-related losses were 6,027.20 (millions of dollars); 10 % of the estimated losses were related to the business interruption of the region. By far, the largest loss was sustained by the residential occupancies which made up over 50 % of the total loss.

Peak Ground Acceleration (Shaking)
Hazus evaluates the geographic distribution of ground shaking as a result of a specific earthquake scenario and expresses ground shaking using several quantitative parameters, including the peak ground acceleration. The peak ground acceleration map associated with this Hazus scenario can be seen on Figure 4-61.

Packet Page No. 520
Tri-City 4-195
Local Hazard Mitigation Plan Update
March 2024
Figure 4-61 Calaveras Fault – 7.43 Magnitude Peak Ground Acceleration Packet Page No. 521
Tri-City 4-196
Local Hazard Mitigation Plan Update
March 2024
Liquefaction
Liquefaction occurs when loose, water-saturated soils are shaken strongly and causes sudden loss of strength and stiffness in soils. This shaking can lead to settlement and horizontal movements of the ground.

The liquefaction probability associated with this Hazus scenario can be seen on Figure 4-62.

Packet Page No. 522
Tri-City 4-197
Local Hazard Mitigation Plan Update
March 2024
Figure 4-62 Calaveras Fault – 7.43 Magnitude Liquefaction Probability Packet Page No. 523
Tri-City 4-198
Local Hazard Mitigation Plan Update
March 2024
Total Loss Estimates
For each study region, information on loss estimates is provided based on that study region’s earthquake risk and general building stock value, which includes building and lifeline related losses on the study region’s available inventory. The total loss estimates associated with this scenario can be seen on Figure 4-63.

Packet Page No. 524
Tri-City 4-199
Local Hazard Mitigation Plan Update
March 2024
Figure 4-63 Calaveras Fault – 7.43 Total Loss
Packet Page No. 525
Tri-City 4-200
Local Hazard Mitigation Plan Update
March 2024
Fire Following Earthquake
As detailed in the above methodology, two iterations of the Fire Following Earthquake were conducted for each primary Hazus Scenario. The results for the two iterations for the Calaveras Scenario are included below.

Fires often occur after an earthquake. Because of the number of fires and the lack of water to fight the fires, they can often burn out of control. Hazus uses a Monte Carlo simulation model to estimate the number of ignitions and the amount of burnt area.
➢ Four maps were created for the 10-mph scenario:
✓ Number of Ignitions is shown on Figure 4-64.
✓ Population Exposure is shown on Figure 4-65.
✓ Value Exposure is shown on Figure 4-66.
✓ Fire Water Demand (gpm) is shown on Figure 4-67.
➢ Four maps were created for the 50-mph scenario
✓ Number of Ignitions is shown on Figure 4-68.
✓ Population Exposure is shown on Figure 4-69
✓ Value Exposure is shown on Figure 4-70
✓ Fire Water Demand (gpm) is shown on Figure 4-71.

Packet Page No. 526
Tri-City 4-201
Local Hazard Mitigation Plan Update
March 2024
Figure 4-64 Calaveras Fault 7.43 Magnitude Number of Ignitions (10 MPH Winds) Packet Page No. 527
Tri-City 4-202
Local Hazard Mitigation Plan Update
March 2024
Figure 4-65 Calaveras Fault 7.43 Magnitude Population Exposure (10 MPH Winds) Packet Page No. 528
Tri-City 4-203
Local Hazard Mitigation Plan Update
March 2024
Figure 4-66 Calaveras Fault 7.43 Magnitude Exposed Values (10 MPH Winds) Packet Page No. 529
Tri-City 4-204
Local Hazard Mitigation Plan Update
March 2024
Figure 4-67 Calaveras Fault 7.43 Magnitude Fire Water Demand in GPM (10 MPH Winds) Packet Page No. 530
Tri-City 4-205
Local Hazard Mitigation Plan Update
March 2024
Figure 4-68 Calaveras Fault 7.43 Magnitude Number of Ignitions (50 MPH Winds) Packet Page No. 531
Tri-City 4-206
Local Hazard Mitigation Plan Update
March 2024
Figure 4-69 Calaveras Fault 7.43 Magnitude Population Exposure (50 MPH Winds) Packet Page No. 532
Tri-City 4-207
Local Hazard Mitigation Plan Update
March 2024
Figure 4-70 Calaveras Fault 7.43 Magnitude Exposed Values (50 MPH Winds) Packet Page No. 533
Tri-City 4-208
Local Hazard Mitigation Plan Update
March 2024
Figure 4-71 Calaveras Fault 7.43 Magnitude Fire Water Demand in GPM (50 MPH Winds) Packet Page No. 534
Tri-City 4-209
Local Hazard Mitigation Plan Update
March 2024
Hayward + Rodgers Creek Fault Hazus Scenario (Epicenter: Fremont; Magnitude: 7.57) The Hazus results for the Hayward + Rodgers Creek Fault Hazus Scenario is summarized below in Table 4-69. Appendix H includes the Earthquake Hazus Global Summary Risk Report for each Hazus defined study region where more detailed information can be obtained. Note: The location of the Hayward Fault on the maps below was noted by the City to not be in the correct location. Foster Morrison was unable to modify the fault location on the maps below as that is the location that FEMA’s Hazus program has recorded for the fault. Its actual location is correct in terms of the analysis (so the table below remains correct).

FEMA was notified of this error.

Table 4-69 Tri-City Planning Area– Hayward + Rodgers Creek Fault HAZUS Earthquake Deterministic Results for 7.57 M Event
Type of Impact Impacts to City from 7.57 Deterministic Earthquake Total Buildings Damaged
(based on 102,000 buildings)
Slight: 39,420
Moderate: 24,508
Extensive: 10,382
Complete: 3,703
Building and Income Related Losses $17,055,480,000
Total Economic Losses
(Includes building, income and lifeline losses)
$18,535,370,000
Casualties
(Based on 2 a.m. time of occurrence)
Without requiring hospitalization: 1,344
Requiring hospitalization: 264
Life threatening: 22
Fatalities: 38
Casualties
(Based on 2 p.m. time of occurrence)
Without requiring hospitalization: 3,083
Requiring hospitalization: 822
Life threatening: 131
Fatalities: 241
Casualties
(Based on 5 p.m. time of occurrence)
Without requiring hospitalization: 2,315
Requiring hospitalization: 657
Life threatening: 199
Fatalities: 185
Damage to Transportation Systems 27 highway bridges, 8 railway bridges, 2 railway facilities, and 1 airport facility with at least moderate damage. 2 highway bridges with complete damage.

Damage to Essential Facilities 59 schools, 1 EOC, 5 police stations, and 2 fire stations with at least moderate damage. 4 school facilities with complete damage.

Damage to Utility Systems 1 wastewater facility, 1 electrical power facility, and 1 communication facility with at least moderate damage. None with complete damage. 2,251 potable water line breaks, 1,131 wastewater line breaks, and 17 natural gas line breaks.

Households without Power/Water Service
(Based on 113,685 total households)
Power loss, Day 1: 113,685
Power loss, Day 3: 113,685
Power loss, Day 7: 113,685
Power loss, Day 30: 113,685
Power loss, Day 90: 113,685
Water loss, Day 1: 113,428
Water loss, Day 3: 113,406
Water loss, Day 7: 113,356
Water loss, Day 30: 112,715
Water loss, Day 90: 0
Displaced Households 11,362 displaced households
Packet Page No. 535
Tri-City 4-210
Local Hazard Mitigation Plan Update
March 2024
Type of Impact Impacts to City from 7.57 Deterministic Earthquake Shelter Requirements 5,637 persons
Debris Generation 2,390,000 tons
Hazus 6.1
Loss Estimates Highlights
Hazus estimates that about 38,593 buildings will be at least moderately damaged. This is over 38.00 % of the buildings in the region. There are an estimated 3,702 buildings that will be damaged beyond repair.

Before the earthquake, the region had 556 hospital beds available for use. On the day of the earthquake, the model estimates that only 173 hospital beds (31.00%) are available for use by patients already in the hospital and those injured by the earthquake. After one week, 60.00% of the beds will be back in service.

By 30 days, 88.00% will be operational.

The total building-related losses were 17,055.48 (millions of dollars); 12 % of the estimated losses were related to the business interruption of the region. By far, the largest loss was sustained by the residential occupancies which made up over 44 % of the total loss.

Peak Ground Acceleration (Shaking)
Hazus evaluates the geographic distribution of ground shaking as a result of a specific earthquake scenario and expresses ground shaking using several quantitative parameters, including the peak ground acceleration. The peak ground acceleration map associated with this Hazus scenario can be seen on Figure 4-72.

Packet Page No. 536
Tri-City 4-211
Local Hazard Mitigation Plan Update
March 2024
Figure 4-72 Hayward + Rodgers Creek Fault - 7.57 Magnitude Peak Ground Acceleration Packet Page No. 537
Tri-City 4-212
Local Hazard Mitigation Plan Update
March 2024
Liquefaction
Liquefaction occurs when loose, water-saturated soils are shaken strongly and causes sudden loss of strength and stiffness in soils. This shaking can lead to settlement and horizontal movements of the ground.

The liquefaction probability associated with this Hazus scenario can be seen on Figure 4-73.

Packet Page No. 538
Tri-City 4-213
Local Hazard Mitigation Plan Update
March 2024
Figure 4-73 Hayward + Rodgers Creek Fault 7.57 Magnitude Liquefaction Probability Packet Page No. 539
Tri-City 4-214
Local Hazard Mitigation Plan Update
March 2024
Total Loss Estimates
For each study region, information on loss estimates is provided based on that study region’s earthquake risk and general building stock value, which includes building and lifeline related losses on the study region’s available inventory. The total loss estimates associated with this scenario can be seen on Figure 4-74.

Packet Page No. 540
Tri-City 4-215
Local Hazard Mitigation Plan Update
March 2024
Figure 4-74 Hayward + Rodgers Creek Fault 7.57 Magnitude Total Loss Packet Page No. 541
Tri-City 4-216
Local Hazard Mitigation Plan Update
March 2024
Fire Following Earthquake
As detailed in the above methodology, two iterations of the Fire Following Earthquake were conducted for each primary Hazus Scenario. The results for the two iterations for the Haywood + Rodgers Creek Scenario are included below.

Fires often occur after an earthquake. Because of the number of fires and the lack of water to fight the fires, they can often burn out of control. Hazus uses a Monte Carlo simulation model to estimate the number of ignitions and the amount of burnt area.
➢ Four maps were created for the 10-mph scenario:
✓ Number of Ignitions is shown on Figure 4-75.
✓ Population Exposure is shown on Figure 4-76.
✓ Value Exposure is shown on Figure 4-77.
✓ Fire Water Demand (gpm) is shown on Figure 4-78.
➢ Four maps were created for the 50-mph scenario:
✓ Number of Ignitions is shown on Figure 4-79.
✓ Population Exposure is shown on Figure 4-80.
✓ Value Exposure is shown on Figure 4-81.
✓ Fire Water Demand (gpm) is shown on Figure 4-82.

Packet Page No. 542
Tri-City 4-217
Local Hazard Mitigation Plan Update
March 2024
Figure 4-75 Hayward + Rodgers Creek Fault 7.57 Magnitude Number of Ignitions (10 MPH Winds)
Packet Page No. 543
Tri-City 4-218
Local Hazard Mitigation Plan Update
March 2024
Figure 4-76 Hayward + Rodgers Creek Fault 7.57 Magnitude Population Exposure (10 MPH Winds)
Packet Page No. 544
Tri-City 4-219
Local Hazard Mitigation Plan Update
March 2024
Figure 4-77 Hayward + Rodgers Creek Fault 7.57 Magnitude Exposed Values (10 MPH Winds)
Packet Page No. 545
Tri-City 4-220
Local Hazard Mitigation Plan Update
March 2024
Figure 4-78 Hayward + Rodgers Creek Fault 7.57 Magnitude Fire Water Demand in GPM (10 MPH Winds)
Packet Page No. 546
Tri-City 4-221
Local Hazard Mitigation Plan Update
March 2024
Figure 4-79 Hayward + Rodgers Creek Fault 7.57 Magnitude Number of Ignitions (50 MPH Winds)
Packet Page No. 547
Tri-City 4-222
Local Hazard Mitigation Plan Update
March 2024
Figure 4-80 Hayward + Rodgers Creek Fault 7.57 Magnitude Population Exposure (50 MPH Winds)
Packet Page No. 548
Tri-City 4-223
Local Hazard Mitigation Plan Update
March 2024
Figure 4-81 Hayward + Rodgers Creek Fault 7.57 Magnitude Exposed Values (50 MPH Winds)
Packet Page No. 549
Tri-City 4-224
Local Hazard Mitigation Plan Update
March 2024
Figure 4-82 Hayward + Rodgers Creek Fault 7.57 Magnitude Fire Water Demand in GPM (50 MPH Winds)
Packet Page No. 550
Tri-City 4-225
Local Hazard Mitigation Plan Update
March 2024
Haywired Scenario (Hayward Fault) HAZUS-MH Earthquake Loss Estimation Deterministic Results for

7.0 M Event
The Hazus results for the Haywired (Hayward Fault) Hazus Scenario is summarized below in Table 4-70.

Appendix H includes the Earthquake Hazus Global Summary Risk Report for each Hazus defined study region where more detailed information can be obtained. Note: The location of the Hayward Fault on the maps below was noted by the City to not be in the correct locations. Foster Morrison was unable to modify the fault location on the maps below as that is the location that FEMA’s Hazus program has recorded for the fault. Its actual location is correct in terms of the analysis (so the table below remains correct). FEMA was notified of this error.

Table 4-70 Tri-City Planning Area– Haywired (Hayward Fault) HAZUS Earthquake Deterministic Results for 7.0 M Event
Type of Impact Impacts to City from 7.0 Deterministic Earthquake Total Buildings Damaged
(based on 102,000 buildings)
Slight: 24,315
Moderate: 5,421
Extensive: 1,472
Complete: 327
Building and Income Related Losses $3,287,230,000
Total Economic Losses
(Includes building, income and lifeline losses)
$4,058,120,000
Casualties
(Based on 2 a.m. time of occurrence)
Without requiring hospitalization: 191
Requiring hospitalization: 27
Life threatening: 2
Fatalities: 3
Casualties
(Based on 2 p.m. time of occurrence)
Without requiring hospitalization: 296
Requiring hospitalization: 55
Life threatening: 9
Fatalities: 12
Casualties
(Based on 5 p.m. time of occurrence)
Without requiring hospitalization: 250
Requiring hospitalization: 55
Life threatening: 9
Fatalities: 12
Damage to Transportation Systems 1 airport facility with at least moderate damage Damage to Essential Facilities 3 schools with at least moderate damage. 0 facilities with complete damage.

Damage to Utility Systems 1 electrical power facility and 2 communications facilities with at least moderate damage.
563 potable water line breaks, 268 wastewater line breaks, and 4 natural gas line breaks.

Households without Power/Water Service
(Based on 113,685 total households)
Power loss, Day 1: 113,685
Power loss, Day 3: 113,685
Power loss, Day 7: 113,685
Power loss, Day 30: 113,685
Power loss, Day 90: 113,685
Water loss, Day 1: 98,615
Water loss, Day 3: 95,442
Water loss, Day 7: 86,276
Water loss, Day 30: 0
Water loss, Day 90: 0
Displaced Households 993 displaced households
Shelter Requirements 499 persons
Packet Page No. 551
Tri-City 4-226
Local Hazard Mitigation Plan Update
March 2024
Type of Impact Impacts to City from 7.0 Deterministic Earthquake Debris Generation 367,000 tons
Hazus 6.1
Loss Estimates Highlights
Hazus estimates that about 7,219 buildings will be at least moderately damaged. This is over 7.00 % of the buildings in the region. There are an estimated 326 buildings that will be damaged beyond repair.

Before the earthquake, the region had 556 hospital beds available for use. On the day of the earthquake, the model estimates that only 443 hospital beds (80.00%) are available for use by patients already in the hospital and those injured by the earthquake. After one week, 93.00% of the beds will be back in service. By 30 days, 98.00% will be operational.

The total building-related losses were 3,287.23 (millions of dollars); 10 % of the estimated losses were related to the business interruption of the region. By far, the largest loss was sustained by the residential occupancies which made up over 42 % of the total loss.

Peak Ground Acceleration (Shaking)
Hazus evaluates the geographic distribution of ground shaking as a result of a specific earthquake scenario and expresses ground shaking using several quantitative parameters, including the peak ground acceleration. The peak ground acceleration map associated with this Hazus scenario can be seen on Figure 4-83.

Packet Page No. 552
Tri-City 4-227
Local Hazard Mitigation Plan Update
March 2024
Figure 4-83 Haywired (Hayward Fault) Scenario 7.0 Magnitude Peak Ground Acceleration Packet Page No. 553
Tri-City 4-228
Local Hazard Mitigation Plan Update
March 2024
Liquefaction
Liquefaction occurs when loose, water-saturated soils are shaken strongly and causes sudden loss of strength and stiffness in soils. This shaking can lead to settlement and horizontal movements of the ground.

The liquefaction probability associated with this Hazus scenario can be seen on Figure 4-84.

Packet Page No. 554
Tri-City 4-229
Local Hazard Mitigation Plan Update
March 2024
Figure 4-84 Haywired (Hayward Fault) Scenario 7.0 Magnitude Liquefaction Probability Packet Page No. 555
Tri-City 4-230
Local Hazard Mitigation Plan Update
March 2024
Total Loss Estimates
For each study region, information on loss estimates is provided based on that study region’s earthquake risk and general building stock value, which includes building and lifeline related losses on the study region’s available inventory. The total loss estimates associated with this scenario can be seen on Figure 4-85.

Packet Page No. 556
Tri-City 4-231
Local Hazard Mitigation Plan Update
March 2024
Figure 4-85 Haywired (Hayward Fault) Scenario 7.0 Magnitude Total Loss Packet Page No. 557
Tri-City 4-232
Local Hazard Mitigation Plan Update
March 2024
Fire Following Earthquake
As detailed in the above methodology, two iterations of the Fire Following Earthquake were conducted for each primary Hazus Scenario. The results for the two iterations for the Haywired (Hayward Fault) Scenario are included below.

Fires often occur after an earthquake. Because of the number of fires and the lack of water to fight the fires, they can often burn out of control. Hazus uses a Monte Carlo simulation model to estimate the number of ignitions and the amount of burnt area.
➢ Four maps were created for the 10-mph scenario:
✓ Number of Ignitions is shown on Figure 4-86.
✓ Population Exposure is shown on Figure 4-87.
✓ Value Exposure is shown on Figure 4-88.
✓ Fire Water Demand (gpm) is shown on Figure 4-89.
➢ Four maps were created for the 50-mph scenario:
✓ Number of Ignitions is shown on Figure 4-90.
✓ Population Exposure is shown on Figure 4-91.
✓ Value Exposure is shown on Figure 4-92.
✓ Fire Water Demand (gpm) is shown on Figure 4-93.

Packet Page No. 558
Tri-City 4-233
Local Hazard Mitigation Plan Update
March 2024
Figure 4-86 Haywired (Hayward Fault) Scenario 7.0 Magnitude Number of Ignitions (10 MPH Winds)
Packet Page No. 559
Tri-City 4-234
Local Hazard Mitigation Plan Update
March 2024
Figure 4-87 Haywired (Hayward Fault) Scenario 7.0 Magnitude Population Exposure (10 MPH Winds)
Packet Page No. 560
Tri-City 4-235
Local Hazard Mitigation Plan Update
March 2024
Figure 4-88 Haywired (Hayward Fault) Scenario 7.0 Magnitude Exposed Values (10 MPH Winds)
Packet Page No. 561
Tri-City 4-236
Local Hazard Mitigation Plan Update
March 2024
Figure 4-89 Haywired (Hayward Fault) Scenario 7.0 Magnitude Fire Water Demand in GPM (10 MPH Winds)
Packet Page No. 562
Tri-City 4-237
Local Hazard Mitigation Plan Update
March 2024
Figure 4-90 Haywired (Hayward Fault) Scenario 7.0 Magnitude Number of Ignitions (50 MPH Winds)
Packet Page No. 563
Tri-City 4-238
Local Hazard Mitigation Plan Update
March 2024
Figure 4-91 Haywired (Hayward Fault) Scenario 7.0 Magnitude Population Exposure (50 MPH Winds)
Packet Page No. 564
Tri-City 4-239
Local Hazard Mitigation Plan Update
March 2024
Figure 4-92 Haywired (Hayward Fault) Scenario 7.0 Magnitude Exposed Values (50 MPH Winds)
Packet Page No. 565
Tri-City 4-240
Local Hazard Mitigation Plan Update
March 2024
Figure 4-93 Haywired Scenario 7.0 Magnitude Fire Water Demand in GPM (50 MPH Winds) Packet Page No. 566
Tri-City 4-241
Local Hazard Mitigation Plan Update
March 2024
San Andreas Scenario (Epicenter: Bay Bridge; Magnitude: 8.04) The Hazus results for the San Andreas Fault Hazus Scenario is summarized below in Table 4-71. Appendix H includes the Earthquake Hazus Global Summary Risk Report for each Hazus defined study region where more detailed information can be obtained.

Table 4-71 Tri-City Planning Area– San Andreas Fault HAZUS Earthquake Deterministic Results for 8.04 M Event
Type of Impact Impacts to City from 8.04 Deterministic Earthquake Total Buildings Damaged
(based on 102,000 buildings)
Slight: 25,938
Moderate: 5,918
Extensive: 2,318
Complete: 556
Building and Income Related Losses $4,072,960,000
Total Economic Losses
(Includes building, income and lifeline losses)
$4,558,370,000
Casualties
(Based on 2 a.m. time of occurrence)
Without requiring hospitalization: 269
Requiring hospitalization: 42
Life threatening: 3
Fatalities: 5
Casualties
(Based on 2 p.m. time of occurrence)
Without requiring hospitalization: 459
Requiring hospitalization: 96
Life threatening: 15
Fatalities: 24
Casualties
(Based on 5 p.m. time of occurrence)
Without requiring hospitalization: 377
Requiring hospitalization: 100
Life threatening: 58
Fatalities: 26
Damage to Transportation Systems None with at least moderate damage Damage to Essential Facilities 4 schools with at least moderate damage. 0 facilities with complete damage.

Damage to Utility Systems 1 electrical power facility, and 3 communication facilities with at least moderate damage.
803 potable water line breaks, 403 wastewater line breaks, and 6 natural gas line breaks.

Households without Power/Water Service
(Based on 113,685 total households)
Power loss, Day 1: 113,685
Power loss, Day 3: 113,685
Power loss, Day 7: 113,685
Power loss, Day 30: 113,685
Power loss, Day 90: 113,685
Water loss, Day 1: 107,645
Water loss, Day 3: 106,623
Water loss, Day 7: 103,868
Water loss, Day 30: 6,937
Water loss, Day 90: 0
Displaced Households 1,731 displaced households
Shelter Requirements 860 persons
Debris Generation 471,000 tons
Hazus 6.1
Packet Page No. 567
Tri-City 4-242
Local Hazard Mitigation Plan Update
March 2024
Loss Estimates Highlights
Hazus estimates that about 8,792 buildings will be at least moderately damaged. This is over 9.00 % of the buildings in the region. There are an estimated 555 buildings that will be damaged beyond repair.

Before the earthquake, the region had 556 hospital beds available for use. On the day of the earthquake, the model estimates that only 424 hospital beds (76.00%) are available for use by patients already in the hospital and those injured by the earthquake. After one week, 91.00% of the beds will be back in service.

By 30 days, 97.00% will be operational.

The total building-related losses were 4,072.96 (millions of dollars); 11 % of the estimated losses were related to the business interruption of the region. By far, the largest loss was sustained by the residential occupancies which made up over 44 % of the total loss.

Peak Ground Acceleration (Shaking)
Hazus evaluates the geographic distribution of ground shaking as a result of a specific earthquake scenario and expresses ground shaking using several quantitative parameters, including the peak ground acceleration. The peak ground acceleration map associated with this Hazus scenario can be seen on Figure 4-94.

Packet Page No. 568
Tri-City 4-243
Local Hazard Mitigation Plan Update
March 2024
Figure 4-94 San Andreas Fault – 8.04 Magnitude Peak Ground Acceleration Packet Page No. 569
Tri-City 4-244
Local Hazard Mitigation Plan Update
March 2024
Liquefaction
Liquefaction occurs when loose, water-saturated soils are shaken strongly and causes sudden loss of strength and stiffness in soils. This shaking can lead to settlement and horizontal movements of the ground.

The liquefaction probability associated with this Hazus scenario can be seen on Figure 4-95.

Packet Page No. 570
Tri-City 4-245
Local Hazard Mitigation Plan Update
March 2024
Figure 4-95 San Andreas Fault 8.04 Magnitude Liquefaction Probability Packet Page No. 571
Tri-City 4-246
Local Hazard Mitigation Plan Update
March 2024
Total Loss Estimates
For each study region, information on loss estimates is provided based on that study region’s earthquake risk and general building stock value, which includes building and lifeline related losses on the study region’s available inventory. The total loss estimates associated with this scenario can be seen on Figure 4-96.

Packet Page No. 572
Tri-City 4-247
Local Hazard Mitigation Plan Update
March 2024
Figure 4-96 San Andreas Fault 8.04 Total Loss
Packet Page No. 573
Tri-City 4-248
Local Hazard Mitigation Plan Update
March 2024
Fire Following Earthquake
As detailed in the above methodology, two iterations of the Fire Following Earthquake were conducted for each primary Hazus Scenario. The results for the two iterations for the San Andreas Scenario are included below.

Fires often occur after an earthquake. Because of the number of fires and the lack of water to fight the fires, they can often burn out of control. Hazus uses a Monte Carlo simulation model to estimate the number of ignitions and the amount of burnt area.
➢ Four maps were created for the 10-mph scenario:
✓ Number of Ignitions is shown on Figure 4-97.
✓ Population Exposure is shown on Figure 4-98.
✓ Value Exposure is shown on Figure 4-99.
✓ Fire Water Demand (gpm) is shown on Figure 4-100.
➢ Four maps were created for the 50-mph scenario:
✓ Number of Ignitions is shown on Figure 4-101.
✓ Population Exposure is shown on Figure 4-102.
✓ Value Exposure is shown on Figure 4-103.
✓ Fire Water Demand (gpm) is shown on Figure 4-104.

Packet Page No. 574
Tri-City 4-249
Local Hazard Mitigation Plan Update
March 2024
Figure 4-97 San Andreas Fault 8.04 Magnitude Number of Ignitions (10 MPH Winds) Packet Page No. 575
Tri-City 4-250
Local Hazard Mitigation Plan Update
March 2024
Figure 4-98 San Andreas Fault 8.04 Magnitude Population Exposure (10 MPH Winds) Packet Page No. 576
Tri-City 4-251
Local Hazard Mitigation Plan Update
March 2024
Figure 4-99 San Andreas Fault 8.04 Magnitude Exposed Values (10 MPH Winds) Packet Page No. 577
Tri-City 4-252
Local Hazard Mitigation Plan Update
March 2024
Figure 4-100 San Andreas Fault 8.04 Magnitude Fire Water Demand in GPM (10 MPH Winds) Packet Page No. 578
Tri-City 4-253
Local Hazard Mitigation Plan Update
March 2024
Figure 4-101 San Andreas Fault 8.04 Magnitude Number of Ignitions (50 MPH Winds) Packet Page No. 579
Tri-City 4-254
Local Hazard Mitigation Plan Update
March 2024
Figure 4-102 San Andreas Fault 8.04 Magnitude Population Exposure (50 MPH Winds) Packet Page No. 580
Tri-City 4-255
Local Hazard Mitigation Plan Update
March 2024
Figure 4-103 San Andreas Fault 8.04 Magnitude Exposed Values (50 MPH Winds) Packet Page No. 581
Tri-City 4-256
Local Hazard Mitigation Plan Update
March 2024
Figure 4-104 San Andreas Fault 8.04 Magnitude Fire Water Demand in GPM (50 MPH Winds) Packet Page No. 582
Tri-City 4-257
Local Hazard Mitigation Plan Update
March 2024
Table 4-72 Tri-City Planning Area – HAZUS-MH Earthquake Loss Estimation Scenario Comparison Type of Impact Calaveras Fault
(CN+CC+CS+CE)
Impacts to City from 7.43
Deterministic Earthquake
Hayward and Rodgers
Creek Fault
(RC+HN+HS)
Impacts to City from 7.57
Deterministic Earthquake
Hayward Fault
Haywired (HN+HS)
Impacts to City from 7.0
Deterministic Earthquake
San Andreas Fault
(SAO+SAN+SAP+SAS)
Impacts to City from 8.04
Deterministic Earthquake
Total Buildings Damaged
(based on 102,000 buildings)
Slight: 34,485
Moderate: 10,737
Extensive: 3,324
Complete: 802
Slight: 39,420
Moderate: 24,508
Extensive: 10,382
Complete: 3,703
Slight: 24,315
Moderate: 5,421
Extensive: 1,472
Complete: 327
Slight: 25,938
Moderate: 5,918
Extensive: 2,318
Complete: 556
Building and Income Related
Losses
$6,072,200,000 $17,055,480,000 $3,287,230,000 $4,072,960,000 Total Economic Losses
(Includes building, income and
lifeline losses)
$6,694,910,000 $18,535,370,000 $4,058,120,000 $4,558,370,000 Casualties
(Based on 2 a.m. time of
occurrence)
Without requiring
hospitalization: 410
Requiring hospitalization: 64
Life threatening: 4
Fatalities: 7
Without requiring hospitalization:
1,344
Requiring hospitalization: 264
Life threatening: 22
Fatalities: 38
Without requiring hospitalization:
191
Requiring hospitalization: 27
Life threatening: 2
Fatalities: 3
Without requiring hospitalization:
269
Requiring hospitalization: 42
Life threatening: 3
Fatalities: 5
Casualties
(Based on 2 p.m. time of
occurrence)
Without requiring
hospitalization: 655
Requiring hospitalization: 134
Life threatening: 20
Fatalities: 32
Without requiring hospitalization:
3,083
Requiring hospitalization: 822
Life threatening: 131
Fatalities: 241
Without requiring hospitalization:
296
Requiring hospitalization: 55
Life threatening: 9
Fatalities: 12
Without requiring hospitalization:
459
Requiring hospitalization: 96
Life threatening: 15
Fatalities: 24
Casualties
(Based on 5 p.m. time of
occurrence)
Without requiring
hospitalization: 534
Requiring hospitalization: 138
Life threatening: 74
Fatalities: 34
Without requiring hospitalization:
2,315
Requiring hospitalization: 657
Life threatening: 199
Fatalities: 185
Without requiring hospitalization:
250
Requiring hospitalization: 55
Life threatening: 9
Fatalities: 12
Without requiring hospitalization:
377
Requiring hospitalization: 100
Life threatening: 58
Fatalities: 26
Damage to Transportation
Systems
1 bridge with at least moderate
damage
27 highway bridges, 8 railway
bridges, 2 railway facilities, and 1
airport facility with at least moderate
damage. 2 highway bridges with
complete damage.
1 airport facility with at least
moderate damage
None with at least moderate damage
Packet Page No. 583
Tri-City 4-258
Local Hazard Mitigation Plan Update
March 2024
Type of Impact Calaveras Fault
(CN+CC+CS+CE)
Impacts to City from 7.43
Deterministic Earthquake
Hayward and Rodgers
Creek Fault
(RC+HN+HS)
Impacts to City from 7.57
Deterministic Earthquake
Hayward Fault
Haywired (HN+HS)
Impacts to City from 7.0
Deterministic Earthquake
San Andreas Fault
(SAO+SAN+SAP+SAS)
Impacts to City from 8.04
Deterministic Earthquake
Damage to Essential Facilities 4 schools and 1 EOC with at least moderate damage. 0
facilities with complete damage.
59 schools, 1 EOC, 5 police
stations, and 2 fire stations with at
least moderate damage. 4 school
facilities with complete damage.
3 schools with at least moderate
damage. 0 facilities with complete
damage.
4 schools with at least moderate
damage. 0 facilities with complete
damage.

Damage to Utility Systems 1 wastewater facility, 1
electrical power facility, and 2
communication facilities with
at least moderate damage. 0
facilities with complete damage.
1,018 potable water line breaks,
511 wastewater line breaks, and
8 natural gas line breaks.
1 wastewater facility, 1 electrical
power facility, and 1 communication
facility with at least moderate
damage. None with complete
damage. 2,251 potable water line
breaks, 1,131 wastewater line breaks,
and 17 natural gas line breaks.
1 electrical power facility and 2
communications facilities with at least
moderate damage.
563 potable water line breaks, 268
wastewater line breaks, and 4 natural
gas line breaks.
1 electrical power facility, and 3
communication facilities with at least
moderate damage.
803 potable water line breaks, 403
wastewater line breaks, and 6 natural
gas line breaks.

Households without
Power/Water Service
(Based on 113,685 total
households)
Power loss,
Day 1: 113,685
Power loss,
Day 3: 113,685
Power loss,
Day 7:

Power loss,
Day 30:
113,685
Power loss,
Day 90:
113,685
Water loss,
Day 1:
110,435
Water loss,
Day 3:
109,958
Water loss,
Day 7:
108,722
Water loss,
Day 30:
72,925
Water loss,
Day 90: 0
Power loss, Day 1:
113,685
Power loss, Day 3:
113,685
Power loss, Day 7:
113,685
Power loss, Day
30: 113,685
Power loss, Day
90: 113,685
Water loss,
Day 1:
113,428
Water loss,
Day 3: 113,406
Water loss,
Day 7: 113,356
Water loss,
Day 30:
112,715
Water loss,
Day 90: 0
Power loss, Day
1: 113,685
Power loss, Day
3: 113,685
Power loss, Day
7: 113,685
Power loss, Day
30: 113,685
Power loss, Day
90: 113,685
Water loss, Day
1: 98,615
Water loss, Day
3: 95,442
Water loss, Day
7: 86,276
Water loss, Day
30: 0
Water loss, Day
90: 0
Power loss,
Day 1: 113,685
Power loss,
Day 3: 113,685
Power loss,
Day 7: 113,685
Power loss,
Day 30:
113,685
Power loss,
Day 90:
113,685
Water loss, Day 1:
107,645
Water loss, Day 3:
106,623
Water loss, Day 7:
103,868
Water loss, Day 30:
6,937
Water loss, Day 90:
0 Displaced Households 2,703 displaced households 11,362 displaced households 993 displaced households 1,731 displaced households Shelter Requirements 1,328 persons 5,637 persons 499 persons 860 persons Debris Generation 624,000 tons 2,390,000 tons 367,000 tons 471,000 tons Packet Page No. 584
Tri-City 4-259
Local Hazard Mitigation Plan Update
March 2024
Impacts from Earthquake (and its subhazards)
Earthquakes can strike without warning and cause dramatic changes to the landscape of an area that can have devastating impacts on the built environment. The greatest impact is to life safety of the Tri-City Planning Area residents and visitors. Other impacts to the Planning Area would include damages to infrastructure such as roads, bridges, and dams; damages and loss of services to utilities and critical infrastructure, including those related to gas, power, water, wastewater and communication systems; damages to structures and other development; and possible loss of life and injuries.

Earthquakes can also cause failure of dams, levees, and reservoirs. Facilities and land downslope from dams or water reservoirs or behind levees might be subject to flooding, if the dams, reservoirs, or levees fail as a result of an earthquake. The Planning Area has locations with significant flood risk that include facilities downslope from dams or reservoirs or behind levees.

Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure, utilities, and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Significant economic impact (jobs, sales, tax revenue) to the community; and ➢ Negative impact on commercial and residential property values These losses may be worsened in the future due to the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development.

A large nearby earthquake can also increase the probability of secondary earthquake hazards affecting the Planning Area, including a surface fault rupture, liquefaction, landslides, and fire following earthquakes.

These cascading events compound the impacts to the Planning Area during an earthquake.

Surface Fault Rupture
When a fault rupture extends to the earth’s surface, the displacement can catastrophically damage structures or utilities. Fissuring, settlement, and permanent horizontal and vertical ground shifting often accompany large earthquakes. Such ground failures can significantly increase damage and may be a contributing cause of damage. Studies after the 1994 Northridge Earthquake showed that when ground failure was involved, damage to residential dwellings was three to four times greater than average shake damage. Because of their geographic extent and their tendency to be buried, networked infrastructures such as water, power, communication, and transportation lines are particularly vulnerable to ground failures.

Fault ruptures itself contributes very little to damage unless the structure or system element crosses the active fault; however, liquefaction can occur further from the source of the earthquake. In general, newer construction is more earthquake resistant than older construction due to enforcement of improved building codes. Manufactured housing is very susceptible to damage because their foundation systems are rarely braced for earthquake motions. Locally generated earthquake motions and associated liquefaction, even Packet Page No. 585
Tri-City 4-260
Local Hazard Mitigation Plan Update
March 2024
from very moderate events, tend to be more damaging to smaller buildings, especially those constructed of unreinforced masonry (URM) and soft story buildings.

Liquefaction
Ground settlement during liquefaction can cause damage when the amount of settlement varies significantly across the length of a structure. Liquefaction can occur in susceptible soils and can severely damage bridges, wharves, piers, and other structures at ports and harbors, as well as underground utility lines and structures.

Earthquake-Induced Landslides
Landslides caused by earthquakes can be widespread over the area of highest shaking intensity and also at greater distances if hillsides are in a susceptible condition. Earthquake landslides can significantly damage structures and transportation and utility lifelines.

Fire Following Earthquake
Earthquakes are often responsible for igniting fires that can contribute to a considerable share of the overall damage in a disaster. The fires can start from a variety of sources: appliances with natural gas pilot lights might tip, damaged electrical equipment might spark, and gas line connections might break. Recently, in the South Napa Earthquake, a number of mobile homes were destroyed and damaged when the gas connection to a home broke. In the Loma Prieta Earthquake, 36 fires broke out in San Francisco alone but luckily were quickly contained in large part due to the abnormally calm wind that evening, and the fires’ proximity to the Bay that allowed a fire boat to pump water to the fire where the water lines had failed. In the 1906 earthquake, over 3.5 square miles of San Francisco burned, representing 80 percent of San Francisco’s property value at the time.

Fires after earthquakes may severely strain fire departments that must respond to multiple simultaneous ignitions. Impaired communications, water supply, transportation, and other demands such as structural collapses, hazardous materials releases, or medical emergencies affect fire department response. A few characteristics can make specific facilities more vulnerable to fire following earthquake. If a building collapses, there is a high risk for gas or electrical lines to start “seed” fires that then impact undamaged neighboring structures or start wildfires. Areas of liquefaction, fault rupture, and landslide are more vulnerable to fire. There is a greater potential for underground gas mains to break due to ground displacements, and water lines in the area might also be damaged, which could prevent the ability to fight a fire with regular water resources. Areas that are largely built with wood frames or shingle roofs might be less prone to earthquake damage but are at a heightened risk for the spread of fires.

Future Development
Earthquakes and liquefaction hazards are taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

Packet Page No. 586
Tri-City 4-261
Local Hazard Mitigation Plan Update
March 2024

4.3.11. Flood: (1% and 0.2% Annual Chance)
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
Flooding is the rising and overflowing of a body of water onto normally dry land. Floods are among the costliest natural disasters in terms of human hardship and economic loss nationwide. Floods can cause substantial damage to structures, landscapes, and utilities and can cause life safety issues. Floods can be extremely dangerous. Six inches of moving water can knock over a person given a strong current. A car will float in less than two feet of moving water and can be swept downstream into deeper waters. Floods kill more people trapped in vehicles than anywhere else.

During a flood, people can also suffer heart attacks or electrocution due to electrical equipment short outs.

Floodwaters can transport large objects downstream which can damage or remove stationary structures, such as dam spillways. Ground saturation can result in instability, collapse, or other damage. Objects can also be buried or destroyed through sediment deposition. Floodwaters can also break utility lines and interrupt services. Standing water can cause damage to crops, roads, foundations, and electrical circuits.

Direct impacts, such as drowning, can be limited with adequate warning and public education about what to do during floods. Where flooding occurs in populated areas, warning and evacuation will be of critical importance to reduce life and safety impacts from any type of flooding.

There are three primary types of freshwater flood events in the Tri-City Planning Area: riverine and lake, flash flooding, and urban stormwater. Regardless of the type of flood, the cause is often the result of severe weather and excessive rainfall, either in the flood area or upstream reaches. ➢ Riverine and lake flooding is the most common type of flood event and occurs when a watercourse exceeds its “bank-full” capacity. Riverine flooding generally occurs as a result of prolonged rainfall, or rainfall that is combined with already saturated soils from previous rain events. The duration of riverine floods may vary from a few hours to many days. Factors that directly affect the amount of flood runoff include precipitation amount, intensity and distribution, the amount of soil moisture, seasonal variation in vegetation, snow depth, and water-resistance of the surface due to urbanization.

The warning time associated with slow rise floods assists in life and property protection. ➢ The term “flash flood” describes localized floods of great volume and short duration. In contrast to riverine flooding, this type of flood usually results from heavy rainfall on a relatively small drainage area. Precipitation of this sort usually occurs in the winter and spring. Flash floods often require immediate evacuation within the hour.
➢ Stormwater/Urban flood events have increased as land has been converted from fields or woodlands to roads and parking lots and lost its ability to absorb rainfall. Urbanization increases runoff by two to six times that of natural terrain. This is discussed in the Section 4.3.12 below.

Packet Page No. 587
Tri-City 4-262
Local Hazard Mitigation Plan Update
March 2024
The Tri-City Planning Area is also at risk to flooding resulting from dam and levee failures. Dam failure flooding is discussed separately in Section 4.3.7 of this document, while levee failures are discussed in Section 4.3.14. Regardless of the type of flood, the cause is often the result of severe weather and excessive rainfall, either in the flood area or upstream reach. Areas of the Planning Area are also at risk to Coastal Flooding and Sea Level Rise, which is discussed in Section 4.3.7 of this document.

The potential for flooding can change and increase through various land use changes and changes to land surface, resulting in a change to the floodplain. Environmental changes can create localized flooding problems in and outside of natural floodplains by altering or confining natural drainage channels. These changes are most often created by human activity.

Location and Extent
The area adjacent to a channel is the floodplain (see Figure 4-105). Floodplains are illustrated on inundation maps, which show areas of potential flooding and water depths. In its common usage, the floodplain most often refers to that area that is inundated by the 100-year flood, the flood that has a one percent chance in any given year of being equaled or exceeded (1% annual chance flood). The 1% annual chance flood is the national minimum standard to which communities regulate their floodplains through the National Flood Insurance Program (NFIP). The 500-year flood is a flood that has a 0.2 percent chance of being equaled or exceeded in any given year (0.2% annual chance flood). The potential for flooding can change and increase through various land use changes and changes to land surface, which result in a change to the floodplain.

A change in environment can create localized flooding problems inside and outside of natural floodplains by altering or confining natural drainage channels. These changes are most often created by human activity.

Packet Page No. 588
Tri-City 4-263
Local Hazard Mitigation Plan Update
March 2024
Figure 4-105 Floodplain Schematic
Source: FEMA
Hydrologic Regions
According to Cal DWR, California is divided into 10 hydrologic regions. The Tri-City Planning Area is traversed by one hydrologic region – the San Francisco Bay Hydrologic Region:
➢ The San Francisco Bay Hydrologic Region covers approximately 2.88 million acres (4,500 square miles) and includes all of San Francisco and portions of Marin, Sonoma, Napa, Solano, San Mateo, Santa Clara, Contra Costa, and Alameda counties. The region corresponds to the boundary of RWQCB

2. Significant geographic features include the Santa Clara, Napa, Sonoma, Petaluma, Suisun-Fairfield, and Livermore valleys; the Marin and San Francisco peninsulas; San Francisco, Suisun, and San Pablo bays; and the Santa Cruz Mountains, Diablo Range, Bolinas Ridge, and Vaca Mountains of the Coast Range. While being the smallest in size of the 10 Hydrologic Regions, the region has the second largest population in the State. Major population centers include the cities of San Francisco, San Jose and Oakland.

A map of the California’s hydrological regions is provided in Figure 4-106.

Packet Page No. 589
Tri-City 4-264
Local Hazard Mitigation Plan Update
March 2024
Figure 4-106 California Hydrologic Regions
Source: California Department of Water Resources
Floodplain Mapping
FEMA established standards for floodplain mapping studies as part of the NFIP. The NFIP makes flood insurance available to property owners in participating communities adopting FEMA-approved local floodplain studies, maps, and regulations. Floodplain studies that may be approved by FEMA include federally funded studies; studies developed by state, city, and regional public agencies; and technical studies generated by private interests as part of property annexation and land development efforts. Such studies may include entire stream reaches or limited stream sections depending on the nature and scope of a study.

Packet Page No. 590
Tri-City 4-265
Local Hazard Mitigation Plan Update
March 2024
Flood Insurance Study (FIS)
The FIS develops flood-risk data for various areas of the community that will be used to establish flood insurance rates and to assist the community in its efforts to promote sound floodplain management. The Tri-City Planning Area is covered by the Alameda County FIS (dated 12/21/2018).

Digital Flood Insurance Rate Maps (DFIRM)
As part of its Map Modernization program, FEMA has been converting paper FIRMS to digital FIRMs (DFIRMs). These digital maps:
➢ Incorporate the latest updates (Letters of Map Revision (LOMRs) and Letters of Map Amendment (LOMAs)
➢ Utilize community supplied data
➢ Verify the currency of the floodplains and refit them to community supplied basemaps ➢ Upgrade the FIRMs to a GIS database format to set the stage for future updates and to enable support for GIS analyses and other digital applications
➢ Solicit community participation
DFIRMs for Alameda County have been developed and are being used for the flood analysis for this LHMP.

The Tri-City Planning Area is covered by the Alameda County DFIRM (dated 12/21/2018), with much of the mapped flood zones within the Planning Area seeing limited change from the flood zones established in the 2009 DFIRMs. FEMA DFIRM flood zones and the Planning Area are shown in Figure 4-107.

Packet Page No. 591
Tri-City 4-266
Local Hazard Mitigation Plan Update
March 2024
Figure 4-107 Tri-City Planning Area– FEMA DFIRM Flood Zones Packet Page No. 592
Tri-City 4-267
Local Hazard Mitigation Plan Update
March 2024
Table 4-73 details the DFIRM mapped flood zones located within the Planning Area.

Table 4-73 Tri-City Planning Area– DFIRM Detailed Flood Zones Flood Zone Description Flood Zone
Present in
Planning Area
A 1% annual chance flooding: No base flood elevations provided. Mandatory flood insurance purchase requirements and floodplain management standards apply.

X
AE Regulatory
Floodway
1% annual chance flood: Regulatory floodway; Base flood elevations provided X AE 1% annual chance flooding: Base flood elevations provided. Mandatory flood insurance purchase requirements and floodplain management standards apply.

X
AH Areas subject to inundation by 1-percent-annual-chance shallow flooding (usually areas of ponding) where average depths are between one and three feet. Base Flood Elevations (BFEs) derived from detailed hydraulic analyses are shown in this zone. Mandatory flood insurance purchase requirements and floodplain management standards apply.

X
AO Areas subject to inundation by 1-percent-annual-chance shallow flooding (usually sheet flow on sloping terrain) where average depths are between one and three feet. Average flood depths derived from detailed hydraulic analyses are shown in this zone. Mandatory flood insurance purchase requirements and floodplain management standards apply.

X
VE Coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.

X
Shaded X 0.2% annual chance flooding: The areas between the limits of the 1% annual chance flood and the 0.2-percent-annual-chance (or 500-year) flood. Flood insurance is not mandatory but is available.

X
X Protected by
Levee
Areas protected by levees from 1% annual chance flood event. Levee protection places these areas in the 0.2% annual chance flood zone. Flood insurance is not mandatory but is available.

X
D Areas with possible but undetermined flood hazards. No flood hazard analysis has been conducted. Flood insurance rates are commensurate with the uncertainty of the flood risk.

X
X (unshaded) No flood hazard X
Source: FEMA
Flood extents are usually measured in depths of flooding, aerial extent of the floodplain, as well as flood zones that a location falls in (i.e., 1% or 0.2% annual chance flood). Expected flood depths in the Tri-City Planning Area vary and are not well defined. Flood durations in the Planning Area tend to be short to medium term, or until either the storm drainage system can catch up or flood waters move downstream.

Aerial flood extent from the FEMA DFIRMs is shown on Table 4-74.

Packet Page No. 593
Tri-City 4-268
Local Hazard Mitigation Plan Update
March 2024
Table 4-74 Tri-City Planning Area – Geographical DFIRM Flood Extents Jurisdiction
/Flood Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
1% Annual
Chance Flood
Hazard
16,440 20.27% 809 1.74% 15,631 45.36%

0.2% Annual
Chance Flood
Hazard
3,359 4.14% 2,790 5.98% 569 1.65%
Other Areas 61,290 75.58% 43,029 92.28% 18,261 52.99%
Fremont
Total
81,089 100.00% 46,628 100.00% 34,462 100.00%
Newark
1% Annual
Chance Flood
Hazard
4,712 32.08% 687 7.20% 4,025 78.14%

0.2% Annual
Chance Flood
Hazard
2,771 18.86% 2,452 25.71% 319 6.18%
Other Areas 7,205 49.06% 6,398 67.08% 807 15.67%
Newark Total 14,688 100.00% 9,537 100.00% 5,151 100.00% Union City
1% Annual
Chance Flood
Hazard
926 5.55% 223 2.39% 703 9.59%

0.2% Annual
Chance Flood
Hazard
65 0.39% 35 0.38% 29 0.40%
Other Areas 15,678 94.06% 9,083 97.23% 6,595 90.01%
Union City
Total
16,668 100.00% 9,341 100.00% 7,327 100.00%
Alameda County Water District
1% Annual
Chance Flood
Hazard
29,393 27.52% 1,808 2.83% 27,585 64.39%

0.2% Annual
Chance Flood
Hazard
6,195 5.80% 5,278 8.25% 918 2.14%
Other Areas 71,222 66.68% 56,885 88.92% 14,337 33.47%
Alameda
County Water
District Total
106,810 100.00% 63,970 100.00% 42,840 100.00%
Packet Page No. 594
Tri-City 4-269
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction
/Flood Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Union Sanitary District
1% Annual
Chance Flood
Hazard
3,905 5.04% 1,089 1.72% 2,815 19.88%

0.2% Annual
Chance Flood
Hazard
6,114 7.89% 5,257 8.30% 857 6.05%
Other Areas 67,484 87.07% 56,997 89.98% 10,486 74.06%
Union
Sanitary
District Total
77,502 100.00% 63,344 100.00% 14,159 100.00%
Source: FEMA 12/21/2018 DFIRM
CA DWR Floodplain Mapping
FEMA DFIRMs are just one measure of flood risk in a community. Also to be considered when evaluating the flood risks in the Tri-City Planning Area are various floodplain maps developed by Cal DWR for various areas throughout California.

DWR Best Available Maps
The FEMA regulatory maps provide just one perspective on flood risks in the Tri-City Planning Area.

Senate Bill 5 (SB 5), enacted in 2007, authorized the California DWR to develop the Best Available Maps (BAM) displaying 100- and 200-year floodplains originally for areas located within the Sacramento-San Joaquin (SAC-SJ) Valley watershed. DWR has expanded the BAM to cover all counties in the State and to include 500-year floodplains.

Different than the FEMA DFIRMs which have been prepared to support the NFIP and determining the need for flood insurance, the BAMs are provided for informational purposes and are intended to reflect current 100- and 500-year (0.2%) event risks using the best available data. The 100-year floodplain limits on the BAM are a composite of multiple 100-year floodplain mapping sources. It is intended to show all currently identified areas at risk for a 100-year flood event, including FEMA’s 100-year floodplains. The BAM maps are comprised of different engineering studies performed by FEMA, Corps, and DWR for assessment of potential 100- and 500-year floodplain areas. These studies are used for different planning and/or regulatory applications. They are for the same flood frequency; however, they may use varied analytical and quality control criteria depending on the study type requirements.

The value in the BAMs is that they provide a bigger picture view of potential flood risk to the Planning Area than that provided in the FEMA DFIRMs. This provides the community and residents with an additional tool for understanding potential flood hazards not currently mapped as a regulated floodplain.

Improved awareness of flood risk can reduce exposure to flooding for new structures and promote increased protection for existing development. Informed land use planning will also assist in identifying levee maintenance needs and levels of protection. By including the FEMA 100-year floodplain, it also supports identification of the need and requirement for flood insurance.

Packet Page No. 595
Tri-City 4-270
Local Hazard Mitigation Plan Update
March 2024
These BAM floodplain maps for Planning Area can be seen in Figure 4-108.

Figure 4-108 Tri-City Planning Area – Best Available Map Source: California DWR, map created 6/13/2023
Legend explanation: Blue - FEMA 100-Year, Orange – Local 100-Year (developed from local agencies), Red – DWR 100-year (Awareness floodplains identify the 100-year flood hazard areas using approximate assessment procedures.), Pink – USACE 100- Year (2002 Sac and San Joaquin River Basins Comp Study), Yellow – USACE 200-Year (2002 Sac and San Joaquin River Basins Comp Study), Tan – FEMA 500-Year, Grey – Local 500-Year (developed from local agencies), Purple – USACE 500-Year (2002 Sac and San Joaquin River Basins Comp Study).

Past Occurrences
Disaster Declaration History
There have been 19 state and 19 federal disaster declarations due to flooding in Alameda County as shown in Table 4-75.

Packet Page No. 596
Tri-City 4-271
Local Hazard Mitigation Plan Update
March 2024
Table 4-75 Alameda County Disaster Declarations 1950-2023 from Flood Disaster Type State Declarations Federal Declarations
Count Years Count Years
Flood (including heavy
rains and storms)
19 1950, 1955, 1957, 1958 (twice),
1962, 1963, 1970, 1982, 1983
(twice), 1986, 1995 (twice),
1997, 1998, 2008, 2017 (twice)
20 1955, 1958, 1962 (twice), 1970,
1982, 1983, 1986, 1995 (twice),
1997, 1998, 2005, 2006, 2017
(three), 2023 (three)
Source: Cal OES, FEMA
The Planning Team noted that winter of 2022/2023 multiple atmospheric rivers affected the State and the Planning Area. This was also the case in the winter of 2023/2024. More information on these events can be found in the respective jurisdictional annexes to this LHMP Update.

NCDC Events
The NCDC tracks flood events for each County since 1996. These are shown on Table 4-76 for Alameda County.

Table 4-76 Alameda County NCDC Flooding Events 1/1/1996-12/31/2022* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Flash Flood 12 0 0 0 0 $100,000 $0
Flood 43 0 0 0 0 $44,325,500 $0
Heavy Rain 5 0 2 0 1 $60,000 $30,000
Total 60 0 2 0 1 $44,485,500 $30,000
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of Alameda County.

Planning Committee Events
Discussions of Planning Committee events for each jurisdiction can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrences
1% Annual Chance Flood
Occasional—This is the flood that has a 1- percent chance of being equaled or exceeded in the Tri-City Planning Area in any given year. Thus, the 1% annual chance flood could occur more than once in a relatively short period of time.

0.2% Annual Chance Flood
Unlikely—The flood has a 0.2 percent chance of being equaled or exceeded in the Tri-City Planning Area in any given year.

Packet Page No. 597
Tri-City 4-272
Local Hazard Mitigation Plan Update
March 2024
Climate Change and Flood
The 2016/2017/2022 LHMPs noted that the frequency and severity of coastal flooding is expected to gradually increase as sea level gradually rises. For riverine flooding, flood risk in a given location often increases with time because increasing development within the watershed increases runoff, and because development and fill within floodplains or sedimentation in a river channel may increase flood elevations.

Flood risk at a given location may also decrease over time if flood control structures such as levees or upstream dams for flood control are constructed or improved. Climate change and its effect on flooding is discussed using three sources:
➢ 2021 CAS
➢ Cal-Adapt
➢ National Center for Atmospheric Research
California Climate Adaptation Strategy
According to the CAS, climate change may affect flooding in California and the Planning Area. While average annual rainfall may increase or decrease slightly, the intensity of individual rainfall events is likely to increase during the 21st century. It is possible that average soil moisture and runoff could decline, however, due to increasing temperature, evapotranspiration rates, and spacing between rainfall events.

Reduced snowpack and increased number of intense rainfall events are likely to put additional pressure on water infrastructure which could increase the chance of flooding associated with breaches or failures of flood control structures such as levees and dams.

Cal Adapt
Cal Adapt future precipitation projections were shown in Figure 4-30 in Section 4.3.4. These could affect flooding in the Tri-City Planning Area.

National Center for Atmospheric Research
Also, according to the National Center for Atmospheric Research in Boulder, Colorado, atmospheric rivers are likely to grow more intense in coming decades, as climate changes warms the atmosphere enabling it to hold more water.

Vulnerability Assessment
Vulnerability—High
Historically, the Tri-City Planning Area has always been at risk to flooding during the rainy season from November through April. The Alameda County FIS noted that floods result from prolonged heavy rainfall and are characterized by high peak flows of moderate duration and by a large volume of runoff. Flooding is more severe when antecedent rainfall has resulted in saturated ground conditions. Several areas of the Planning Area are subject to flooding by the overtopping of rivers and creeks, levee failures, and the failure of urban drainage systems that cannot accommodate large volumes of water during severe rainstorms. In addition to the major rivers, there are many streams, channels, canals, and creeks that serve the drainage Packet Page No. 598
Tri-City 4-273
Local Hazard Mitigation Plan Update
March 2024
needs of the Planning Area and communities surrounding it. There is significant threat of flooding in areas of the Planning Area from several of these streams. These streams can be prone to rapid flooding with little notice.

Much of the Planning Area is at some measure of vulnerability to floods. An assessment of a community’s vulnerability to flood begins with an understanding of local exposure to flood. This is included int the discussion of the Planning Area’s Assets at Risk to this hazard.

Assets at Risk
The Planning Area has mapped FEMA flood hazard areas. GIS was used to determine the possible impacts of flooding within the Planning Area and how the risk varies across the Tri-City Planning Area. The following methodology was utilized in determining assets at risk to the 1% annual chance flood event and

0.2% annual chance flood event.

Methodology (Parcel and Structures)
2023 Alameda County Parcel/Assessor Data was used as the basis for the Tri-City inventory of parcels, values, and acres. Alameda County has a FEMA effective DFIRM dated 12/21/2018, which was obtained from FEMA’s National Flood Hazard Layer to perform the flood analysis. In some cases, there are parcels in multiple flood zones, such as Zone A, Zone X, or Shaded X. GIS was used to create a centroid, or point representing the center of the parcel polygon. DFIRM flood data was then overlaid on the parcel layer. For the purposes of this analysis, the flood zone that intersected a parcel centroid was assigned the flood zone for the entire parcel. The parcels and associated values were segregated and analyzed in this fashion to determine parcels and values at risk to the flood hazard for the Tri-City Planning Area.

Methodology (Loss Estimate)
The loss estimate for flood is based on the total of improved and contents value. Improved parcels include those with improved structure values identified in the Alameda County Assessor’s database. Only improved parcels and the value of their structure improvements were included in the flood loss analysis.

The value of land is not included in the loss estimates as generally the land is not at loss to floods, just the value of improvements and structure contents. The land value is represented in the detailed flood tables, but is primarily present to show the value of the land associated with each flood zone.

The land use categories for the Tri-City Planning Area (derived from general plan land use descriptions) were used to develop estimated content replacement values (CRV) that are potentially at loss from hazards, using FEMA Hazus methodologies as previously described in Section 4.2. The CRVs were added to the improved parcel values.

Once the potential value of affected parcels was calculated, a damage factor was applied to obtain loss estimates by flood zone. When a flood occurs, seldom does the event cause total loss of an area or building.

Potential losses from flooding are related to a variety of factors including flood depth, flood velocity, building type, and construction. The percentage of damage is primarily related to the flood depth. FEMA’s flood benefit/cost module uses a simplified approach to model flood damage based on building type and flood depth. The values at risk in the flood analysis tables were refined by applying an average damage Packet Page No. 599
Tri-City 4-274
Local Hazard Mitigation Plan Update
March 2024
estimation of 20% of the total building value. The 20% damage estimate utilized FEMA’s Flood Building Loss Table based on an assumed average flood depth of 2 feet. The end result of the flood hazard analysis is an inventory of the numbers, types, and values of parcels subject to the flood hazard.

People and Populations
All people and populations located in the 1% and 0.2% annual chance floodplains are at some risk to flooding. Certain vulnerable populations located within areas prone to flooding may be at increased risk to this hazard, especially during a large event with minimal advance notice. These vulnerable populations include: the unhoused, those with limited mobility, and those that lack the resources to leave the area.

Tri-City Planning Area residents that live in the 1% and 0.2% annual chance floodplains are often the most vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to the Planning Area’s residential population residing within these hazard areas, the DFIRM flood zones were overlayed on the parcel layer and linked to the Assessor Data. Those residential parcel centroids that intersect the flood zones were counted and multiplied by the 2020 Census Bureau average household factors for each jurisdiction. This is shown in Table 4-77.

Table 4-77 Tri-City Planning Area – Improved Residential Parcels and Population by FEMA DFIRM Flood Zone by Jurisdiction
Jurisdiction
1% Annual Chance 0.2% Annual Chance
Improved
Residential
Parcels
Population at
Risk
Improved
Residential
Parcels
Population at
Risk
City of Fremont 280 837 3,667 10,964
City of Newark 258 857 2,050 6,806
City of Union City 356 1,200 252 849
Source: FEMA DFIRM 12/21/2018, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023, 2020 US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City (3.37).

These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums as well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

Structures
Certain structures in the Tri-City Planning Area are at risk of DFIRM flooding and primarily include those structures located within the 1% and 0.2% annual chance floodplains. GIS was used to determine the possible impacts of flooding on parcels and structures within the Planning Area. Table 4-78 shows parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), estimated content replacement values, and total values in the Planning area. This is shown for the 1% and 0.2% annual chance flood zones, as well as for those properties that fall outside of the mapped FEMA DFIRM flood zones.

Packet Page No. 600
Tri-City 4-275
Local Hazard Mitigation Plan Update
March 2024
Table 4-78 Tri-City Planning Area – Count and Value of Parcels (and Structures) in FEMA DFIRM 1% and 0.2% Annual Chance Flood Zones by Jurisdiction Jurisdiction
/ Flood
Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont
1% Annual
Chance Flood
Hazard
934 406 $414,526,782 $748,428,979 $859,718,876 $2,022,674,637

0.2% Annual
Chance Flood
Hazard
4,684 4,161 $1,990,481,907 $3,064,142,751 $2,484,150,767 $7,538,775,425 Other Areas 78,629 73,564 $20,306,306,743 $41,644,070,893 $24,851,695,009 $86,802,072,645 Fremont
Total
84,247 78,131 $22,711,315,432 $45,456,642,623 $28,195,564,652 $96,363,522,707 Newark
1% Annual
Chance Flood
Hazard
850 285 $409,592,873 $591,325,221 $681,200,593 $1,682,118,687

0.2% Annual
Chance Flood
Hazard
2,301 2,080 $561,495,519 $1,263,386,061 $821,589,229 $2,646,470,809 Other Areas 14,007 13,021 $3,218,815,821 $6,369,551,848 $3,989,939,277 $13,578,306,946 Newark
Total
17,158 15,386 $4,189,904,213 $8,224,263,130 $5,492,729,099 $17,906,896,442 Union City
1% Annual
Chance Flood
Hazard
498 386 $174,623,202 $389,391,236 $303,384,322 $867,398,760

0.2% Annual
Chance Flood
Hazard
273 255 $74,226,171 $151,700,109 $78,185,120 $304,111,400 Other Areas 17,831 16,848 $3,747,943,216 $8,120,663,111 $5,049,837,749 $16,918,444,076 Union City
Total
18,602 17,489 $3,996,792,589 $8,661,754,456 $5,431,407,191 $18,089,954,236 Alameda County Water District (Service Territory)
1% Annual
Chance Flood
Hazard
2,428 1,129 $1,061,497,211 $1,796,381,645 $1,915,191,863 $4,773,070,719

0.2% Annual
Chance Flood
Hazard
7,269 6,498 $2,626,264,042 $4,479,234,478 $3,383,930,673 $10,489,429,193 Other Areas 110,180 103,382 $27,213,412,011 $56,142,706,107 $33,945,020,501 $117,301,138,619 Packet Page No. 601
Tri-City 4-276
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction
/ Flood
Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Alameda
County
Water
District
(Service
Territory)
Total
119,877 111,009 $30,901,173,264 $62,418,322,230 $39,244,143,037 $132,563,638,531 Union Sanitary District (Service Territory)
1% Annual
Chance Flood
Hazard
1,992 1,070 $947,347,736 $1,738,439,645 $1,857,886,250 $4,543,673,631

0.2% Annual
Chance Flood
Hazard
7,254 6,494 $2,615,013,887 $4,477,575,346 $3,383,035,205 $10,475,624,438 Other Areas 110,114 103,395 $27,182,838,969 $56,086,909,305 $33,861,914,641 $117,131,662,915 Union
Sanitary
District
(Service
Territory)
Total
119,360 110,959 $30,745,200,592 $62,302,924,296 $39,102,836,096 $132,150,960,984 Source: FEMA 12/21/2018 DFIRM, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone **This parcel count only includes those parcels in the 0.2% annual chance flood zone, exclusive of the 1% annual chance flood zone.

The 0.2% annual chance flood, in actuality, also includes all parcels in the 1% annual chance flood zone.

Table 4-79 shows Planning Area loss estimates and improved values at risk by FEMA 1% and 0.2% annual chance flood zones. More detailed tables and discussions can be found in each jurisdiction’s respective annex to this Base Plan.

Table 4-79 Tri-City Planning Area – FEMA DFIRM Flood Loss Estimates by Jurisdiction Jurisdiction/
Flood Zone
Total
Parcel
Count
Improved
Parcel
Count
Improved
Structure
Value
Estimated
Contents
Value
Total Value Loss Estimate Loss
Ratio
Fremont
1% Annual
Chance Flood
Hazard
934 406 $748,428,979 $859,718,876 $1,608,147,855 $321,629,571 0.47%

0.2% Annual
Chance Flood
Hazard
4,684 4,161 $3,064,142,751 $2,484,150,767 $5,548,293,518 $1,109,658,704 1.63% Other Areas 78,629 73,564 $41,644,070,893 $24,851,695,009 $66,495,765,902 $13,299,153,180 19.51% Fremont
Total
84,247 78,131 $45,456,642,623 $28,195,564,652 $73,652,207,275 $14,730,441,455 21.61% Packet Page No. 602
Tri-City 4-277
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction/
Flood Zone
Total
Parcel
Count
Improved
Parcel
Count
Improved
Structure
Value
Estimated
Contents
Value
Total Value Loss Estimate Loss
Ratio
Newark
1% Annual
Chance Flood
Hazard
850 285 $591,325,221 $681,200,593 $1,272,525,814 $254,505,163 2.05%

0.2% Annual
Chance Flood
Hazard
2,301 2,080 $1,263,386,061 $821,589,229 $2,084,975,290 $416,995,058 3.36% Other Areas 14,007 13,021 $6,369,551,848 $3,989,939,277 $10,359,491,125 $2,071,898,225 16.69% Newark
Total
17,158 15,386 $8,224,263,130 $5,492,729,099 $13,716,992,229 $2,743,398,446 22.10% Union City
1% Annual
Chance Flood
Hazard
498 386 $389,391,236 $303,384,322 $692,775,558 $138,555,112 1.09%

0.2% Annual
Chance Flood
Hazard
273 255 $151,700,109 $78,185,120 $229,885,229 $45,977,046 0.36% Other Areas 17,831 16,848 $8,120,663,111 $5,049,837,749 $13,170,500,860 $2,634,100,172 20.81% Union City
Total
18,602 17,489 $8,661,754,456 $5,431,407,191 $14,093,161,647 $2,818,632,329 22.27% Alameda County Water District (Service Territory)
1% Annual
Chance Flood
Hazard
2,428 1,129 $1,796,381,645 $1,915,191,863 $3,711,573,508 $742,314,702 0.80%

0.2% Annual
Chance Flood
Hazard
7,269 6,498 $4,479,234,478 $3,383,930,673 $7,863,165,151 $1,572,633,030 1.69% Other Areas 110,180 103,382 $56,142,706,107 $33,945,020,501 $90,087,726,608 $18,017,545,322 19.31% Alameda
County
Water
District
(Service
Territory)
Total
119,877 111,009 $62,418,322,230 $39,244,143,037 $101,662,465,267 $20,332,493,053 21.79% Union Sanitary District (Service Territory)
1% Annual
Chance Flood
Hazard
1,992 1,070 $1,738,439,645 $1,857,886,250 $3,596,325,895 $719,265,179 0.77%

0.2% Annual
Chance Flood
Hazard
7,254 6,494 $4,477,575,346 $3,383,035,205 $7,860,610,551 $1,572,122,110 1.69% Other Areas 110,114 103,395 $56,086,909,305 $33,861,914,641 $89,948,823,946 $17,989,764,789 19.33% Packet Page No. 603
Tri-City 4-278
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction/
Flood Zone
Total
Parcel
Count
Improved
Parcel
Count
Improved
Structure
Value
Estimated
Contents
Value
Total Value Loss Estimate Loss
Ratio
Union
Sanitary
District
(Service
Territory)
Total
119,360 110,959 $62,302,924,296 $39,102,836,096 $101,405,760,392 $20,281,152,078 21.80% Source: FEMA 12/21/2018 DFIRM, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone **This parcel count only includes those parcels in the 0.2% annual chance flood zone, exclusive of the 1% annual chance flood zone.

The 0.2% annual chance flood, in actuality, also includes all parcels in the 1% annual chance flood zone.

Insurance Coverage, Claims Paid, and Repetitive Losses
Standard property insurance does not include flood coverage because of the relatively high risk. The NFIP provides flood insurance to residents in those communities that participate in the NFIP. Federal financial assistance requires the purchase of flood for structures located within a 100-year floodplain – a requirement that affects nearly all mortgages financed through commercial lending institutions. Flood insurance is also recommended for all structures protected by levees, even if not mapped within a floodplain.

Each City in the Planning Area participates in the National Flood Insurance Program. The two Districts are not eligible jurisdictions for purposes of the NFIP. A summary of insurance coverages in each city can be found in Table 4-80. More details can be found in each respective city’s annex to this Base Plan.

Table 4-80 Tri-City Planning Area - Percentage of Policy Holders to Improved Parcels in the 1% Annual Chance Floodplain by City Jurisdictions
Jurisdiction Improved Parcels in
SFHA (1% Annual
Chance) Floodplain*
Insurance Policies
in the SFHA (1%
Annual Chance)
Floodplain
Percentage of 1%
Annual Chance
Floodplain Parcels
Currently Insured
City of Fremont 406 86 21.2%
City of Newark 285 13 4.6%
City of Union City 386 35 9.1%
Source: FEMA 12/21/2018 DFIRM, FEMA CIS
Critical Facilities and Infrastructure, and Community Lifelines Flooding presents a threat to critical facilities and infrastructure, and community lifelines. Critical infrastructure plays an immensely important role in our communities. As previously noted, communities rely on roads, rail corridors, and related biking and pedestrian routes for transportation, and on water infrastructure for drinking water, wastewater service, and draining streets of rainwater. Damage to any one of these systems can threaten public safety, wreak havoc on daily life, impact properties far from flood zones, and result in economic impacts that cascade throughout California. The following GIS analysis Packet Page No. 604
Tri-City 4-279
Local Hazard Mitigation Plan Update
March 2024
identifies critical facilities and infrastructure at risk to 1% and 0.2% annual chance flooding, followed by a discussion on vulnerability of community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
1% and 0.2% annual chance flooding presents a threat to life and property, including community lifelines in the Planning Area. Community lifelines that would be vulnerable to flooding include:
➢ Safety and Security – Search and rescue and swiftwater teams may be called on to perform riskier duties during times of flooding. Police, Fire, EMS, and Public Works personnel are often called on to respond during flood emergencies. During large events, these services may become stretched. ➢ Food, Hydration, and Shelter - Public health can also be at risk from flooding. Floodwater is often contaminated with sewage, which can lead to illness and affect clean drinking water. ➢ Health and Medical – Loss of life and injuries can occur during significant flood events, Flooding may complicate the ability to transport the injured possibly requiring rerouting of injured to other facilities.
➢ Energy – Floods can cause power grid issues and lead to power outages. During extreme flood events gas lines may break or otherwise be damaged from erosion and debris in floodwaters. ➢ Communications – Communication infrastructure can be inundated by a flood event causing damage and disruption in service. As well an influx of service calls to dispatch centers for reporting of flooding, power outages, or other issues can occur. Messaging systems need to be deployed during these times to let the public know about lane and road closures, washouts, debris on roads, and requirements for evacuations or sheltering.
➢ Transportation – Transport networks can be affected, such as flood damage to bridges, railways and roads. This can cause lane and road closures. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents and impact evacuation routes. Life safety can also be an issue on flooded roads.
➢ Hazardous Material – Hazardous material facilities can be affected by flooding. Releases during these times can be comingles with flood waters, contaminate drinking water, as well as create additional exposures to the environment.
➢ Water Systems – Floods can affect the ability for water and wastewater systems to operate, since many are located near flood zones.

Generally, even major flood events are temporary events with flood waters receding back to pre-storm levels at the conclusion of the storm. However, depending on the location, duration, and magnitude and severity of any given flood event, some of these community lifelines may be overwhelmed in the short term.

Natural, Historic, and Cultural Resources
Large flood events can affect natural, historic, and cultural resources. There are a number of ways floodwaters can impact natural resources and the environment: Wildlife habitats can be destroyed by Packet Page No. 605
Tri-City 4-280
Local Hazard Mitigation Plan Update
March 2024
floodwaters. Contaminated floodwater can pollute rivers and habitats. Silt and sediment can destroy natural areas. Riverbanks and natural levées can be eliminated as rivers reach bankfull capacity. Rivers can be widened, and deposition can increase downstream. Trees can be uprooted by high-velocity water flow.

Plants that survive the initial flood may die due to being inundated with water. Historic and cultural resources may also be affected. Generally, the impacts are associated with damage to structures within the flooded areas, but other cultural resources such as those associated with Native Americans and old tribal areas can also be disturbed, damaged and lost during extreme flood events. Any of these resources that fall in the flood zones would be vulnerable.

Economic Assets and Community Activities of Value
Major flood events could affect any economic asset that lies in the floodplain and can have long lasting effects. This could cause those businesses and economic assets within these areas to close or relocate. This could cause temporary or permanent loss of sales tax revenue. These events can also affect those economic assets outside of the floodplain, at least in the short term until the Planning Area has sufficiently recovered.

Impacts from Flood: 1% and 0.2% Annual Chance Flood
Floods are among the costliest natural disasters in terms of human hardship and economic loss nationwide.

Large flood events, including those associated with 1% and 0.2% annual chance floods, can cause substantial damage to structures, landscapes, and utilities as well as life safety issues. People may be swept away in floodwaters, causing injuries or deaths. Floods can be extremely dangerous, and even six inches of moving water can knock over a person given a strong current. During a flood, people can also suffer heart attacks or electrocution due to electrical equipment short outs. Direct impacts, such as drowning, can be limited with adequate warning and public education about what to do during floods.

Floodwaters can transport large objects downstream which can damage or remove stationary structures.

Structures can be damaged directly from floodwaters and can also be damaged from trees falling as a result of water-saturated soils. Ground saturation can result in instability, collapse, or other damage. Objects can also be buried or destroyed through sediment deposition. Floodwaters can also break utility lines and interrupt services causing power outages. The interruption of power causes major problems and can result in the closure of governmental offices and community businesses. Public schools may also be required to close or be placed on a delayed start schedule. Roads can be damaged and closed, causing safety and evacuation issues.

Standing water can cause damage to crops, roads, foundations, and electrical circuits. Other problems connected with flooding and stormwater runoff include erosion, sedimentation, degradation of water quality, loss of environmental resources, and economic impacts.

Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure, utilities, and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Significant economic impact (jobs, sales, tax revenue) to the community; and ➢ Negative impact on commercial and residential property values Packet Page No. 606
Tri-City 4-281
Local Hazard Mitigation Plan Update
March 2024
Health Hazards from Flooding
According to FEMA, certain health hazards are also common to flood events. While such problems are often not reported, three general types of health hazards accompany floods. The first comes from the water itself. Floodwaters carry anything that was on the ground that the upstream runoff picked up, including dirt, oil, animal waste, and lawn, farm, and industrial chemicals. Pastures and areas where cattle and other livestock are kept or their wastes are stored can contribute polluted waters to the receiving streams.

Floodwaters also saturate the ground, which leads to infiltration into sanitary sewer lines. When wastewater treatment plants are flooded, there is nowhere for the sewage to flow. Infiltration and lack of treatment can lead to overloaded sewer lines that can back up into low-lying areas and homes. Even when it is diluted by flood waters, raw sewage can be a breeding ground for bacteria such as e. coli and other disease-causing agents.

The second type of health problem arises after most of the water has gone. Stagnant pools can become breeding grounds for mosquitoes, and wet areas of a building that have not been properly cleaned breed mold and mildew. A building that is not thoroughly cleaned becomes a health hazard, especially for small children and the elderly.

Another health hazard occurs when heating ducts in a forced air system are not properly cleaned after inundation. When the furnace or air conditioner is turned on, the sediments left in the ducts are circulated throughout the building and breathed in by the occupants. If a water system loses pressure, a boil order may be issued to protect people and animals from contaminated water.

The third problem is the long-term psychological impact of having been through a flood and seeing one’s home damaged and irreplaceable keepsakes destroyed. The cost and labor needed to repair a flood-damaged structure puts a severe strain on people, especially the unprepared and uninsured. There is also a long-term problem for those who know that their homes can be flooded again. The resulting stress on floodplain residents takes its toll in the form of aggravated physical and mental health problems.

Future Development
Flooding is taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.12. Flood: Localized/Stormwater
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Packet Page No. 607
Tri-City 4-282
Local Hazard Mitigation Plan Update
March 2024
Hazard/Problem Description
Localized, stormwater flooding also occurs throughout the Tri-City Planning Area, primarily during the rainy season from November through April. Prolonged heavy rainfall contributes to a large volume of runoff resulting in high peak flows of moderate duration. Flooding is more severe when previous rainfall has created saturated ground conditions. Storm drain culverts and drainage systems have a finite capacity.

When rainfall exceeds this capacity, or the system is clogged, water accumulates in areas until it reaches a level of overland release. This type of flooding may occur when intense storms occur over areas of developed areas.

The Planning Area is traversed by several streams and drainages. The development that has occurred during the past has accentuated existing drainage problems and has increased the potential for localized flooding.

Continued construction of new buildings increases the area of impermeable surface and thus the amount of storm water that flows through the Planning Area’s storm drain systems.

Location and Extent
In the Tri-City Planning Area, numerous locations and roads throughout not included in the FEMA 1% and

0.2% annual chance floodplains are subject to flooding in heavy rains. These are discussed in each jurisdictional annex to this LHMP Update. In addition to flooding, damage to these areas during heavy storms includes pavement deterioration, washouts, landslides, debris areas, erosion, and downed trees. The frequency and type of damage or flooding that occurs varies from year to year, depending on the quantity of precipitation and runoff.

Vulnerable areas are mostly adjacent to creeks that flow through the Tri-City Planning Area; although other areas can be affected where water is conveyed and collected. There is no established scientific scale or measurement system for localized flooding. Localized flooding is generally measured by depth of flooding, volume of water, runoff velocity, and the area affected. Localized flooding often happens quickly and has a short speed of onset and short duration, with flood waters receding when the storm drainage system can catch up or when the water is absorbed into the ground.

Past Occurrences
Disaster Declaration History
There have been 19 state and 19 federal disaster declarations due to flooding (and localized flooding and heavy rains and storms) in Alameda County as shown in Table 4-81. These events caused localized flooding in the Tri-City Planning Area.

Packet Page No. 608
Tri-City 4-283
Local Hazard Mitigation Plan Update
March 2024
Table 4-81 Alameda County Disaster Declarations 1950-2023 from Flood Disaster Type State Declarations Federal Declarations
Count Years Count Years
Flood (including heavy
rains and storms)
19 1950, 1955, 1957, 1958 (twice),
1962, 1963, 1970, 1982, 1983
(twice), 1986, 1995 (twice),
1997, 1998, 2008, 2017 (twice)
19 1955, 1958, 1962 (twice), 1970,
1982, 1983, 1986, 1995 (twice),
1997, 1998, 2005, 2006, 2017
(three), 2023 (twice)
Source: Cal OES, FEMA
NCDC Events
The NCDC does not track localized flooding.

Planning Committee
The Planning Committee noted major events that occurred in 2017 and 2023 associated with the disaster declarations above. More detail on each jurisdictions previous events can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrences
Highly Likely—Natural drainage systems located throughout the Tri-City Planning Area have a finite capacity to convey water. Likewise, storm drainage systems have a finite capacity generally based on the design criteria. When rainfall exceeds the capacity of natural and storm drainage systems or systems clog, water accumulates until it reaches a level of overland release. Due to aging and often undersized infrastructure, this type of flooding will continue to occur annually during heavy rains.

Climate Change and Localized Flood
Cal Adapt future precipitation projections were shown in Figure 4-30 in Section 4.3.4. While average annual rainfall may decrease slightly, the intensity of individual rainfall events is likely to increase during the 21st century, increasing the likelihood of overwhelming stormwater systems built to historical rainfall averages. This makes localized flooding more likely.

Vulnerability Assessment
Vulnerability—Medium
Flood vulnerability and their impacts vary by location and severity of any given flood event and will likely only affect certain areas of the Planning Area during specific times. Based on the risk assessment, it is evident that floods will continue to have potentially significant economic impacts to certain areas of the Tri-City Planning Area. However, while flooding can cause significant impacts depending on the duration and volume of precipitation and the drainage in any given area, many of the floods in the Planning Area are minor, localized flood events that are more of a nuisance than a disaster.

Packet Page No. 609
Tri-City 4-284
Local Hazard Mitigation Plan Update
March 2024
Many areas of the Planning Area are at some measure of vulnerability to localized flooding. An assessment of a community’s vulnerability to localized flood begins with an understanding of local exposure to localized flooding. This is included in the discussion of the Planning Area’s Assets at Risk to this hazard.

Assets at Risk
Assets at risk from localized flood include people and populations; structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

People and Populations
People and populations are traditionally not highly vulnerable to localized flooding, but their structures and contents can be at risk. Localized flooding may also cause transportation issues as roads and lanes are impacted or closed and affect the ability for people to travel throughout the Planning Area.

Structures
Structures in areas with localized flooding can be affected if floodwaters intrude into the structure.

Structures in low lying areas, or those with basements can be at greater risk. Buildings with older foundations that are prone to water intrusion are also at greater risk. Once water finds its way into a structure, it tends to continue to do so until the path that brings water into a structure is mitigated.

Critical Facilities and Infrastructure, and Community Lifelines Localized flooding, while often more of a nuisance, can cause damage to critical facilities and infrastructure during a heavy rain and storm event. Any facility that experiences localized flooding can be impacted.

Utilities and other critical infrastructure can all be affected, causing interruptions in service until repairs can be made. For example, water and wastewater systems can be vulnerable to heavy rains and flood events. Rainfall creates a high water table, surging streams and creeks, and saturates soil. Infiltration of stormwater into water and wastewater systems may occur and presents a threat to public health and safety, when the infrastructure is no longer able to meet operational needs and local demands.

Due to the relatively minor nature of localized flooding, community lifelines are unlikely to be overwhelmed. There may be minor vulnerabilities to the following:
➢ Safety and Security – Law Enforcement/Security, Fire Service, and Community Safety officials may be needed to close roads and redirect traffic during localized flood events. These agencies may also experience flooded roads when responding to emergencies. ➢ Communications – Unless directly affected by flooding, communication systems are not likely to be impacted. Warnings and Messaging may be required to reroute traffic away from localized flooding areas.
➢ Transportation – Highways, roads, and bridges may be temporarily blocked until localized floodwaters recede.
➢ Water Systems – Water and wastewater systems can be infiltrated during localized flooding events.

Stormwater drainage systems are often undersized and inadequate to convey the volume of flood waters.

Packet Page No. 610
Tri-City 4-285
Local Hazard Mitigation Plan Update
March 2024
Natural, Historic, and Cultural Resources
Natural resource assets may have some vulnerabilities to localized flood during major storm events, but can benefit from floodwaters, often by design. Many parks and green spaces are designed to take overflow water and release it into the underlying soils and natural areas. Wetlands areas in the Planning Area actually help reduce the risk of flooding, as they can absorb excess rainfall that would have to be drained away from impervious surfaces. Flooding can provide many benefits to the natural environment, including recharging wetlands and groundwater, increasing fish production, creating wildlife habitat, and rejuvenating soil fertility. These smaller localized flooding events often provide more benefits to the environment in comparison to negative impacts associated with large flood events. Historic and cultural resources may be at some measure of vulnerability if they are located in areas subject to repeated localized flooding.

Economic Assets and Community Activities of Value
Localized flooding occurs on an annual basis throughout the Tri-City Planning Area during storm events.

Most of these events have limited impacts and include those associated with localized flooding due to undersized drainage systems, affecting nearby roads, structures, and other nearby assets. Unless directly affected by localized flooding, these events are unlikely to affect the Planning Area’s key economic assets.

Community activities of value may have minor vulnerabilities if a localized flood event were to occur during the activity. This may cause the activity to be relocated, cancelled, or rescheduled.

Impacts from Localized Flood
Primary concerns associated with stormwater flooding include impacts to infrastructure that provides a means of ingress and egress throughout the community. Ground saturation can result in instability, collapse, or other damage to trees, structures, roadways and other critical infrastructure. Objects can also be buried or destroyed through sediment deposition. Floodwaters can break utility lines and interrupt services. Standing water can cause damage to crops, roads, and foundations. Other problems connected with flooding and stormwater runoff include erosion, sedimentation, degradation of water quality, losses of environmental resources, and certain health hazards.

Life safety issues from localized flooding would be more limited. The amount and type of damage or flooding that occurs varies from year to year and from storm to storm, depending on the quantity of precipitation and runoff. Localized flooding impacts may be exacerbated in the future due to the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development.

Impacts may be exacerbated in the future due to the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development.

More detail on each jurisdiction’s previous events can be found in their respective annexes to this LHMP Update.

Packet Page No. 611
Tri-City 4-286
Local Hazard Mitigation Plan Update
March 2024
Future Development
Localized flooding is taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.13. Landslide
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
Like its earthquake‐generating faults, California’s mountainous terrain is a consequence of dynamic geologic processes in operation as the North American Plate grinds past the Pacific Plate. According to the CGS, a landslide is a general term for a variety of mass-movement processes that generate a down-slope movement of mud, soil, rock, and/or vegetation. Landslides are classified into many different types based on form and type of movement. They range from slow‐moving rotational slumps and earth flows, which can slowly distress structures but are less threatening to personal safety, to fast‐moving rock avalanches and debris flows that are a serious threat to structures and have been responsible for most fatalities during landslide events. For the purposes of this LHMP Update, the term landslide includes mudslides, debris flows, and rockfalls that tend to occur suddenly; as well as hillside erosion, which is a similar process that tends to occur on smaller scales and more gradually but can exacerbate landslide events.

Landslides, debris flows and mudslides are closely related to flooding, as both processes are related to precipitation, runoff, and the saturation of ground by water. In addition, landslides, mud flows, and debris flows can occur on small, steep stream channels and are often mistaken for floods. However, landslide events may be much more destructive than floods because of their higher densities, high debris loads, and high velocities.

Natural conditions that contribute to landslide, mudslides, debris flows, hillside and streambank erosion, include the following:
➢ Degree of slope
➢ Water (heavy rain, river flows, or wave action)
➢ Unconsolidated soil or soft rock and sediments
➢ Lack of vegetation (no stabilizing root structure)
➢ Previous wildfires and other forest disturbances (discussed in Section 4.3.17) ➢ Road building, excavation, and grading
➢ Earthquake
The 2023 State of California Hazard Mitigation Plan noted that more than one third of California is mountainous terrain that generally trends parallel to the coast, forming a barrier that captures moisture from Packet Page No. 612
Tri-City 4-287
Local Hazard Mitigation Plan Update
March 2024
offshore storms originating in the Gulf of Alaska and Mexico. Steep topography, weak rocks, heavy winter rains, and occasional earthquakes all lead to slope failures more frequently than would otherwise occur under gravity alone. This is true in the sloped areas bordering the Planning Area where the topography is characterized by rolling hills and ridges.

Location and Extent
Landslides can be expected in areas with steep slopes and weak soils. It can also occur in areas where erosion has previously occurred. Both winter storms (precipitation-induced) and earthquake triggered landslides tend to occur in or near places that have experienced previous landslides. However, landslides may also occur in other locations over time.

Figure 4-109 shows the CGS areas at susceptible to deep seated landslides. The legend on Figure 4-109 shows the susceptibility scale (from 0-X with 0 being the least and X being the most susceptible) that the CGS uses to show the susceptibility of landslides. It is a primarily a combination of slope class and rock strength. Geographic extents of these classes for the Planning Area are shown on Table 4-82. According to the 2023 State Hazard Mitigation Plan, the susceptibility classes were further categorized into Very High (susceptibility class X) and High (susceptibility classes VII, VIII, & IX) for exposure analysis. The rest of the classes were not categorized. CGS mapping indicates that the eastern portions of the Planning Area and surrounding area are at high to very high susceptibility areas for landslides. This can be seen in the darker orange and red colors. The speed of onset of landslide is often short, especially in post-wildfire burn scar areas, but it can also take years for a slope to fail. Landslide duration is usually short, though digging out and repairing landslide areas can take some time.

Packet Page No. 613
Tri-City 4-288
Local Hazard Mitigation Plan Update
March 2024
Figure 4-109 Tri-City Planning Area – Susceptibility to Deep Seated Landslides Packet Page No. 614
Tri-City 4-289
Local Hazard Mitigation Plan Update
March 2024
Table 4-82 Tri-City Planning Area – Susceptibility to Deep Seated Landslides Geographical Extents by Class and Jurisdiction
Jurisdiction/
Susceptibility
to DeepSeated
Landslide
Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
0 62,158.14 81.8% 43,375.35 93.0% 18,782.79 64.0%
III 366.77 0.5% 55.77 0.1% 311.00 1.1%
IX 4,850.10 6.4% 868.98 1.9% 3,981.12 13.6%
V 1,915.73 2.5% 745.99 1.6% 1,169.74 4.0%
VI 376.85 0.5% 39.62 0.1% 337.22 1.1%
VII 2,091.28 2.8% 776.29 1.7% 1,314.98 4.5%
VIII 2,014.88 2.7% 520.81 1.1% 1,494.07 5.1%
X 2,195.42 2.9% 237.37 0.5% 1,958.06 6.7%
Fremont
Total
75,969.16 100.0% 46,620.18 100.0% 29,348.98 100.0%
Newark
0 13,256.48 99.1% 9,489.94 99.7% 3,766.54 97.5%
III 0 0.0% 0 0.0% 0 0.0%
IX 2.79 0.0% 0.22 0.0% 2.57 0.1%
V 21.10 0.2% 10.96 0.1% 10.13 0.3%
VI 0 0.0% 0 0.0% 0 0.0%
VII 96.18 0.7% 15.53 0.2% 80.65 2.1%
VIII 2.96 0.0% 0.71 0.0% 2.25 0.1%
X 0 0.0% 0 0.0% 0 0.0%
Newark Total 13,379.51 100.0% 9,517.37 100.0% 3,862.14 100.0% Union City
0 11,105.35 66.8% 8,753.13 93.7% 2,352.22 32.3%
III 756.11 4.5% 48.92 0.5% 707.19 9.7%
IX 409.40 2.5% 108.46 1.2% 300.94 4.1%
V 101.81 0.6% 35.71 0.4% 66.10 0.9%
VI 885.21 5.3% 59.13 0.6% 826.09 11.3%
VII 1,918.21 11.5% 238.89 2.6% 1,679.31 23.0%
VIII 1,103.02 6.6% 57.25 0.6% 1,045.77 14.3%
X 350.52 2.1% 39.79 0.4% 310.74 4.3%
Union City
Total
16,629.64 100.0% 9,341.28 100.0% 7,288.36 100.0%
Packet Page No. 615
Tri-City 4-290
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction/
Susceptibility
to DeepSeated
Landslide
Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Alameda County Water District (Service Territory)
0 90,701.58 92.2% 61,601.08 96.3% 29,100.50 84.5%
III 102.00 0.1% 28.84 0.0% 73.16 0.2%
IX 2,142.47 2.2% 290.77 0.5% 1,851.70 5.4%
V 1,187.03 1.2% 600.47 0.9% 586.56 1.7%
VI 92.22 0.1% 30.74 0.0% 61.48 0.2%
VII 1,760.77 1.8% 887.26 1.4% 873.51 2.5%
VIII 915.27 0.9% 310.39 0.5% 604.88 1.8%
X 1,490.04 1.5% 190.90 0.3% 1,299.14 3.8%
Alameda
County Water
District Total
98,391.37 100.0% 63,940.44 100.0% 34,450.94 100.0%
Union Sanitary District (Service Territory)
0 72,371.73 94.2% 60,901.80 96.2% 11,469.93 84.7%
III 104.90 0.1% 49.78 0.1% 55.12 0.4%
IX 796.47 1.0% 302.82 0.5% 493.65 3.6%
V 967.91 1.3% 596.92 0.9% 371.00 2.7%
VI 89.85 0.1% 49.00 0.1% 40.85 0.3%
VII 1,372.40 1.8% 907.01 1.4% 465.39 3.4%
VIII 623.76 0.8% 313.26 0.5% 310.49 2.3%
X 532.79 0.7% 196.47 0.3% 336.32 2.5%
Union
Sanitary
District Total
76,859.81 100.0% 63,317.06 100.0% 13,542.76 100.0%
Source: CGS
Past Occurrences
Disaster Declaration History
There have been no disaster declarations associated with landslides in Alameda County, as shown in Table 4-5. However, many of the flood and heavy rain and storm disaster declarations likely resulted in some landslide issues in or around the Tri-City Planning area.

NCDC Events
The NCDC contains no records for landslides in Alameda County.

Packet Page No. 616
Tri-City 4-291
Local Hazard Mitigation Plan Update
March 2024
Planning Committee Events
Discussions of Planning Committee events for each jurisdiction can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrences
Likely— There are multiple areas with vulnerability to landslides, mudslides, and debris flows to the TriCity Planning Area. Due to the topography in and around the Planning Area and the rainfall the area receives during the winter, future occurrences of landslide, mudslide, and debris flow will occur annually and are considered likely.

Climate Change and Landslides
According to the 2021 CAS and Cal-Adapt, increased precipitation may result from climate change.

Increased precipitation makes areas more vulnerable to landslide potential. More information on precipitation increases can be found in Section 4.3.4.

Vulnerability Assessment
Vulnerability—Medium
Portions of the Tri-City Planning Area is at some measure of vulnerability to landslide. An assessment of a community’s vulnerability to landslide begins with an understanding of local exposure to landslide. This is included in the discussion of the Planning Area’s Assets at Risk to this hazard.

Assets at Risk
Assets at risk from landslide include people and populations; structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

Methodology
The 2011 California Geologic Survey Deep Seated Landslide Susceptibility data was obtained for the TriCity Planning Area. The 2023 Alameda County Parcel/Assessor Data was used as the basis for the inventory of all parcels within the Tri-City Planning Area. GIS was used to overlay the landslide hazard layer onto the parcel layer, and where the landslide susceptibility classes intersected a parcel centroid, it was assigned with that hazard class for the entire parcel.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

People and Populations
All populations located within areas of landslide susceptibility, especially in the High to Very High hazard areas (i.e., Classes VII to X) are at some vulnerability to landslide. This includes those people residing in Packet Page No. 617
Tri-City 4-292
Local Hazard Mitigation Plan Update
March 2024
these landslide potential areas as well as those that might reside or work within the landslide run out areas.

People residing in these areas may also be cut off from transportation routes if roads and streets providing a means of ingress and egress are impacted. Certain vulnerable populations may be at greater risk due to the often sudden onset of a landslide event and include: the unsheltered, those with limited mobility, and those that lack the resources to leave the area.

Tri-City Planning Area residents that live in the High and Very High landslide susceptibility areas are often the most vulnerable, but those who live in in the landslide run out areas (which are not mapped) are also vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to Planning Area’s residential population residing within these hazard areas, an analysis was conducted of those who physically reside in the mapped landslide susceptibility areas. The CGS Susceptibility to Deep Seated Landslide maps were overlayed on the parcel layer and linked to the assessor data. Those residential parcel centroids that intersect the High or Very High risk areas (Class VII or higher) were counted and multiplied by the 2020 Census Bureau average household factors each jurisdiction in the Planning Area. Analysis results are shown in Table 4-83.

Table 4-83 Tri-City Planning Area – Improved Residential Parcels and Population in Susceptibility to Deep Seated Landslides - Classes VII, VIII, IX, and X by Jurisdiction Deep Seated Landslide
Class/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
Class VIII
City of Fremont 558 1,668
City of Newark 43 143
City of Union City 52 175
Class IX
City of Fremont 283 846
City of Newark 84 279
City of Union City 36 121
Class X
City of Fremont 218 652
City of Newark 8 27
City of Union City 26 88
Source: CGS, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), 2020 US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City 3.37.

These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums and well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

Packet Page No. 618
Tri-City 4-293
Local Hazard Mitigation Plan Update
March 2024
Structures
Landslides can affect the built environment of the Tri-City Planning Area and those structures located within the High to Very High hazard areas (i.e., Classes VII to X) are especially vulnerable, as are the structures located within the landslide run out areas. The CGS Deep Seated Landslide Susceptibility layer was overlaid with the County parcel (structure) layer in GIS and linked to the assessor data. The mapped landslide areas are shown on Figure 4-109. Table 4-84 summarizes parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), estimated content replacement values, and total values in the Planning Area for deep seated landslide classes.

Table 4-84 Tri-City Planning Area – Count and Value of Parcels (and Structures) Susceptible to Deep Seated Landslide by Jurisdiction
Jurisdiction /
Susceptibility
to DeepSeated
Landslide
Class
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont
0 78,271 72,828 $20,274,884,322 $40,769,786,789 $25,796,108,004 $86,840,779,115 III 33 24 $8,887,389 $14,973,551 $7,486,775 $31,347,715 V 1,798 1,677 $748,055,015 $1,519,712,931 $760,785,797 $3,028,553,743 VI 37 24 $10,230,044 $20,455,557 $16,190,176 $46,875,777 VII 2,765 2,494 $1,012,771,725 $1,897,555,572 $997,713,067 $3,908,040,364 VIII 627 567 $288,901,531 $555,553,977 $276,730,452 $1,121,185,960 IX 438 292 $184,354,112 $313,256,137 $159,683,993 $657,294,242 X 297 225 $184,418,004 $365,348,109 $180,866,388 $730,632,501 Fremont
Total
84,266 78,131 $22,712,502,142 $45,456,642,623 $28,195,564,652 $96,364,709,417 Newark
0 16,945 15,248 $4,127,403,042 $8,152,660,662 $5,447,436,205 $17,727,499,909 V 95 43 $23,937,601 $22,690,382 $11,345,191 $57,973,174 VII 107 87 $35,823,015 $46,096,086 $32,539,703 $114,458,804 VIII 11 8 $2,740,555 $2,816,000 $1,408,000 $6,964,555
Newark
Total
17,158 15,386 $4,189,904,213 $8,224,263,130 $5,492,729,099 $17,906,896,442 Union City
0 18,098 17,112 $3,898,436,147 $8,462,877,308 $5,303,614,153 $17,664,927,608 III 33 12 $3,022,570 $3,746,350 $1,974,459 $8,743,379
V 69 63 $16,063,999 $26,014,916 $13,007,455 $55,086,370 VI 28 7 $4,385,094 $59,129,379 $57,440,357 $120,954,830 VII 219 180 $41,042,182 $70,940,382 $35,538,544 $147,521,108 Packet Page No. 619
Tri-City 4-294
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction /
Susceptibility
to DeepSeated
Landslide
Class
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
VIII 68 53 $16,097,385 $17,958,145 $9,288,240 $43,343,770 IX 48 36 $14,098,205 $12,918,786 $6,459,390 $33,476,381 X 39 26 $3,647,007 $8,169,190 $4,084,593 $15,900,790
Union City
Total
18,602 17,489 $3,996,792,589 $8,661,754,456 $5,431,407,191 $18,089,954,236 Alameda County Water District (Service Territory)
0 113,442 105,253 $28,359,809,498 $57,504,883,472 $36,706,490,767 $122,571,183,737 III 41 34 $9,054,757 $16,303,932 $8,151,965 $33,510,654 V 1,938 1,775 $782,166,691 $1,565,813,628 $782,906,809 $3,130,887,128 VI 30 26 $10,902,851 $65,771,746 $60,999,485 $137,674,082 VII 3,030 2,744 $1,080,791,852 $2,008,423,621 $1,060,298,180 $4,149,513,653 VIII 679 620 $301,197,441 $571,156,540 $283,077,338 $1,155,431,319 IX 408 311 $172,850,096 $314,890,560 $159,421,744 $647,162,400 X 309 246 $184,400,078 $371,078,731 $182,796,749 $738,275,558 Alameda
County Water
District
(Service
Territory)
Total
119,877 111,009 $30,901,173,264 $62,418,322,230 $39,244,143,037 $132,563,638,531 Union Sanitary District (Service Territory)
0 113,024 105,230 $28,229,157,944 $57,404,356,724 $36,570,095,695 $122,203,610,363 III 42 35 $9,142,791 $16,506,501 $8,354,534 $34,003,826 V 1,881 1,747 $768,427,116 $1,552,232,728 $776,116,359 $3,096,776,203 VI 33 26 $10,961,827 $65,771,746 $60,999,485 $137,733,058 VII 3,016 2,746 $1,074,043,607 $2,011,364,273 $1,064,190,946 $4,149,598,826 VIII 668 617 $298,874,567 $564,701,573 $279,849,854 $1,143,425,994 IX 394 312 $169,660,241 $316,912,020 $160,432,474 $647,004,735 X 302 246 $184,932,499 $371,078,731 $182,796,749 $738,807,979 Union
Sanitary
District
(Service
Territory)
Total
119,360 110,959 $30,745,200,592 $62,302,924,296 $39,102,836,096 $132,150,960,984 Source: CGS, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) Packet Page No. 620
Tri-City 4-295
Local Hazard Mitigation Plan Update
March 2024
Critical Facilities and Infrastructure and Community Lifelines Landslides present a threat to critical facilities and infrastructure, and community lifelines. The following analysis discusses critical facilities and infrastructure, followed by community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Community lifelines at risk to landslide include:
➢ Safety and Security – Many Planning Area personnel would be involved in response and recovery efforts. This includes police, fire, EMS, public works, and other personnel. ➢ Food, Hydration, and Shelter – As homes are damaged, shelter needs would significantly increase.

Temporary housing would be to be established. Water supplies could be offline for an extended period.

Residents, visitors and others caught in a large event would need to find sources of food and water until the Planning Area recovers.
➢ Health and Medical – Injuries and deaths can occur. This causes EMS calls and ER visits to spike.

Transporting patients to medical facilities may be difficult. Depending on the extent of injuries and deaths the capacity of medical facilities could be strained and eventually overwhelmed. ➢ Energy – The power grid may be damaged from landslide. Fuel transportation may need to be delayed or rerouted, causing temporary shortages.
➢ Communications – Communications systems may be damaged during landslide events. Messaging boards and alerts need to be then put into place to ensure public safety and order. ➢ Transportation – Major damage can occur to roads and bridges in the Planning Area. Damage can also occur to rail lines and airports in and near the Planning Area. Roads may be closed due to damage, or to debris on the roads from earthquake events. These closures could be place for an extended period while debris clearing efforts are undertaken to allow repairs to be made. ➢ Hazardous Material – Hazardous materials facilities can be compromised during times of landslide events causing releases of contaminants into the environment. Natural gas pipelines can be affected by earthquakes. This can affect not only residents, but those who are charged with responding to or resolving the spill/rupture.
➢ Water Systems – Water, drainage, and wastewater systems can be damaged.

As shown on Figure 4-109, the Tri-City Planning Area has limited areas of landslide vulnerability, with most of these areas located in the foothills to the east. As such, impacts to community lifelines from landslides in the Planning Area would be limited. Community lifelines are not likely to be overwhelmed by a landslide event.

Natural, Historic, and Cultural Resources
Landslides can affect natural, historic, and cultural resources that lie in the landslide area, or the landslide run out area. Landslides can destroy large tracts of forest and open space areas, destroy wildlife habitat, and remove productive soils and vegetation from slopes. It can also fill in waterways, impact water quality, Packet Page No. 621
Tri-City 4-296
Local Hazard Mitigation Plan Update
March 2024
and potentially affect flooding potential. Natural resources that fall in the High or Very High susceptibility classes shown on Figure 4-109 would be most vulnerable, as well as those in the run out areas. As shown on the map, this would include a relatively small area of the developed area, since most of this occurs in the undeveloped areas in the Planning Area.

Economic Assets and Community Activities of Value
Landslides can affect economic assets and community activities of value if they fall into the higher landslide susceptibility areas, the landslide run out areas, or if economic assets are cut off from transportation routes in the Planning Area. Very few, if any, economic assets would be at risk, Since most of the landslide risk is in the foothills area in the east of the Planning Area that is bordered by mostly residential homes, most economic assets in the Planning Area are unlikely to be affected. Very few community activities of value occur in areas threatened by landslide.

Impacts from Landslide
Any type of landslide may result in damages or complete destruction of buildings in their path, as well as deaths and injuries. Landslides can cause road blockages by depositing debris on road surfaces or road damage if the road surface itself slides downhill. Utility lines and pipes are also prone to breakage in slide areas. Large landslides can collapse into water bodies, causing tsunamis or seiches. Landslides can relocate river channels. Landslides and debris flows can also impact water quality and the storage capacity of surface water reservoirs used to store potable water.

Landslides can collapse into water bodies, causing tsunamis or seiches. In 1958, a magnitude 8 earthquake collapsed a hillside into Lituya Bay, Alaska, causing a water splash wave that reached 1,720 feet up a mountain slope, stripping all vegetation. A massive landslide into the Vaoint Reservoir in Italy in 1963 caused a water splash wave that swept 800 feet over the top of a dam, causing a major flood that killed an estimated 2,600 people below. Landslides can relocate river channels, as occurred during the Oso mudslide in Washington State in March 2014. This occurred in an area not considered landslide prone on local maps.

Landslides and debris flows can impact water quality and the storage capacity of surface water reservoirs used to store potable water.

Landslides, debris flows, and mud flows impacts vary by location and severity of any given event and will likely only affect certain areas of the Planning Area susceptible to landslide. Based on the risk assessment, there is limited potential for significant landslides to occur in the Planning Area. Most, but not all, of the historic landslides in the Planning Area have been minor, localized events that are more of a nuisance than a disaster. Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure, utilities, and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Significant economic impact (jobs, sales, tax revenue) to the community; and ➢ Negative impact on commercial and residential property values Packet Page No. 622
Tri-City 4-297
Local Hazard Mitigation Plan Update
March 2024
These impacts may be exacerbated by the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development.

Future Development
Landslide, mudslide, and debris flows are taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.14. Levee Failure
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
A levee is a raised area that runs along the banks of a stream or canal. Levees reinforce the banks and help prevent flooding by containing higher flow events to the main stream channel. By confining the flow to a narrower steam channel, levees can also increase the speed of the water. Levees can be natural or manmade. A natural levee is formed when sediment settles on the stream bank, raising the level of the land around the stream. Man-made levees are formed by the hauling of sediment and fill in order to protect the area behind the levee.

Levees can provide strong flood protection, but they are not failsafe. Levees are often designed to protect against a specific flood level and could be overtopped during severe weather events or a dam failure. Levees reduce, not eliminate, the risk to individuals and structures located behind them. A levee system failure or overtopping can create severe flooding and high-water velocities. It’s important to remember that no levee provides protection from events for which it was not designed, and proper operation and maintenance are necessary to reduce the probability of failure.

Under-seepage refers to water flowing under the levee through the levee foundation materials, often emanating from the bottom of the landside slope and ground surface and extending landward from the landside toe of the levee. Through-seepage refers to water flowing through the levee prism directly, often emanating from the landside slope of the levee. Both conditions can lead to failure by several mechanisms, including excessive water pressures causing foundation heave and slope instabilities, slow progressing internal erosion, and piping leading to levee slumping.

Rodents burrowing into and compromising the levee system can also contribute to a levee failure as can erosion of the leveed area. Levee failure can also be caused by high winds creating wave action and high tides, especially combined with storm events. Figure 4-110 depicts the causes of levee failure.

Packet Page No. 623
Tri-City 4-298
Local Hazard Mitigation Plan Update
March 2024
Figure 4-110 Potential Causes of Levee Failure
Source: USACE
Overtopping failure occurs when the flood water level rises above the crest of a levee. As shown in Figure 4-111, overtopping of levees can cause greater damage than a traditional flood due to the often, lower topography behind the levee.

Figure 4-111 Flooding from Levee Overtopping
Source: Levees in History: The Levee Challenge. Dr. Gerald E. Galloway, Jr., P.E., Ph.D., Water Policy Collaborative, University of Maryland, Visiting Scholar, USACE, IWR.

Packet Page No. 624
Tri-City 4-299
Local Hazard Mitigation Plan Update
March 2024
Location and Extent
The National Levee Database and the Alameda County FIS were searched for levee locations in and near the Tri-City Planning Area. According to the National Levee Database, there are 130 levees in Alameda County, many of which protect lands in the Tri-City Planning Area. This can be seen for the Tri-City Planning Area in Figure 4-112. The red lines indicate the levee segments. Certain of these levees are certified as providing protection from the 1% annual chance flood event. The areas behind these levees are noted by FEMA as X Protected by Levee Areas. These areas are shown on Figure 4-112 and detailed in Table 4-85.

Levee failure in the Planning Area would likely have a short onset, and the duration would be short.

However, if the levee failed during an atmospheric river event, the duration could be prolonged.

Packet Page No. 625
Tri-City 4-300
Local Hazard Mitigation Plan Update
March 2024
Figure 4-112 Tri-City Planning Area– Levee Locations
Packet Page No. 626
Tri-City 4-301
Local Hazard Mitigation Plan Update
March 2024
Figure 4-113 Tri-City Planning Area – FEMA DFIRM X Protected by Levee Flood Zone Packet Page No. 627
Tri-City 4-302
Local Hazard Mitigation Plan Update
March 2024
Table 4-85 Tri-City Planning Area – Geographical FEMA DFIRM X Protected by Levee Flood Zone by Jurisdiction
Jurisdiction /
Flood Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
X Protected by
Levee
1,440 1.775% 1,318 2.826% 122 0.354%
Newark
X Protected by
Levee
0 0.00% 0 0.00% 0 0.00%
Union City
X Protected by
Levee
0 0.00% 0 0.00% 0 0.00%
Alameda County Water District
X Protected by
Levee
1,440 1.348% 1,318 2.060% 122 0.285%
Union Sanitary District
X Protected by
Levee
1,440 1.858% 1,318 2.080% 122 0.863%
Source: FEMA 12/21/2018 DFIRM
Past Occurrences
Disaster Declaration History
There have been no disaster declarations for levee failure in Alameda County as shown on Table 4-5.

NCDC Events
The NCDC does not track levee failure events.

Planning Committee Events
Discussions of Planning Committee events for each jurisdiction can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrences
Unlikely – The Planning Committee determined the likelihood of levee failure is occasional. This rating was in part determined due to issues surrounding ongoing maintenance of the levee system as well as many of the levees not being certified as providing protection against the 1% annual chance flood within the Planning Area. It was noted that other hazards like earthquakes, floods, and coastal flooding and sea level rise could increase the likelihood of future occurrence.

Packet Page No. 628
Tri-City 4-303
Local Hazard Mitigation Plan Update
March 2024
Climate Change and Levee Failure
In general, increased flood frequency in California is a predicted consequence of climate change.

Mechanisms whereby climate change leads to an elevated flood risk include more extreme precipitation events and shifts in the seasonal timing of river flows. This threat may be particularly significant because recent estimates indicate the additional force exerted upon the levees is equivalent to the square of the water level rise. These extremes are most likely to occur during storm events, leading to more severe damage from waves and floods.

Vulnerability Assessment
Vulnerability—Medium
The probability of levee failure is increasing over time due to increased storms and flooding potential from global climate change. Levee failure flooding can occur as the result of partial or complete collapse of an impoundment, and often results from prolonged rainfall and flooding. A levee failure can range from a small uncontrolled release to a catastrophic failure. The primary danger associated with levee failure is the high velocity flooding of those properties downstream of the breach. Vulnerability to levee failures is generally confined to the areas subject to inundation downstream of the levee. In addition, levee failure can cause stream bank erosion, which can in some instances have effects worse than those of flooding itself.

Note: the analysis of Tri-City Planning Area vulnerability to levee failure in this section is primarily based on the X protected by Levee flood zone based on availability of data. The X Protected by Levee flood zone is part of the 0.2% annual chance floodplain, as the levee is certified by FEMA as protecting against the 1% annual chance flood. Other levees within the Planning Area were not analyzed due to the lack of available data. However, while not certified, these other levees provide some level of flood protection to surrounding areas and are also subject to failure during heavy storm and rain events.

Portions of the Tri-City Planning Area are at some measure of vulnerability to levee failure. An assessment of a community’s vulnerability to levee failure begins with an understanding of local exposure to levee failure. This is included in the discussion of the Planning Area’s Assets at Risk to this hazard. It should be noted that in the following sections, only the certified levees are analyzed.

Assets at Risk
Assets at risk from levee failure include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

Methodology
2023 Alameda County Parcel/Assessor Data was used as the basis for the Tri-City inventory of parcels, values, and acres. Alameda County has a FEMA effective DFIRM dated 12/21/2018, which was obtained from FEMA’s National Flood Hazard Layer to perform the flood analysis. In some cases, there are parcels in multiple flood zones, such as Zone A, Zone X, or Shaded X. GIS was used to create a centroid, or point representing the center of the parcel polygon. DFIRM flood data was then overlaid on the parcel layer. For Packet Page No. 629
Tri-City 4-304
Local Hazard Mitigation Plan Update
March 2024
the purposes of this analysis, the flood zone that intersected a parcel centroid was assigned the flood zone for the entire parcel. The parcels and associated values were segregated and analyzed in this fashion to determine parcels and values at risk to the flood hazard for the Tri-City Planning Area.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

People and Populations
Populations in the floodplains are at risk to flooding, including the X Protected by Levee flood zone.

Certain vulnerable populations may be at greater risk to the effects of levee failure flooding. Certain vulnerable populations may be at a greater risk of a sudden levee failure, including the unsheltered, those with limited mobility and those that lack the resources to leave the area.

Planning Area residents that live in the X Protected by Levee flood zones are often the most vulnerable to certified levees Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To evaluate the population of residents of the Planning Area that live within the X Protected by Levee flood zone, the DFIRM flood zones were overlayed on the parcel layer and linked to the Assessor data. Those residential parcel centroids that intersect the X Protected by Levee flood zone were counted and multiplied by the 2020 Census Bureau average household factors for each jurisdiction. Results are shown in Table 4-86.

Table 4-86 Tri-City Planning Area – Improved Residential Parcels and Population in FEMA DFIRM X Protected by Levee Flood Zone and Jurisdiction
Jurisdiction
X Protected by Levee
Improved Residential
Parcels
Population at Risk
City of Fremont 0 0
City of Newark 0 0
City of Union City 0 0
Source: FEMA DFIRM 11/2/2018, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), 2020 US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City (3.37) These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums and well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

Structures
A levee failure can affect the built environment of the Tri-City Planning Area, with some structures in the Planning Area at risk to a levee failure event. GIS was used to determine the possible impacts of levee failure flooding from X Protected by Levee flood zones within the Planning Area. Table 4-87 shows the parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), estimated Packet Page No. 630
Tri-City 4-305
Local Hazard Mitigation Plan Update
March 2024
content replacement values, and total values by property use in the Planning Area that fall in FEMA X Protected by Levee flood zone.

Table 4-87 Tri-City Planning Area – Count and Value of Parcels (and Structures) in FEMA DFIRM X Protected by Levee Flood Zone by Jurisdiction
Jurisdiction
/ Flood
Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont
X Protected
by Levee
194 179 $441,856,625 $582,713,918 $824,216,164 $1,848,786,707 Newark
X Protected
by Levee
0 0 $0 $0 $0 $0
Union City
X Protected
by Levee
0 0 $0 $0 $0 $0
Alameda County Water District (Service Territory)
X Protected
by Levee
194 179 $441,856,625 $582,713,918 $824,216,164 $1,848,786,707 Union Sanitary District (Service Territory)
X Protected
by Levee
194 179 $441,856,625 $582,713,918 $824,216,164 $1,848,786,707 Source: FEMA 11/2/2018 DFIRM, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone Critical Facilities and Infrastructure, and Community Lifelines Levee failure flooding presents a threat to critical facilities and infrastructure, and community lifelines.

Critical infrastructure failures such as loss of power, impacts to potable and wastewater treatment systems, and road and bridge failures can all be caused by levee failure events, depending on the magnitude of the resulting flood. The following analysis discusses critical facilities and infrastructure at risk to levee failure flooding, followed by a discussion on vulnerability of community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Levee failure flooding presents a threat to life and property, including community lifelines in the Tri-City Planning Area. Community lifelines that would be vulnerable to levee failure flooding include:

Packet Page No. 631
Tri-City 4-306
Local Hazard Mitigation Plan Update
March 2024
➢ Safety and Security – Search and rescue and swiftwater teams may be called on to perform riskier duties during times of levee failure and flooding. Police, Fire, EMS, and Public Works personnel are often called on to respond during flood emergencies which at times may stretch their capacity. ➢ Food, Hydration, Shelter – Floodwater is often contaminated with sewage and other contaminants, which can lead to illness and affect clean drinking water. These life safety and public health issues can tax the ability of the health and medical systems to provide necessary services, even if only temporarily. ➢ Health, and Medical – Loss of life and injuries can occur during significant levee failure events.

Flooding may complicate the ability to transport the injured possibly requiring rerouting of injured to other facilities. Public health can also be at risk from flooding. ➢ Energy – Levee failure flooding could affect power distribution locations in the Planning Area. Power outages may occur. Fuel supplies may be temporarily cut off until levees are repaired (allowing for transport of fuel to resume).
➢ Communications – Communication infrastructure can be inundated by a levee failure event causing damage and an interruption in service. As well, an influx of service calls to dispatch centers for reporting of flooding, power outages, or other issues can occur. Messaging systems may need to be deployed during these times to let the public know about road and lane closures, washouts, and debris or flooding on roads.
➢ Transportation – Highways and local roads may experience levee failure flooding. This can cause lane or road closures, bridge closures and significantly limit mobility in the Planning Area. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents and impact evacuation routes.
➢ Hazardous Material – Hazardous material facilities can be affected by levee failure flooding.

Hazardous materials releases can occur if waters that overtop levees rupture storage tanks and other containment structures and cause them to spill into streams, rivers or drainage systems. Releases during these times can be comingled with flood waters, contaminate drinking water, as well as create additional exposures to the environment.
➢ Water Systems – Floods from levee failures can affect the ability for water and wastewater systems to operate, since many are located near leveed areas.

Given the small amount of area that falls in the X Protected by Levee flood zones shown on Figure 4-113, these community lifelines are unlikely to be overwhelmed during a levee failure event.

Natural, Historic, and Cultural Resources
Large levee failure events can affect natural, historic, and cultural resources. There are a number of ways levee failures and associated floodwaters can impact natural resources and the environment: Wildlife habitats can be destroyed. Contaminated floodwater can pollute rivers and habitats. Silt and sediment can destroy natural areas. Riverbanks and natural levées can be eliminated as rivers reach bankfull capacity.

Rivers can be widened, and deposition can increase downstream. Trees can be uprooted by high-velocity water flow. Plants that survive the initial flood may die due to being inundated with water. Historic and cultural resources may also be affected. Generally, the impacts are associated with damage to structures within the areas protected by levees, but other cultural resources such as those associated with Native Americans and old tribal areas can also be disturbed, damaged and lost during extreme levee failure events.

Any of these that fall in the X Protected by Levee flood zones would be vulnerable.

Packet Page No. 632
Tri-City 4-307
Local Hazard Mitigation Plan Update
March 2024
Economic Assets and Community Activities of Value
Major levee failure flooding events could affect any economic asset that lies in the areas protected by levees.

These events can also affect those economic assets outside of the areas protected by levees, at least in the short term until floodwaters have receded and the Planning Area has sufficiently recovered. The Planning Area felt that a levee failure would have little bearing on community activities of value, unless a failure had a direct impact on the activity while it was occurring.

Impacts from Levee Failure
Floods and their impacts vary by location, including the added impacts associated with a levee failure flood event, and will only affect certain areas of the Tri-City Planning Area that are in areas protected by levees.

Based on the X Protected by Levee analysis, as well as the large number of non-certified levees, it is evident that levee failure floods could potentially have significant impacts to areas of the Planning Area protected by levees, depending on the severity of the event. Impacts that are not quantified, but could be anticipated in large future levee failure events, include:
➢ Injury and loss of life.
➢ Commercial and residential structural and property damage. ➢ Disruption of and damage to public critical infrastructure and services. ➢ Health hazards associated with mold and mildew, contamination of drinking water, etc. ➢ Impacts to natural resource areas, including stream bank erosion. ➢ Damage to roads/bridges resulting in loss of mobility.

These impacts may be exacerbated by the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development.

In addition to flood related levee failures, the levees in the Planning Area are at risk to failure during earthquake. Levee failure flooding could accompany an earthquake if a dam or storage reservoir or tank fails. Severe ground shaking from an earthquake event can cause a dam to fail or overflow to the surrounding area.

Channels and water courses with earthen banks and levees are particularly vulnerable and could collapse in a major earthquake resulting in partial or complete blockage of channels causing flooding upstream of the impoundment. Shoreline levees could also collapse, eliminating or impairing the control capabilities of the system. Levees are especially susceptible to rapid settlement due to liquefaction or horizontal spreading of underlying soils.

Future Development
Levee failures are taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

Packet Page No. 633
Tri-City 4-308
Local Hazard Mitigation Plan Update
March 2024

4.3.15. Subsidence
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard Profile
Hazard/Problem Description
Land subsidence, as defined by the CGS, is the sinking of the land over man-made or natural underground voids. Subsidence can result in serious structural damage to buildings, roads, irrigation ditches, underground utilities, and pipelines. It can disrupt and alter the flow of surface or underground water.

Weight, including surface developments such as roads, reservoirs, and buildings and manmade vibrations from such activities as blasting or heavy truck or train traffic can accelerate the natural processes of subsidence. Fluctuations in the level of underground water caused by pumping or by injecting fluids into the earth can initiate sinking to fill the empty space previously occupied by water or soluble minerals. This can also cause sinkholes to occur. The consequences of improper use of land subject to ground subsidence can be excessive economic losses, including the high costs of repair and maintenance for buildings, irrigation works, highways, utilities, and other structures. This hazard profile covers non-earthquake subsidence. Earthquake based subsidence is discussed in the Earthquake discussion (Section 4.3.10) above.

The 2023 State Hazard Mitigation Plan noted that subsidence happens either due to natural processes (organic soil decomposition) or as a result of human activities (groundwater pumping). Groundwater pumping is more likely to affect the Tri-City Planning Area. Fine-grained sediments (clays and silts) in an aquifer system are the main causes of land subsidence due to groundwater pumping. Such sediments tend to be deposited in random orientations with a lot of room between them to store water. However, when groundwater levels fall, the sediments are rearranged into stacks that occupy less space and have less space between them to store water.

Location and Extent
The 2023 State of California Hazard Mitigation Plan noted that subsidence happens either due to natural processes or as a result of human activities and in the Tri-City Planning Area is most likely associated with groundwater pumping and draw down of aquifers. In other cases, pits and wells may have been abandoned and backfilled with undocumented fill materials. Existing pits and wells backfilled with undocumented materials may be subject to differential settlement, which causes structures to shift, and often become damaged, due to the uneven lowering of the earth. Differential settlement is closely related to subsidence, which is the sudden sinking or gradual downward settling of the earth’s surface with little or no horizontal movement. Subsidence can be caused by natural geologic processes or by human activity such as subsurface mining or pumping of oil or groundwater. There is no scientific scale for measuring subsidence.

It is traditionally measured in historical changes in land elevations. The speed of onset may be gradual or sudden.

Packet Page No. 634
Tri-City 4-309
Local Hazard Mitigation Plan Update
March 2024
Figure 4-114 shows known areas of subsidence risk in California today. Figure 4-115 shows the critically over-drafted groundwater basins in California. The areas shown are potentially more susceptible to subsidence.

Figure 4-114 Tri-City Planning Area – Areas of Potential Land Subsidence Source: 2023 State of California Hazard Mitigation Plan Packet Page No. 635
Tri-City 4-310
Local Hazard Mitigation Plan Update
March 2024
Figure 4-115 Tri-City Planning Area – Critically Over-Drafted Groundwater Basins Source: 2023 State of California Hazard Mitigation Plan Additionally, there is concern about levees built with Bay Mud. During periods of shaking, there is concern the levees will lose integrity. More information on this can be found in the Union Sanitary District annex to this Base Plan.

Past Occurrences
Disaster Declaration History
There have been no past federal or state disaster declarations due to subsidence, as detailed in Table 4-5.

Packet Page No. 636
Tri-City 4-311
Local Hazard Mitigation Plan Update
March 2024
NCDC Events
The NCDC data does not track subsidence events.

Planning Committee Events
Discussions of Planning Committee events for each jurisdiction can be found in their respective annexes to this LHMP Update.

Probability of Future Occurrences
Likely—California’s land subsidence is tied to prolonged droughts and simultaneous record-breaking heat.

When the state endures prolonged periods of drought, surface water stores are depleted, and the reliance on groundwater for water supply is increased. Given the frequency and duration of these types of events, it is reasonable to assume an increase in probability of subsidence events as well. Subsidence due to water drawdown may occur in areas in and around the Planning Area.

Climate Change and Subsidence
Changes in precipitation, reduced snowpack, and more frequent droughts are likely to increase the demand on groundwater sources, risking overdraft, ground subsidence, and decreased water quality.

Vulnerability Assessment
Vulnerability—Low
California’s land subsidence is often tied to prolonged droughts and simultaneous record-breaking heat.

When the state endures prolonged periods of drought, surface water stores are depleted, and the reliance on groundwater for water supply is increased. A discussion of assets at risk follows.

Assets at Risk
Assets at risk from subsidence include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

People and Populations
Since subsidence generally happens over a long period of time, there is only a minimal risk to people and populations. Tri-City Planning Area groundwater levels have been lowered due to pumping; no related subsidence has resulted. Under the ACWD directed groundwater recharge program, groundwater levels are now stable.

Packet Page No. 637
Tri-City 4-312
Local Hazard Mitigation Plan Update
March 2024
Structures
All structures in the Tri-City Planning Area bear some measure of risk to subsidence. Subsidence could cause damages as building footings become unstable. However, as noted above, area groundwater levels have been lowered due to pumping, and no related subsidence has resulted. According to the Alameda County Water District, a groundwater recharge program has been successful, and groundwater levels are now stable. A sinkhole (though rare) could affect a structure.

Critical Facilities and Infrastructure and Community Lifelines All critical facilities in the Tri-City Planning Area bear some measure of risk to subsidence. Gradual sinking could cause foundation damages. If a sinkhole were to open as a result of subsidence, there could be damages to infrastructure and lifelines. A sinkhole (though rare) could affect critical facilities, infrastructure, or community lifelines. The likelihood of this is low.

Natural, Historic, and Cultural Resources
All natural, historic, and cultural resources in the Tri-City Planning Area bear some measure of risk to subsidence. Gradual sinking could cause foundation damages. A sinkhole (though rare) could affect a structure. Historic structures built when building codes were less restrictive may be at greater risk should a sinkhole occur.

Economic Assets and Community Activities of Value
Economic assets bear some measure of risk to subsidence. Subsidence could cause damages as building footings become unstable. Community activities of value are thought to have little to no risk from subsidence.

Impacts from Subsidence
Effects of land subsidence in California include increased flood risk in low-lying areas, damage to buildings and infrastructure, loss of groundwater aquifers, and damage to aquatic ecosystems. As the land sinks, it can experience increased flooding and adverse impacts on sewer lines, stormwater drainage systems, and other impacts to critical facilities and infrastructure. As subsidence progresses, areas protected by levees can be impacted. Compaction of the aquifer system due to subsidence may permanently decrease its capacity to store water.

These impacts can be exacerbated by the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development. Impacts in the Tri-City Planning Area are expected to be minimal, as limited areas of subsidence exist and no past occurrences in the Planning Area have been noted.

Packet Page No. 638
Tri-City 4-313
Local Hazard Mitigation Plan Update
March 2024
Future Development
Subsidence is taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.16. Tsunami
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
The 2023 State of California Hazard Mitigation Plan defines a tsunami as a wave triggered by any form of land displacement along the edge or bottom of an ocean or lake. This can be submarine landslides or submarine dip slip fault ruptures that result in seafloor uplift or down‐drop. This mass movement often translates to a tsunami or gravity wave within the overlying water. The coastline of California and the San Francisco Bay are at risk to tsunami both from land displacement events occurring locally or from those from many miles away.

Tsunamis travel radially outward from the point of initiation. The size of a tsunami is proportional to the mass movement that generated the tsunami. The speed of a tsunami is proportional to the depth of the water in which the tsunami originated. Tsunamis can travel at great speeds but in the open ocean result in relatively little wave height above the mean sea level as the energy is distributed throughout the water column. The wave length of a tsunami is much longer than wind generated waves, making it hard to detect in the open ocean.

As a tsunami approaches the shore and the depth of the water column decreases, the energy in the wave pushes the wave crest above the water surface resulting in a large wave height. Wave run‐up is the elevation above mean sea level on dry land that a tsunami reaches. Run‐up is what causes inundation of coastal areas that are below the run‐up height. Identifying tsunami hazards requires 1) evaluating the potential for submarine mass movement both locally and at great ocean distances, and 2) identifying coastal regions within the direct or indirect path of a potential tsunami wave that are below the run‐up height.

There are two types of tsunamis—local and distant. Local tsunamis are more threatening because they afford at‐risk populations only a few minutes to find safety. Distant tsunamis allow for more notice to atrisk populations that a tsunami is inbound. California is vulnerable to, and must consider, both types.

Tsunamis can travel at speeds of over 600 miles per hour in the open ocean and can grow to over 50 feet in height when they approach a shallow shoreline, causing severe damage to coastal development. Recent studies of the continental shelf off the California coast indicate a potential for underwater landslides capable of generating damaging tsunamis that could threaten coastal communities. As well, tsunami events Packet Page No. 639
Tri-City 4-314
Local Hazard Mitigation Plan Update
March 2024
originating as far away as Alaska and Japan can also trigger events that could be damaging to California coastal areas.

Location and Extent
Tsunami can affect lower lying areas of the Tri-City Planning Area adjacent to the Bay or tidally influenced rivers. This occurs in Planning Area along the San Francisco Bay area. There is no scientific scale for tsunami, only depth of inundation and measure of the water penetration inland. Speed of onset can be short (minutes to hours). CGS has prepared maps for tsunami coastal evacuation zones. The CGS Coastal Evacuation Zone is shown on Figure 4-116 and geographic extents are detailed in Table 4-88. In these maps, there is no zone classification other than inside or outside the evacuation zone.

Packet Page No. 640
Tri-City 4-315
Local Hazard Mitigation Plan Update
March 2024
Figure 4-116 Tri-City Planning Area – Tsunami Coastal Evacuation Zone Packet Page No. 641
Tri-City 4-316
Local Hazard Mitigation Plan Update
March 2024
Table 4-88 Tri-City Planning Area – Coastal Evacuation Zone Geographical Extents by Jurisdiction
/ Jurisdiction Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont 21,139.77 26.9% 447.87 1.0% 20,691.91 64.9%
Newark 4,210.69 28.7% 363.71 3.8% 3,846.98 74.8%
Union City 476.81 2.9% 0.55 0.0% 476.27 6.5%
Alameda
County Water
District
28,780.72 27.6% 823.07 1.3% 27,957.65 69.1%
Union Sanitary
District
1,780.08 2.3% 96.46 0.2% 1,683.62 11.9%
Source: CGS
Past Occurrences
Disaster Declaration History
There have been no past federal or state disaster declarations due to tsunami, according to Table 4-5.

NCDC Events
The NCDC has tracked tsunami events in each County dating back to 1996. The events in Alameda County are shown in Table 4-89. This is from a March 11, 2011, event. This was from an earthquake off the coast of Japan. This is often referred to as the Fukushima earthquake, as the tsunami caused a meltdown of three reactors at the Fukushima Daiichi nuclear power plant. More information can be found in the Hazard Mitigation Planning Team events section below.

Table 4-89 Alameda County NCDC Tsunami Events 1/1/1996–12/31/2022* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Tsunami 1 0 0 0 0 $50,000 $0
Total 1 0 0 0 0 $50,000 $ 0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of the Planning Area and outside of Alameda County.

Planning Committee Events
The 2021 Alameda County LHMP reported that more than 71 tsunamis have been recorded in San Francisco Bay since 1854. Most of these tsunamis were generated by earthquakes in distant subduction zones near Russia, Japan, or Alaska. The worst tsunami to hit the Bay Area was generated in Alaska by a M 9.2 earthquake on March 27, 1964. This event produced a 2-foot runup in the nearby City of Alameda and a 4-foot runup in the City of Oakland. On March 11, 2011, a tsunami generated in Japan from the Fukushima Packet Page No. 642
Tri-City 4-317
Local Hazard Mitigation Plan Update
March 2024
earthquake resulted in a 2-foot runup in the nearby cities of Alameda and Berkeley. Minor damage to docks and piles was reported. No damage was reported in the Tri-City Planning Area.

Likelihood of Future Occurrence
Unlikely – Strong earthquakes, or other major land displacement events, occurring near the Tri-City Planning Area or elsewhere on the Pacific “Ring of Fire,” especially Alaska, give the Planning Area limited warning of the overwhelming waves that move up to 600 mph. A massive earthquake in the central Aleutian Islands of Alaska could send 30-foot waves to the nearby coast within about five hours. Since earthquakes of this magnitude are somewhat rare, the likelihood of future occurrence is unlikely.

Climate Change and Tsunami
Earthquakes are the main cause of tsunamis in the Pacific Ocean. According to the CAS, climate change is unlikely to increase earthquake frequency or strength.

Vulnerability Assessment
Vulnerability—Medium
Tsunamis arrive as a series of successive crests (high water levels) and troughs (low water levels). These successive crests and troughs can occur anywhere from 5 to 90 minutes apart; however, they usually occur 10 to 45 minutes apart. As a tsunami enters the shoaling waters near a coastline, its speed diminishes, its wavelength decreases, and its height increases greatly. The first wave usually is not the largest. Several larger and more destructive waves often follow the first one. As tsunamis reach the shoreline, they may take the form of a fast-rising tide, a cresting wave, or a bore (a large, turbulent wall-like wave). The bore phenomenon resembles a step-like change in the water level that advances rapidly (from 10 to 60 miles per hour).

Portions of the Tri-City Planning Area are at some measure of vulnerability to tsunami. An assessment of a community’s vulnerability to tsunami begins with an understanding of local exposure to tsunami. This is included in the discussion of the Planning Area’s Assets at Risk to this hazard.

Assets at Risk
Assets at risk from tsunami include people and populations; structures; critical facilities and infrastructure and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

Methodology
2023 Alameda County Parcel/Assessor Data was used as the basis for the Tri-City inventory of parcels, values, and acres. The Tsunami Coastal Evacuation Zones were gathered from the CGS and used to perform the tsunami analysis. In some cases, there are parcels in multiple flood zones, such as Zone A, Zone X, or Shaded X. GIS was used to create a centroid, or point representing the center of the parcel polygon.

Tsunami evacuation zone data was then overlaid on the parcel layer. The parcels and associated values Packet Page No. 643
Tri-City 4-318
Local Hazard Mitigation Plan Update
March 2024
were segregated and analyzed in this fashion to determine parcels and values at risk to the tsunami hazard for the Tri-City Planning Area.

People and Populations
People and populations in the tsunami evacuation zones are at risk to high velocity wave or flood inundation. Certain vulnerable populations within areas prone to a tsunami event may be at increased risk to this hazard, especially during a large event with minimal advance notice. These vulnerable populations include: the unhoused, those with limited mobility, and those that lack the resources to leave the area. Given the coastal location of a potential Tsunami, people that live, work, visit, or recreate in these areas would be at risk. Risks to people include drowning as well as being injured or killed by debris that gets added to the floodwaters in this type of event.

Planning Area residents that live in the tsunami coastal evacuation zone would be the most vulnerable. To further evaluate the impact to the residential populations within the Planning Area, the CGS Tsunami Coastal Evacuation Zone was overlayed on the parcel layer and linked to the Assessor data to identify parcels with a residential property use. Based on this data no residential parcels were identified in the tsunami evacuation zone, thus no people “officially” reside in these areas. However, there is always the potential for unhoused individuals and transient populations to temporarily live in these areas which may put them at greater vulnerability to a tsunami.

Structures
Certain structures in the Planning Area are at risk from tsunami. GIS was used to determine the possible impacts of tsunami inundation within the Planning Area. The CGS Tsunami Coastal Evacuation Zone was overlaid with the 2022 Alameda County Parcel/Assessor database. Table 4-90 shows the parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), estimated content replacement values, and total values in the Planning Area by jurisdiction use that fall in the CGS Tsunami Coastal Evacuation Zone.

Table 4-90 Tri-City Planning Area – Count and Value of Parcels (and Structures) in Tsunami Coastal Evacuation Zone by Jurisdiction
Jurisdiction /
Tsunami
Coastal
Evacuation
Zone
Total Parcel
Count
Improved
Parcel Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont
Tsunami
Coastal
Evacuation
Zone
276 7 $96,814,653 $139,827,797 $152,213,294 $388,855,744 Packet Page No. 644
Tri-City 4-319
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction /
Tsunami
Coastal
Evacuation
Zone
Total Parcel
Count
Improved
Parcel Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Newark
Tsunami
Coastal
Evacuation
Zone
935 320 $281,402,205 $228,818,764 $112,796,934 $623,017,903 Union City
Tsunami
Coastal
Evacuation
Zone
39 2 $24,094,799 $2,264,465 $2,264,465 $28,623,729
Alameda County Water District (Service Territory)
Tsunami
Coastal
Evacuation
Zone
1,330 335 $414,935,597 $375,060,400 $272,783,067 $1,062,779,064 Union Sanitary District (Service Territory)
Tsunami
Coastal
Evacuation
Zone
812 275 $294,031,039 $342,644,430 $248,354,097 $885,029,566 Source: CGS, Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), Critical Facilities and Infrastructure and Community Lifelines As previously noted, communities rely on roads, rail corridors, and related biking and pedestrian routes for transportation, and on water infrastructure for drinking water, wastewater service, and draining streets of rainwater. Damage to any one of these systems can threaten public safety, wreak havoc on daily life, impact properties far from flood zones, and result in economic impacts that cascade throughout California. These can be affected by a tsunami. Tsunami inundation presents a threat to critical facilities and infrastructure, and community lifelines as discussed in the following sections.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Tsunami inundation presents a threat to life and property in the Tri-City Planning Area, including impacts to community lifelines. Community lifelines that would be vulnerable to flooding include:

Packet Page No. 645
Tri-City 4-320
Local Hazard Mitigation Plan Update
March 2024
➢ Safety and Security – Search and rescue teams may be called on to perform riskier duties during a tsunami event. Police, Fire, EMS, and Public Works personnel are often called on to respond during flood emergencies. During large events, these services may become stretched. ➢ Food, Hydration, Shelter –Floodwater is often contaminated with sewage, which can lead to illness and affect clean drinking water. Those who are displaced by tsunami may need to be provided both clean drinking water, as well as food.
➢ Health and Medical – Loss of life and injuries can occur during significant tsunami events. A large tsunami flood event may make locating and rescuing affected individuals extremely difficult; many may we washed out to the Bay. As well associated flooding may complicate the ability to transport the injured possibly requiring workarounds or rerouting of injured to other facilities. Public health can also be at risk. Floodwaters generated from a tsunami can become contaminated, which can lead to illness and affect clean drinking water. Floodwaters can also pick up large amounts of debris which can further injure those that get caught up in the floodwaters.
➢ Energy – Floods can cause power grid issues and lead to power outages. During tsunami flood events gas lines may break or otherwise be damaged from erosion and debris in floodwaters. ➢ Communications – Communication systems in these areas can be damaged. An influx of service calls to dispatch centers for reporting of flooding, power outages, or other issues can occur. Messaging systems need to be deployed during these times to let the public know about closures of roads, beaches, and coastal areas as well as any requirements for evacuations or sheltering. ➢ Transportation – Transportation networks can be affected, such as flood and debris damage to bridges, railways and roads. This can cause road closures and cut off entire areas. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents. Life safety can also be an issue on roads flooded by a tsunami. ➢ Hazardous Material – Hazardous material facilities can be affected by tsunami flooding. Releases during these times can cause public health concerns, contaminate drinking water, and can cause impacts to natural systems and the environment.
➢ Water Systems – Tsunami flooding can affect the ability for water and wastewater systems to operate, especially in areas where pipes and critical infrastructure are located within tsunami evacuation zones.

During a tsunami event, many community lifelines in the Tri-City Planning Area have some level of vulnerability, but it is unlikely that any of these lifelines would be overwhelmed.

Natural, Historic, and Cultural Resources
A tsunami event can affect natural, historic and cultural resources located within the coastal areas of the Planning Area within the Tsunami Coastal Evacuation Zone. Wildlife habitats and wetland areas can be damaged or destroyed by floodwaters. This is true in the marshland and Don Edwards Park areas around the Tri-City Planning Area. Contaminated floodwaters can pollute rivers and habitats. Silt and sediment can destroy natural areas. Trees can be uprooted by high-velocity water flow. Historic and cultural resources may also be affected. Generally, the impacts are associated with damage to historic structures within the tsunami inundation areas, but other cultural resources such as those associated with Native Americans and old tribal areas can also be disturbed, damaged and lost during extreme tsunami events.

Economic Assets and Community Activities of Value
Tsunami events can cause direct damage to economic assets such as businesses and commercial centers located in affected areas. Based on the hazard parcel analysis, numerous commercial and industrial parcels Packet Page No. 646
Tri-City 4-321
Local Hazard Mitigation Plan Update
March 2024
as well as government/institutional use parcels are located in these coastal areas. During extreme events, the economy may slow while recovery efforts are prioritized. Business revenue may be reduced during extended events. Community activities and events in these coastal areas may be cancelled or rescheduled.

Impacts from Tsunami
Coastal areas located within Tsunami Coastal Evacuation Zone could be significantly affected by a tsunami.

Tsunamis can cause loss of life, damage to property and critical facilities and infrastructure, and adversely impact the environment and local economies. Tsunami inundation can result in flooding, erosion and scouring, water contamination, and spread of disease due to standing water.

Natural resource areas, marsh areas, and wetlands lie along the coastal areas, and could be negatively impacted by tsunami inundation. Water quality issues can also occur due to contamination of floodwaters.

Loss of wetlands and marsh lands from erosion and wetland migration due to tsunami inundation can reduce the natural filtration provided by wetland plants, also increasing contributing to water quality issues.

Healthy coastal ecosystems can be degraded or lost.

Future Development
Tsunami is taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.17. Wildfire
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Tri-City Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; and how climate change can affect this hazard.

Hazard/Problem Description
California is recognized as one of the most fire‐prone and consequently fire‐adapted landscapes in the world. The combination of complex terrain, Mediterranean climate, and productive natural plant communities, along with ample natural and aboriginal ignition sources, has created conditions for extensive wildfires. Wildland fire is an ongoing concern for the Planning Area. Generally, the fire season extends from early spring through late fall of each year during the hotter, dryer months. However, in recent years, wildfire season is more of a year around event. Fire conditions arise from a combination of high temperatures, low moisture content in the air and fuel, an accumulation of vegetation, and high winds.

Potential losses from wildfire include human life, structures and other improvements, natural and cultural resources, quality and quantity of water supplies, cropland, timber, and recreational opportunities.

Economic losses could also result. Smoke and air pollution from wildfires can be a severe health hazard.

In addition, catastrophic wildfire can create favorable conditions for other hazards such as flooding, landslides and mudflows, and erosion during the rainy season. Additional losses could occur if PG&E Packet Page No. 647
Tri-City 4-322
Local Hazard Mitigation Plan Update
March 2024
initiates a power shutdown during extreme fire weather conditions. This is discussed in greater detail at the end of Section .

Wildfire Smoke and Air Quality
Smoke from wildfires is made up of gas and particulate matter, which can be easily observed in the air. Air quality standards have been established to protect human health with the pollutant referred to as PM2.5 which consists of particles 2.5 microns or less in diameter. These smaller sizes of particles are responsible for adverse health effects because of their ability to reach the lower regions of the respiratory tract.

As noted above, the 2023 State Hazard Mitigation Plan noted that the danger of wildfire smoke comes primarily from particulate matter 2.5 (PM2.5). On a given day, California wildfires can produce 10 times more PM2.5 air pollution than is produced by all other pollution sources combined. The small particles in PM2.5 pollution are capable of reaching deep into the lungs, causing a host of complications, including significantly increased risks of heart disease, respiratory disease, asthma, and premature mortality. Smoke from wildfires that burn homes and other structures can additionally contain toxic materials such as asbestos and heavy metals. Studies indicate that wildfire smoke is up to 10 times more harmful than other forms of PM2.5 pollution.

Location and Extent
Wildfire is part of California’s natural ecology. However, its danger and cost have increased as fire-prone areas across the State have been increasing as well. This is especially true in the Tri-City Planning Area.

Over the years, fire suppression practices and invasive plants have contributed to fuel build-up and increased the risk of more catastrophic wildfire events.

Wildland fires affect grass, forest, and brushlands, as well as any structures located within them. Where there is human access to wildland areas the risk of fire increases due to a greater chance for human carelessness and historical fire management practices. Generally, there are four major factors that sustain wildfires and allow for predictions of a given area’s potential to burn. These factors include fuel, topography, weather, and human actions.
➢ Fuel – Fuel is the material that feeds a fire and is a key factor in wildfire behavior. Fuel is generally classified by type and by volume. Fuel sources are diverse and include everything from dead tree leaves, twigs, and branches to dead standing trees, live trees, brush, and cured grasses. Also to be considered as a fuel source are manmade structures, such as homes and other associated combustibles.

The type of prevalent fuel directly influences the behavior of wildfire. Fuel is a primary factor that is under human control.
➢ Topography – An area’s terrain and land slopes affect its susceptibility to wildfire spread. Both fire intensity and rate of spread increase as slope increases due to the tendency of heat from a fire to rise via convection. The arrangement of vegetation throughout a hillside can also contribute to increased fire activity on slopes.
➢ Weather – Weather components such as temperature, relative humidity, wind, and lightning also affect the potential for wildfire. High temperatures and low relative humidity dry out fuels that feed wildfires, creating a situation where fuel will ignite more readily and burn more intensely. Thus, during periods of drought, the threat of wildfire increases. Wind is the most treacherous weather factor. The greater Packet Page No. 648
Tri-City 4-323
Local Hazard Mitigation Plan Update
March 2024
a wind, the faster a fire will spread and the more intense it will be. In addition to wind speed, wind shifts can occur suddenly due to temperature changes or the interaction of wind with topographical features such as slopes or steep hillsides. Winds have caused power lines to arc and become fire risks to the Planning Area. Lightning also ignites wildfires. Lightning can come both during thunderstorms, or can be dry lightning. In 2020, a lightning siege caused multiple fires near the Planning Area. During much of the year (winter and spring months), temperatures in the East Bay are moderate, and vegetation is relatively moist and less prone to catastrophic wildfires. Summers often bring overnight and morning fog along the hills until around noon, with moist midday winds blowing westerly in from the coast.

However, with limited precipitation during Summer and Fall, vegetation dries out and is more susceptible to wildfire ignitions and spread. When combined with a phenomenon known as “Diablo winds” the potential for an out of control wildfire exists. These hot, dry winds blow from the east, often in the early morning when major fires are least expected. They can fan the flames of small sparks into wildfires that have been observed to move down from a ridge top in 30 minutes, expand to one square mile in an hour, and consume hundreds of residences in one day. The limited days each year when all of the high fire danger conditions—low humidity, high temperatures, and hot, dry Diablo winds blowing in from the east—are extreme are labeled Red Flag days, and often occur in the fall months.
➢ Human Actions – Most wildfires are ignited by human action, the result of direct acts of arson, carelessness, or accidents. Many fires originate in populated areas along roads and around homes, and are often the result of arson or careless acts such as the disposal of cigarettes, use of equipment or debris burning. Recreation areas that are located in high fire hazard areas also result in increased human activity that can increase the potential for wildfires to occur.

Fires can have a quick speed of onset, especially during periods of drought. Fires can burn for a short period of time, or may have durations lasting for a week or more. Wildfire can affect any area of the Planning Area; however, CAL FIRE has mapped areas in California that are at risk to wildfire.

Methodologies for this analysis and maps showing the various Fire Hazard Severity Zones, which range from Urban-Unzoned to Very High, can be found in the Vulnerability Assessment below. Geographic extents of wildfire can be seen on Figure 4-117 and is detailed by jurisdiction in Table 4-91.

Packet Page No. 649
Tri-City 4-324
Local Hazard Mitigation Plan Update
March 2024
Figure 4-117 Tri-City Planning Area – CAL FIRE Fire Hazard Severity Zones Packet Page No. 650
Tri-City 4-325
Local Hazard Mitigation Plan Update
March 2024
Table 4-91 Tri-City Planning Area – CAL FIRE Fire Hazard Severity Zones Geographical Extents by Jurisdiction
Jurisdiction/
Fire Hazard
Severity Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
Fremont
Very High 16.07 0.0% 0.99 0.0% 15.08 0.0%
High 15,948.10 18.7% 4,734.21 10.2% 11,213.89 29.0%
Moderate 2,559.08 3.0% 1,107.90 2.4% 1,451.18 3.8%
NonWildland/NonUrban19,373.45 22.7% 176.31 0.4% 19,197.14 49.7% Urban
Unzoned
47,394.13 55.6% 40,606.59 87.1% 6,787.54 17.6%
Fremont
Total
85,290.82 100.0% 46,626.00 100.0% 38,664.82 100.0%
Newark
Very High 0 0.0% 0 0.0% 0 0.0%
High 2,478.89 16.9% 1,530.64 16.0% 948.25 18.4%
Moderate 935.49 6.4% 844.18 8.9% 91.31 1.8%
NonWildland/NonUrban3,120.03 21.2% 240.25 2.5% 2,879.78 55.9% Urban
Unzoned
8,153.84 55.5% 6,922.42 72.6% 1,231.42 23.9%
Newark Total 14,688.25 100.0% 9,537.48 100.0% 5,150.76 100.0% Union City
Very High 62.74 0.4% 0.00 0.0% 62.74 0.9%
High 6,253.69 37.5% 656.35 7.0% 5,597.34 76.4%
Moderate 498.23 3.0% 301.27 3.2% 196.96 2.7%
NonWildland/NonUrban173.12 1.0% 26.57 0.3% 146.55 2.0% Urban
Unzoned
9,680.36 58.1% 8,357.09 89.5% 1,323.27 18.1%
Union City
Total
16,668.15 100.0% 9,341.29 100.0% 7,326.86 100.0%
Alameda County Water District (Service Territory)
Very High 4.11 0.0% 0 0.0% 4.11 0.0%
High 13,047.47 12.2% 5,508.25 8.6% 7,539.22 17.6%
Moderate 3,193.37 3.0% 2,058.96 3.2% 1,134.41 2.7%
Packet Page No. 651
Tri-City 4-326
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction/
Fire Hazard
Severity Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
NonWildland/NonUrban24,781.85 23.2% 443.13 0.7% 24,338.72 57.0% Urban
Unzoned
65,657.08 61.5% 55,957.92 87.5% 9,699.16 22.7%
Alameda
County Water
District Total
106,683.89 100.0% 63,968.27 100.0% 42,715.62 100.0%
Union Sanitary District (Service Territory)
Very High 0 0.0% 0 0.0% 0 0.0%
High 8,750.39 11.3% 5,248.70 8.3% 3,501.69 24.7%
Moderate 3,007.67 3.9% 2,045.80 3.2% 961.86 6.8%
NonWildland/NonUrban1,121.91 1.4% 98.49 0.2% 1,023.42 7.2% Urban
Unzoned
64,620.36 83.4% 55,949.15 88.3% 8,671.21 61.2%
Union
Sanitary
District Total
77,500.32 100.0% 63,342.14 100.0% 14,158.18 100.0%
Source: CAL FIRE
Fire Responsibility Areas
There are numerous state and federal wildland fire protection agencies that have responsibility within California, Alameda County and the Tri-City Planning Area. CAL FIRE has a legal responsibility to provide fire protection on all SRA lands, which are defined based on land ownership, population density and land use. There are also numerous local fire departments and fire protection districts that serve local areas, many of whom have mutual aid agreements with each other as well as state and federal agencies for fire suppression and protection. Fire Responsibility Areas are generally categorized by Federal Responsibility Areas (FRA), State Responsibility Areas (SRA) and Local Responsibility Areas (LRA).

Locations of each responsibility area are shown in Figure 4-118. As shown, almost the entire Tri-City Planning Area falls in the LRA. The Don Edwards National Wildlife Refuge is the only area in the FRA.

As such, no tabular analysis was performed.

Packet Page No. 652
Tri-City 4-327
Local Hazard Mitigation Plan Update
March 2024
Figure 4-118 Tri-City Planning Area – Fire Responsibility Areas by FRA, SRA, LRA Packet Page No. 653
Tri-City 4-328
Local Hazard Mitigation Plan Update
March 2024
Past Occurrences
Disaster Declaration History
There have been 1 federal and 2 state disaster declarations due to wildfire in Alameda County. This can be seen in Table 4-92. These were from the 1991 Tunnel Fire and the 1970 Fish Canyon Fire.

Table 4-92 Alameda County Disaster Declarations 1950-2022 from Wildfire Disaster Type Federal Declarations State Declarations
Count Years Count Years
Wildfire 1 1970 2 1970, 1991
Source: Cal OES, FEMA
NCDC Events
The NCDC has tracked wildfire events in each County dating back to 1993. The events in Alameda County are shown in Table 4-93.

Table 4-93 Alameda County NCDC Storm Events 1/1/1950-12/31/2022* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Wildfire 18 0 0 6 1 $10,000 $0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of the Planning Area and outside of Alameda County.

CAL FIRE Events
CAL FIRE, USDA Forest Service Region 5, Bureau of Land Management (BLM), the National Park Service (NPS), Contract Counties and other agencies jointly maintain a comprehensive fire perimeter GIS layer for public and private lands throughout the state. The data covers fires going back to 1878. For the National Park Service, Bureau of Land Management, and US Forest Service, fires of 10 acres and greater are reported. For CAL FIRE, timber fires greater than 10 acres, brush fires greater than 50 acres, grass fires greater than 300 acres, and fires that destroy three or more residential dwellings or commercial structures are reported. CAL FIRE recognizes the various federal, state, and local agencies that have contributed to this dataset, including USDA Forest Service Region 5, BLM, National Park Service, and numerous local agencies.

Fires may be missing altogether or have missing or incorrect attribute data. Some fires may be missing because historical records were lost or damaged, fires were too small for the minimum cutoffs, documentation was inadequate, or fire perimeters have not yet been incorporated into the database. Also, agencies are at different stages of participation. For these reasons, the data should not be used for statistical or analytical purposes.

The data provides a reasonable view of the spatial distribution of past large fires in California Figure 4-119 shows fire history for the area surrounding the Tri-City Planning Area, colored by the size of the acreage Packet Page No. 654
Tri-City 4-329
Local Hazard Mitigation Plan Update
March 2024
burned. This map contains fires from 1950 to 2022. Each of them was tracked by CAL FIRE. Many more small fires have occurred but were not included in the analysis.

Packet Page No. 655
Tri-City 4-330
Local Hazard Mitigation Plan Update
March 2024
Figure 4-119 Tri-City Planning Area – Wildfire History 1950 to 2022 Packet Page No. 656
Tri-City 4-331
Local Hazard Mitigation Plan Update
March 2024
Planning Committee Events
Discussions of Planning Committee events for each jurisdiction can be found in their respective annexes to this LHMP Update.

Likelihood of Future Occurrences
Highly Likely — Conventional thought states that from May to October of each year, the Tri-City Planning Area faces a serious wildland fire threat. Recently, it is as though the fire threat is almost year around.

Fires will continue to occur on an annual basis in and near the Planning Area. The threat of wildfire and potential losses are constantly increasing as human development and population increase and the wildland urban interface areas expand. Due to its adjacent high fuel load and long, dry summers, the Planning Area continues to be at risk from wildfire. The likelihood that fires will occur in a given year is almost 100%.

Most of the fires are extinguished quickly and burn less than an acre or only a few acres. Larger fires burning tens of acres, hundreds of acres or more occur much less frequently.

Climate Change and Wildfire
Climate change and its effect on wildfire near the Planning Area has been discussed by Cal-Adapt.

Cal-Adapt Predictions
Warmer temperatures can exacerbate drought conditions. Drought often kills plants and trees, which serve as fuel for wildfires. Warmer temperatures could increase the number of wildfires and pest outbreaks, such as the western pine beetle. Cal-Adapt’s wildfire tool predicts the potential increase in the amount of burned areas for the year 2090-2099, as compared to recent (2010) conditions. This is shown in Figure 4-120.

Based on this model, Cal-Adapt predicts that wildfire risk in Alameda County will increase moderately at the end of the century. However, wildfire models can vary depending on the parameters used. Cal-Adapt does not take landscape and fuel sources into account in their model. In all likelihood, in the Tri-City Planning Area, precipitation patterns, high levels of heat, topography, and fuel load will determine the frequency and intensity of future wildfire.

Packet Page No. 657
Tri-City 4-332
Local Hazard Mitigation Plan Update
March 2024
Figure 4-120 Tri-City Planning Area – Projected Increase in Wildfire Burn Areas Source: Cal-Adapt
Wildfire scenario projections were done by Cal-Adapt, based on statistical modeling from historical data of climate, vegetation, population density, and fire history. The fire modeling ran simulations on five variables on a monthly time step - Large fire presence/absence, Number of fires given presence, Area burned in a grid cell given a fire, High severity burned area given a fire and emissions. These are shown on Figure 4-121. The upper chart shows modeled annual averages of area burned for the Planning Area under the RCP 4.5 scenario, while the lower chart shows modeled annual averages of area burned for the Planning Area under the RCP 8.5 scenario.

Packet Page No. 658
Tri-City 4-333
Local Hazard Mitigation Plan Update
March 2024
Figure 4-121 Tri-City Planning area – Future Annual Averages of Acres Burned under RCP

4.5 and 8.5 Scenarios
Source: Cal-Adapt
Packet Page No. 659
Tri-City 4-334
Local Hazard Mitigation Plan Update
March 2024
Vulnerability Assessment
Vulnerability—High
Risk and vulnerability to the Tri-City Planning Area from wildfire is of significant concern. Wildfire is not the only hazard that the Planning Area faces, but it is one of the most significant hazards, based on the number, severity, and proximity of wildfires to the Planning Area over the last several years and the increasing potential for a large catastrophic wildfire. Wildfires that occur in the Tri-City Planning Area occur from a variety of both natural and manmade causes. The Planning Area can be affected both by fires that start on or near Planning Area lands as well as those that start elsewhere and move in to the Planning Area. In addition to burning large areas of land, air quality can be affected in the Planning Area by fires occurring inside the Planning Area as well as those from many miles away. As growth continues and populations increase in the Planning Area, the potential for wildfires will also increase.

The whole of the Tri-City Planning Area is at some measure of vulnerability to wildfire. An assessment of a community’s vulnerability to wildfire begins with an understanding of local exposure to wildfire. This is included in the assets at risk discussion that follows the smoke and air quality discussion below.

Assets at Risk
Assets at risk from wildfire include people and populations; structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. These are discussed in the following sections.

It should be noted for all sections below that more specific information may be found in each participating jurisdiction’s annex to this Base Plan.

Methodology
As part of the Fire and Resource Assessment Program (FRAP), CAL FIRE was mandated to map areas of significant fire hazards based on fuels, terrain, weather, and other relevant factors. These zones, referred to as FHSZs, then define the application of various mitigation strategies to reduce risk associated with wildland fires.

Fire hazard is a way to measure the physical fire behavior so that people can predict the damage a fire is likely to cause. Fire hazard measurement includes the speed at which a wildfire moves, the amount of heat the fire produces, and most importantly, the burning fire brands that the fire sends ahead of the flaming front.

The fire hazard model developed by CAL FIRE considers the wildland fuels. Fuel is that part of the natural vegetation that burns during wildfire. The model also considers topography, especially the steepness of the slopes. Fires burn faster as they burn up-slope. Weather (temperature, humidity, and wind) has a significant influence on fire behavior. The model recognizes that some areas of California have more frequent and severe wildfires than other areas. Finally, the model considers the production of burning fire brands (embers) how far they move, and how receptive the landing site is to new fires.

Packet Page No. 660
Tri-City 4-335
Local Hazard Mitigation Plan Update
March 2024
In 2007, CAL FIRE updated its Fire Hazard Severity Zone (FHSZ) maps for the State of California to provide updated map zones, based on new data, science, and technology that will create more accurate zone designations such that mitigation strategies are implemented in areas where hazards warrant these investments. The zones will provide specific designation for application of defensible space and building standards consistent with known mechanisms of fire risk to people, property, and natural resources. The program is still ongoing with fire hazard severity zone maps being updated based on designated responsibility areas: FRA, SRA, and LRA.

CAL FIRE mapped the SRA Fire Hazard Severity Zones (FHSZs), or areas of significant fire hazard, based on fuels, terrain, weather, and other relevant factors. Within the Planning Area, the Alameda Draft (c1fhszl06_1) and Adopted (fhszs06_3_1) datasets were utilized for the analysis and contained all FHSZ hazard classes from Very High to Urban Unzoned. Since it is possible for any given parcel to intersect with multiple categories for purposes of this analysis, the parcel centroid was used to determine which FHSZ to assign to each parcel. Once completed, the parcel boundary layer was joined to the centroid layer and values were transferred based on the identification number in the Assessor’s database and the parcel layer.

Based on this approach, the FHSZs for the Planning Area were determined and further broken out by land use and included information on both land and improved values.

This methodology is used below for the FHSZ analysis of people and populations, structures, and critical facilities at risk as well as with respect to future development areas.

People and Populations
All populations are at some vulnerability to wildfire. Certain vulnerable populations are at greater risk to the effects of wildfire as well as smoke and air quality issues that wildfires bring. Vulnerable populations include:
➢ Unhoused
➢ Infants and children under age five and their caregivers ➢ Elderly (65 and older)
➢ Individuals with disabilities
➢ Individuals’ dependent on medical equipment
➢ Individuals who exercise or recreate outdoors
➢ Individuals who work outdoors
➢ Individuals with impaired mobility
Planning Area residents that live in CAL FIRE FHSZs are often the most vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to the residential population within the Planning Area, CAL FIRE’s wildfire hazard layers were overlayed on the parcel layer and linked to the Assessor data. Those residential parcel centroids that intersect the mapped layers were counted and multiplied by the 2020 Census Bureau average household factors for each jurisdiction. These are shown by jurisdiction in Table 4-94.

Packet Page No. 661
Tri-City 4-336
Local Hazard Mitigation Plan Update
March 2024
Table 4-94 Tri-City Planning Area – Improved Residential Parcels and Population by CAL FIRE Fire Hazard Severity Zone by Jurisdiction
Jurisdiction
Very High High Moderate
Improved
Residential
Parcels
Population
at Risk
Improved
Residential
Parcels
Population
at Risk
Improved
Residenti
al Parcels
Population
at Risk
City of Fremont 0 0 4,966 14,848 2,717 8,124
City of Newark 0 0 1,782 5,916 472 1,567
City of Union City 0 0 592 1,995 580 1,955
Source: CAL FIRE, 2020 US Census Bureau – City of Fremont (2.99); City of Newark (3.32); City of Union City 3.37.

These numbers reflect low end estimates as the property use categories based on the Assessor data utilized for this LHMP Update assumes all residential properties are single family residences. However, many of the residential parcels actually include multi-family units, including apartments, condominiums and well as duplexes and triplexes. These variations in residential property use were not accounted for in the analysis, which skews populations results to be lower.

Structures
All structures in the Tri-City Planning Area have some risk to wildfire. GIS was used to determine the possible impacts of wildfire within the Planning Area. Summary analysis results for each jurisdiction in the Planning Area are shown in Table 4-95, which summarizes total parcel counts, improved parcel counts and their structure values by fire hazard severity zone.

Table 4-95 Tri-City Planning Area – Count and Value of Parcels (and Structures) by CAL FIRE Fire Hazard Severity Zone by Jurisdiction
Jurisdiction /
Fire Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Fremont
Very High 6 0 $0 $0 $0 $0
High 6,528 5,297 $3,363,204,423 $6,276,880,497 $4,457,670,541 $14,097,755,461 Moderate 3,311 2,812 $1,215,755,103 $2,464,416,083 $1,390,706,082 $5,070,877,268 NonWildland/NonUrban680 447 $274,730,875 $590,653,554 $330,695,278 $1,196,079,707 Urban
Unzoned
73,741 69,575 $17,858,811,741 $36,124,692,489 $22,016,492,751 $75,999,996,981 Fremont
Total
84,266 78,131 $22,712,502,142 $45,456,642,623 $28,195,564,652 $96,364,709,417 Newark
Very High 0 0 $0 $0 $0 $0
High 2,441 1,819 $780,191,541 $1,507,491,007 $917,426,257 $3,205,108,805 Packet Page No. 662
Tri-City 4-337
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction /
Fire Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Moderate 574 477 $141,642,095 $224,772,940 $149,092,441 $515,507,476 NonWildland/NonUrban33 1 $8,044,636 $3,339,480 $3,339,480 $14,723,596 Urban
Unzoned
14,110 13,089 $3,260,025,941 $6,488,659,703 $4,422,870,921 $14,171,556,565 Newark Total 17,158 15,386 $4,189,904,213 $8,224,263,130 $5,492,729,099 $17,906,896,442 Union City
Very High 0 0 $0 $0 $0 $0
High 754 606 $162,252,835 $443,224,895 $320,312,114 $925,789,844 Moderate 636 583 $119,237,193 $270,650,194 $135,588,384 $525,475,771 NonWildland/NonUrban40 31 $19,220,609 $27,543,990 $13,771,994 $60,536,593 Urban
Unzoned
17,172 16,269 $3,696,081,952 $7,920,335,377 $4,961,734,699 $16,578,152,028 Union City
Total
18,602 17,489 $3,996,792,589 $8,661,754,456 $5,431,407,191 $18,089,954,236 Alameda County Water District (Service Territory)
Very High 0 0 $0 $0 $0 $0
High 9,505 7,688 $4,291,952,275 $8,227,226,132 $5,709,072,011 $18,228,250,418 Moderate 4,489 3,859 $1,452,964,881 $2,943,837,767 $1,667,189,572 $6,063,992,220 NonWildland/NonUrban785 479 $294,108,664 $621,537,024 $347,806,752 $1,263,452,440 Urban
Unzoned
105,098 98,983 $24,862,147,444 $50,625,721,307 $31,520,074,702 $107,007,943,453 Alameda
County Water
District
(Service
Territory)
Total
119,877 111,009 $30,901,173,264 $62,418,322,230 $39,244,143,037 $132,563,638,531 Union Sanitary District (Service Territory)
Very High 0 0 $0 $0 $0 $0
High 9,252 7,620 $4,161,501,446 $8,162,380,849 $5,649,570,138 $17,973,452,433 Moderate 4,458 3,859 $1,446,208,627 $2,943,837,767 $1,667,189,572 $6,057,235,966 NonWildland/NonUrban553 477 $289,854,398 $617,960,142 $344,229,870 $1,252,044,410 Packet Page No. 663
Tri-City 4-338
Local Hazard Mitigation Plan Update
March 2024
Jurisdiction /
Fire Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Estimated
Contents
Value
Total Value
Urban
Unzoned
105,097 99,003 $24,847,636,121 $50,578,745,538 $31,441,846,516 $106,868,228,175 Union
Sanitary
(Service
Territory)
District Total
119,360 110,959 $30,745,200,592 $62,302,924,296 $39,102,836,096 $132,150,960,984 Source: Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023), CAL FIRE Critical Facilities and Infrastructure, and Community Lifelines Wildfire presents a threat to critical facilities and infrastructure, and community lifelines. The following analysis identifies critical facilities and infrastructure at risk to wildfire, followed by a discussion of vulnerability of community lifelines.

Critical Facilities and Infrastructure
Analysis of critical facilities in each jurisdiction in the Tri-City Planning Area can be found in their respective annexes to this LHMP Update.

Community Lifelines
Wildfire presents a threat to life and property, including to community lifelines in the Tri-City Planning Area. Community lifelines that would be vulnerable to wildfire include:
➢ Safety and Security –Police, Fire, and EMS personnel are often called on to respond during fire emergencies. This would be especially true if a wildfire occurred in or near the Planning Area.

Emergency resources may be stretched during a large event. ➢ Food, Hydration, Shelter – Shelters may need to be opened to handle those displaced by a wildfire.

Food and water would need to be provided.
➢ Health and Medical – There may be injuries and deaths from wildfire. Patient movement from accident scenes by EMS may have to be rerouted due to fire or smoke issues. Hospitals could see an influx of injured. Public health can be at risk from air quality issues from smoke. ➢ Energy – Wildfires could impact large areas of above ground electric infrastructure, causing widespread power outages. Even the threat of wildfire can cause power outages when fire weather conditions lead to PSPS events. Fire may cause fuel transportation to be delayed, causing local shortages.
➢ Communications – Communication systems can be damaged during a wildfire. An influx of service calls to dispatch centers for reporting of wildfire, power outages, or other issues can occur. Calls to and from family and friends during a wildfire can further overwhelm communication systems such as cell towers and other infrastructure. Demand may exceed the capacity of these systems to remain operational during response efforts. Messaging systems need to be deployed during these times to let the public know about road closures or evacuation routes. ➢ Transportation – Highways and local roads may see closures. These closures can affect response personnel (EMS, Fire, Police) as well as cause additional traffic issues for residents. Evacuation routes may be affected and overwhelmed during a large event.

Packet Page No. 664
Tri-City 4-339
Local Hazard Mitigation Plan Update
March 2024
➢ Hazardous Material – hazardous material facilities can be affected by wildfire. A release during these times can cause additional risk to responders, as well as additional exposure to the environment. ➢ Water Systems – Water systems may be taxed during wildfires. Access to water for firefighting can also be a challenge if power outages occur in affected areas. Wastewater systems can also be affected by an increase in silt, debris ash, and other materials entering the systems.

A large wildfire event could temporarily overwhelm many facilities and community lifelines in the Tri-City Planning Area.

Natural, Historic, and Cultural Resources
Natural, historic, and cultural resources located within areas at risk to wildfire would be vulnerable. Should a wildfire occur in the Planning Area, the impacts to natural, historic, and cultural resources could be extensive and include air pollution, contamination from water runoff containing toxic products, and other environmental discharges or releases from burned materials affecting soils, habitat areas, wildlife, and aquatic resources. Historic and cultural resources can be affected and are often more vulnerable due to their older age, construction type, and lack of fire prevention infrastructure such as sprinklers.

Economic Assets and Community Activities of Value
Wildfires in the Planning Area can cause direct damage to economic assets such as businesses and commercial centers located in affected areas. During extreme events, the economy may slow while recovery efforts are prioritized. Business revenue may be reduced during extended events. Community activities and events in areas affected by wildfire (and smoke and air quality issues) may be cancelled or rescheduled.

Impacts from Wildfire
Potential impacts from wildfire include loss of life and injuries; damage to structures (commercial, industrial, and residential) and other improvements, natural and cultural resources, croplands, and timber; and loss of recreational opportunities. Wildfires can cause short-term and long-term disruption to the TriCity Planning Area. Fires can have devastating effects on watersheds through loss of vegetation and soil erosion, which may impact the Planning Area by changing runoff patterns, increasing sedimentation, reducing natural and reservoir water storage capacity, and degrading water quality. Fires can also affect air quality in the Planning Area; smoke and air pollution from wildfires can be a severe health hazard. Smoke impacts may come from wildfires outside the Planning Area, as well as from within.

Although the physical damages and casualties arising from wildland-urban interface fires may be severe, it is important to recognize that they also cause significant economic impacts by resulting in a loss of function of buildings and infrastructure. Economic impacts of loss of transportation and utility services may include traffic delays/detours from road and bridge closures and loss of electric power, potable water, and wastewater services. Schools and businesses can be forced to close for extended periods of time. Recently, the threat of wildfire, combined with the potential for high winds, heat, and low humidity, has caused PG&E to initiate a PSPS which can also significantly impact a community through loss of services, business closures, and other impacts associated with loss of power for an extended period. In addition, catastrophic Packet Page No. 665
Tri-City 4-340
Local Hazard Mitigation Plan Update
March 2024
wildfire can create favorable conditions for other hazards such as flooding, landslides, and erosion during the rainy season.

The impacts of a fire are felt long after the fire is extinguished. In addition to the loss of property in fires, the loss in vegetation and changes in surface soils alters the environment. When supporting vegetation is burned, hillsides become destabilized and prone to erosion. The burnt surface soils are harder and absorb less water. When winter rains come, this leads to increased runoff, erosion, and landslides in hilly areas.

Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure, utilities, and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Significant economic impact (jobs, sales, tax revenue) to the community; and ➢ Negative impact on commercial and residential property values Wildfire smoke can have negative effects to those who live in or near a fire burn area. Smoke and air pollution from wildfires can be a severe health hazard. Significant wildfires occurring in nearby northern California communities since the 2016/2017 (though not 2022) LHMP Updates have created significant air pollution affecting area residents. Planning Area residents have been affected by wildfire smoke and poor air quality, from fires both within the East Bay area and from those much further away. During 2018 during the Camp Fire in Butte County, the Planning Area experienced 13 days of the worst air quality previously experienced in the region. It was reported that during this period, residents could not see to drive or bike or hike as one could not see the trails, or trees, or cars, or other people. This occurred during the Lightning Complex Fire in 2020.

All of these impacts may be exacerbated by the effects of climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development.

Future Development
Wildfire is taken into account in future development in each of the jurisdictions of the Tri-City Planning area. Information on future development by jurisdiction can be found in each jurisdiction’s annex to this Base Plan.

4.3.18. Natural Hazards Summary
Table 4-96 summarizes the results of the hazard identification and hazard profile for the Tri-City Planning Area based on the hazard identification data and input from the various sources utilized in the Risk Assessment, including the Planning Committee. For each hazard profiled in Section 4.3, this table includes the likelihood of future occurrence and whether the hazard is considered a priority hazard for the Tri-City Planning Area based on the hazard profiles and vulnerability assessment.

Packet Page No. 666
Tri-City 4-341
Local Hazard Mitigation Plan Update
March 2024
Priority Hazards
As detailed in the hazard identification section, those hazards identified as a high or medium significance in Table 4-96 are considered priority hazards for mitigation planning. Those hazards that occur infrequently or have little or no impact on each jurisdiction in the Tri-City Planning Area were determined to be of low significance and not considered a priority hazard. Significance was determined based on the hazard profile, focusing on key criteria such as frequency, extent, and resulting damage, including deaths/injuries and property, natural and cultural resources, and economic damage. The ability of a jurisdiction to reduce losses through implementation of existing and new mitigation measures was also considered as to the significance of a hazard. This assessment was used by the Planning Committee to prioritize those hazards of greatest significance to each jurisdiction in the Tri-City Planning Area, enabling the jurisdictions to focus resources where they are most needed.

Table 4-96 Hazard Identification and Initial Determination of Priority Hazards Hazard
Likelihood of
Future
Occurrence
Fremont
Priority
Hazard
Newark
Priority
Hazard
Union
City
Priority
Hazard
ACWD
Priority
Hazard
USD
Priority
Hazard
Climate Change Highly Likely Y Y Y N Y
Coastal Flooding and Sea Level
Rise
Highly Likely Y Y Y N Y
Dam Failure Unlikely Y Y Y Y N
Drought & Water Shortage Likely N Y Y Y Y
Earthquake Occasional/
Highly Likely

Y Y Y Y Y
Flood: 1%/0.2% annual chance Occasional Y Y Y N N
Flood: Localized/Stormwater
Flooding
Highly Likely Y Y Y N Y
Landslide Likely Y N Y N N
Levee Failure Unlikely Y N N N N
Severe Weather: Extreme Cold
and Freeze
Highly Likely Y N N N N
Severe Weather: Extreme Heat Highly Likely Y Y Y N Y
Severe Weather: Heavy Rain and
Storms
Highly Likely Y Y Y Y Y
Severe Weather: High Winds Highly Likely Y N N N N
Subsidence Likely N N N N Y
Tsunami Unlikely Y Y N N N
Wildfire Highly Likely Y N Y N N
Packet Page No. 667
Tri-City 4-342
Local Hazard Mitigation Plan Update
March 2024

4.4 Capability Assessment
A capability assessment for each participating jurisdiction is included in their respective annexes to this Base Plan.

Packet Page No. 668
Tri-City 5-1
Local Hazard Mitigation Plan Update
March 2024
Chapter 5 Mitigation Strategy
44 CFR §201.6(c)(3) and §201.7(c)(3): [The plan shall include] a mitigation strategy that provides the jurisdiction’s blueprint for reducing the potential losses identified in the risk assessment, based on existing authorities, policies, programs and resources, and its ability to expand on and improve these existing tools.

This section describes the mitigation strategy process and mitigation action plan for this Tri-City 2024 LHMP Update. It describes how the all participating jurisdictions met the following requirements from the 10-step planning process:
➢ Planning Step 6: Set Goals
➢ Planning Step 7: Review Possible Activities
➢ Planning Step 8: Draft an Action Plan

5.1 Mitigation Strategy: Overview
The results of the planning process, the risk assessment, the goal setting, the identification of mitigation actions, and the hard work of the Planning Committee led to the mitigation strategy and mitigation action plan for this LHMP Update. As part of the LHMP Update process, a comprehensive review and update of the mitigation strategy portion of the 2016/2017/2022 LHMPs was conducted. Some of the initial goals and objectives from the previous LHMPs were refined and reaffirmed, some goals were deleted, and others were added. The end result was a new set of goals, to reflect the completion of or progress towards the 2016/2017/2022 actions, the updated risk assessment, and the new priorities of participating jurisdictions and this 2024 LHMP Update.

To support the updated mitigation strategy including updated goals, the mitigation actions from 2016/2017/2022 LHMPs were reviewed and assessed for their value in reducing risk and vulnerability to the Tri-City Planning Area from identified hazards and further evaluated for their inclusion in this LHMP Update (See Chapter 2 What’s New). Section 5.2 below identifies the new goals and objectives of this 2024 LHMP Update and Section 5.4 details the new mitigation action plan.

Taking all of the above into consideration, the participating jurisdictions and Planning Committee developed the following umbrella mitigation strategy for this LHMP Update:
➢ Communicate the hazard information collected and analyzed through this planning process as well as mitigation success stories so that the community better understands what can happen where and what they themselves can do to be better prepared.
➢ Implement the mitigation action plan recommendations of this Plan. ➢ Use existing rules, regulations, policies, and procedures already in place. ➢ Monitor multi-objective management opportunities so that funding opportunities may be shared and packaged, and broader constituent support may be garnered.

Packet Page No. 669
Tri-City 5-2
Local Hazard Mitigation Plan Update
March 2024

5.1.1. Continued Compliance with NFIP
Given the nature and extent of the flood hazard in the Tri-City Planning Area, an emphasis will be placed on continued compliance with the National Flood Insurance Program (NFIP) by all communities. The jurisdictional annexes for the three cities, as the three eligible NFIP communities, provide an overview of their flood management programs and continued compliance with the NFIP. For the City of Fremont, the only participating CRS community, their annex also includes a description of their CRS program. While ACWD and USD, as districts, are not eligible NFIP communities many of their mitigation actions and projects contain measures to promote effective floodplain management throughout the Tri-City Planning Area.

5.1.2. Integration of Mitigation with Post Disaster Recovery and Mitigation Strategy Funding Opportunities
Hazard mitigation actions are essential to weaving long-term resiliency into all community recovery efforts so that at-risk infrastructure, development, and other community assets are stronger and more resilient for the next severe storm event. Mitigation measures to reduce the risk and vulnerability of a community to future disaster losses can be implemented in advance of a disaster event and also as part of post-disaster recovery efforts.

Mitigation applied to recovery helps communities become more resilient and sustainable. It is often most efficient to fund eligible infrastructure mitigation through FEMA’s Public Assistance mitigation program if the asset was damaged in a storm event. Mitigation work can be added to project worksheets if they can be proven to be cost-beneficial.

Integration of mitigation into post disaster recovery efforts should be considered by all communities as part of their post disaster redevelopment and mitigation policies and procedures. Ppost-disaster redevelopment and mitigation policies and procedures are evaluated and updated as part of the Emergency Operations Plan (EOP) updates and other emergency management plans for each community.

These EOP’s and other emergency management documents, through its policies and procedures, seek to mitigate the effects of hazards, prepare for measures to be taken which will preserve life and minimize damage, enhance response during emergencies and provide necessary assistance, and establish a recovery system in order to return the community to their normal state of affairs. Mitigation is emphasized as a major component of recovery efforts.

Mitigation Strategy Funding Opportunities
An understanding of the various funding streams and opportunities enable the communities to match identified mitigation projects with the grant programs that are most likely to fund them. Additionally, some of the funding opportunities can be utilized together. Mitigation grant funding opportunities available preand post- disaster include the following.

Packet Page No. 670
Tri-City 5-3
Local Hazard Mitigation Plan Update
March 2024
FEMA HMA Grants
Cal OES administers four main types of HMA grants: (1) Hazard Mitigation Grant Program, (2) PreDisaster Mitigation Program, (3) Flood Mitigation Assistance Program, and (4) Building Resilient Infrastructure and Communities. Eligible applicants for the HMA include state and local governments, certain private non-profits, and federally recognized Indian tribal governments. While private citizens cannot apply directly for the grant programs, they can benefit from the programs if they are included in an application sponsored by an eligible applicant.

FEMA Public Assistance Section 406 Mitigation
The Robert T. Stafford Disaster Relief and Emergency Assistance Act provides FEMA the authority to fund the restoration of eligible facilities that have sustained damage due to a presidentially declared disaster. The regulations contain a provision for the consideration of funding additional measures that will enhance a facility’s ability to resist similar damage in future events.

Community Development Block Grants
The California Department of Housing and Community Development administers the State’s Community Development Block Grant (CDBG) program with funding provided by the U.S. Department of Housing and Urban Development. The program is available to all non-entitlement communities that meet applicable threshold requirements. All projects must meet one of the national objectives of the program – projects must benefit 51 percent low- and moderate-income people, aid in the prevention or clearance of slum and blight, or meet an urgent need. Grant funds can generally be used in federally declared disaster areas for CDBG eligible activities including the replacement or repair of infrastructure and housing damaged during, or as a result of, the declared disaster.

Small Business Loans
SBA offers low-interest, fixed-rate loans to disaster victims, enabling them to repair or replace property damaged or destroyed in declared disasters. It also offers such loans to affected small businesses to help them recover from economic injury caused by such disasters. Loans may also be increased up to 20 percent of the total amount of disaster damage to real estate and/or leasehold improvements to make improvements that lessen the risk of property damage by possible future disasters of the same kind.

Increased Cost of Compliance
Increased Cost of Compliance (ICC) coverage is one of several resources for flood insurance policyholders who need additional help rebuilding after a flood. It provides up to $30,000 to help cover the cost of mitigation measures that will reduce flood risk. ICC coverage is a part of most standard flood insurance policies available under NFIP.

Packet Page No. 671
Tri-City 5-4
Local Hazard Mitigation Plan Update
March 2024

5.2 Goals and Objectives
Requirement 44 CFR §201.6(c)(3)(i) and §201.7(c)(3)(i): [The hazard mitigation strategy shall include a] description of mitigation goals to reduce or avoid long-term vulnerabilities to the identified hazards.

Up to this point in the planning process, the participating jurisdictions, along with the Planning Committee, have organized resources, assessed hazards and risks, and documented mitigation capabilities. The resulting goals, objectives, and mitigation actions were developed based on these tasks. The Planning Committee held a series of meetings and exercises designed to achieve a collaborative mitigation strategy as described further throughout this section. Appendix C documents the information covered in these mitigation strategy meetings, including information on the goals development and the identification and prioritization of mitigation alternatives by the Planning Committee.

During the initial goal-setting meeting, the Planning Committee reviewed the results of the hazard identification, vulnerability assessment, and capability assessment. This analysis of the risk assessment identified areas where improvements could be made and provided the framework for the Planning Committee to formulate planning goals and objectives and to develop the mitigation strategy for the TriCity Planning Area.

Goals were defined for the purpose of this mitigation plan as broad-based public policy statements that:
➢ Represent basic desires of the community;
➢ Encompass all aspects of community, public and private; ➢ Are nonspecific, in that they refer to the quality (not the quantity) of the outcome; ➢ Are future-oriented, in that they are achievable in the future; and ➢ Are time-independent, in that they are not scheduled events.

Goals are stated without regard to implementation. Implementation cost, schedule, and means are not considered. Goals are defined before considering how to accomplish them so that they are not dependent on the means of achievement. Goal statements form the basis for objectives and actions that will be used as means to achieve the goals. Objectives define strategies to attain the goals and are more specific and measurable.

Planning Committee members were provided with the list of goals from the 2016/2017/2022 LHMPs as well as a list of other sample goals to consider. The team was told that they could use, combine, or revise the statements provided or develop new ones, keeping the risk assessment in mind. Each member was asked to provide three goal statements. Goal statements were collected and grouped into similar themes and provided to the Planning Committee. Some of the statements were determined to be better suited as objectives or actual mitigation actions and were set aside for later use. Next, the Planning Committee developed objectives that summarized strategies to achieve each goal. Edits and refinements to these new goals and resulting objectives were provided by the Planning Committee until the team came to consensus on the final goals and objectives for this 2024 LHMP Update.

Packet Page No. 672
Tri-City 5-5
Local Hazard Mitigation Plan Update
March 2024
Based on the risk assessment review and goal setting process, the Planning Committee identified the following goals, which provide the direction for reducing future hazard-related losses within the Tri-City Planning Area.

GOAL 1: Reduce risk and vulnerability of the Tri-City Planning Area to natural hazards (including climate change considerations) and prevent injuries, loss of life, and damage to property, economy, and the environment.

Objectives
➢ Minimize damage to homes, businesses, and public facilities. ➢ Promote public health and safety.
➢ Make every effort to reduce the impacts of hazards and disasters to potable and rechargeable water systems, as well as to wastewater systems.
➢ Promote a disaster resilient and healthy community that adapts to changing climate conditions and mitigates the effects of hazard impacts.
➢ Plan for and implement whole community risk reduction and resiliency strategies. ➢ Identify and integrate mitigation strategies into capital improvement programs. ➢ Reduce risk and vulnerability through the equitable and accessible planning and implementation of hazard mitigation actions and priorities.

GOAL 2: Provide protection and minimize impacts to critical facilities, infrastructure, and community lifelines. Create redundancy and reliability to significantly reduce risk of interruption or failure, minimize loss and the impacts of a disaster, and facilitate recovery.

Objectives:
➢ Identify and implement infrastructure improvements and risk reduction measures to ensure reliability and readiness before, during, and after a disaster.
➢ Identify and secure emergency equipment and resources vital to effective disaster mitigation, response, and recovery efforts.
➢ Develop contingency plans to reduce critical facility and infrastructure failures.

GOAL 3: Promote public education, awareness, and understanding of natural hazards and the risk and vulnerability they present to quality of life, property, environment, and the economy.

Objectives:
➢ Utilize a wide range of outreach and educational tools to engage and educate the whole community, including actions to take before, during, and after a hazard event to build a disaster resistant community. ➢ Foster a culture of resilience by energizing and educating the community. ➢ Encourage individual responsibility and self-sufficiency to minimize impacts to natural hazards. ➢ Establish and outreach evacuation routes and options for sheltering in place for all hazards including potentially large-scale disasters associated with earthquake and dam failure.

Packet Page No. 673
Tri-City 5-6
Local Hazard Mitigation Plan Update
March 2024
Goal 4: Build capacity and capabilities to increase disaster resilience for all hazards with a focus on the whole community.

Objectives:
➢ Develop and enhance public alert and warning capabilities and effectively communicate to the public. ➢ Build and support local capacity and reduce barriers to enable the community to prepare for, respond to, and recover from natural disasters.
➢ Establish and enhance interagency and public-private collaboration and relationships, data sharing, use of shared resources, and mitigation partnerships to reduce hazard related losses, and accelerate recovery, while being respectful of limited tax resources. ➢ Establish a financial plan specific to hazard mitigation, preparedness, response, and recovery efforts. ➢ Increase use of new technologies and high-quality data. ➢ Identify and enhance resources necessary to support implementation of capital projects and improvements that effectively mitigate hazards and impacts to the community. ➢ Develop and provide temporary response and recovery capabilities as needed to support communications, food and shelter, and other resources.
➢ Promote sharing of emergency plans and procedures with all regional partners, including critical partners such as the Red Cross.

Goal 5: Value the natural environment as a partner, recognize the ecological services provided by nature and harness these ecological processes to mitigate hazards.

Objectives:
➢ Preserve and protect natural resources.
➢ Integrate and maximize the integration of natural and beneficial functions of environmental resources into mitigation actions and projects where feasible.
➢ Mitigate undesirable disaster outcomes for the environment, watersheds, and quality of life.

Goal 6: Integrate mitigation principles and strategies into laws, regulations, policies, and guidance to promote cross -functional planning and regulatory initiatives and to support equitable outcomes to benefit the whole community.

Objectives:
➢ Increase disaster resilience among historically underserved populations, individuals with a disability or access and functional needs, and communities disproportionately impacted by disasters and climate change.

Goal 7: Build earthquake resiliency, prevent and reduce earthquake impacts, and mitigate undesirable earthquake outcomes.

Objectives:
➢ Make life safety a priority.
➢ Make every effort to reduce impacts of earthquake to potable and rechargeable water systems and to wastewater systems.

Packet Page No. 674
Tri-City 5-7
Local Hazard Mitigation Plan Update
March 2024
➢ Conduct comprehensive, interagency earthquake planning to include mitigation strategies, education and outreach, and detailed procedures for response and recovery. ➢ Mitigate secondary hazards associated with earthquake events including fire ignition and spread and prioritize measures for minimizing impacts to critical facilities, infrastructure, and community lifelines.

5.3 Identification and Analysis of Mitigation Actions
Requirement: 44 CFR §201.6(c)(3)(ii) and §201.6(c)(3)(ii): [The mitigation strategy shall include a] section that identifies and analyzes a comprehensive range of specific mitigation actions and projects being considered to reduce the effects of each hazard, with particular emphasis on new and existing buildings and infrastructure.

In order to identify and select mitigation actions to support the mitigation goals, each hazard identified in Section 4.1 was evaluated at the completion of the risk assessment as part of the second prioritization process to determine which hazards were priorities for mitigation strategy planning. Only those hazards that were determined to be a priority hazard for each participating jurisdiction were considered further in the development of hazard-specific mitigation actions. Those hazards not considered a priority for mitigation strategy development were eliminated from further consideration because the risk of a hazard event to the participating jurisdiction is unlikely, the vulnerability of the participating jurisdiction is low, or capabilities are already in place to mitigate negative impacts. Further, the resulting mitigation strategy presented in this Chapter focuses on those mitigation actions that each jurisdiction has the authority, resources, and capacity to consider for implementation over the next 5-years covered by this LHMP Update.

Table 5-1 provides a listing of priority hazards by jurisdiction to be addressed in the mitigation strategy portion of this Plan.

Table 5-1 Tri-City Planning Area: Mitigation Action Priority Hazards by Jurisdiction Hazard
Fremont
Priority
Hazard
Newark
Priority
Hazard
Union City
Priority
Hazard
ACWD
Priority
Hazard
USD
Priority
Hazard
Climate Change Y Y Y N Y
Coastal Flooding and Sea Level Rise Y Y Y N Y
Dam Failure Y Y Y Y N
Drought & Water Shortage N Y Y Y Y
Earthquake Y Y Y Y Y
Flood: 1%/0.2% annual chance Y Y Y N N
Flood: Localized/Stormwater Flooding Y Y Y N Y
Landslide Y N Y N N
Levee Failure Y N N N N
Severe Weather: Extreme Cold and
Freeze

Y N N N N
Severe Weather: Extreme Heat Y Y Y N N
Severe Weather: Heavy Rain and Storms Y Y Y Y Y
Packet Page No. 675
Tri-City 5-8
Local Hazard Mitigation Plan Update
March 2024
Hazard
Fremont
Priority
Hazard
Newark
Priority
Hazard
Union City
Priority
Hazard
ACWD
Priority
Hazard
USD
Priority
Hazard
Severe Weather: High Winds and
Tornadoes

Y N N N N
Subsidence N N N N Y
Tsunami Y Y N N N
Wildfire Y N Y N N
It is important to note, however, that all the Hazards addressed in this LHMP are included in the multi-hazard public awareness mitigation actions as well as in other multi-hazard, emergency management actions, and other hazard-specific actions, providing benefits to all participating jurisdictions to this 2024 LHMP Update.

Once it was determined which hazards warranted the development of specific mitigation actions, the participating jurisdictions and Planning Committee analyzed viable mitigation options that supported the identified goals and objectives. The Planning Committee was provided with the following list of categories of mitigation actions, which originate from the Community Rating System:
➢ Prevention
➢ Property protection
➢ Structural projects
➢ Natural resource protection
➢ Emergency services
➢ Public information
The Planning Committee was provided with examples of potential mitigation actions for each of the above categories. The Planning Committee was also instructed to consider both future and existing buildings in considering possible mitigation actions. A facilitated discussion then took place to examine and analyze the options. Appendix C provides a detailed review and discussion of the six mitigation categories to assist in the review and identification of possible mitigation activities or projects. Also utilized in the review of possible mitigation measures is FEMA’s publication on Mitigation Ideas, by hazard type. Prevention type mitigation alternatives were discussed for each of the priority hazards. This was followed by a brainstorming session that generated a list of preferred mitigation actions by hazard.

5.3.1. Prioritization Process
Once the mitigation actions were identified, the Planning Committee was provided with several decisionmaking tools, including FEMA’s recommended prioritization criteria, STAPLEE sustainable disaster recovery criteria; Smart Growth principles; and others, to assist in deciding why one recommended action might be more important, more effective, or more likely to be implemented than another. STAPLEE stands for the following:
➢ Social: Does the measure treat people fairly? (e.g., different groups, different generations) ➢ Technical: Is the action technically feasible? Does it solve the problem? Packet Page No. 676
Tri-City 5-9
Local Hazard Mitigation Plan Update
March 2024
➢ Administrative: Are there adequate staffing, funding, and other capabilities to implement the project? ➢ Political: Who are the stakeholders? Will there be adequate political and public support for the project? ➢ Legal: Does the jurisdiction have the legal authority to implement the action? Is it legal? ➢ Economic: Is the action cost-beneficial? Is there funding available? Will the action contribute to the local economy?
➢ Environmental: Does the action comply with environmental regulations? Will there be negative environmental consequences from the action?
In accordance with the DMA requirements, an emphasis was placed on the importance of a benefit-cost analysis in determining action priority. Other criteria used to assist in evaluating the benefit-cost of a mitigation action includes:
➢ Contribution of the action to save life or property
➢ Availability of funding and perceived cost-effectiveness ➢ Available resources for implementation
➢ Ability of the action to address the problem
The initial list of mitigation actions from the 2016/2017/2022 LHMPs and new actions identified during this planning process were reviewed and prioritized using the criteria (alternatives and selection criteria) in Appendix C.

With these criteria in mind, the Planning Committee were each given a set of nine colored dots, three each of red, blue, and green. The dots were assigned red for high priority (worth five points), blue for medium priority (worth three points), and green for low priority (worth one point). The Planning Committee was asked to use the dots to prioritize actions with the above criteria in mind. The point score for each action was totaled. Appendix C contains the total score given to each identified mitigation action.

The process of identification and analysis of mitigation alternatives allowed the Planning Committee to come to consensus and to prioritize recommended mitigation actions. During the voting process, emphasis was placed on the importance of a benefit-cost review in determining project priority; however, this was not a quantitative analysis. The team agreed that prioritizing the actions collectively enabled the actions to be ranked in order of relative importance and helped steer the development of additional actions that meet the more important objectives while eliminating some of the actions which did not garner much support.

Benefit-cost was also considered in greater detail in the development of the Mitigation Action Plan detailed below in Section 5.4 The cost-effectiveness of any mitigation alternative will be further considered in greater detail through performing benefit-cost project analyses when seeking FEMA mitigation grant funding for eligible actions associated with this 2024 LHMP Update.

Recognizing the limitations in prioritizing actions from multiple jurisdictions and departments and the regulatory requirement to prioritize by benefit-cost to ensure cost-effectiveness, the participating jurisdictions and Planning Committee decided to pursue actions that contributed to saving lives and property as first and foremost, with additional consideration given to the benefit-cost aspect of a project.

This process drove the development of a determination of a high, medium, or low priority for each mitigation action, and a comprehensive prioritized mitigation action plan for the Tri-City Planning Area.

Packet Page No. 677
Tri-City 5-10
Local Hazard Mitigation Plan Update
March 2024

5.4 Mitigation Action Plan
Requirement 44 CFR §201.6(c)(3)(iii) and §201.7(c)(3)(iii): [The mitigation strategy section shall include] an action plan describing how the actions identified in section (c)(3)(ii) will be prioritized, implemented, and administered by the local jurisdiction. Prioritization shall include a special emphasis on the extent to which benefits are maximized according to a cost benefit review of the proposed projects and their associated costs.

This mitigation action plan was developed to present the recommendations developed by the Planning Committee for how the Tri-City Planning Area can reduce the risk and vulnerability of people, property, critical facilities and infrastructure, and natural and cultural resources to future disaster losses. Emphasis was placed on both future and existing development. This mitigation action plan summarizes who is responsible for implementing each of the prioritized actions as well as when and how the actions will be implemented. Each action summary also includes a discussion of the benefit-cost review conducted to meet the regulatory requirements of the Disaster Mitigation Act.

Table 5-2 identifies all mitigation actions for participating jurisdictions to this LHMP Update. For each mitigation action item included in Table 5-2, a detailed mitigation implementation strategy has been developed. The detailed descriptions for each mitigation action are included in each respective jurisdictional annex to this LHMP.

The mitigation action plan summarized below contains both new action items developed for this 2024 LHMP Update as well as old actions that were yet to be completed from the 2016/2017/2022 LHMPs.

Table 5-2 indicates whether the action is new or from the 2016/2017/2022 LHMPs and Chapter 2 contains the details for each 2016/2017/2022 mitigation action item indicating whether a given action item has been completed, deleted, or deferred.

As described throughout this 2024 LHMP Update, the Tri-City Planning Area has many risks and vulnerabilities to identified hazards. Although many possible mitigation actions, as detailed in Appendix C, were brainstormed and prioritized during the mitigation strategy meetings, the resulting mitigation strategy presented in this Chapter 5 of this LHMP focuses only on those mitigation actions that are both reasonable and realistic for the communities to consider for implementation over the next 5-years covered by this 2024 Update. Thus, only a portion of the actions identified in Appendix C have been carried forward into the mitigation strategy presented in Table 5-2. Although many good ideas were developed during the mitigation action brainstorming process, the reality of determining which priority actions to develop and include in this LHMP Update came down to the actual priorities of communities, individuals and departments based in part on department direction, staffing, and available funding. The overall value of the mitigation action table in Appendix C is that it represents a wide-range of mitigation actions that can be consulted and developed for this LHMP Update during annual plan reviews and the formal 5-year update process.

It is also important to note that the participating jurisdictions have numerous existing, detailed action descriptions, which include benefit-cost estimates, in other planning documents, such as stormwater and drainage plans, flood and water management plans, climate plans, and capital improvement budgets and reports. These actions are considered to be part of this LHMP, and the details, to avoid duplication, should Packet Page No. 678
Tri-City 5-11
Local Hazard Mitigation Plan Update
March 2024
be referenced in their original source document. The Planning Committee also realizes that new needs and priorities may arise as a result of a disaster or other circumstances and reserves the right to support new actions, as necessary, as long as they conform to the overall goals of this LHMP Update.

Further, it should be clarified that the actions included in this mitigation strategy are subject to further review and refinement; alternatives analyses; and reprioritization due to funding availability and/or other criteria. The participating jurisdictions are not obligated by this document to implement any or all of these projects. Rather this mitigation strategy represents the desires of the jurisdictions to mitigate the risks and vulnerabilities from identified hazards. The actual selection, prioritization, and implementation of these actions will also be further evaluated in accordance with the mitigation categories and criteria contained in Appendix C.

It should be noted that many of the projects submitted by each jurisdiction in Table 5-2 benefit all jurisdictions whether or not they are the lead agency. Further, many of these mitigation efforts are collaborative efforts among multiple local, state, and federal agencies. In addition, the public outreach actions, as well as many of the emergency services actions, apply to all hazards regardless of hazard priority.

Collectively, this multi-jurisdictional mitigation strategy includes only those actions and projects which reflect the actual priorities and capacity of each jurisdiction to implement over the next 5-years covered by this 2024 LHMP Update.

Packet Page No. 679
Tri-City 5-12
Local Hazard Mitigation Plan Update
March 2024
Table 5-2 Tri-City Planning Area Mitigation Actions
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
City of Fremont Actions
Multi-Hazard Actions
Action 1. In the Safety Element of
the General Plan, update reference to
the Local Hazard Mitigation Plan.

New Action X X Public Information,
Prevention, Property
Protection
Action 2. Promote multi-hazard
home mitigation strategies through
public education and outreach.
2016 Action
(modified)
X X X Public Information,
Prevention, Property
Protection
Action 3. In the Fremont Municipal
Code, continuously adopt, or exceed,
California Building Code standards.
2016 Action
(modified)
X X Prevention, Property
Protection
Action 4. Maintain and expand
auxiliary power capabilities at
identified Critical Facilities.
2016 Action
(modified)
Emergency Services,
Structural Projects
Action 5. Enhance GIS mapping
of natural hazard risks, with Critical
Facilities and Lifeline overlays.
2016 Action
(modified)
Prevention,
Emergency Services
Action 6. Enhance GIS mapping
of real-time threat and hazard
conditions, with Emergency Services
overlays.
2016 Action
(modified)
Emergency Services,
Public Information
Action 7. Improve failover data
and voice communications capabilities
in support of emergency response and
continuity of operations.
2016 Action
(modified)
Emergency Services
Action 8. Study the feasibility of
constructing a new emergency
operations center facility.

New Action Emergency Services
Action 9. Enhance Public Alert
and Warning capabilities.

New Action Public Information,
Emergency Services
Action 10. Improve the resilience
and safety of electrical and natural gas
utilities.

New Action X X Prevention,
Structural Projects
Climate Change Actions
Action 11. Implement Climate Ready
Fremont.
2016 Action X X Prevention,
Natural Resource
Protection
Action 12. Implement the Urban
Forest Management Plan.

New Action X X Prevention,
Natural Resource
Protection
Packet Page No. 680
Tri-City 5-13
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 13. Prioritize growth in
transit-oriented development areas, as
identified in the General Plan, and
along designated corridors intersecting
those areas. Preserve open space in
shoreline and hill areas.

New Action X X Property Protection,
Natural Resource
Protection
Coastal Flooding and Sea Level Rise; Dam Failure; Flood: 1%/0.2%, Localized Flooding; Levee Failure; Severe Weather: Heavy Rain and Storms, Wind Actions
Action 14. Maintain or improve the
City of Fremont’s National Flood
Insurance Program, Community
Rating System classification.
2016 Action X X X Prevention,
Property Protection,
Natural Resource
Protection,
Emergency Services,
Public Information
Action 15. CRS Activities 310-370:

Maintain and expand Public
Information regarding flood risk,
conducting regular public outreach.

New Action X X X Prevention,
Public Information,
Property Protection
Action 16. CRS Activities 410-450:

Maintain and update floodplain
Mapping and Regulations
New Action X X X Prevention,
Public Information,
Natural Resource
Protection
Action 17. Conduct flood damage
reduction projects, including but not
limited to regular drainange system
maintenance and projects to identify,
assess, and mitigate flood damage and
impacts.
2016 Action
(modified)
X X X Prevention,
Natural Resource
Protection,
Structural Projects
Action 18. CRS Activities 610-630:

Maintain and improve flood Warning
and Response capabilities.

New Action X X X Public Information,
Emergency Services,
Structural Projects
Action 19. Prevent and protect
against embankment failure and floodinduced debris flows along waterways located within City-owned properties.

New Action X X X Prevention, Property
Protection
Action 20. Become a recognized
National Weather Service
StormReady® community.

New Action X X X Public Information,
Emergency Services
Action 21. Coordinate with owners
of Extremely High Hazard and High
Hazard dams which may inundate
areas of Fremont by reviewing
Emergency Action Plans, providing
updated emergency contacts, and
participating in periodic exercises.

New Action X X X Public Information,
Emergency Services
Earthquake Actions
Packet Page No. 681
Tri-City 5-14
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 22. Assess the status of all
buildings subject to the “Earthquake
Hazard Reduction and Retrofit”
provisions of the Fremont Municipal
Code. Conduct enforcement of any
subject buildings which do not
comply.
2016 Action
(modified)
X Prevention,
Property Protection
Action 23. Develop seismically
resilient water supply solutions to
support post-earthquake firefighting
operations.
2016 Action
(modified)
X X Property Protection,
Structural Projects,
Emergency Services
Action 24. Evaluate seismic risk to
Lifelines (e. g., roads and bridges,
water, natural gas, and/or electrical
distribution) using data collection and
Hazus modeling.

New Action X X Structural Projects
Action 25. Ensure development
complies with the Alquist-Priolo
Earthquake Fault Zone Act, and
otherwise avoid development of
public facilities or intensive residential,
commercial, or industrial development
in the immediate vicinity of the
Hayward Fault.

New Action X Property Protection
Action 26. Implement earthquake
early warning technologies to protect
emergency services and the public.

New Action X X Public Information
Emergency Services
Property Protection
Landslide Actions
Action 27. Land protection from
landslides through geotechnical
monitoring
2016 Action
(modified)
X X Prevention.

Property Protection,
Natural Resource
Protection
Action 28. Prevent and protect
against landslide and mudslides
through slope stabilization, retaining
walls, and other improvements.

New Action X X Prevention.

Property Protection,
Natural Resource
Protection
Tsunami Actions
Action 29. Post Tsunami Zone and
Tsunami Evacuation Route signage in
designated Tsunami Hazard Areas.

New Action X X X Public Information
Action 30. Become a recognized
National Weather Service
TsunamiReady® community.

New Action X X X Public Information,
Emergency Services
Wildfire Actions
Packet Page No. 682
Tri-City 5-15
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 31. Conduct vegetation
management on public and private
property to reduce wildfire risk.
2016 Action
(modified)
X X Prevention,
Property Protection,
Natural Resource
Protection
Action 32. Support neighborhoodbased applications to become recognized Firewise USA®
Communities, in accordance with
National Fire Prevention Association
standards.

New Action X X Prevention,
Property Protection,
Natural Resource
Protection
Action 33. In areas prone to
wildfire, prevent and protect against
heat-induced failure of roadways and
utilities by using heat-resistant
construction materials.

New Action X X Prevention,
Structural Projects
Action 34. Improve air filtration
systems at select public facilities (i. e.,
those otherwise fit to function as Air
Quality Relief Centers) to effectively
mitigate the effects of wildfire smoke.

New Action Emergency Services
City of Newark Actions
Multi-Hazard Actions
Action 1. Integrate Local Hazard
Mitigation Plan into Safety Element of
General Plan
New Action X X Prevention
Action 2. Enhance Public
Education and Awareness of Natural
Hazards and Public Understanding of
Disaster Preparedness
New Action X X Public Information
Action 3. Continuously adopt the
most current building standards and
include appendices to mitigate hazards
such as but not limited to Floods,
Wildfires, and Earthquake.

New Action X X X Prevention
Action 4. Hardening and Retrofit of
Existing Facilities
New Action X X Prevention
Emergency Services
Property Protection
Action 5. Critical Facilities Back-Up
Power
2017 Action X X Prevention
Emergency Services
Property Protection
Action 6. Update and enhance the
GIS data systems and mapping for
water-related climate hazards /
Mapping Water-Related Climate
Hazards
New Action X X Prevention
Climate Change Actions
Packet Page No. 683
Tri-City 5-16
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 7. Sea Level Rise Resiliency
Plan
2017 Action X X X Prevention
Coastal Flooding and Sea Level Rise, Dam Failure, Flood 1%/0.2%, Localized Flooding, Severe Weather Heavy Rains and Storm Actions
Action 8. Maintain good standing
under NFIP and create public outreach
program and awareness
New Action X X X Prevention
Public Information
Action 9. Partner with Alameda
County Flood Control and Water
Conservation District (ACFCD) to
identify mitigation option for various
projects
2017 Action X X X Prevention
Property Protection
Structural Projects
Natural Resource
Protection
Action 10. Alameda County Flood
Control and Water Conservation Water
District (ACFCD) Line H and Line I
Improvements
2017 Action X X X Property Protection
Structural Projects
Natural Resource
Protection
Action 11. Install storm drainage
improvements at Lindsay Tract
2017 Action X X X Property Protection
Structural Projects
Natural Resource
Protection
Action 12. Develop a Storm Drain
Master Plan
2017 Action X X X Prevention
Property Protection
Structural Projects
Natural Resource
Protection
Action 13. Ensure Emergency
Action Plans from Dam partners has
current emergency contacts in their
plans and that we participate in
exercises conducted by our partners
New action X X Prevention
Property Protection
Structural Projects
Natural Resource
Protection
Earthquake and Tsunami Actions
Action 14. Complete railroad
overcrossing at Central Avenue
2017 Action X X Structural Projects
Action 15. Establish Tsunami zone
& evacuation route signage in City’s
designated areas and education program
New action X X Prevention
Property Protection
Natural Resource
Protection
Wildfire and Severe Weather Extreme Heat Actions
Action 16. Replace Eucalyptus
Groves with non-hazardous tree species
2017 Action X X Prevention
Property Protection
Natural Resource
Protection
Action 17. Urban Forest Master Plan
development
2017 Action X X Prevention
Property Protection
Natural Resource
Protection
Packet Page No. 684
Tri-City 5-17
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
City of Union City Actions
Multi-Hazard Actions
Action 1. Integrate Local Hazard
Mitigation Plan into Safety Element of
General Plan
2017 Action X X Prevention
Action 2. Enhance Public
Education and Awareness of Natural
Hazards and Public Understanding of
Disaster Preparedness
2017 Action X X X Public Information
Action 3. Acquire two 4-wheel drive
emergency response vehicles capable of
supporting emergency/disaster workers
with enhanced safety when traveling
into and out of disaster zones or
dangerous locations.
2017 Action X X Emergency Services
Action 4. Incident Commanders
Established And ICS Trained
2017 Action X X Emergency Services
Action 5. Acquire Two Emergency
Mobile Command Centers
2017 Action X X Emergency Services
Action 6. Acquire four radio
charging stations for spare radios
2017 Action X X Emergency Services
Action 7. Consider Participation in
Incentive-Based Programs such as the
Community Rating System, Tree City
and Storm Ready.
2017 Action X X X Prevention
Action 8. Conduct a seismic and
functional assessment of the CERT
trailer behind Fire Station #31, for use
as the designated alternate EOC site.
2017 Action X X Emergency Services
Action 9. Acquire Emergency
Generators for the City's Critical
Facilities, Specifically Fire Station #31,
Senior Center, and Corporation Yard
2017 Action X X Property Protection
Property Protection
Action 10. Conduct a Feasibility
Study to Identify Temporary Morgue
Facilities
2017 Action X X Emergency Services
Action 11. Develop a Disaster
Debris Management Plan
2017 Action X X X Prevention
Emergency Services
Action 12. Develop a long-term
urban forest management plan to
address adverse future impacts on the
City's natural resources.

New Action X X Prevention
Property Protection
Natural Resource
Protection
Action 13. Conduct a Feasibility
Study to Review Necessary
Improvement Required to Make Critical
Facilities for Recovering Families After
Crisis
New Action X X Prevention
Emergency Services
Packet Page No. 685
Tri-City 5-18
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 14. Establish a BroadbandWiFi network in the Station District2017 Action X X Prevention Emergency Services
Action 15. Establish a BroadbandWiFi Network Backbone Infrastructure along Major Throughfares Throughout
the City.
2017 Action X X Prevention
Emergency Services
Climate Change Actions
Action 16. Climate Action Plan
Update
New Action X X X Prevention
Property Protection
Natural Resource
Protection
Coastal Flooding and Sea Level Rise, Dam Failure, Flood 1%/0.2%, Localized Flooding, Severe Weather Heavy Rains and Storm Actions
Action 17. Maintain good standing
under the National Flood Insurance
Program by implementing programs
that meet or exceed the minimum NFIP
requirements. Such programs include
enforcing an adopted flood damage
prevention ordinance, participating in
floodplain mapping updates, and
providing public assistance and
information on floodplain requirements
and impacts.
2017 Action X X X Prevention
Action 18. Implement Stormwater
Master Plans
New Action X X X Prevention
Property Protection
Structural Projects
Natural Resource
Protection
Action 19. Ensure Emergency
Action Plans from Dam partners has
current emergency contacts in their
plans and that we participate in
exercises conducted by our partners
New Action X X Prevention
Property Protection
Natural Resource
Protection
Drought Actions
Action 20. Develop and Maintain a
Landscape Design Manual to Provide
General Guidance and Education to the
Public on Water efficiency in
Landscaping and to serve as a Resource
for Water Efficient Landscape design
and Installation Including lists of
Recommended Site Appropriate Native
and Drought-Tolerant Plant Species.
2017 Action X X Prevention
Property Protection
Natural Resource
Protection
Earthquake and Tsunami Actions
Packet Page No. 686
Tri-City 5-19
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 21. Work with ACWD to
Design and Install Seismically Resilient
Backbone Pipeline through
Liquefaction Soils in Union City.
2017 Action X X Emergency Services
Structural Projects
Property Protection
Natural Resource
Protection
Action 22. Conduct a Feasibility
Study to Review the Highway Overpass
Bridge of Alvarado-Niles Rd. over I880, for any Seismic Upgrades. 2017 Action X X Structural Projects
Action 23. Coordinate with the City
of Hayward to Conduct a Feasibility
Study to Review any Seismic Upgrades
for the I-880 Overpass over Whipple
Road
2017 Action X X Structural Projects
Action 24. Construct Grade
Separations on the Niles Subdivisions
and the Oakland Subdivision in the
Decoto Neighborhood and on the
Coast Subdivision on Union City Blvd,
Smith Street, Dyer Street, and Alvarado
Blvd.
2017 Action X X Structural Projects
Wildfire and Severe Weather Extreme Heat Actions
Action 25. Acquire handheld GPS
trackers to develop an urban tree
inventory for monitoring the health of
trees and identifying potentially
dangerous or dead trees.
2017 Action X X Prevention
Natural Resource
Protection
Action 26. Develop a long-term
urban forest management plan to
address adverse future impacts on the
City’s natural resources
2017 Action X X Prevention
Natural Resource
Protection
ACWD Actions
Multi-Hazard Actions
Action 1. Develop and maintain an
asset management program that tracks
natural hazard events.
2022 Action X X X Prevention
Action 2. Reevaluate standby
generator needs and purchase and
install as needed
2022 Action X X Prevention
Emergency Services
Property Protection
Action 3. Retrofit and/or update
District tanks and reservoirs to improve
seismic resilience.
2022 Action X X Property Protection
Structural Projects
Action 4. Consider the purchase
and installation of fuel cells as
alternative emergency power backup
systems at Newark Desalination Facility
and the Blending Facility.
2022 Action X X Prevention
Emergency Services
Property Protection
Packet Page No. 687
Tri-City 5-20
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 5. Repair diversion capability
through the Kaiser embankment to
ensure post disaster groundwater
recharge capabilities and to protect the
natural and beneficial functions of the
Kaiser Ponds.
2022 Action X X X Property Protection
Structural Projects
Natural Resource
Protection
Action 6. As needed, review, update
and enhance intertie agreements with
the City of Hayward and the City of
Milpitas.
2022 Action X X Prevention
Property Protection
Emergency Services
Action 7. Study water supply
reliability alternatives including recycled
water, and Lake Del Valle and Los
Vaqueros reservoir storage expansion
projects to improve water supply
capabilities from catastrophic losses of
supply.
2022 Action X X Prevention
Property Protection
Emergency Services
Action 8. Continue to participate in
local emergency response trainings and
exercises.
2022 Action X X Emergency Services
Action 9. Continue to integrate the
capital improvement program with the
LHMP.
2022 Action X X Prevention
Property Protection
Structural Projects
Emergency Services
Natural Resource
Protection
Drought and Water Shortage
Action 10. Continue to prioritize and
implement distribution system
replacements and improvements to
identified critical consumers and/or
vulnerable areas.
2022 Action X X Prevention
Property Protection
Natural Resource
Protection
Action 11. Install a second Deep
Aquifer water well at the Mowry
Wellfield.
2022 Action X X Prevention
Emergency Services
Property Protection
Natural Resource
Protection
Action 12. Blend Facility for PFAS. 2022 Action X X Prevention Structural Projects
Action 13. Complete a redesign of
blending facility to allow low
production and neat chemical feed.
2022 Action Prevention
Structural Projects
Action 14. Complete desalinization
facility reliability enhancements as
indicated in the Integrated Resources
Plan.
2022 Action Structural Projects
Property Protection
Natural Resource
Protection
Earthquake Actions
Packet Page No. 688
Tri-City 5-21
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Action 15. Design and install a
seismically resilient backbone pipeline
through liquefiable soils, primarily in
Union City.
2022 Action X X Emergency Services
Structural Projects
Property Protection
Natural Resource
Protection
Action 16. Install emergency
isolation valves into the distribution
system with remote operation capability,
as appropriate.
2022 Action X X Emergency Services
Structural Projects
Property Protection
Natural Resource
Protection
Action 17. Enhance Booster
Pumping to the Upper Zones (for
example PR-1 or Seven Hills)
2022 Action X X Emergency Services
Structural Projects
Property Protection
Natural Resource
Protection
USD Actions
Multi-Hazard Actions
Action 1. Public Education
Outreach
2017 Action X X Property Protection
Emergency Services
Action 2. Enhanced Treatment and
Site Upgrade (ETSU)- Phase 1A
Campus Building and Aeration Basin
Modifications; Phase 1B Secondary
Clarifiers & Effluent Facilities; Phase
1C Plant Equalization Storage
2017 Action X X Property Protection
Structural Projects
Climate Change Actions
Action 3. Irvington Pump Station
Solar & Battery Project
New Action X X Property Protection
Emergency Services
Action 4. Battery Storage & 3rd
Cogen
New Action X X Public Information
Sea Level Rise, Earthquake Actions
Action 5. Field Ops Building
Seismic Upgrade
2017 Action X X Property Protection
Structural Projects
Drought/Water Shortage Actions
Action 6. Digester #8 New Action X X Property Protection Structural Projects
Earthquake Actions
Action 7. Seismic Retrofit of
Concrete Structures
2017 Action X X Property Protection
Structural Projects
Action 8. Newark Pump Station
Emergency Outfall
2017 Action X X Property Protection
Structural Projects
Natural Resource
Protection
Action 9. Seismic upgrade of
Primary Clarifier 1-4
2017 Action X X Property Protection
Structural Projects
Packet Page No. 689
Tri-City 5-22
Local Hazard Mitigation Plan Update
March 2024
Action Title
New Action/
Previous
Action
Address
Current
Development
Address
Future
Development
Continued
NFIP
Compliance Mitigation Type
Sea Level Rise, Subsidence Actions
Action 10. Forcemain Alameda
Creek Crossing Ground Stabilization
2017 Action X X Property Protection
Structural Projects
Natural Resource
Protection
Packet Page No. 690
Tri-City 6-1
Local Hazard Mitigation Plan Update
March 2024
Chapter 6 Plan Adoption
44 CFR §201.6(c)(5): [The local hazard mitigation plan shall include] documentation that the plan has been formally approved by the governing body of the jurisdiction requesting approval of the plan (e.g., City Council, county commissioner, Tribal Council).

The purpose of formally adopting this 2024 LHMP Update is to secure buy-in from each participating jurisdiction, raise awareness of the Plan, and formalize the Plan’s approval and implementation. The adoption of this LHMP Update completes Planning Step 9 of the 10-step planning process: Adopt the Plan, in accordance with the requirements of DMA 2000. For the three incorporated communities this adoption resolution also includes compliance with AB 2140 requiring adoption by reference or incorporation into the Safety Element of the General Plan. Two resolutions were created – one for the three incorporated communities and one for the two Special Districts.

The governing board for each jurisdiction has adopted this 2024 LHMP Update by passing a resolution. A copy of the generic resolutions is included in Appendix D: Adoption Resolution.

Packet Page No. 691
Tri-City 7-1
Local Hazard Mitigation Plan Update
March 2024
Chapter 7 Plan Implementation and Maintenance
44 CFR §201.6(c)(4): [The plan maintenance process shall include a] section describing the method and schedule of monitoring, evaluating, and updating the mitigation plan within a five-year cycle.

Implementation and maintenance of this 2024 Tri-City LHMP Update is critical to the success of hazard mitigation in the Tri-City Planning Area. Plan implementation and maintenance is Planning Step 10 of the 10-step planning process. Accordingly, this chapter provides an overview of the overall strategy for Plan implementation and maintenance and outlines the method and schedule for monitoring, updating, and evaluating the Plan. The chapter also discusses incorporating the Plan into existing planning mechanisms and how to address continued public involvement in local hazard mitigation planning.

Chapter 3, Planning Process, includes information on the implementation and maintenance process since the adoption of the 2016/2017/2022 LHMP Updates. This chapter includes information on the implementation and maintenance process for the development of this Plan, the 2024 LHMP Update.

7.1 Implementation
Once adopted, this 2024 Tri-City LHMP Update faces the truest test of its worth: implementation. While the Plan contains many worthwhile actions, the participating jurisdictions – the Cities of Fremont, Newark, and Union City; ACWD; and USD – will need to decide which action(s) to undertake first. Two factors should be considered when making that decision: the priority assigned to the Mitigation Actions in the Plan and funding availability. Low or no-cost actions most easily demonstrate progress toward successful Plan implementation.

An important implementation mechanism that is highly effective and low-cost is incorporation of the hazard mitigation plan recommendations and their underlying principles into other plans and mechanisms such as local general plans, stormwater plans, Emergency Operations Plans (EOPs), evacuation plans, and other hazard and emergency management planning efforts by the participating jurisdictions. These jurisdictions already implement policies and programs to reduce losses to life and property from hazards. This 2024 LHMP Update builds upon the momentum developed through prior, related planning and mitigation programs and recommends implementing actions, where possible, through other programs.

Mitigation is most successful when it is incorporated into the day-to-day functions and priorities of government and development. Implementation can be accomplished by adhering to the schedules identified for each action through sustained collaborative efforts, highlighting the mutual benefits of proposed mitigation actions, and the Tri-City jurisdictions, its stakeholders, and the public. This is achieved through the routine actions of monitoring agendas, attending meetings, and promoting mitigation initiatives to enhance the safety and sustainability of the community. Additional mitigation strategies may include consistent and ongoing enforcement of existing policies and the vigilant review of programs for coordination and multi-objective opportunities to enhance mitigation.

Packet Page No. 692
Tri-City 7-2
Local Hazard Mitigation Plan Update
March 2024
Simultaneously, it is important to continuously monitor potential funding opportunities to finance mitigation actions. This may include identifying funding sources to meet local matching funds requirements under FEMA pre- and post-disaster mitigation grant programs, and other sources. When funding does become available, the participating jurisdictions will be better positioned to capitalize on the opportunity.

Responsibility for Implementation of Goals and Activities The elected officials, executive leadership teams, responsible staff and departments, and emergency management offices of the participating jurisdictions are charged with implementation of various activities in the 2024 LHMP Update. During the quarterly reviews as described later in this section, each participating jurisdiction should conduct an assessment of progress toward meeting the goals and activities of the LHMP Update. At that time, recommendations may be made to modify timeframes for the completion of identified mitigation actions, identify funding sources, and work with responsible entities to implement the actions.

On a quarterly basis, the priority of various mitigation actions may be adjusted. Some activities that are found not to be feasible may be removed from the Plan entirely, while other mitigation actions unforeseen during Plan development process may be added.

7.1.1. Role of the LHMP Update Planning Committee in Implementation and Maintenance
With adoption of this Plan, each participating jurisdiction will be responsible for LHMP implementation and maintenance. The Planning Committee identified in Chapter 3 (or a similar committee) will reconvene quarterly each year to ensure mitigation strategies are being implemented and the Cities continue to maintain compliance with the NFIP. The City of Fremont Fire Department, Office of Emergency Services (Fremont OES) or alternate agency, will continue in its role as project lead for LHMP implementation and maintenance. As such, the City of Fremont, as LHMP project lead or alternate lead, and all participating jurisdictions will continue their relationship, and will plan to convene a similar LHMP Update Planning Committee when preparing the subsequent LHMP update. The Fremont OES project lead or alternate, with support from participating jurisdictions and the LHMP Update Planning Committee will:
➢ Act as a forum for hazard mitigation issues;
➢ Disseminate hazard mitigation ideas and activities to all participants; ➢ Pursue the implementation of high-priority, low/no-cost recommended actions; ➢ Ensure hazard mitigation remains a consideration for community decision makers; ➢ Maintain a vigilant monitoring of multi-objective cost-share opportunities to help the community implement the Plan’s recommended actions for which no current funding exists; ➢ Monitor and assist in the implementation and update of this Plan; ➢ Report on plan progress and recommended changes to the governing boards for all participating jurisdictions; and
➢ Inform and solicit input from the public.

The primary duty of the participating jurisdictions and the Planning Committee is to see the LHMP Update successfully carried out and to report to their governing boards and the public on the status of LHMP implementation and mitigation opportunities. Other duties include reviewing and promoting mitigation Packet Page No. 693
Tri-City 7-3
Local Hazard Mitigation Plan Update
March 2024
proposals, considering stakeholder concerns about hazard mitigation, passing concerns on to appropriate entities, and posting relevant information about the LHMP on the websites of participating jurisdictions.

7.2 Maintenance
Plan maintenance implies an ongoing effort to monitor and evaluate LHMP implementation and to update the Plan as progress, roadblocks, or changing circumstances are encountered.

7.2.1. Maintenance Schedule
Fremont OES or alternate agency, as project lead, in conjunction with the LHMP leads for all participating jurisdictions, is responsible for initiating Plan reviews. In order to monitor progress and update the mitigation strategies identified in the mitigation action plan, Fremont OES, LHMP leads from other participating jurisdictions, and the Planning Committee will revisit this Plan quarterly each year and following a hazard event. The Planning Committee will meet quarterly to review progress on Plan implementation and the City of Fremont, as the participating CRS community, will provide annual evaluation reports for CRS Activity 510 in accordance with their CRS program requirements. The Planning Committee will also submit a five-year written update to the State and FEMA Region IX, unless disaster or other circumstances (e.g., changing regulations) require a change to this schedule. With this 2024 LHMP Update anticipated to be fully approved and adopted in mid-2024, the next required written update of the Plan must be completed by mid-2029. Fremont OES, or another department from the participating jurisdictions, will initiate the Plan update – which may include applying for grant funding to hire professional services to assist in preparing the 2029 LHMP Update. The 2029 LHMP Update development process should be initiated in 2026 to ensure the 2029 LHMP Update can be funded and completed by this 2024 Tri-City LHMP’s expiration date.

7.2.2. Maintenance Evaluation Process
Evaluation of progress can be achieved by monitoring changes in vulnerabilities identified in the Plan.

Changes in vulnerability can be identified by noting:
➢ Decreased vulnerability as a result of implementing recommended actions; ➢ Increased vulnerability as a result of failed or ineffective mitigation actions; ➢ Increased vulnerability as a result of new development (and/or annexation); and/or ➢ Increased vulnerability resulting from unforeseen or new circumstances.

Updates to this Plan will:
➢ Consider changes in vulnerability due to action implementation; ➢ Document success stories where mitigation efforts have proven effective; ➢ Document areas where mitigation actions were not effective; ➢ Document any new hazards that may arise or were previously overlooked; ➢ Incorporate new data or studies on hazards and risks; ➢ Incorporate new capabilities or changes in capabilities; ➢ Incorporate growth and development-related changes to infrastructure inventories; and Packet Page No. 694
Tri-City 7-4
Local Hazard Mitigation Plan Update
March 2024
➢ Incorporate new action recommendations or changes in action prioritization.

Changes will be made to this Plan to accommodate for actions that have failed or are not considered feasible after a review of their consistency with established criteria, time frame, community priorities, and/or funding resources. All mitigation actions will be reviewed during the monitoring and update of this Plan to determine feasibility of future implementation. Updating of this LHMP will be by written changes and submissions, as the participating jurisdictions and Planning Committee deems appropriate and necessary, and as approved by the governing boards of each participating jurisdiction. In keeping with the five-year update process, the Planning Committee will convene public meetings to solicit public input on this LHMP Update and its routine maintenance, and the final product will be again adopted by the governing boards of each participating jurisdiction.

Quarterly Plan Review Process
For the LHMP Update review process, the Fremont OES lead or alternate, and the LHMP leads for each of the participating jurisdictions, will be responsible for facilitating, coordinating, and scheduling reviews and maintenance of the LHMP. The LHMP is intended to be a living document. The review of the 2024 LHMP Update will normally occur on a quarterly basis each year and will be conducted by the Planning Committee as follows:
➢ Fremont OES or alternate lead will place an advertisement in the local newspaper advising the public of the date, time, and place for each quarterly review of the LHMP Update and will be responsible for leading the meeting to review the Plan.
➢ Notices will be mailed to the members of the Planning Committee, federal, state, and local agencies, non-profit groups, local planning agencies, representatives of business interests, neighboring communities, and others advising them of the date, time, and place for the review. ➢ County/City/District officials will be noticed by email and telephone or personal visit and urged to participate.
➢ Members of any participating jurisdiction’s planning commissions and other appointed commissions and groups will also be noticed by email and either by telephone or personal visit. ➢ Prior to the review, department heads and others tasked with implementation of the various activities will be queried concerning progress on each activity in their area of responsibility and asked to present a report at the review meeting.
➢ The local news media will be contacted, and a copy of the current LHMP will be available for public comment at the City of Fremont as project lead or alternate lead. ➢ After the review meeting, minutes of the meeting and a quarterly report will be prepared by the Planning Committee and forwarded to the news media (public) and the Verisk/CRS specialist for the CRS program(s). The report will also be presented to the City of Fremont City Council, as the CRS community, for review, and a request will be made that the Council take action to recognize and adopt any changes resulting from the review.
➢ A copy of the 2024 LHMP Update will be continually posted on the LHMP website for the participating jurisdictions and the City of Fremont LHMP website will also include the annual CRS Activity 510 report.

Packet Page No. 695
Tri-City 7-5
Local Hazard Mitigation Plan Update
March 2024
Criteria for Quarterly Reviews
The criteria recommended in 44 CFR 201 and 206 will be utilized in reviewing and updating the 2024 LHMP Update. More specifically, the reviews should include the following information:
➢ Community growth or change in the past quarter.
➢ The number of substantially damaged or substantially improved structures by flood zone. ➢ The renovations to public infrastructure including water, sewer, drainage, roads, bridges, gas lines, and buildings.
➢ Natural hazard occurrences that required activation of the Emergency Operations Center(s) (EOC) and whether or not the event resulted in a federal disaster declaration. ➢ Natural hazard occurrences that were not of a magnitude to warrant activation of the EOC or a federal disaster declaration but were severe enough to cause damage in the community or closure of businesses, schools, or public services.
➢ The dates of hazard events and descriptions.
➢ Documented damages due to the events.
➢ Closures of places of employment or schools and the number of days closed. ➢ Road or bridge closures due to the hazard and the length of time closed. ➢ Assessment of the number of private and public buildings damaged and whether the damage was minor, substantial, major, or if buildings were destroyed. The assessment will include residences, mobile homes, commercial structures, industrial structures, and public buildings, such as schools and public safety buildings.
➢ Review of any changes in federal, state, and local policies to determine the impact of these policies on the community and how and if the policy changes can or should be incorporated into the next LHMP Update. Review of the status of implementation of projects (mitigation strategies) including projects completed will be noted. Projects behind schedule will include a reason for delay of implementation.

7.2.3. Incorporation into Existing Planning Mechanisms
Another important implementation mechanism that is highly effective and low-cost is incorporation of the 2024 LHMP Update recommendations and their underlying principles into other jurisdictional plans and mechanisms. Where possible, Plan participants will use existing plans and/or programs to implement hazard mitigation actions. As previously stated in Section 7.1 of this Plan, mitigation is most successful when it is incorporated into the day-to-day functions and priorities of government and development. The point is re-emphasized here. As described in this LHMP’s capability assessment, the participating jurisdiction’s already implement policies and programs to reduce losses to life and property from hazards.

This Plan builds upon the momentum developed through previous and related planning efforts and mitigation programs and recommends implementing actions, where possible, through these other program mechanisms. These existing mechanisms include:
➢ General and master plans
➢ Emergency Operations Plans and other emergency management efforts ➢ Jurisdictional ordinances
➢ Flood/stormwater management/master plans
➢ Climate Plans
➢ Capital Improvement Plans and budgets
Packet Page No. 696
Tri-City 7-6
Local Hazard Mitigation Plan Update
March 2024
➢ Other plans and policies outlined in the capability assessment ➢ Other plans, regulations, and practices with a mitigation focus Planning Committee members involved in these other planning and program mechanisms will be responsible for integrating the findings and recommendations of this LHMP with these other plans, programs, etc., as appropriate. As described in Section 7.1 Implementation, incorporation into existing planning mechanisms will be done through the routine actions of:
➢ monitoring other planning/program agendas;
➢ attending other planning/program meetings;
➢ participating in other planning processes; and
➢ monitoring community budget meetings for other community program opportunities.

The successful implementation of this mitigation strategy will require constant and vigilant review of existing plans and programs for coordination and multi-objective opportunities that promote a safe, sustainable community.

Examples of incorporation of the 2024 LHMP Update into existing planning mechanisms include:

1. As recommended by Assembly Bill 2140, the Cities should adopt (by reference or incorporation) this LHMP into the Safety Element of their General Plan. Evidence of such adoption (by formal, certified resolution and text within the body of the Safety Element) shall be provided to CAL OES and FEMA.

2. Integration of flood actions identified in this mitigation strategy with implementation priorities in existing Watershed, Flood, and Stormwater Drainage Plans. Key people responsible for development and implementation of Flood Plans and Stormwater Master Plans participated on the Planning Committee. Key projects were identified and integrated specifically into this LHMP, while others currently of lessor priority should be referenced in their source document. Actual implementation of these projects will likely occur through the flood and stormwater plans’ processes through the efforts of each responsible jurisdiction and department.

3. Integration of many of the infrastructure, roads, and facility improvement projects with the jurisdictional Capital Improvement Programs.

4. Use of risk assessment information to inform future updates of the hazard analysis in the Emergency Operations Plans and related emergency management efforts for all participating jurisdictions.

Efforts should continuously be made to monitor the progress of mitigation actions implemented through these other planning mechanisms and, where appropriate, their priority actions should be incorporated into updates of this LHMP.

7.2.4. Continued Public Involvement
Continued public involvement is a crucial element of successful Plan implementation. The update process provides an opportunity to solicit participation from new and existing stakeholders and to publicize success stories from the 2024 LHMP implementation and seek additional public comment. The Plan maintenance and update process will include continued public and stakeholder involvement and input through attendance at designated committee meetings, web postings, press releases to local media, and through public hearings.

Packet Page No. 697
Tri-City 7-7
Local Hazard Mitigation Plan Update
March 2024
Public Involvement Process for Quarterly Reviews
The public will be noticed by placing an advertisement in the newspaper specifying the date and time for the review and inviting public participation. The Planning Committee, local, state, and regional agencies will be notified and invited to attend and participate.

Public Involvement for Five-year Update
When the participating jurisdictions and Planning Committee reconvenes for the next LHMP Update, they will coordinate with all stakeholders participating in the planning process—including those that joined the committee since the planning process began—to update and revise the Plan. In reconvening, the Planning Committee will identify a public outreach subcommittee, which will be responsible for coordinating the activities necessary to involve the greater public. The subcommittee will develop a plan for public involvement and will be responsible for disseminating information through a variety of media channels detailing the LHMP update process. As part of this effort, public meetings will be held, and public comments will be solicited on the LHMP Update draft. The subcommittee will also coordinate this public outreach process with any public information programs established pursuant to the current guidelines from the Community Rating System (CRS) program. In addition, continued public involvement and outreach efforts will place an emphasis on identifying and inviting representatives from underserved and vulnerable populations to be part of the next, 2029 Tri-City LHMP Update. As a starting point the underserved and vulnerable population groups identified for this 2024 LHMP Update will be contacted to invite them to the 2029 LHMP Update process with additional groups identified and added to meet the ongoing goal of mitigation planning for the whole community.

Packet Page No. 698
Tri-City City of Newark Annex B-1
Local Hazard Mitigation Plan Update
March 2024
Annex B City of Newark
Table of Contents
Annex B City of Newark......................................................................................................................B-1 B.1 Introduction...............................................................................................................................B-1 B.2 Planning Process.......................................................................................................................B-2 B.3 Community Profile....................................................................................................................B-3 B.3.1. Geography and Climate ....................................................................................................B-5 B.3.2. History...............................................................................................................................B-5 B.3.3. Economy and Tax Base.....................................................................................................B-6 B.4 Risk Assessment .......................................................................................................................B-8 B.4.1. Assets Inventory and Growth and Development Trends ..................................................B-8 B.4.2. Hazard Identification.......................................................................................................B-36 B.4.3. Hazard Profiles and Vulnerability to Specific Hazards ..................................................B-38 B.5 Capability Assessment..........................................................................................................B-241 B.5.1. Regulatory Mitigation Capabilities...............................................................................B-241 B.5.2. Administrative/Technical Mitigation Capabilities........................................................B-252 B.5.3. Fiscal Mitigation Capabilities.......................................................................................B-253 B.5.4. Mitigation Education, Outreach, and Partnerships .......................................................B-254 B.5.5. Other Mitigation Efforts................................................................................................B-255 B.6 Mitigation Strategy ...............................................................................................................B-255 B.6.1. Mitigation Goals and Objectives...................................................................................B-255 B.6.2. NFIP Mitigation Strategy..............................................................................................B-255 B.6.3. Mitigation Actions........................................................................................................B-257 B.1 Introduction
This Annex details the hazard mitigation planning elements specific to the City of Newark a previously participating jurisdiction of the 2017 Union City/Newark Multi-Jurisdictional Hazard Mitigation Plan (LHMP or Plan) Update. This Annex is not intended to be a standalone document but appends to and supplements the information contained in the Base Plan document. As such, all sections of the Base Plan, including the planning process and other procedural requirements apply to and were met by the City. This Packet Page No. 699
Tri-City City of Newark Annex B-2
Local Hazard Mitigation Plan Update
March 2024
Annex provides additional information specific to Newark, with a focus on providing additional details on the risk assessment and mitigation strategy for this jurisdiction.

B.2 Planning Process
As described above, Newark followed the planning process detailed in Chapter 3 of the Base Plan. In addition to providing representation on the Tri-City Planning Committee, the City formulated their own internal planning team to support the broader planning process requirements. Internal planning participants, their positions, and how they participated in the planning process are shown in Table B-1. Additional details on Plan participation and City representatives are included in Appendix A.

Table B-1 City of Newark – Planning Team
Name Position/Title How Participated
Ricardo Martinez Emergency Services
Coordinator
Participated in the leadership team, planning & public meeting, also the sub-committee and research
Lenka Hovorka Assistant City
Manager
Participated in the planning committee
Soren Fajeau Director Public
Works
Participated in the planning committee and providing information Matthew Farrell Chief Building
Official
Participated in the planning and sub-committee and providing information.

Tonya Connolly Public Works
Superintendent
Participated in the planning committee and providing information Jolie Macis Captain Participated in the planning committee Steven Turner Director Community
Development
Participated in the planning committee and providing information Peter Fong Information
Technology Analyst
Participated in the planning committee and providing information Peter Beireis Recreation
Supervisor
Participated in the planning committee
Krysten Lee Director Finance Participated in the planning committee Gloria Del Rosario Accounting Manager Participated in the planning committee and providing information Diana Cangco Principal Civil
Engineer
Participated in the planning and sub-committee and providing information.

Art Interiano Deputy Community
Development
Director
Provided information for this project.

Carmelisa Lopez Senior Planner Participated in the planning committee and providing information Anne Stedlar Economic
Development
Manager
Provided information for this project.

Ben Peralta Director of Campus
Police Services+
Participated in the planning committee and providing information Jeff Luepke Division Chief Participated in the planning committee and providing information Packet Page No. 700
Tri-City City of Newark Annex B-3
Local Hazard Mitigation Plan Update
March 2024
Name Position/Title How Participated
Lincoln Casimere Emergency Manager Participated in the planning committee and providing information Coordination with other community planning efforts is paramount to the successful implementation of this LHMP Update. This section provides information on how the City integrated the previously FEMA approved 2017 Plan into existing planning mechanisms and programs. Specifically, the City incorporated into or implemented the 2017 LHMP through other plans and programs shown in Table B-2.

Table B-2 2017 City of Newark LHMP Incorporation
Planning Mechanism 2017 LHMP Was
Incorporated/Implemented In.

Details: How was it incorporated?
General Plan Includes Land use and Environmental Hazards elements with information regarding planning area composition and polices consistent with hazard mitigation as objectives.

Newark Municipal Code Reviewed for relevant information regarding regulatory consistency with plan goals and objectives.

Capital Improvement Plan Reviewed to identify cross planning initiatives for inclusion as mitigation projects.

B.3 Community Profile
The community profile for the City of Newark is detailed in the following sections. Figure B-1 displays a City map and the location of Newark within the Tri-City Planning Area.

Packet Page No. 701
Tri-City City of Newark Annex B-4
Local Hazard Mitigation Plan Update
March 2024
Figure B-1 City of Newark
Packet Page No. 702
Tri-City City of Newark Annex B-5
Local Hazard Mitigation Plan Update
March 2024
B.3.1. Geography and Climate
Newark is a city in Alameda County, California, situated on the southeast edge of the San Francisco Bay.

It is located 35 miles south of San Francisco, 30 miles south of Oakland, 20 miles north of San Jose, and 395 miles north of Los Angeles. Newark is an enclave, surrounded by the city of Fremont. The three cities of Newark, Fremont, and Union City make up the Tri-City area. The western edge of Newark lies near the southern end of the San Francisco Bay. State Route 84 runs along the northwest border of the City and continues as the Dumbarton Bridge to cross the San Francisco Bay to reach Menlo Park. Interstate 880 serves as the eastern boundary of the City with Fremont. The U.S. Census Bureau reports the City has a total area of 13.9 square miles, of which, 13.88 square miles is land, and 0.02 square miles is water. The City has a mean elevation of 20 feet above sea level. Newark is bordered by the Don Edwards San Francisco Bay National Wildlife Habitat, hosting the largest wetland restoration project on the west coast of the U.S.

Historically the Tri-City Planning Area was overlaid with tidal marshes, sloughs, ponds, willow groves, and creeks. Most of these historical features no longer exist due to development of a creek and storm drain network and present-day watershed boundaries. Development has also resulted in the culverting and channelization of many creeks, and the filling of portions of the bay and tidal marsh lands or diking of tidal marsh lands for salt evaporators or farming.

The climate in Newark is described as Mediterranean, characterized by warm, dry summers and mild winters. U.S. Climate Data reports the average annual high temperature in Newark is 68.7 Fahrenheit (°F), with an average annual low of 50.9°F. The average annual precipitation – rainfall – is 15.11 inches. July has the warmest temperatures of the year with an average high of 79°F. December and January have the coolest temperatures of the year with an average low of 42°F.

B.3.2. History
The San Francisco Bay region was once home to the Muwekma Ohlone Tribe. The first European settlement was Mission San José, founded on June 11, 1797, by the Franciscan order. It was the fourteenth Spanish mission established in California in what is currently the City of Fremont. In the mid-1850’s European settlers established landings and warehouses along the east bay, and ranchers purchased property to start businesses. An Englishman bought an interest in a swamp reclamation project and hired Mr. J. Barr Robertson, a Scotsman, to oversee his interests. Mr. Robertson was a director of the California Land Investment Co., Ltd., London, England, and eventually bought out the interest in the land from the Englishman. Mr. Robertson named the land 'Newark' after the castle "Newark" in Port Glasgow, Scotland.

In the late 1870’s, Alfred Davis, a San Francisco capitalist, and Jim Fair, a Comstock millionaire completed the South Pacific Coast Railroad from Dumbarton Point south all the way to Santa Cruz. Soon, a railroad station, roundhouse, and railroad shop buildings were being erected in the center of Newark. Eventually, the railroad was extended north from Newark to Alameda, providing direct ferry service to San Francisco.

The completion of the railroad precipitated additional development in Newark.

Hotels and stores were soon erected, along with some of the first manufacturing industries, including a railroad car building firm, and a foundry which later manufactured Wedgewood stoves. The production of salt, which had been underway in the Newark area since the 1850s was also a major enterprise. Acquisitions Packet Page No. 703
Tri-City City of Newark Annex B-6
Local Hazard Mitigation Plan Update
March 2024
and mergers of salt production companies throughout the Bay area ultimately resulted in formation of the Arden Salt Company, predecessor to Leslie Salt Company and the current Cargill Salt.

In the early 1950s, subdivisions began sprouting throughout Southern Alameda County and talk of incorporation was in the air. In 1953, a group representing six communities commissioned a study to incorporate six communities into one city. Leaders in Newark decided to go it alone and withdrew from the venture after rejecting an industrial zoning for the entire town. The Newark Chamber of Commerce began its own movement toward incorporation of Newark. In September 1955, this effort paid off with the incorporation of Newark as the first new city in Alameda County in 47 years.

B.3.3. Economy and Tax Base
US Census estimates show economic characteristics for the City of Newark. These are shown in Table B-3 and Table B-4. Mean household income in the City was $168,380. Median household income in the City was $144,011.

Table B-3 City of Newark – Civilian Employed Population 16 years and Over Industry Estimated
Employment
Percent
Agriculture, forestry, fishing and hunting, and mining 68 0.3% Construction 1,644 6.2%
Manufacturing 4,545 17.2%
Wholesale trade 848 3.2%
Retail trade 2,606 9.8%
Transportation and warehousing, and utilities 958 3.6%
Information 996 3.8%
Finance and insurance, and real estate and rental and leasing 1,215 4.6% Professional, scientific, and management, and administrative and waste management services
5,124 19.4%
Educational services, and health care and social assistance 5,259 19.9% Arts, entertainment, and recreation, and accommodation and food services 1,603 6.15% Other services, except public administration 887 3.4%
Public administration 715 2.7%
Source: US Census Bureau American Community Survey 2021 Estimates Table B-4 City of Newark – Income and Benefits
Income Bracket Percent
<$10,000 2.6%
$10,000 – $14,999 0.6%
$15,000 - $24,9999 2.8%
$25,000 – $34,999 3.0%
Packet Page No. 704
Tri-City City of Newark Annex B-7
Local Hazard Mitigation Plan Update
March 2024
Income Bracket Percent
$35,000 – $49,999 5.2%
$50,000 – $74,999 7.1%
$75,000 – $99,999 11.9%
$100,000 – $149,999 20.5%
$150,000 – $199,999 15.3%
$200,000 or more 30.9%
Source: US Census Bureau American Community Survey 2021 Estimates Major employers in the City include:
➢ Lucid;
➢ Cargill;
➢ Vitesse System;
➢ Allogene;
➢ MITAC;
➢ TripleRing;
➢ Unigen;
➢ Mission Linen;
➢ Golden State Lumber;
➢ Home Depot;
➢ ATUM;
➢ PEBCO;
➢ Matheson Tri-Gas;
➢ Vector Labs;
➢ META;
➢ San Francisco Bay Brands;
➢ Aspire Bakeries;
➢ Sepheid;
➢ Kateeva;
➢ Prologis;
➢ WorldPac;
➢ NEFAB;
➢ FedEx;
➢ Sanmina; and
➢ Nordstrom.

In addition to these major employers, the City noted that there are over 1,600 hotel rooms in the City which significantly contribute to the City’s tax base. A list of major hotels in the City and the number of rooms are included below:
➢ Aloft (172);
➢ Chase Suites (140);
➢ Courtyard (181);
➢ DoubleTree by Hilton (315);
➢ Homewood Suites (192);
➢ Hyatt Place (110);
➢ Residence Inn (168);
Packet Page No. 705
Tri-City City of Newark Annex B-8
Local Hazard Mitigation Plan Update
March 2024
➢ SpringHill Suites (119);
➢ StayBridge Suites (104);
➢ Wyndham Garden (101).

The City of Newark has a varied tax base. It can be seen in Table B-5.

Table B-5 City of Newark Tax Base
Property Use Precent of Tax Base
Agricultural 0.05%
Commercial 14.96%
Government/ Institutional 0.25%
Industrial 14.13%
Recreational 0.02%
Residential 69.05%
Unknown 0.13%
Utilities 0.00%
Vacant 1.41%
Newark Total 100.0%
Source: Alameda County Parcel/Assessor Data (Source: City of Fremont, May 2023) B.4 Risk Assessment
As defined by FEMA, risk is a combination of hazard, vulnerability, and exposure. “It is the impact that a hazard would have on people, services, facilities, and structures in a community and refers to the likelihood of a hazard event resulting in an adverse condition that causes injury or damage.” The City of Newark risk assessment identifies and profiles relevant hazards and assesses the exposure of lives, property, infrastructure, and the environment to these hazards. The process allows for a better understanding of the City’s potential risk to hazards and provides a framework for developing and prioritizing mitigation actions to reduce risk from future hazard events.

Building on the Community Profile above, a risk assessment was performed for the City. This includes the following sections:
➢ B.4.1 Assets Inventory and Growth and Development Trends ➢ B.4.2 Hazard Identification
➢ B.4.3 Hazard Profiles and Vulnerability to Specific Hazards B.4.1. Assets Inventory and Growth and Development Trends This section provides an inventory of the City of Newark’s total assets potentially at risk to hazards and an overview of growth and development trends. This section is discussed into two parts:

Packet Page No. 706
Tri-City City of Newark Annex B-9
Local Hazard Mitigation Plan Update
March 2024
➢ Asset Inventory – The assets inventory identifies Newark’s total assets, including the people and populations: structures; critical facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. This data is not hazard specific, but is representative of total assets within the City, potentially at risk to identified hazards as discussed in Section B.4.3 Hazard Profiles and Vulnerability to Specific Hazards. ➢ Growth and Development Trends – A discussion of growth and development trends in the City, both current and future, is presented.

Assets Inventory
The City’s asset inventory is detailed in the following sections:
➢ People and Populations
➢ Structures
➢ Critical Facilities and Infrastructure, and Community Lifelines ➢ Natural, Historic, and Cultural Resources
➢ Economic Assets and Community Activities of Value
A discussion of each of these assets follows and serves as the template for the asset discussion for each hazard in Section B.4.3.

People and Populations
The most important asset within any community are the people and populations that reside in the community. This section includes an inventory of past and current populations of the City and also discusses socially vulnerable populations and underserved communities as a subsection of people and populations located within the City and potentially at risk to hazards. Information from the City, US Census Bureau, California Department of Finance, and other sources as detailed below form the basis of this discussion.

Historic Population Trends and Current Population
Population growth can increase the number of people living in hazard prone areas. Newark has 47,459 residents, as of January 1, 2023. In recent decades, Newark’s population has seen rapid growth, with an increase of 15.3 percent from 2000 to 2020; this rate is above that of the region as a whole, at 14.8 percent.

In 2020, the population of Newark was estimated to be 48,966 (CA Department of Finance). From 1990 to 2000, the population increased by 12.2 percent, while it increased by just 0.2 percent during the first decade of the 2000s. In the most recent decade, the population increased by 15 percent. The population of Newark makes up three percent of the population in Alameda County. Newark has seen growth rates as shown in Table B-6.

Table B-6 City of Newark – Population Changes Since 1950 Year Population Change % Change
1950 1,532 – –
1960 9,884 8,352 545.2%
1970 27,153 17,269 174.7%
Packet Page No. 707
Tri-City City of Newark Annex B-10
Local Hazard Mitigation Plan Update
March 2024
Year Population Change % Change
1980 32,126 4,973 18.3%
1990 37,861 5,735 17.9%
2000 42,471 4,610 12.2%
2010 42,573 102 0.2%
2020 47,529 4,956 11.6%
2023 47,459 -70 -0.1%
Source: US Census Bureau, California Department of Finance Newark’s population has experienced many changes in demographics over time. In recent years the population of youth has declined slightly with continued growth in those 55 and over. In 2019, Newark’s youth population under the age of 18 was 10,015 and the senior population 65 and older was 6,038. These age groups represent 21.2 percent and 12.8 percent of Newark’s population.

As discussed, the population is getting older, with a large increase in the population aged 60 and over. This can be seen in Table B-7.

Table B-7 City of Newark – Populations under 19 and over 60 Years of Age Age Group 2000 2010 2020
0-19 30% 28% 16.3%
60 and over 12% 15% 18.2%
Source: US Census Bureau, City of Newark Housing Element Since 2000, the percentage of residents in Newark identifying as White has decreased – and at the same time, the percentage of residents of all other races and ethnicities has increased – by 18.6 percentage points, with the 2019 population standing at 11,168. In absolute terms, the Asian / API, Non-Hispanic population increased the most while the White, Non-Hispanic population decreased the most. In 2020, 23.7 percent of Newark’s population was White while 4 percent was African American, 33.9 percent was Asian, and 34.8 percent was Latinx.

Special Populations and Disadvantaged Communities
The City is a very socially and economically diverse community, and many residents that are socially or economically disadvantaged or vulnerable due to varying reasons reside within the City. The City and surrounding County are no strangers to large natural disasters which have had a direct impact on the populations of the area. Thus, it is important to consider the potential effects of hazard events and disasters on these more vulnerable populations. Socially vulnerable and disadvantaged communities in the City are discussed by the following sources:
➢ CDC Social Vulnerability Index
➢ CA DWR Disadvantaged Community Mapping
➢ FEMA Community Disaster Resilience Zones
➢ City Planning Team Input
Packet Page No. 708
Tri-City City of Newark Annex B-11
Local Hazard Mitigation Plan Update
March 2024
CDC Social Vulnerability Index
Every community must prepare for and respond to a hazard event, including the range of natural hazards addressed in this Plan, from severe weather extremes to large potentially catastrophic events such as wildfires or earthquakes. A number of factors, including poverty, lack of access to transportation, and crowded housing may weaken a community’s ability to prevent human suffering and financial loss in a disaster. These factors are known as social vulnerability.

Social vulnerability refers to the potential negative effects on communities caused by external stresses on human health. Such stresses include natural or human-caused disasters, or disease outbreaks. Reducing social vulnerability can decrease both human suffering and economic loss. The Agency for Toxic Substances and Disease Registry (ATSDR) Geospatial Research, Analysis & Services Program (GRASP) created databases to help emergency response planners and public health officials identify and map communities that will most likely need support before, during, and after a hazardous event. The U.S. Center for Disease Control (CDC) used these databases to create the CDC Social Vulnerability Index (CDC SVI), which uses 15 U.S. census variables to help local officials identify communities that may need additional support before, during, or after disasters.

CDC SVI uses U.S. Census data to determine the social vulnerability of every census tract. Census tracts are subdivisions of counties for which the Census collects statistical data. The CDC SVI ranks each tract on 15 social factors, including poverty, lack of vehicle access, and crowded housing, and groups them into four related themes. Each tract receives a separate ranking for each of the four themes, as well as an overall ranking. Maps of the four themes for the City are shown in the figures below.

The overall SVI map is shown in Figure B-2; the socioeconomic SVI for the census tracts in and around the City are shown in Figure B-3; the household composition SVI is shown in Figure B-4; the minority and language SVI is shown in Figure B-5; and the housing and transportation SVI is shown in Figure B-6.

Overall, the maps indicate that, in general, the City sees little change in social vulnerability regardless of location.

Packet Page No. 709
Tri-City City of Newark Annex B-12
Local Hazard Mitigation Plan Update
March 2024
Figure B-2 City of Newark – Overall Social Vulnerability Source: CDC Social Vulnerability Index – map retrieved 10/03/2023 Level of Vulnerability Rating: Yellow – Low; Green – Low/Medium; Aqua – Medium/High; Blue – High; Grey Hatched – No Data; Grey – Not Available
Figure B-3 City of Newark – Socioeconomic Status Vulnerability Source: CDC Social Vulnerability Index – map retrieved 10/03/2023 Level of Vulnerability Rating: Yellow – Low; Light Green – Low/Medium; Green – Medium/High; Dark Green – High; Grey Hatched – No Data; Grey – Not Available
Packet Page No. 710
Tri-City City of Newark Annex B-13
Local Hazard Mitigation Plan Update
March 2024
Figure B-4 City of Newark – Household Characteristics
Source: CDC Social Vulnerability Index – map retrieved 10/03/2023 Level of Vulnerability Rating: Yellow – Low; Light Orange– Low/Medium; Orange – Medium/High; Dark Orange – High; Grey Hatched – No Data; Grey – Not Available
Figure B-5 City of Newark – Racial and Ethnic Minority Status Source: CDC Social Vulnerability Index – map retrieved 10/3/2023 Level of Vulnerability Rating: Yellow – Low; Light Purple – Low/Medium; Purple – Medium/High; Dark Purple – High; Grey Hatched – No Data; Grey – Not Available
Packet Page No. 711
Tri-City City of Newark Annex B-14
Local Hazard Mitigation Plan Update
March 2024
Figure B-6 City of Newark – Housing Type and Transportation Source: CDC Social Vulnerability Index – map retrieved 10/03/2023 Level of Vulnerability Rating: Faint Purple – Low; Light Purple – Low/Medium; Blue – Medium/High; Dark Blue – High; Grey Hatched – No Data; Grey – Not Available
CA DWR Disadvantaged Community Mapping
The California Department of Water Resources (CA DWR) has developed a web-based application to assist local agencies and other interested parties in evaluating disadvantaged community (DAC) status throughout the State, using the definition provided by Proposition 84 Integrated Regional Water Management (IRWM) Guidelines (2016). A statewide Census Tract Geographic Information Services (GIS) Tiger file is used to determine if a census tract is DAC or not by adding American Community Survey Median Household Income data at the census tract level. Only those census geographies that meet the DAC definition are shown on the map (i.e., only those with an annual median household income (MHI) that is less than 80 percent of the Statewide annual MHI (PRC Section 75005(g)). In addition, those census geographies having an annual MHI that is less than 60 percent of the Statewide annual MHI are shown as “Severely Disadvantaged Communities” (SDAC).

The DAC Mapping Tool is an interactive map application that allows users to overlay the following three US Census geographies as separate data layers: Census Place, Census Tract, and Census Block Group.

The DAC map for the City is shown in Figure B-7. In general, the map shows limited to no areas of disadvantaged communities.

Packet Page No. 712
Tri-City City of Newark Annex B-15
Local Hazard Mitigation Plan Update
March 2024
Figure B-7 City of Newark – Disadvantaged Communities
Source: CA DWR – map retrieved 10/03/2023
FEMA Community Disaster Resilience Zones
Community Disaster Resilience Zones aim to build and strengthen community resilience across the nation by driving federal, public, and private resources to the most at-risk and in-need communities. The Community Disaster Resilience Zones Act uses FEMA’s National Risk Index to identify the most at-risk and in-need communities to identify resilience zones. Designated zones will be prioritized for targeted federal support, such as increased cost-share for resilience and mitigation projects, lessening the financial burden on communities to perform resilience-related activities. On September 6, 2023, FEMA announced the initial 483 designations in all 50 states and the District of Columbia. Figure B-8 shows these zones in teal green. None of these zones intersect the City of Newark.

Packet Page No. 713
Tri-City City of Newark Annex B-16
Local Hazard Mitigation Plan Update
March 2024
Figure B-8 City of Newark – FEMA Community Disaster Resilience Zones Source: FEMA. Map retrieved 10/4/2023.

City Planning Team Input
The City Planning Team noted that the City of Newark 2023-2031 Housing Element discusses special populations in the City. Discussions for seniors, those with disabilities, people experiencing homelessness, large households, female headed households, extremely low income households, and farmworkers were included. These are discussed below.

Seniors
Seniors in Newark are a growing population, as long-time residents continue to age and the City adds more affordable senior rental housing. As of the 2020 US Census, there are 6,005 Seniors in Newark. Seniors in Newark overwhelmingly are homeowners at every income level, with low-income seniors having the highest percentage of renters at 37 percent. Low-income seniors experience higher rates of cost burden than moderate and above moderate-income counterparts. 37 percent of very low-income seniors are cost burdened with 22 percent extremely cost burdened.

Available affordable housing for seniors in Newark includes: Newark Gardens, Newark Gardens, Newark Station, and Timber Senior Housing is under construction with an anticipated completion later this year. As the senior population continues to grow, there will be increased need for housing that is accessible, affordable to those on fixed incomes, and allows residents to age in place. In addition to increased types of Packet Page No. 714
Tri-City City of Newark Annex B-17
Local Hazard Mitigation Plan Update
March 2024
housing options, seniors need support with the maintenance of their existing homes and their age and spaces that are accessible.

Disabled Citizens
People with disabilities often face additional housing challenges. Encompassing a broad group of individuals living with a variety of physical, cognitive and sensory impairments, many people with disabilities live on fixed incomes and often need accessible designed housing to live more independent lives. In Newark, eight percent of the population has a disability of any kind, with the majority being ambulatory. Due to housing challenges of affordability, accessibility and discrimination, 87 percent of people with disabilities live with family members in Newark.

People Experiencing Homelessness
People experiencing homelessness have steadily increased in Alameda County since 2017, with 9,747 sheltered and unsheltered people at the most recent point in time count on February 22, 2022. The City of Newark has a documented reduction of people experiencing homelessness, from 89 in 2019, to 58 sheltered and unsheltered people in 2022. The point in time count found a total of 32 unsheltered individuals, with 34 percent, or 11 people, living in a tent, with 8 living outside and 7 in an RV. Fewer people were found living in their car, at 6 people or 19 percent. It is no surprise that the largest number of people outside of shelters are living in tents, as the locations with the highest concentrations of people experiencing homelessness are in the undeveloped areas along highway 84, in the Eucalyptus grove, and along the 880.

These sites are all concentrated in the Mirabeau and Mayhews Landing areas, in the northern portion of the City due to the proximity of open space for tents along the freeway.

Large Households
Large Families are considered to have 5 or more people, bringing about the need for larger housing units with three bedrooms or more. Newark has a larger percentage of families with 3 or more people than Alameda County and the Bay Area, with 38 percent of households with 3 or more, and 19 percent of households with five or more people. While Newark has a large inventory of single-family homes, the cost of rent and ownership place many of these homes beyond reach for families. Families also face costs such as childcare, increased transportation and medical care that further reduce their housing budget allowance.

The pace of construction of multifamily and affordable units has not kept pace with that of market rate single family homes in Newark.

Female Headed Households
Government Code Section 65583(a)(7) identifies families with female heads of households as a group that may have special housing needs and requires the City to analyze the housing needs of these households.