There are several types of drought which can often be defined regionally based on their effects:
• Meteorological drought is usually defined by a period of below average water supply, based on the degree of dryness (in comparison to normal or average) and the duration of the dry period. Drought onset generally occurs with a meteorological drought.
• 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.
Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, focusing on precipitation shortages, soil water deficits, reduced ground water or reservoir levels needed for irrigation. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
177
• Hydrological drought is defined as deficiencies in surface and subsurface water supplies. It is generally measured as stream flow, snowpack, and as lake, reservoir, and groundwater levels. Hydrological drought usually occurs following periods of extended precipitation shortfalls.
• 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.
Location and Previous Occurrences
Historically, California has experienced multiple severe droughts. According to the California Department of Water Resources (DWR), droughts exceeding three years are relatively rare in Northern California, the source of much of the State’s developed water supply. The 1929-34 drought established the criteria commonly used in designing storage capacity and yield of large Northern California reservoirs. The driest single year of California’s measured hydrologic record was 2013. A drought emergency was declared for the state in 2014, and lifted in 2017 after a series of strong winter storms.
The U.S. Drought Monitor provides a general summary of current drought conditions. See Figure
3.57 for drought conditions in 2023, Figure 3.58 for drought conditions in 2020 and Figure 3.59 for drought conditions in 2016.
Figure 3.57: U.S. Drought Monitor for California (2023) Source: USDA
l ~<;>U·N· TY OF
~ ARIN
a
~
U.S. Drought Monitor
California
October 31, 2023
(Released Thursday, Nov. 2, 2023)
Valid 8 a.m. EDT
Drought Conditions (Percent Area)
None 00-04 01-04 02-04
Current £14~ 066 0,00 0Jl0 000 000
Last Week
J0-2,4,2023
£,4,32 5,68 0.00 0,00 0.00 0.00
3MonthsAgo 74.43 25,57 1>52 000 000 0.00 Of.(}1.201:
Stlrtof
Calendar Year 0,00 10000 97,93 7114 2710 0,00 01.0:J.2023 Start of
Water Year 94,01 599 0,07 0.00 0,00 0,00 09-$2023
One Vear Ago
U,Qf"'Q22. 0,00 10000 ~ 77 9, ss 4306 16.57
~
c::::JNone D2 Severe Drought
D DO Abnormally Dry - D3 Extreme Drought
c:J 01 Moderale Drought - D4 Excepttonal Droughl
The Drou{fnl Momror foouses on broad-scale cond/11011s Local condiflons may vary. Fo, mO/tJ ,ntormatlon on the Qbughl Momlor. go lo hNps l/droughlmonrtor;unl.BdiJIAIJoul,aspX Author:
Brian Fuchs
National Drought Mitigation Center
USDA
-
droughtmonitor.unl.edu
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
178
Figure 3.58: U.S. Drought Monitor for California (2020) Source: USDA
l ~<;>U·N· TY OF
~ ARIN
a
~
U.S. Drought Monitor
California
July 28, 2020
(Released Thursday, Jul. 30, 2020)
Valid 8 a.m. EDT
lntensitv:
LJ None
LJ DO Abnormally Dry
D D1 Moderate Drought
D D2 Severe Drought
- D3 Extreme Drought
- D4 ExcepUonal Drought
The Drought Monitor focuses on broad-scale
condiUons. Local conditions may vary. For more
information on the Drought Monitor, go to
https:1/droughtmonitor. unl.edu/About. aspx
Author:
Richard Heim
NCEI/NOM
~SDA (., @ {.
droughtmonitor.unl.edu
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
179
Figure 3.59: U.S. Drought Monitor for California (2016) Source: USDA
Figure 3.60: Water Supply Conditions in California 2005-2018 Source: 2018 State of California Hazard Mitigation Plan l ~<;>U·N· TY OF
~ ARIN
a
~
U.S. Drought Monitor
California
February 1 Statewide conditions
Department of Water Resources
California Cooperative Snow Surveys
March 15, 2016
(Re/oased Thursday, Mar. 17, 2016)
Valid 8 a.m. EDT
Droug//1 ConditiOns (Percent Area)
None- C0-0• 01-04 02-04 ... ~. Current 0.4:l 99.57 g3.za 7.l.64 55.31 J.H4 Last Week 0.43 93.57 97.49 83 16 60.86 38.40 J.MCIH
31.1ontnsAQo 0.14 W.86 S7.:J.3 !!0.63 69.09 44.84 fM l.•:wu St!Wtol Cetend er 't e...,r 0,00 100 00 97,33 87,55 69,07 44,84 f2,,2j,-2Qf:5 Start or 'WiterYeM 0.14 ro.B6 Sl.33 92.36 71.08 46.00
M:?/.:tlfS
One Year Ago
3"1'?',~i:HS 0.16 93.B• 98. 11 93.44 67.46 l9.92
Intensity:
O0l'bnorrn YD l'I 1111 O3E xtrem-eDroug t
01 .U.odcr11te DrougM 1111 04 Exo::ption,ail Orcn.rr.iH - 02Smro Dn>u "11
n w DIOtsg!'lt UOtli!O( (OCUS9-S on lYOOd-~are CO:ldi!jon-5'. t..ocalcond4JOM may 11&.ry See accom.oan.Ylna text w mma,y torfOtGCas:J. star9ft1iel'tt!S.
Author:
Richard Heim
NCEIINOAA
http :fldroughtmonltor.unl.edu/
2so~-------------------------------------
215
200+------------------------------------1
150 (ll
(ll
~
~
0 ~ a;
a.
so
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 = Snowpack = Preciptation Runoff to Date --Reservoir Storage 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
180
A drought emergency for the State of California was issued on January 17, 2014. This declaration came on the heels of a report that stated that California had the least amount of rainfall in its 163-year history. Drought conditions worsened through 2014 and into 2015. On April 1, 2015, following the lowest snowpack ever recorded, actions were announced by the State that would save water, increase enforcement to prevent wasteful water use, streamline the State’s drought response, and invest in new technologies to make California more drought resilient. The State Water Resources Control Board was directed to implement mandatory water reductions in cities and towns across California to reduce water usage by 25 percent.
This savings amounted to approximately 1.5 million acre-feet of water through the end of 2015.
In July 2021, the State of California added Marin County to its list of counties falling under its state of emergency regarding deepening drought conditions and record-breaking high temperatures statewide. After hearing details about local dry conditions and water supplies, the Marin County Board of Supervisors voted unanimously on May 18, 2021 to declare a local emergency and acknowledge the imminent threat of disaster. The declaration acknowledged the extent and impacts of the drought in Marin, which is severely affecting dairies and ranchers in West Marin. It also made the County eligible for California Disaster Assistance and other forms of state funding and resources. The local declaration cleared the way for state authorities to aid response and recovery efforts available to the County, water suppliers, farmers, impacted businesses and residents. In August 2021, with reservoir levels at historic lows, both MMWD and NMWD declared a water shortage emergency and adopted mandatory water use restrictions, with respective reduction goals of 40 percent and 20 percent. In October 2021, the Governor of California signed a proclamation extending the drought emergency statewide. In March 2023 the Governor eased drought restrictions and ended the drought emergency.
All areas of the Marin County OA could experience drought, including vegetated areas where drier conditions could lead to an increase in wildfires and tree mortality.
Impacts
Drought impacts are wide-reaching and may be economic, environmental, and/or societal. The most significant impacts associated with drought in the planning area are those related to water intensive activities such as agriculture, wildfire protection, municipal usage, commerce, tourism, recreation, and wildlife preservation. During a drought, allocations go down, which results in reduced water availability. Voluntary conservation measures are typically implemented during extended droughts. A reduction of electric power generation and water quality deterioration are also potential problems. Drought conditions can also cause soil to compact and not absorb water well, potentially making an area more susceptible to flooding.
Drought can have secondary impacts. For example, drought is a major determinant of wildfire hazard, in that it creates greater propensity for fire starts and larger, more prolonged conflagrations fueled by excessively dry vegetation, along with reduced water supply for firefighting purposes. Drought is also an economic hazard. Significant economic impacts on California’s agriculture industry can occur as a result of short‐ and long‐term drought conditions; these include hardships to farmers, farm workers, packers, and shippers of agricultural products. Health and property impacts, such as water contamination (especially private wells), economic losses to individuals, physical and mental health impacts may also occur. In some cases, droughts can also cause significant increases in food prices to the consumer due to shortages, causing possible food insecurity or dietary changes, which may lead to poorer health outcomes. Drought can also result in lack of water and subsequent feed available to grazing l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
181
livestock, potentially leading to risk of livestock death and resulting in losses to the State’s and Marin County’s agricultural economy.
Based on historical information, the occurrence of drought in California, including the Marin County OA, 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 is often 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.
Figure 3.61: Drought Impacts
Source: National Drought Mitigation Center
1 ~<;>U·N· TY OF a ~ ARIN ~
Natural Climate Valiability
Precipitation deficiency
(amount, intensity, timing)
Reduced infiltration, runoff
deep percolation, and
ground water recharge
High temp., high winds, low
relative humidity, greater
sunshine, less cloud cover
Increased evaporation
and transpiration
Soil water deficiency
Plant water stress, reduced
biomass and yield
i6
u ·-o,_ ... o- _o,
o=
'-0 o ...
~Q
:E
------- -----------------·------------- Reduced streamflow, inflow to reservoirs, lakes, and ponds;
reduced weti ands,
wildlife habitat
] ... ·er;,
o_
oo
......
~ - - - - - - - - - _'--_ _ - _ - _ - _- _- _ - _ ....,...._ - _- _ - _ - _ - _ - _----' _ - - - - - - - - - - - :c - Economic Im acts social Im acts Environmental Im acts
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
182
Drought also has a significant impact on tree mortality. Figures 3.64 shows the impact of tree mortality in Marin County in 2022.
Figure 3.62: 2022 Locations of Tree Mortality in the Marin County OA Source: CALFIRE
Extent and Probability
Scientists expect that climate change will lead to more frequent and more intense droughts statewide. Overall, precipitation levels are expected to stay similar, and may even increase in some places. However, the state’s current data say that there will be more years with extreme levels of precipitation, both high and low, as a result of climate change. This is expected to cause more droughts that last longer and are more intense, compared to historical norms.
Higher air temperatures are expected to increase evaporation, causing more water loss from lakes and reservoirs and decreasing soil moisture to greater depths. 1 ~<;>U·N· TY OF a
~ ARIN ~
y
181.) I'll
P~talumcf
0 1:577,791
3 s4Mi1 Francisco.
H
p
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
183
Table 3.10: Marin County OA Hazard Risk Assessment – Drought Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Moderate High High 16.00
City of
Belvedere
Highly
Likely Extensive Moderate High High 16.00
Town of
Corte Madera Likely Extensive Weak High Medium 13.00
Town of
Fairfax Occasional Extensive Weak Medium Low 10.00
City of
Larkspur Occasional Extensive Moderate High Medium 13.00 City of
Mill Valley Likely Extensive Weak High Medium 13.00
City of
Novato Likely Extensive Weak High Medium 13.00
Town of
Ross Likely Extensive Moderate Medium High 14.00
Town of
San Anselmo Likely Extensive Extreme High High 17.00
City of
San Rafael Likely Extensive Moderate High Medium 14.00
City of
Sausalito Unlikely Negligible None Low Low 4.00
Town of
Tiburon
Highly
Likely Extensive Moderate High High 16.00
Bolinas
Public Utility
District
Highly
Likely Extensive Severe High High 17.00
Las Gallinas
Valley
Sanitary
District
Likely Limited None High Medium 10.00
North Marin
Water
District
Occasional Extensive Severe High Medium 14.00
Southern
Marin Fire
District
Likely Significant Severe High Medium 14.00
Table 3.10: Marin County OA Hazard Risk Assessment – Drought Source: Profiled Jurisdictions and Districts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
184
Vulnerability
The vulnerability of the Marin County OA to drought is countywide, but impacts may vary by area and include reduction in water supply, agricultural losses, and an increase in dry fuels.
During drought, declines in surface water flows can be detrimental to water supplies for agriculture and cities, hydropower production, navigation, recreation, and natural ecosystems, particularly habitat for aquatic and riparian species. Communities in the Marin County OA, may experience water shortages during drought conditions which lead to mandatory water use restrictions and possibly the importation of water. During drought events, the flow of water in creeks and streams is reduced, creating more slow-moving or standing water. This can concentrate sediment and toxins in the low water levels, causing harm to plants and animals.
Many fish species also rely on specific water temperatures and stream flow speeds, especially for spawning and egg incubation, and changes to stream velocity as a result of drought conditions can affect reproduction. Droughts can also indirectly lead to more wildfires, and the stress caused by water shortages can weaken plants, making them more susceptible to pests and diseases. As drought persists, longer-term impacts can emerge, such as land subsidence, seawater intrusion, and damage to ecosystems. During prolonged or severe drought, County residents would be impacted by water use restrictions and changes to water supply.
Climate Change and Future Development Considerations
Climate change increases the odds of worsening drought. Warmer temperatures enhance evaporation, which reduces surface water and dries out soils and vegetation. This makes periods with low precipitation in the summer drier than they would be in cooler conditions.
Climate also alters the timing of water availability as warmer winter temperatures cause less precipitation to fall. During droughts, communities in the Marin County OA may have limited access to water for household use, including drinking, cooking, cleaning, and watering plants, as well as for agriculture, transportation, and power generation. Drought may lead to higher water costs, rationing, or even the decimation of important water sources like wells in the Marin County OA. As more people move into the Marin County OA, additional strain will be placed on the OA’s water supply. Drought can affect livestock and crops in the Marin County OA, impacting its economy. Drought can increase the occurrence and severity of wildfires and tree mortality in the Marin County OA. Impacts to residents and infrastructure from wildfire as a result of drought will increase as more development occurs in the mountainous areas of the Marin County OA where wildfires are more likely to occur. Drought also increases the amount of carbon dioxide in the atmosphere, including by decreasing land productivity, which reduces the amount of vegetation storing carbon dioxide. In addition, increases in drought-related wildfire and soil erosion can release carbon dioxide sequestered in trees and plants back into the atmosphere. This will only worsen climate change for the Marin County OA into the future.
When considering future development, the Marin County OA can help prepare for both future droughts and climate change by practicing and promoting water conservation and enhancing water efficiency throughout landscapes, city plans, and water infrastructure. The Marin County OA can also identify alternative water supplies, create drought emergency plans, and encourage farmers to plant drought-resistant crops.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
185
3.3.4 EARTHQUAKE
Earthquakes are sudden rolling or shaking events caused by movement under the earth’s surface. Earthquakes happen along cracks in the earth's surface, called fault lines, and can be felt over large areas, although they usually last less than one minute.
The amount of energy released during an earthquake is usually expressed as a magnitude and is currently measured by seismologists on the Moment Magnitude (Mw Scale). The Mw Scale was developed to succeed the previously used Richter Scale and is measured on a scale of zero to ten with increasing values reflecting increasing intensity.
The other commonly used measure of earthquake severity is intensity, which is an expression of the amount of shaking at any given location on the ground service. Intensity is most commonly measured on the Modified Mercalli Intensity (MMI) Scale (see Figure 3.63).
Figure 3.63: Modified Mercalli Intensity Scale
Figure 3.64 gives intensities (measured on the MMI scale) that are typically observed at locations near the epicenter or earthquakes of different magnitudes. l ~<;>U·N· TY OF
~ ARIN
Intensity Shaking
Not felt
Weak
Ill Weak
IV Light
V Moderate
VI Strong
VII Very
strong
Severe
Violent
a
~
Description/Damage
Not felt except by a very few under especially favorable conditions.
Felt only by a few persons at rest,especially on upper floors of buildings.
Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake.
Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.
Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck stri king building. Standing motor cars roc ked noticeably.
Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.
Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.
Damage negligible in buildings of good design and construction; sl ight to moderate in well-built ordinary structu res; considera ble damage in poorly built or badly designed structures; some chimneys broken.
Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.
Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.
Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
186
Figure 3.64: Mercalli Scale vs. Magnitude
The extent of ground shaking also depends in large part on how soft the underlying soil is. Soft soils amplify ground shaking (see Figure 3.65). This was observed during the 1989 Loma Prieta Earthquake when the most significant damages experienced in San Francisco were in the Marina District, which was built on fill.
Figure 3.65: Soil Types
l ~<;>U·N· TY OF
~ ARIN
Soil Vs>
type 1500
A m/ sec
1500
Soil
type m/ sec >
Vs> 750
B
m/sec
750
Soil m/ sec>
Type Vs>350
C m/ sec
350
Soil
Type m/ sec>
Vs> 200
D m/ sec
Soil 200
Type m/ sec>
E Vs
a
~
Richter
Magnitude Scale
1.0-2.9
3.0-3.9
4.0 -4.9
5.0-5.9
6.0-6.9
7 .0 or higher
Typical Maximum
Modified Mercalli
Intensity Scale
I
TI-Ill
.._
IV-V
I VJ-Vil
VII- IX --
VIII or higher
Includes unweathered intrusive igneous rock. Occurs infrequently in the bay area. We consider it with type B (both A and Bare represented by the color blue on the map). Soil types A and B do not contribute greatly to shaking amplification.
Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock. (M esozoic rocks are between 245 and 64 million years old. The Fra nciscan Complex is a Mesozoic unit that is common in the Bay Area.) Includes some Quaternary (less than 1.8 million years old) sands, sandstones and mudstones, some Upper Tertiary (1.8 to 24 million years old) sandstones, mudstones and limestone, some Lower Tertiary (24 to 64 million years old) mud stones and sandstones, and Franciscan melange and serpentinite.
Includes some Quaternary muds, sands, gravels, silts and mud. Significant amplification of shaking by these soils is generally expected.
Includes water-satu rated mud and artificial fill. The strongest amplification of shaking due is expected for this soil type.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
187
An earthquake 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.
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.
Location and Previous Occurrences
The potential for earthquake damage exists throughout Marin County because of a combination of the number of active faults within and near the County and the presence of soils vulnerable to liquefaction. These faults are shown on the California Geological Survey (CGS) Fault Activity Map of California (see Figure 3.68. Fault Activity Map below). Descriptions of the most significant active faults to Marin are provided below.
San Andreas fault: The San Andreas Fault traverses Marin County running north and south in the western quarter of the county. It enters Marin on the Pacific Coast near Bolinas, follows the path of Highway 1 and Tomales Bay, exiting Marin at sea just west of Dillon Beach. Hayward fault: the eastern, more heavily populated part of Marin is less than ten miles from the northern section of the Hayward fault. Rodgers Creek fault: The northern part of Marin is less than ten miles from the Rodgers Creek fault. See Figure 3.66 for a map of earthquake faults and probability of shaking across the Marin County OA.
Earthquake Shake Intensity
The colors on Figures 3.66 and 3.67 represent the level of ground shaking intensity of a potential future earthquake. The result is expressed as the level of ground shaking (expressed as a percentage of gravity) that on average occurs every 500 years.
This map 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 2500 year average repeat time. The relatively long-period (1.0 second) earthquake shaking is shown here. Long period-shaking affects tall, relatively flexible buildings, but also correlates well with overall earthquake damage.
Earthquake Shaking Potential Maps for California depict expected intermediate period (1s or 1hz) ground motions with 2% exceedance probability in 50 years. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
188
Figure 3.66: Earthquake Faults and Probability of Shaking in the Marin County OA Sources: Marin County OEM, USGS
l ~<;>U·N· TY OF
~ ARIN
/
\
\
I
(
\
i
I
I
I
/
/
/
a
~
Marin County / Full County
Earthquake
DIIICUII
EMERGENCY
MANAGEMENT
San Pablo Bay
Wildlife Area
Legend
Earthquake
1.95 1.85
1.15 1.05
0 1.45
1.35 - 1.25
- 0.95
0.85 0.75
0.65 0.55
0.45 0.35
Marin County OEM / Woody Baker-Cohn
email: [email protected] Ii
Date Printed: 09/22/23
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, (alifornia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS N
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
189
Figure 3.67: Marin County Earthquake Shaking Potential and Critical Facilities Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
I
/
I
/
I
I
(
• Dams
• Military and Qvil
Defense Installations
COl'r'lmunic.atior'l
Facil~ies
Elecbic Power Facllltles
Legend
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Wastewater facilities EarthquakeShaking
Water Supply Facilities 0.45
o.ss AirportS 0.65 Emergency Operations 0.75 Centers
0.85 Marin County
Earthquake
10 1
- 0.95
- I.OS
- I.IS
- 1.25
- 1.35
- 1.45
1.55 1.65
1.75 0
DfllctOI
EMERGENCY
MANAGEMENT
10 Miles
12 21
37 San Pablo Bay
Wildlife Area
1.85 1.95
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 11/01/23 N
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, califomia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/ NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
190
There are faults that do not traverse the Marin County OA that may cause shaking effects to occur inside the County.
According to the Association of Bay Area Governments Resilience Program, “the San Andreas Fault was the source of the magnitude of 7.8 earthquake in 1906. Marin was sparsely inhabited at that time and experienced relatively moderate property loss and only two deaths. The epicenter was just two miles west of San Francisco and West Marin experienced some pronounced earthquake effects. This included a horizontal earth displacement of 21 feet near the head of Tomales Bay.
On October 17, 1989, a magnitude 7.1 earthquake occurred on the San Andreas Fault, the largest earthquake to occur in the San Francisco Bay Area since 1906. This earthquake was named the Loma Prieta Earthquake due to its calculated epicenter. The impact of the Loma Prieta Earthquake was most apparent in the northeast area of Santa Cruz. If the fault rupture location were closer, a strong shaking such as this could have caused severe damage within Marin County, including damage to life-line routes. The Loma Prieta Earthquake was not “the big one,” which is a common reference to an event with a magnitude of 8 or larger (such as the 1906 San Francisco quake).
Impacts
Ground shaking is the primary earthquake hazard. Many factors affect the survivability of structures and systems from earthquake-caused ground motions. These factors include proximity to the fault, direction of rupture, epicenter location and depth, magnitude, local geologic and soils conditions, types and quality of construction, building configurations and heights, and comparable factors that relate to utility, transportation, and other network systems.
Ground motions become structurally damaging when average peak accelerations reach 10 to 15 percent of gravity, average peak velocities reach 8 to 12 centimeters per second, and when the Modified Mercalli Intensity Scale is about VII (18-34 percent peak ground acceleration), which is considered to be very strong (general alarm; walls crack; plaster falls).
Earthquakes can result in liquefaction. Liquefaction is a process whereby soil is temporarily transformed to a fluid form during intense and prolonged ground shaking. Areas most prone to liquefaction are those that are water saturated (e.g., where the water table is less than 30 feet below the surface) and consist of relatively uniform sands that are loose to medium density. In addition to necessary soil conditions, the ground acceleration and duration of the earthquake must be of sufficient energy to induce liquefaction.
Liquefaction during major earthquakes has caused severe damage to structures on level ground as a result of settling, tilting, 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 under a sloping soil mass, the entire mass may flow toward a lower elevation. Of particular concern in terms of developed and newly developing areas are fill areas that have been poorly compacted.
Earthquakes can cause 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. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
191
Earthquakes can also cause seiches, landslides, and dam failures. A seiche is a periodic oscillation of a body of water resulting from seismic shaking or other factors that could cause flooding. Earthquakes may cause landslides, particularly during the wet season, in areas of high water or saturated soils. Earthquake impact on life, property, and environment may include cascading impacts of lifelines loss (water, electricity), loss of housing, injuries and mortality, surge in healthcare facilities, and disruption to EMS services.
Most structures in the Marin County OA, including in the unincorporated area, were built before 1970, when major seismic design changes were made to the building code and are particularly vulnerable to earthquakes and liquefaction. Wood framed homes, however, are light and flexible and can often survive earthquakes with minimal damage as long as the foundations are properly retrofitted (bolted and braced). The County of Marin and its political subdivisions have adopted California Building, Plumbing, Electrical and Mechanical Codes whereby no building or structure is erected, constructed, enlarged, improved, removed, or converted without a permit. Adherence to these codes currently allows the county to gather data on retrofitting and current building code compliance. It is important to note that these data continue to have limitations for assessing overall vulnerability in the county for all structures.
The majority of the Marin County OA’s single-family buildings with foundations to bedrock will perform well in a shake. Modern multi-story buildings with foundations to bedrock should not be subject to collapse, although some serious damage may occur. However, many heavier developed areas of the Marin County OA are built on soft alluvial soils or filled-in water ways.
Due to liquefaction, these soils will significantly increase the shaking effects and will account for the majority of damaged and destroyed structures, regardless of their proximity to the fault line.
Liquefaction occurs when ground shaking causes loose, saturated soil to lose strength and act as a viscous fluid. When liquefaction occurs, it can result in the sidelong movement of large masses of soil, loss of strength in the soil supporting structures causing structures to collapse, and/or consolidation due to soil settlement decreasing soil surface elevations. The county’s topography includes large areas of steep slopes, adding to the vulnerability of earthquake induced disasters with the additional danger of debris flow (landslides). Bluff erosion along the coastal areas also poses unique threats to coastal structures and roads during times of earthquake.
Extent and Probability
An earthquake could occur and affect any area of the Marin County OA, including the unincorporated area. The ABAG Resilience Program analysis shows risk of liquefaction in Corte Madera, Larkspur, Bel Marin Keys, Novato, Ross Valley along creeks (Ross, San Anselmo, Fairfax), San Geronimo, San Rafael, Santa Venetia, communities around Richardson Bay (Belvedere, Marin City, Mill Valley, Sausalito, Strawberry, Tam Valley, Tiburon), Stinson Beach, Tomales Bay-side communities, and the county-owned Gnoss Field Airport.
According to a September 24, 2016 article in the Marin Independent Journal, “The Working Group on California Earthquake Probabilities has updated its earthquake forecast and determined there is a 72 percent probability - up from 63 percent - of at least one earthquake of magnitude 6.7 or greater striking somewhere in the Bay Area before 2043.” The Association of Bay Area Governments (ABAG) Resilience Program projects a 52% chance of a 6.7 or greater earthquake on one of the faults affecting Marin between now and 2036 (21% at San Andreas fault and 31% on Hayward/Rodgers Creek). Supporting this article’s assertions is the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3), which provides authoritative estimates of the magnitude, location, and time-averaged frequency of potentially damaging l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
192
earthquakes in California (see Figure 3.68). Uniform California Earthquake Rupture Forecast primary achievements have been to relax fault segmentation assumptions and to include multifault ruptures, both limitations of the previous model (UCERF2).
Figure 3.68: Uniform California Earthquake Rupture Forecast Version 3 Source: USGS
The September 24, 2016 article goes on to say “Marin sits smack dab (sic) in the middle of two major faults. To the east is the Rodgers Creek-Hayward fault just a few miles from Marin’s shores through San Pablo Bay, which the U.S. Geological Survey estimates has a 33 percent likelihood of a 6.7-magnitude quake or greater in the next 30 years — the highest probability of any Bay Area fault to slip. But movement on those faults could be worse than originally thought.” The Rodgers Creek-Hayward fault, thought to be two separate faults, actually may be linked and have the potential to cause more damage than previously determined, according to USGS research.
“The Rodgers Creek Fault runs from Sonoma County into San Pablo Bay near Marin’s shore.
The Hayward Fault runs through the western part of Alameda County into San Pablo Bay east of San Rafael and Novato. They were thought to be offset by about two miles under San Pablo Bay. But underwater exploration done in 2014 seems to link them. More study will occur to confirm those initial findings.”
l ~<;>U·N· TY OF
~ ARIN
a
~
1/1000 1/100 1110
30--year M ~6-7 likelihood
(percent)
10 UCERF3
Uniform California Earthquake Rupture Forecast (Version 3) 100
Ttvee+dimensional perspective view of the likelihood
that each region of California will experience a
magnitude 6.7 or larger earthquake in the next
30 years (6.7 matches the magnitude of
the 1 994 Northridge earthquake. and
30 years is the typic<II duration
of a homeowner mortgage).
faults are shown by the rectangles outlined in black. The entire cofored area represents greater California,and the white line across the middle defines northern versus southern C,alifornia. Results do not include earthquakes on the Cascadia Subduction Zone, a 750-mile offshore fault that extends about 1 SO miles into California from Oregon and Washington to the north. 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
193
Table 3.11: Marin County OA Hazard Risk Assessment - Earthquake Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Extreme None High 15.00
City of
Belvedere
Highly
Likely Extensive Extreme None High 15.00
Town of
Corte Madera Occasional Extensive Severe None High 12.00 Town of
Fairfax
Highly
Likely Extensive Extreme None High 15.00
City of
Larkspur Occasional Extensive Extreme None High 13.00
City of
Mill Valley Occasional Extensive Extreme Low Medium 13.00 City of
Novato Occasional Extensive Extreme None Medium 12.00
Town of
Ross Likely Significant Severe None Medium 11.00
Town of
San Anselmo Occasional Extensive Extreme High High 16.00 City of
San Rafael Occasional Significant Severe None Medium 10.00 City of
Sausalito Occasional Limited Moderate Low Low 8.00
Town of
Tiburon
Highly
Likely Extensive Extreme None High 15.00
Bolinas
Public Utility
District
Occasional Extensive Severe None High 13.00
Las Gallinas
Valley
Sanitary
District
Occasional Extensive Extreme None Medium 12.00
North Marin
Water
District
Occasional Extensive Extreme Low Medium 13.00
Southern
Marin Fire
District
Occasional Extensive Extreme None High 13.00
Table 3.11: Marin County OA Hazard Risk Assessment – Earthquake Source: Profiled Jurisdictions and Districts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
194
Vulnerability
The areas most vulnerable to earthquake in the Marin County OA, including the unincorporated area, are on bay mud and current and former marshlands. Many of these areas have been artificially filled over the last century. Other areas with some risk of liquefaction include those along creeks due to fluvial and alluvial deposits. Unfortunately, much of Marin’s residential areas and infrastructure are located on former marshes and along creeks. Tens of thousands of acres of residential areas, along with roads, airports, military facilities, retail centers, schools, hospitals, prisons, jails, government administration centers, convention centers, recreation areas, croplands/pasture are in areas vulnerable to liquefaction in the Marin County OA.
For all three faults mentioned above that run through the Marin County OA, many areas of the most severe vulnerability to earthquake coincide with the heavily populated Highway 101 corridor on the eastern side of the county. Numerous unincorporated communities with large populations and buildings lie in this area. According to the ABAG Resilience Program, a 7.8 magnitude earthquake on the San Andreas fault would leave 3,100 homes in the Marin County OA uninhabitable, displace 6,200 households, and result in total building damage of $1,260 billion dollars. Because many people in the region do not have earthquake insurance, many homeowners will not be able to afford to rebuild their homes.
In addition to damaging buildings, a 7.8 magnitude San Andreas earthquake could close 77 roads in Marin due to faulting, liquefaction, debris flow/ landslide, shaking damage to bridges and interchanges, threat of building collapse, structural damage to highway and rail structures, small hazardous material releases, water and gas pipe leaks, and other miscellaneous reasons for closure.
Figure 3.69 shows the social vulnerability of Marin County populations to earthquake in relation to the rest of California.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
195
Figure 3.69: Population/Social Vulnerability to an Earthquake in California Source: 2018 State of California Hazard Mitigation Plan 1 ~<;>U·N· TY OF a ~ ARIN ~
0 25 SO 100 MRes
cal Poly - San Luis Obispo
City and Reeional Pi nning
June 2018
Popu lation/Soc1:a II Vulnerability
with Earthquake Hazard
R,eliative Vulnerability
High
Low
Grid cell size approximate, y
•one square kilometer.
Cells with population < 75
are not mapped.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
196
Climate Change and Future Development Considerations
There is no direct link between climate change and seismic activity that could impact the Marin County OA, so climate change is not expected to cause any changes to the frequency or intensity of seismic shaking. According to a 2018 study by the Institute of Physics (IOP), climate change could result in “isostatic rebounds,” or a sudden upward movement of the crust because of reduced downward weight caused by glaciers. As glaciers are known to melt when overall global temperatures increase, climate change could indirectly lead to an increase in seismicity in the Marin County OA. Climate change could also impact earthquakes felt in the Marin County OA as droughts can further deteriorate existing fault lines and pumping groundwater can put further pressure on the earth’s crust. Future development in the populated areas of Marin County OA where seismic shaking and subsidence are more prevalent could exacerbate the impacts of an earthquake.
3.3.5 FLOODING
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.
The area adjacent to a channel is the floodplain. 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. The 100-year flood is the national minimum standard to which communities regulate their floodplains through the National Flood Insurance Program. The 200-year flood is one that has 0.5% chance of being equaled or exceeded each year. The 500-year flood is the flood that has a 0.2 percent chance of being equaled or exceeded in any given year. 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 such as construction of bridges or channels. In areas where flow contains high sediment load, such as Easkoot Creek in Stinson Beach (due to an active landslide upstream), the flow carrying capacity of the channel may be reduced dramatically during a single flood event. Coastal floodplains may also change over time as waves and currents alter the coastline (especially wetlands) and sea levels rise.
Flooding can occur in several ways:
Riverine flooding – Riverine flooding, defined as when a watercourse exceeds its “bank-full” capacity, generally occurs as a result of prolonged rainfall, or rainfall that is combined with snowmelt and/or already saturated soils from previous rain events. This type of flood occurs in river systems whose tributaries may drain large geographic areas and include one or more independent river basins. The onset and duration of riverine floods may vary from a few hours to many days and is often characterized by high peak flows combined with a large volume of runoff. 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. In the Marin County OA, riverine flooding can occur anytime from November through April and is largely caused by heavy and continued rains, sometimes combined with snowmelt, increased outflows from upstream dams, and heavy flow from tributary streams. These intense storms can overwhelm the local waterways as well as the integrity of flood control structures. Flooding is more severe when l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
197
antecedent rainfall has resulted in saturated ground conditions. The warning time associated with slow rise riverine floods assists in life and property protection.
Flash flooding – Flash flooding describes localized floods of great volume and short duration.
This type of flood usually results from a 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 and thus early threat identification and warning is critical for saving lives.
Localized/Stormwater flooding – Localized flooding problems are often caused by flash flooding, severe weather, or an unusual amount of rainfall. Flooding from these intense weather events usually occurs in areas experiencing an increase in runoff from impervious surfaces associated with development and urbanization as well as inadequate storm drainage systems.
Tidal flooding – Tidal flooding develops when high tides exceed either the top of bank elevation of tidal sloughs and channels, or the crest of bay levees. An especially high tide event that occurs during alignment of the gravitational pull between the sun and the moon, causes tidal water levels to rise to higher-than normal levels. King tides are normal, predictable events that occur semi-annually during winter months. Typically storms in which high tides coincide with peak stormwater flow are the most damaging.
The area is also at risk of flooding resulting from levee failures and dam failures. Dam failure flooding is discussed separately in the Dam Failure Section of this document; levee failure flooding is discussed separately in the Levee Failure Section of this document. 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.
A weather pattern called the “Atmospheric River” contributes to the flooding potential of the area. An Atmospheric River brings warm air and rain to the West. A relatively common weather pattern brings southwest winds to the Pacific Northwest or California, along with warm, moist air. The moisture sometimes produces many days of heavy rain, which can cause extensive flooding. The warm air also can melt the snowpack in the mountains, which further aggravates the flooding potential. In the colder parts of the year, the warm air can be cooled enough to produce heavy, upslope snow as it rises into the higher elevations of the Sierra Nevada or Cascades. Forecasters and others on the West Coast often used to refer to this warm, moist air as the “Pineapple Express” because it comes from around Hawaii where pineapples are grown.
A diagram of an atmospheric river event is shown in Figure 3.70. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
198
Figure 3.70: Diagram of an Atmospheric River Event
Source: NOAA
The Marin County OA is susceptible to various types of flood events. In coastal areas, flooding may occur when strong winds or tides result in a surge of seawater into areas that are above the normal high tide line. Other types of flooding in Marin include isolated ponding and stormwater overflow. Isolated ponding is when pools form on the ground and can occur in any area that doesn’t drain effectively – for example, in a natural depression in the landscape.
Stormwater overflow is when storm drains back up. Stormwater drainage systems quickly convey rainwater through underground pipes to creeks and the Bay. When the stormdrains are obstructed or broken or when the water bodies to which they lead to are already full, water backs up onto the streets. Although stormwater overflow and isolated ponding also occur throughout the County, the effects are typically not widespread or significantly damaging.
Location and Previous Occurrences
Figure 3.71 shows the Federal Emergency Management Agency (FEMA) flood hazard zones in the Marin County OA, using the Flood Insurance Rate Maps (FIRMs) for Marin County. l ~ <;>U·N· TY OF
~ ARIN
a
~
The science behind atmospheric rivers
An-~IC-(Alll~•!lcrnir,gc~~<>lw..f .,.,i,.~.,•-li1o14k- ~•f~!;lo~Pf~ •1 ,ol,•l~l'fld•IIClwe ~lo\'tli •\-\lrmdSt~ WtwftNl>-llilllkl ..... i"--'lhtM:Jul'll ""m,wl)(lf1ioff..wl<-toC. h ~I'll~, n.:.,gh """'IAAI "'" •)"11!1m lhol ·,lmj:l1p,<'lldo'b<niolloJI ...,,.,. "'"""'...,. allfle l•!I","""" pcr-1u1Alls..., attt,eeru,..,.,.W,11 •md- <~ <>I .U,,U,.'"9 t1>~ loduclnQ rnull1M,.ooouu""9 "'""!Qllt.icd.o,rugtto~t,,ond~. ~,.,..,...,..,...,..,.,.._,.,,...,,.,,,"" 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
199
Figure 3.71: FIRM Zones in the Marin County OA
Source: FEMA
1 ~<;>U·N· TY OF a ~ ARIN ~
Special Flood Hazard Areas
Flood Zone
A
AE
III AH
Ill Ao
111111 V
lll vE
N
A
0 10
----======:::JMiles
5 Data Source: Marin Map, 2018
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
200
Major county watersheds where significant numbers of structures are at risk from riverine flooding include Coyote Creek, Arroyo Corte Madera del Presidio, East and West Creek watersheds, Corte Madera Creek, Novato and Rush Creeks, Miller Creek, Easkoot Creek (Stinson Beach), Gallinas Creek. Additionally, many locations along Richardson Bay, Tomales Bay, lower Las Gallinas Creek, the San Rafael Canal, East San Rafael and Novato shores, and the outer Pacific coastline are vulnerable to coastal flooding.
In many cases, where there is a significant history of flooding there is a Marin County Flood Control & Water Conservation District “Flood Zone” established. There are 8 County Flood Zones located in the following areas as described in Table 3.11 .
Table 3.11: The 100-year, 200-year and 500-year floodplains in the Marin County OA Zone No. Name Location
1 Novato Northern Marin: Most of City of Novato and some surrounding areas within the Novato Creek watershed.
3 Richardson Bay
Southern Marin: Marin City watershed, Coyote Creek
watershed (includes Tamalpais Valley and Almonte); Arroyo Corte Madera del Presidio watershed and Ryan Creek
watershed (both include much of the City of Mill Valley), and a watershed including Sutton Manor/Alto/part of Strawberry. 4 Bel Aire
Southern Marin: East and West Creek watersheds which
run through the Bel Aire neighborhood of the Town of
Tiburon and part of (unincorporated) Strawberry.
5 Stinson Beach West Marin: Part of the lower Easkoot Creek watershed at Stinson Beach
6 San Rafael
Meadows
Central Marin: A part of the Las Gallinas Creek
watershed in the City of San Rafael across from the
County Civic Center.
7 Santa Venetia Central Marin: The unincorporated community of Santa Venetia along Las Gallinas Creek.
9 Ross Valley
Central Marin: The Corte Madera Creek watershed, including the towns of Fairfax, San Anselmo, Ross, and Larkspur, as well as unincorporated parts of San Anselmo, Fairfax,
Kentfield and Greenbrae.
10 Inverness West Marin: Inverness, along the west shore of Tomales Bay and the East flank of Inverness Ridge.
Figure 3.72: The 100-year, 200-year and 500-year floodplains in the Marin County OA. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
201
Figure 3.73: 100, 200, 500-Year Floodplains in the Marin County OA Source: Marin OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
\
I
/
I
I
(
Legend
• Dams
Military and Ovil
Defense Installations
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
Marin County
Flooding
•
•
\
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Petaluma
0 2,5 -5
...
D1111:EOI
EMERGENCY
MANAGEMENT
Boyes Hot
Springs El Verano
Sonoma
on
e ,ere
alito
_..,,
_..,.
• Water Supply Facilities Flooding
Airports 500 Year Flood Plain
100 Year Flood Plain
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/30/23
County of Marin, callfornia State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, califomia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
202
Several unincorporated communities in Marin County lie in a special flood hazard area (the 100- year floodplain), which are shown below along with the 500-year floodplain, where applicable.
Figure 3.74 shows the 100-year floodplain in the Lagunitas area.
Figure 3.74: 100-Year Floodplain – Lagunitas
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a ~ ARIN ~
\
::__\ .... -,i&i,.,,_ ... _/ ----.,
'
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
203
Figure 3.75 shows the 100-year floodplain in the Forest Knolls are.
Figure 3.75: 100-Year Floodplain – Forest Knolls Area
Source: Marin County, 11/27/23
Figure 3.76 shows the 100-year floodplain in the San Geronimo area.
Figure 3.76: 100-Year Floodplain – San Geronimo Area
Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
i
,..,
a
~
,!
j
'!
/ ...
\
\ \
\"
\ ~
(
{
\
,--
~. .. ""'
,,
,,
.. ,_
........ ..........
J 1 . i
M:wric.Thc:rnlt ·-- --
II
I
I
\ c.........., '\
Thor,,.-,r,_
ltFrandoDflM~
I
j
'[
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
204
Figure 3.77 shows the 100-year floodplain in the Woodacre area.
Figure 3.77: 100-Year Floodplain – Woodacre Area
Source: Marin County, 11/27/23
Figure 3.78 shows the 100-year floodplain in Tocoloma.
Figure 3.78: 100-Year Floodplain – Tocoloma
Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
\
a
~
"°""""°"'-Ulepr,.1 ---~~
\
\
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
205
Figure 3.79 shows the 100-year floodplain in Nicasio.
Figure 3.79: 100-Year Floodplain – Nicasio
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
206
Figure 3.80 shows the 100-year floodplain outside of Nicasio to the east.
Figure 3.80: 100-Year Floodplain –Nicasio East
Source: Marin County, 11/27/23
Figure 3.81 shows the 100-year floodplain in Olema.
Figure 3.81: 100-Year Floodplain –Olema
Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
\
\
.....
'
/
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
207
Figure 3.82 shows the 100-year floodplain in Point Reyes Station and the area immediately south.
Figure 3.82: 100-Year Floodplain – Point Reyes Station Area - South Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
208
Figure 3.83 shows the 100-year floodplain in the northern end of Point Reyes Station.
Figure 3.83: 100-Year Floodplain – Point Reyes Station Area - North Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
I
/
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
209
Figure 3.84 shows the 100-year floodplain in the Inverness Park area.
Figure 3.84: 100-Year Floodplain – Inverness Park Area
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
210
Figure 3.85 shows the 100-year floodplain in the area south of Inverness.
Figure 3.85: 100-Year Floodplain – Inverness South
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
211
Figure 3.86 shows the 100-year floodplain in Inverness.
Figure 3.86: 100-Year Floodplain – Inverness
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
212
Figure 3.87 shows the 100-year floodplain in Reynolds/Marconi area.
Figure 3.87: 100-Year Floodplain – Reynolds and Marconi Area Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
213
Figure 3.88 shows the 100-year floodplain in the Marshall area.
Figure 3.88: 100-Year Floodplain – Marshall Area
Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
214
Figure 3.89 shows the 100-year floodplain in the Tomales area.
Figure 3.89: 100-Year Floodplain – Tomales Area
Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
lpn
. HU
J
t
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
215
Figure 3.90 shows the 100-year floodplain in the area north of Bolinas.
Figure 3.90: 100-Year Floodplain – Bolinas North
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
216
Figure 3.91 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in Bolinas and the area west of Stinson Beach.
Figure 3.91: 100-Year and 500-Year Floodplain – Bolinas and Stinson Beach West Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
217
Figure 3.92 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in Stinson Beach.
Figure 3.92: 100-Year and 500-Year Floodplain – Stinson Beach Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
Ull.NIAvenue
I I \ ~ I ... !
I ' C...,i,,I""' ~ j I \ ••••·r
I \ j
J
i l~A~~
; 6U&navo1aAvenue
, .. ""' .... , .. I
j
J
1 /j •
\
r+. ...
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
218
Figure 3.93 shows the 100-year floodplain in Muir Beach.
Figure 3.93: 100-Year and 500-Year Floodplain – Muir Beach Source: Marin County, 11/27/23
Figure 3.94 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in the Tamalpais Valley Area.
Figure 3.94: 100-Year and 500-Year Floodplain – Tamalpais Valley Area Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
219
Figure 3.95 shows the 100-year floodplain in Alto and Strawberry.
Figure 3.95: 100-Year and 500-Year Floodplain – Alto and Strawberry Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
/;
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
220
Figure 3.96 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in Kentfield and Greenbrae.
Figure 3.96: 100-Year and 500-Year Floodplain – Kentfield and Greenbrae Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
V
..,).,. : .
~ { . ..-
. ....__
" .. f
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
221
Figure 3.97 shows the 100-year floodplain in California City.
Figure 3.97: 100-Year Floodplain – Marin City
Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
222
Figure 3.98 shows the 100-year floodplain in Lucas Valley and Marinwood.
Figure 3.98: 100-Year Floodplain – Lucas Valley and Marinwood Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
I
I ! !
\ ; \ \
A
I J
I,
'
I
• !
,.,
'
I'.
.;"
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
223
Figure 3.99 shows the 100-year floodplain in Saint Vincent.
Figure 3.99: 100-Year Floodplain – Saint Vincent
Source: Marin County, 11/27/23
Figure 3.100 shows the 100-year and 500-year floodplain in the Santa Venetia area.
Figure 3.100: 100-Year and 500-Year Floodplain – Santa Venetia Area Source: Marin County, 11/27/23
1 ~<;>U·N· TY OF a
~ ARIN ~
l
l
L
'· I
l
.,/'<I' I ....
I
I Ii I I
I I I
"""_,.
I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
224
Figure 3.101 shows the 100-year floodplain (blue) and the 500-year floodplain (brown) in the San Pedro Hill area.
Figure 3.101: 100-Year and 500-Year Floodplain – San Pedro Hill Area Source: Marin County, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
225
Figure 3.102 shows the 100 and 500-year floodplains in Novato with critical facilities including the Marin County Landfill and the Marin County Airport.
Figure 3.102: Novato Flooding - Marin County Landfill and Marin County airport Source: Marin County
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / Novato Area
Flooding
OI0rtlPrl
Slat
Legend
• Dams Fi re Stations
Military and Civil Hospitals and Medical
Defense Installations Facilities
Communication 0 Police / Sheriff Stations
Facilities Schools
Electric Power Facilities Flooding Airports
0 Emergency Operations 500 Year Flood Plain
Centers 100 Year Flood Plain
· 2
omcu,
EMERGENCY
MANAGEMENT
Miles
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
226
Figure 3.103 shows the100- and 500-year floodplain in San Rafael Area.
Figure 3.103: Flooding in San Rafael Area
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / San Rafael Area
Flooding
Legend
e Dams
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
e Water Supply Facilities
Airports
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Flooding
500 Year Flood Plain
100 Year Flood Plain
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, Geoli $ap Rafael
... .
•
OfFIClllf
EMERGENCY
MANAGEMENT
an
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
227
Figure 3.104 shows the 100-year floodplain in Bel Marin Keys.
Figure 3.104: 100-Year Floodplain – Bel Marin Keys
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / Southern Marin
Flooding
omClOI
EMERGENCY
MANAGEMENT
Legend
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
Airports
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Flooding
500 Year Flood Plain
100 Year Flood Plain
f
Little Reed
Heights
Sausalito
alito !'
0 Belvedere
0 1.2
--c=:::::i•---Miles
Woody Baker-Cohn
arinCounty.org
Date /23
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS Bureau of Land Management, EPA, NPS, USDA 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
228
Figure 3.105 shows the 100-year floodplain in Bolinas.
Figure 3.105: Stinson - Bolinas Area Flooding
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County/ Stinson - Solinas
Flooding
OfllCIOf
EMERGENCY
MANAGEMENT
Woodville
Solinas
Legend
e Dams
Communication
Facilities
Electric Power Facilities
Fire Stations
Hospitals and Medical
Facilities
Schools
Flooding
500 Year Flood Plain
100 Year Flood Plain
0 0.3 0.6 1.2
Miles
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/30/23
Stinson
Bea~
~ N
County of Marin, callfornla State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
229
Figure 3.106 shows flood control zones in the Marin County OA.
Figure 3.106: Flood Control Zones in the Marin County OA Source: Marin County
l ~<;>U·N· TY OF
~ ARIN
a
~
l
I
I
I
·~ ... ~~ ....
Flood Control Zone
Zone 1 - Novato
Zone 3 • Richardson Bay
......
Zone 4 • Bel Aire and S1tav.1)erry Circle
Zone 5 • Stinson 80.x
- Zeno 6 - San Rafaol Meadows
- Zone 7 - Santa Venetia
- Zone 9 • Ross Valley
- Zone 10 • Inverness
Flood Control Zones
N
I M l 10
SONOMA
County of Marin
Department of Public Works
www.marinwatersheds.org
\
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
230
Novato Creek in the northern part of the county historically caused damage to large numbers of homes, particularly in the 1960’s, until the Novato Flood Control Project was completed in eight construction phases starting in the 1980’s and continuing through 2006. Novato still experiences some damage during significant winter storms despite the completed Novato Creek Flood Control project. Power outages are also a frequent problem for one of the major pump stations in the area.
Although the current Corte Madera Creek Flood Control project is partially complete (Unit 4 in the Town of Ross is yet to be constructed), flooding will still occur for storms greater than about a 5-year recurrence flood event. Potentially all nine southerly and some centrally located communities of the Marin County OA on this creek are impacted by high tides and heavy rains in above average winter storms. The north-east part of the county, densely populated around the floodplain zones, is threatened every winter and still experiences some damage during winter storms despite the completed Novato Creek Flood Control project.
Since the middle of the last century, the winter/spring storms of 1950, 1955*, 1958*, 1963, 1964*, 1965, 1969*, 1970*, 1973*, 1978, 1980, 1982*, 1983*, 1986*, 1995*, 1996, 1997*, 1998*, 2002, 2005/2006*, 2006*, 2008, 2014, 2017, 2019 and 2023 caused significant damage across the Marin County OA.
*Major Federal Disasters declared for flood.
Flooding in December 1964 and January 1965 had widespread impacts across the Marin County OA. Floods were generally moderate to high. Precipitation was heavy in the San Rafael-Kentfield area. From December 19th-23rd, precipitation was 8.49 inches at Kentfield.
From January 2nd-7th, precipitation at Kentfield was 7.45 inches. The flow in Corte Madera Creek was moderate but the stream flows and overflows of drains caused some local flooding in areas that are subject to frequent flooding in Kentfield. Flood flows in the Walker Creek basin in the northwestern part of Marin County exceeded previous maximum flows.
A major winter storm originating over the Pacific Ocean moved through Marin County in early January 1982. The maximum rainfall from an area of high rainfall in southern Marin County was about 16 inches. The center of this storm was near Kentfield. Large areas of southern and western Marin County had total storm rainfall exceeding 10 inches. Numerous towns were under water, homes and businesses were destroyed, and many roads were damaged across the Marin County OA. The Inverness area was especially hit hard with floodwaters and debris flows. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
231
Figure 3.107: Damage in Inverness from 1982 Storm
Source: Jack Mason Museum of West Marin History
The New Year’s Eve 2005-2006 flood caused widespread damage in the Marin County OA.
Easkoot Creek in Stinson Beach overflowed its banks. At least $219 million in damage was reported in the Marin County OA due to this storm. Over a thousand homes, apartments and businesses across the OA were damaged or destroyed. The Marin City exit off of Highway 101 was inundated with water and water covered all but one lane of southbound 101, creating a giant traffic jam. Western Marin County was scattered with downed trees, flooded roadways and mudslides.
In 2014, Marin County sustained an estimated $13,321,134 in damage from flooding, mudslides, winds, high tides and other storm damage from a December 10th-11th downpour.
There was an estimated $9,324,134 in damage to public property and $3,997,000 in private damages includes 34 homes, 11 businesses and two outbuildings.
In 2017, a powerful February storm thrashed Marin County. Kentfield received 6.3 inches of rain in a 24-hour period. Other rainfall totals for the period included 2.3 inches in Point Reyes.
The College of Marin closed its Kentfield campus because of the storm, and nine school districts canceled classes. Eleven private schools were closed. Pacific Gas and Electric Co. reported thousands of power outages in Marin, including in Kentfield and Lagunitas. Olema Road was closed at Westbrae Drive because of mud, flooding and debris, and flooding was reported on Sir Francis Drake Boulevard at the Bon Air Shopping Center in Greenbrae. In the San Geronimo Valley, flooding closed Sir Francis Drake Boulevard at West Cintura Avenue in Lagunitas. The National Park Service closed Muir Woods National Monument because of the weather. The Lagunitas School District and the Laguna Joint School canceled classes, while the BolinasStinson Union School District closed the Stinson Beach campus and held classes at the Bolinas campus.
In 2019, a storm on February 13th brought heavy rains to Marin County, saturating the ground and exacerbating high tides. County-maintained roads washed out and creeks overflowed their banks, endangering public infrastructure. Flooding occurred in Marin City and was particularly severe in areas of rural Marin. Highway 1 was impassable south of Tomales Petaluma Road and Sir Francis Drake Boulevard was only passable with high-clearance vehicles at Mount l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
232
Vision Road in Inverness. Rainfall totals for the storm included 4.3 inches on Mount Tamalpais and 4.16 inches in Kentfield.
Figure 3.108: Flooding in Marin City – 2019 Storm
Source: Marin Independent Journal
In 2023, a storm on January 9th battered Marin county with rain and wind. Rainfall totaled 0.91 inches in Dillon Beach, 1.14 inches in Point Reyes Station, 1.69 inches in Kentfield, 3.04 inches in Woodacre and 2.04 inches on the middle peak of Mount Tamalpais. The Lagunitas School District, Shoreline Unified School District and two elementary schools in the Ross Valley School District stayed closed. More than 4,700 PG&E customers across the Marin County OA had no power at one point.
Impacts
Floods can cause substantial damage to structures, landscapes, and utilities as well as life safety issues throughout the Marin County OA, including in the unincorporated area.
Floodwaters can transport large objects downstream, which can damage or remove stationary structures. Ground saturation can result in instability, collapse, or other damage. Objects can also be buried or destroyed through sediment deposition. Floodwaters can also break utilities lines and interrupt services. Standing water can cause damage to crops, roads, foundations, and electrical circuits. Certain health hazards are also common to flood events. Standing water can also cause septic tank failure and well contamination. Standing water and wet structures can become breeding grounds for microorganisms such as bacteria, mold, and viruses. This can cause disease, trigger allergic reactions, and damage materials long after the flood. When floodwaters contain sewage or decaying animal carcasses, infections become a concern. 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.
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 hogs are kept or their wastes are stored can contribute polluted waters to the receiving streams.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
233
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. Floodwaters may scour stream banks, edging properties closer to the floodplain or causing structures to collapse into floodwaters. Flooding is also responsible for hazards such as landslides when high flows oversaturate soils on steep slopes, causing them to fail. Hazardous materials spills are also a secondary hazard of flooding if storage tanks rupture and spill into streams, rivers, or storm drains.
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 home 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.
Additional growth in or around the Marin County OA could contribute to increased flooding in the county. Many historic and cultural resources are located in the mapped flood zones.
The impact of damage resulting from the flooding hazard, as mentioned, can be extremely variable. Nevertheless, most damage results from rising water that inundates residences and buildings, damage to infrastructure and critical facilities, and loss of ingress and egress by the population in the affected areas and the inability of the jurisdictions emergency response capabilities. Damage from flooding can range from minimal, where the damage to an individual home can be on the order of a few thousand dollars to the complete loss of a building or loss of life from the inability to evacuate from the rising floodwaters.
The diversity and dispersion of the Marin County OA’s flood hazards, in addition to the tendency for floods to be flashy in nature, make response to emergencies more difficult and increase the need for planning and community awareness in areas of increased flood risk. While property damage to structures within 100-year flood zones is a major concern, damage to roads, utilities, and other supporting infrastructure located in these zones can potentially impact areas of the community outside of the flood zones as well.
Arroyo Corte Madera del Presidio is at risk of overtopping due to less than a 5-year flow. On average Corte Madera Creek and Easkoot Creek are at risk of overflowing their banks due to 5- 10 year flow events. Novato Creek overflows in some locations due to 10-year flow. Coyote l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
234
Creek and Gallinas Creek are more vulnerable to overtopping due to tidal elevations and may be able to carry 100-year riverine flows at low tides.
Extent and Probability
In areas such as Marin County that do not have extended periods of below-freezing temperatures or significant snowfall, floods usually occur during the season of highest precipitation or during heavy rainfalls after prolonged dry periods. Marin County is dry during the late spring, summer, and early fall and receives most of its rain during the winter months. The rainfall season extends from November through April, with most rainfall occurring during this period. Due to varying microclimates within the County, rainfall measured in water year 2016- 2017 where there are Marin County Flood Control & Water Conservation District-owned gages ranged inland from as low as 47 inches in Novato to over 82 inches in Kentfield. Along the coast, rainfall ranged from 36 inches at Oceana Marin to 45 inches at Point Reyes Station.
In should be noted winter 2016-2017 was an unusually wet year. An average of 56 inches of rain falls each year at the summit of Mount Tamalpais, at 2,572 feet elevation. The rain collects in several channels, flowing down steep slopes and onto broad, flat valleys, many of which are populated. The valleys usually only receive on average 32 inches of rain per year, thus flows from the uplands contribute greatly to flows on the valley floor. During most rainfall events, waterways remain within their channels or underground pipes until they reach a bay or the ocean.
The Marin County OA has several major 100-year and 500-year floodplains which are mapped by FEMA in the most recent Flood Insurance Rate Maps (FIRM), several of which were recently updated in 2016 and 2017 (see above). While they may look small relative to the size of the County as a whole, the bulk of the floodplains are located in some of the County’s most heavily populated areas along the eastern shoreline: notably portions of Novato, San Rafael, and Mill Valley. These floodplains vary in size, probability and severity of inundation, underlying causes (riverine, tidal, etc.), and potential impacts to the communities in them. The areas of most concern are located in what is designated by FEMA as a 100-year flood zone or Special Flood Hazard Area (SFHA). What is currently considered a 100-year flood may occur more often due to climate change. Due to the increased probabilities of flooding (1% chance in any given year), these properties face high insurance premiums and major restrictions on further development.
Along the Pacific Ocean there are a number of homes in Stinson Beach which are mapped as being in a VE zone. A VE zone is a 100-year flood zone where tsunamis or other forms of wave action threaten low lying coastal areas.
For some of the developments along the San Francisco Bay, such as Santa Venetia and Tamalpais Valley, the main issues concern poor drainage due to flat terrain and/or differential settlement, low elevation relative to the tides, and the reliance on a system of pumps and levees to keep floodwaters from inundating homes. Runoff collecting in this area can be especially difficult to remove during high tides.
Other more inland areas, such as areas along Corte Madera Creek and its tributaries, have higher elevations yet still contain properties located in 100-year flood zones. This is mainly due to threats caused by local creeks which have a tendency to overflow their banks when rainfall reaches critical levels. Properties along Novato Creek and its tributaries face similar threats.
The main stems of these creeks and many of their tributaries are constrained by development on the banks.
When flooding occurs in the Marin County OA, depths are commonly on the order of 0-2 feet in streets and sidewalks. This level occurs when storm drains are overwhelmed and/or during king l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
235
tides. Flood depths on the order of 2- 4 feet have occurred in recent memory and represent significant flood events that caused damage to structures and property. 1982 was the most extreme flood of record along Corte Madera Creek in Central Marin County and probably had some inundations depths as high as 5 feet. In 2016 the FEMA San Francisco Bay Coastal Study became effective and raised the static Base Flood Elevation of the Bay to an elevation of 10-feet NAVD88. This level of flooding has not been observed but is feasible in any given year.
If this level of tidal flooding was to occur along the bay shoreline there would be inundation depths as much as 6-8 feet in neighborhoods such as Santa Venetia.
On the Marin County OA’s outer coast V zones have BFEs of up to 22 feet according to FIRMs updated August 2017. In the unincorporated community of Stinson Beach this corresponds to a maximum inundation depth of 8-10 feet. Although some houses were destroyed by wave action and storm surge during the 1982 event, nothing approaching this level of inundation has occurred in recorded history here.
The other index for extent is the speed of onset of flooding or the rainfall-runoff lag time, which doesn’t apply to tidal flooding. The riverine flooding comes directly from rainfall runoff of adjacent uplands in the County’s series of relatively small, short watersheds. While antecedent moisture is a big factor, this flash flooding is typically short duration and directly associated with the magnitude of the passing storm system. These storms, often in the form of atmospheric rivers coming off the Pacific Ocean, can last anywhere from a few hours to a day or two. The speed of onset of flooding ranges from minutes to about 2 hours after the precipitation exceeds the drainage capacity.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
236
Table 3.12: Marin County OA Hazard Risk Assessment – Flooding Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Limited Severe High Medium 14.00
City of
Belvedere
Highly
Likely Limited Severe High Medium 14.00
Town of
Corte Madera Likely Significant Severe High High 15.00
Town of
Fairfax Occasional Limited Moderate Medium Medium 10.00 City of
Larkspur Occasional Limited Severe High Medium 12.00
City of
Mill Valley Occasional Extensive Severe Medium Medium 13.00 City of
Novato Likely Negligible Weak Medium Low 8.00
Town of
Ross
Highly
Likely Significant Severe High High 16.00
Town of
San Anselmo Occasional Limited Moderate Medium Medium 10.00 City of
San Rafael
Highly
Likely Significant Severe High High 16.00
City of
Sausalito Likely Significant Moderate High Medium 13.00 Town of
Tiburon
Highly
Likely Limited Severe High Medium 14.00
Bolinas
Public Utility
District
Likely Limited Moderate High Medium 12.00
Las Gallinas
Valley
Sanitary
District
Likely Significant Moderate Medium High 13.00
North Marin
Water
District
Occasional Significant Severe High Medium 13.00
Southern
Marin Fire
District
Likely Limited Moderate Medium Medium 11.00
Table 3.12: Marin County OA Hazard Risk Assessment – Flooding Source: Profiled Jurisdictions and Districts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
237
Vulnerability
Prior to development, the Marin County OA’s flat lowlands flooded frequently. When rain fell on the Marin County OA, it infiltrated into the ground and moved slowly toward creek channels. The ground acted like a sponge, storing water and releasing it slowly. While water moved underground, it was naturally cleansed by physical and biological processes. Annual floods brought life-giving water to parched floodplains, nourishing them with fresh sediment. They recharged aquifers and allowed fish to swim over normally dry land that was rich with food.
Tides flooded biologically rich marshes along the bay perimeter twice a day. When humans began to develop the land, they created conflicts between what was built and the natural tendency of creeks to flood. Much of the development in the Marin County OA was built in floodprone areas which put it at risk of inundation. Roads, parking lots, roofs, and other impervious surfaces prevent water from infiltrating the ground. Instead, the water moves quickly across the landscape into pipes and creeks further increasing flood risk downstream. Homes, commercial areas, schools, hospitals, police and fire stations, roads and highways, sanitary sewers and waterlines, sewage treatment plants, pump stations are all located in floodplains in the Marin County OA.
All of Marin County OA’s watersheds are small and largely prone to flash flooding. Flash floods are particularly dangerous. The National Weather Service (NWS) defines a flash flood as one in which the peak flow travels the length of a watershed within a 6-hour period. These floods arise when storms produce a high volume of rainfall in a short period over a watershed where runoff collects quickly. They often affect populated areas of the Marin County OA’s cities and towns.
They often strike with little warning and are accompanied by high velocity flow.
All incorporated cities and towns in the Marin County OA have flood risk – and are in fact participants in the National Flood Insurance Program. Even those that are not in a Marin County Flood Control & Water Conservation District “Flood Zone,” have robust maintenance and capital improvement programs that help manage and mitigate flood risk. These cities without District Flood Zones include most of San Rafael and Tiburon, and all of Corte Madera, Sausalito, and Belvedere. Additionally, San Anselmo, Ross, Larkspur, Fairfax, Mill Valley and Novato have flood mitigation programs that operate largely independently of the Flood District, although extensive coordination of activities and collaboration with the Flood District is facilitated through the Marin County Watershed Program (part of the County Department of Public Works). Every city and town, and many unincorporated communities in Marin contain FEMA Special Flood Hazard Areas (SFHA), meaning they lie in the 100-year floodplain and have at least a 1% chance of flooding in a given year. They all participate in the National Flood Insurance Program and many of the structures in the SFHA carry FEMA flood insurance or private flood insurance.
Flood risk to the Marin County OA’s incorporated cities and towns are discussed in their respective Annexes. Most unincorporated communities in the Marin County OA have some level of flood risk, as discussed below:
Lagunitas, Forest Knolls, San Geronimo and Woodacre all lie along San Geronimo Creek.
Dozens of homes lie in the 100-year floodplain of the creek and could be susceptible to flooding.
Sir Francis Drake Boulevard could be susceptible to flooding where it is crossed by Lagunitas Creek and San Geronimo Creek at the south end of Lagunitas. Several road bridges on the south side of San Geronimo Creek that connect residential communities to Sir Francis Drake Boulevard could be susceptible to flooding that could cut off ingress and egress to the area.
Numerous residences and businesses in Nicasio and along Lucas Valley Road to the west of Nicasio lie in the 100-year floodplain and could be susceptible to flooding. Nicasio Valley Road could flood in several places on both sides of Nicasio. Numerous buildings in Tocoloma, including the Tocoloma PG&E substation, lie in the 100-year floodplain. Sir Francis Drake l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
238
Boulevard could also be susceptible to flooding where Lagunitas Creek crosses it at Platform Bridge Road.
Much of Olema west of Highway 1 and along Olema Creek is in the 100-year floodplain. There are numerous residences and businesses in this area, including the Olema Campground. The southern end of Point Reyes Station is particularly susceptible to flooding, including the area where Highway 1 intersects with Sir Francis Drake Boulevard. There are numerous homes and businesses in this area, along with the CalTrans Point Reyes Maintenance Station that lie in the 100-year floodplain. Flooding along Highway 1 and Sir Francis Drake Boulevard from either Lagunitas Creek or Tomales Bay could affect ingress and egress to Point Reyes Station, Inverness and Point Reyes National Seashore. Several buildings in the south and west sides of Point Reyes Station and at the U.S. Coast Guard Station lie in the 100-year floodplain and could be susceptible to flooding. Highway 1 and several homes north of Point Reyes Station also lie in the 100-year floodplain and could be susceptible to flooding.
Several homes, businesses and sections of Sir Francis Drake Boulevard from Inverness Park to Inverness lie in the 100-year floodplain and could be susceptible to flooding from either Tomales Bay or inland canyons.
Sections of the east shore of Tomales Bay along Highway 1, including around Reynolds and Marconi, lie in the 100-year flood plain and are susceptible to flooding. Most of the residences and businesses in Marshall lie in the 100-year floodplain and could be susceptible to flooding from Tomales Bay. While most of Tomales is outside the 100-year floodplain, the area south of it has numerous residences and businesses along Keys Creek and Walker Creek that are in the 100-year floodplain and could be susceptible to flooding.
An area north of Bolinas along Pine Gulch Creek and the Bolinas lagoon lie in the 100-year floodplain. Numerous residences, the Bolinas-Stinson Elementary School, and a section of Olema Bolinas Road are in this area and could be susceptible to flooding. While most of Bolinas lies outside the 100-year floodplain, there are numerous residences along Bolinas Lagoon and Bolinas Bay that are in the 100-year floodplain and could be susceptible to flooding. Most of the residences in Stinson Beach along Dipsea Road and Seadrift Road in Stinson Beach lie in the 500-year floodplain, though several lie in an area of the 100-year floodplain and could be particularly susceptible to coastal flooding. Most of the residences closer to Stinson Beach along Cale del Arroyo lie in the 100-year floodplain and could be susceptible to flooding, with some that could be particularly susceptible to coastal flooding. Some homes, the Stinson Beach Fire Station 32, and the Stinson County Water District Office lie in the 500-year plain in this area and could also be susceptible to flooding. Numerous residences and businesses in and around the southern core of Stinson Beach lie in the 500 and 100-year floodplain and could be susceptible to flooding.
The east side of Muir Beach along Railroad Creek lies in the 100-year floodplain. Numerous residences and a section of Highway 1 could be susceptible to flooding in this area. Flooding of Highway 1 could affect ingress and egress north towards Stinson Beach.
Most of the Tamalpais Junction area of Tamalpais Valley along Coyote Creek and the creek along Tennessee Valley Road lies in the 100-year floodplain, with a smaller section lying in the 500-year floodplain. Numerous residences lie in the 500-year floodplain and could be susceptible to either creek flooding or flooding from Richardson Bay. Hundreds of residences, a church, the Tamalpais Valley Community Center, part of the Tamalpais Valley Elementary School, a large shopping center with numerous businesses, the CalTrans Manzanita Station, sections of Highway 1, a section of Highway 101 and the Commodore Center Heliport all lie in l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
239
the 100-year floodplain and could be susceptible to flooding. Most of the Strawberry and Alto areas lie outside the 100 and 500-year floodplain, though dozens of residences, several apartment complexes, numerous commercial buildings and part of the Strawberry Point Middle School lie in the 100-year floodplain and could be susceptible to flooding. A small area north of Keil Cove on the Tiburon Peninsula where there are several homes also lies in the 100- yearfloodplain and could be susceptible to flooding.
A large part of Kentfield lying along Corte Madera Creek is in the 100-year floodplain. Dozens of homes, numerous businesses and shopping centers, the Adeline E. Kent Middle School, parts of the College of Marin and the Kentfield Hospital, and sections of major thoroughfares including Sir Francis Drake Boulevard and College Avenue lie in this area and could be susceptible to flooding. Most of the College of Marin (including the College of Marin Police Department), part of the Kentfield Hospital and the Marin Health Medical Center, all of Marin Catholic High School and Anthony G. Bacich Elementary School, the Kentfield Fire Station #17, several medical facilities, dozens of homes, numerous businesses and a large section of Sir Francis Drake Boulevard in the Kentfield area lie in the 500-year floodplain and could be susceptible to flooding. There are dozens of homes in the Greenbrae area that lie in the 500- year floodplain and could be susceptible to flooding. A section of California City on the north side near Anderson Drive and the railroad tracks lie in the 100-year floodplain and there are several homes here along with the Montessori School of Central Marin that could be susceptible to flooding.
The 100-year floodplain in Lucas Valley and Marinwood is mostly confined to Miller Creek and while most buildings and infrastructure are not in the 100-year floodplain, part of it runs along the edge of Lucas Valley Elementary School, the Miller Creek Middle School and the Marin County Juvenile Complex that could all be susceptible to flooding. There are several bridges, including on Lucas Valley Road and Highway 101, along with several homes in Marinwood that lie in the 100-year floodplain and could be susceptible to flooding. Part of the Saint Vincent School in Saint Vincent is also in the 100-year floodplain and could be susceptible to flooding.
The northwestern corner of Santa Venitia along the San Venetia Open Space Preserve lies in the 100-year floodplain, and there are several hundred homes along with a few pump stations and critical care facilities in this area that could be susceptible to flooding. Sections of San Pedro Boulevard and areas of San Pedro Point, including part of the McNear Brickyard, lie in the 100-year floodplain and could be susceptible to flooding. Several homes in the unincorporated County along San Pedro Boulevard near San Rafael lie in either the 100-year or 500-year floodplain and could be susceptible to flooding.
Part of the County Redwood Landfill and all of the Marin County airport, including the access road, lie in the 100-year floodplain and could be susceptible to flooding. This area is mostly marshland that could experience coastal flooding. Most of the Green Point-Black Point area lies outside the 100-year floodplain though there are several homes in the Black Point area near marshland that lie in the 100-year floodplain and could be susceptible to flooding.
Numerous homes in Bel Marin Keys and sections of Bel Marin Keys Boulevard lie in the 100- year floodplain and could be susceptible to flooding. A flooding event could affect ingress and egress to Bel Marin Keys.
San Antonio Creek forms part of the boundary between Marin and Sonoma Counties from the area around Chileno Valley Road east to the Petaluma River and there are several homes along it that lie in the 100-year floodplain and that could be susceptible to flooding. There are also l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
240
several road bridges that cross the creek in the 100-year floodplain and that could be susceptible to flooding.
Figure 3.109 shows the social vulnerability of the Marin County OA’s population to flooding in relation to the rest of California.
Figure 3.109: Population/Social Vulnerability to Flooding in California Source: 2018 State of California Hazard Mitigation Plan l ~<;>U·N· TY OF
~ ARIN
a
~
0 25 50 100 Miles
I
Cal Poly- San Luis Obispo
City and Regional Planning
June 2018
Population/Social Vulnerability
with Flood Hazard
Relative Vulnerability
High
Low
Grid cell size approximately
one square kilometer.
Cells with population <75
are not mapped.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
241
Climate Change and Future Development Considerations
Climate change is expected to affect California's precipitation patterns, which are likely to influence future flood events. A 2017 study found that the number of very intense precipitation days in California is projected to more than double by the end of the century, increasing 117 percent, making it likely that flood events will become more frequent in the Marin County OA.
Climate change is expected to alter rainfall patterns in Northern California, including the Marin County OA. As the climate warms, rain events are predicted to become more intense. The Marin County OA will likely experience more rain inundation events that lead to flooding and increase the potential threat of dam and levee failure, tree mortality, and other potential hazards. Sea level rise as a result of climate change will exacerbate the impacts of tidal flooding in the lowland areas of the Marin County OA. Future development in these areas will expose more people and infrastructure to the effects of flooding in the Marin County OA.
Development in marshland of the Marin County OA would expose additional people and infrastructure to flooding as marshlands act as a natural buffer to storm surge.
3.3.6 LAND SUBSIDENCE
Land subsidence is a gradual settling or sudden sinking of the Earth's surface owing to subsurface movement of earth materials. The principal causes are aquifer-system compaction, drainage of organic soils through groundwater pumping, underground mining, hydrocompaction, natural compaction, sinkholes, and thawing permafrost. More than 80 percent of the identified subsidence in the United States is a consequence of underground water exploitation. The increasing development of land and water resources threatens to exacerbate existing land-subsidence problems and initiate new ones.
Sinkholes can form in three primary ways. Dissolution sinkholes form when dissolution of the limestone or dolomite is most intensive where the water first contacts the rock surface.
Aggressive dissolution also occurs where flow is focused in preexisting openings in the rock, such as along joints, fractures, and bedding planes, and in the zone of water-table fluctuation where groundwater is in contact with the atmosphere. See Figure 3.110 for a picture and description of how dissolution sinkholes form.
Figure 3.110: Dissolution Sinkhole Formation
Source: USGS
Cover-subsidence sinkholes tend to develop gradually where the covering sediments are permeable and contain sand. In areas where cover material is thicker, or sediments contain more clay, cover-subsidence sinkholes are relatively uncommon, are smaller, and may go 1 ~<;>U·N· TY OF a ~ ARIN ~
Thin overburden Rain
---1 r- --,---
Rainfall and surface water percolate through
joints in the limestone. Dissolved carbonate
rock is carried away from the surface and a
small depression gradually forms.
On exposed carbonate surfaces. a depression
may focus surface drainage, accelerating the
dissolution process. Debris carried into the
developing sinkhole may plug the outflow,
ponding water and creating wetlands.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
242
undetected for long periods. See Figure 3.111 for a picture and description of how coversubsidence sinkholes form.
Figure 3.111: Cover-Subsidence Sinkhole Formation
Source: USGS
Cover-collapse sinkholes may develop abruptly over a period of hours and cause catastrophic damages. They occur where the covering sediments contain a significant amount of clay. Over time, surface drainage, erosion, and deposition of sediment transform the steep-walled sinkhole into a shallower bowl-shaped depression. See Figure 3.112 for a picture and description of how cover-collapse sinkholes form.
Figure 3.112: Cover-Collapse Sinkhole Formation
Source: USGS
New sinkholes have been correlated to land-use practices, especially from groundwater pumping and from construction and development practices that cause land subsidence.
Sinkholes can also form when natural water-drainage patterns are changed and new waterdiversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created. The substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.
The overburden sediments that cover buried cavities in the aquifer systems are delicately balanced by groundwater fluid pressure. The water below ground helps to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes in sinkhole-prone areas. If pumping results in a lowering of groundwater levels, then underground structural failure, and thus, sinkholes, can occur. 1 ~ <;>U·N· TY OF a ~ ARIN ~
Granular sediments spall
into secondary openings
in the underlying carbonate
rocks.
:o vero~en' •.
A column of overlying sediments settles into the
vacated spaces (a process
termed "piping").
Sediments spall into a cavity. As spalling continues, the cohesive covering sediments form a structural
arch.
Gverei:irden - - - - - - - - -
,most1¥,d<¥)- ~- - - - - - - - y·----. ."I_.·•,,,,-,,~ _,..-~ Dissolution and infilling continue, forming a noticable depression in the land
surface.
The cavity migrates upward by progressive roof
collapse.
The slow downward erosion
eventually forms small surface depressions I inch to
several feet in depth and
diameter.
The cavity eventually
breaches the ground surface, creating sudden and
dramatic sinkholes.
r
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
243
Location and Previous Occurrences
Collapsible soils with the potential for subsidence (i.e., vertical displacement of the ground surface over a locality or region) are more present in the low-lying flatland deposits along the Marin County OA’s valley basins and bays, including in the unincorporated area. In the low-lying exposed areas in nearly every community, except Kentfield, subsidence is an ongoing issue.
Roadways throughout the Marin County OA along the shoreline, notably US Highway 101, and roads in lower Paradise Cay, already experience subsidence. See Figure 3.113 for a map of land subsidence and uplift in California and the Marin County OA from 2007-2018. Areas of increased subsidence occur along San Francisco Bay with an area of uplift on both sides of the northern end of Tomales Bay.
Figure 3.113: Land Subsidence in California 2007-2018 with Marin County Cutout l ~<;>U·N· TY OF
~ ARIN
J,.
a
~
Pacific Ocean
')f __ 1"'0"-0 -' ~"' '---
\
I
\
Vertical Land Motion Rate (mm/year)
0 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
244
Source: NASA
Figure 3.114 shows the areas of the United States where certain rock types that are susceptible to dissolution in water occur. In these areas the formation of underground cavities can form, and sinkholes can happen. These rock types are evaporites (salt, gypsum, and anhydrite) and carbonates (limestone and dolomite).
Figure 3.114: U.S. Rock types Susceptible to Water Dissolution Source: USGS
Impacts
Land subsidence has the potential to damage drinking water wells and infrastructure throughout the Marin County OA, including in the unincorporated area. Loss of drinking water for rural communities can cause health problems as well as significant financial impacts with the redrilling and testing of wells and providing alternate potable water sources for community members. Prolonged drought can exacerbate the impacts from land subsidence. As the water table is drawn down, land can sink even further and damage underground aquifers. Critical infrastructure such as highways, sewer lines, and gas lines can also become undermined due to land subsidence and sinkholes, becoming a threat to public safety and resulting in the devotion of significant financial resources to fix any damages. Sinkholes can form in parking lots, or directly under houses and other structures, potentially causing loss of life and significant damage.
Extent and Probability
Many shoreline properties in the Marin County OA, including in the unincorporated area, are built on fill and mud, and underlying soils will become more saturated under sea level rise conditions and, consequently, vulnerable to increasing rates of subsidence. Subsidence is already a factor for many roads and will likely worsen as the ground becomes saturated with bay or coastal waters further inland. Utilities infrastructure located along the shoreline on fill and mud and in the bay itself, which already experiences the effects of subsidence, will be subject to increased levels of subsidence in the future.
1 ~<;>U·N· TY OF a ~ ARIN ~
~ Evaporite rocks-salt and gypsum
D Karst from evaporite rock
D Karst from carbonate rock
(modified from Davies and Legrand, 1972
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
245
Table 3.13: Marin County OA Hazard Risk Assessment – Land Subsidence Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Occasional Limited Moderate Medium Medium 10.00 City of
Belvedere Occasional Limited Moderate Medium Medium 10.00 Town of
Corte Madera Likely Negligible Weak Low Low 7.00
Town of
Fairfax Occasional Negligible Weak Low Low 6.00
City of
Larkspur Occasional Limited Moderate Medium Medium 10.00 City of
Mill Valley Likely Negligible Moderate Low Low 8.00
City of
Novato Likely Negligible Weak Low Low 7.00
Town of
Ross Unlikely Limited Weak Low Low 6.00
Town of
San Anselmo Unlikely Negligible Moderate Low Low 6.00
City of
San Rafael
Highly
Likely Significant Weak Low Medium 11.00
City of
Sausalito Likely Limited Moderate Medium Medium 11.00
Town of
Tiburon Occasional Limited Moderate Medium Medium 10.00 Bolinas
Public Utility
District
Likely Limited Moderate Medium Medium 11.00
Las Gallinas
Valley
Sanitary
District
Occasional Negligible Weak Low Low 6.00
North Marin
Water
District
Occasional Negligible Moderate Medium None 7.00
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
246
Southern
Marin Fire
District
Unlikely Negligible Severe None Low 6.00
Table 3.13: Marin County OA Hazard Risk Assessment – Land Subsidence Source: Profiled Jurisdictions and Districts
Vulnerability
Land subsidence can severely impact public facilities and infrastructure as well as private development in areas where it occurs through the damage or compete failure of underground utilities, damaged building or utility infrastructure foundations, damaged roadways, etc.
Vulnerable substations; electrical transmission towers and lines; underground natural gas water supply, and sanitary sewer pipelines; pump stations; hazardous facilities, including those with underground storage tanks (e.g., gas stations); and other facilities and infrastructure along the shoreline would be compromised by subsidence. Subsidence can lead to damage to healthcare facilities, private wells, and general drinking water quality. Subsidence can place pressure on underground utility pipelines when roadways begin to sink around the pipes, causing them to bend. Electrical transmission towers, including land-based towers east of Bel Marin Keys and South of Novato over to the Sonoma County border and in the bay off the shores of Corte Madera and Mill Valley, are subject to increased rates of subsidence, which can impact the mounting platforms that support the towers. Landfills are often subjected to subsidence because they are typically located where marshes once existed, and because buried materials settle over time. Jetties, which are structures built into the water to protect a harbor or shore, are also prone to subsidence.
Transportation facilities along the OA’s coastline are vulnerable to subsidence. Increased subsidence could warp the buildings and runways at Marin County Airport in North Novato and San Rafael Airport. Parking and access areas along Richardson Bay, including those in Waldo Point Harbor, are also prone to continuous subsidence. As discussed above, roadways and highways along the shoreline also suffer from subsidence.
Important cultural resources, including archaeological sites at or near the edge of the bay may be vulnerable to subsidence. Vulnerable sites include permanent settlements represented by shell mounds or middens associated with marshes and other locations at or near the edge of the bay where shellfish/marine resources were available.
The areas of the Marin County OA most vulnerable to land subsidence are those underlain with the younger Holocene unconsolidated alluvial and colluvial sediments, and even more so the younger bay muds. In general, Marin County unincorporated community shoreline properties, especially those in Southern Marin on fill in the low-lying areas east of US Highway 101, are the most exposed and vulnerable to subsidence. Almonte, Belvedere, Santa Venetia, Paradise Cay and Bel Marin Keys were built on bay fill and mud, and already experience subsidence. This impacts buildings, roads, and utility infrastructure. These areas could anticipate increased rates of subsidence as bay waters saturate the soil from below.
Land subsidence is an ongoing issue in the low-lying exposed areas of nearly every unincorporated Bayshore community, except for Kentfield, and sea level rise associated with climate change would only exacerbate existing subsidence impacts. 1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
247
Climate Change and Future Development Considerations
Climate change could indirectly influence land subsidence as more severe and prolonged periods of drought may encourage more groundwater withdrawals. In coastal areas like the Marin County OA, land subsidence leads to higher sea levels and increased flood risk. The rate of land subsidence could increase across the Marin County OA as a result of climate change.
The impacts of land subsidence on infrastructure, including roads and underground utilities, in the Marin County OA could increase with future development in the lowland populated areas where land subsidence is more likely to occur.
3.3.7 LEVEE FAILURE
Levee failure is the overtopping, breach or collapse of the levee. Levees can fail in the event of an earthquake, internal erosion, poor engineering/construction or landslides, but levees most commonly fail as a result of significant rainfall or very high tides. During a period of heavy rainfall, the water on the water-body side of the levee can build up and either flow over the top (“overtopping”) or put pressure on the structure causing quickening seepage and subsequent erosion of the earth. The overflow of water washes away the top portion of the levee, creating deep grooves. Eventually the levee weakens, resulting in a breach or collapse of the levee wall and the release of uncontrollable amounts of water. Figure 3.115 shows a levee and the multiple ways it can fail.
Figure 3.115: Levee Failure Mechanisms
Source: University of California
Location and Previous Occurrences
Several Marin County OA communities, such as Tamalpais Valley, Santa Venetia, Corte Madera, Belvedere, and parts of Strawberry, Novato, and Ross Valley are protected by levees. l ~<;>U·N· TY OF
~ ARIN
a
~
Anat.omy of a levee
2, Internal Erosion/Piping
5. Wave lmpa<U
8. Piping •Of substratum
I a. Overtopping 1 b. Overtopping/Jetting
3. Surface Erosion
4. Sliding
6. Structural Impacts
7. Liquefaction
9. Tree damage 10. Slope fa I lure
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
248
Levees are typically earthen embankments designed to contain, control, or divert the flow of water to provide some level of protection from flooding. No levee system provides full protection from all flooding events to the people and structures located behind it. Some level of flood risk exists in the levee-affected areas. Except for one levee system in Novato-Hamilton, none of the County’s levees are FEMA-accredited. Many were built many decades ago (non-engineered) by farmers or developers and material may have been added over the years. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
249
Figure 3.116: Marin County Levee System
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County
Levee
DfllctOI
EMERGENCY
MANAGEMENT
.r>
~,-J'•, • ..,_._) v·
(
•
'
IT]
• o,nl Reyes
National
Seashore
'
•
•
•
•
Legend
e Dams
• Military and Civil
Defense Installations
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
e Water Supply Facilities
Airports
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
• Police / Sheriff Stations
Schools
- Levee Centerline
Levee Inundation
•
IOI
\II
--.,_
•
•
•
•
•
0 2.5 .,,._ ___ { 10
Miles
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/19/23
12 ,.,
37 San Pablo Bay
WIidiife Area
N
County of Marin, callfornia State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, califomia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/ NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
250
The Coyote Creek Left Bank Levee System (COYL) is a federally authorized and non-federally operated and maintained project and is located in the County of Marin on the west shore of Richardson Bay, an arm on the western side of San Francisco Bay where the Coyote Creek drains approximately 2,200 acres of the eastern slopes of the Marin Peninsula. The COYL is
0.96 miles long with a maximum height of four feet. The COYL is one of the two flood protection systems of the Coyote Creek flood control project and is situated along the left bank of the creek when looking downstream. The other system is along the right bank of Coyote Creek. There is only one segment within the COYL. The subject levee system is located along the left bank of Coyote Creek and is approximately 1.5 miles long. The purpose of the levee is to provide flood protection to the community of Tamalpais Valley, California. The channel improvement project for Coyote Creek, located in the County of Marin, California, was authorized by the Chief of Engineers on January 15, 1963, under the provisions of Section 205 of the Flood Control Act of 1948, as amended by the Flood Control Act of 1962. The COYL was completed in February 1965. Improvements to
the project to address
the local subsidence
were completed in
1977. The public
sponsor of the COYL is
the Marin County
Department of Public
Works.
The other Coyote
Creek Levee system is
an additional smaller
levee that was
constructed on the right
bank in 1965. It is 0.22
miles long with a
maximum height of four
feet. The levee from
the Highway 1 bridge to
the downstream end is
no longer maintained.
Figures 3.17 - 3.19
show the levees and
Levee inundation in the
Tamalpais Valley
Figure 3.117: Levees in Tamalpais Valley
Source: U.S. Army Corps of Engineers, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
Tamalpais
Valley
Junction
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
251
Figure 3.118: Levees in Strawberry
Source: U.S. Army Corps of Engineers, 11/27/23
The horseshow shaped levee at the Sewerage Agency of Southern Marin (SASM) shown in Figure 3.121, according to the Mill Valley Department of Public Works, the levee at the SASM is above the high tide water mark and is not technically a levee but rather a berm to hold extra water storage at the side. It is not acting as a flood wall. The City of Mill Valley has no risk of levee failure.
1 ~<?U·N· TY OF a ~ ARIN ~
Stra.,•ber
Rec1ea1011
District
strawberry
Manor
01-::trict
strawberry
Go Iden Ga le Bapt, st
Theologica I Se m 1 nary
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
252
Figure 3.119: Tam Junction Levees
Source: Marin County OEM
Sewerage Agency of Southern
Marin (SASM) berm.
l ~<;>U·N· TY OF
~ ARIN
a
~
Wastewater Facilities
Airports
Emergency Operations
Centers
Fire Stations
Tam Junction
Levee
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Levee Centerline
Levee Inundation
Strawberr y
Manor
0 "' ... ~,>fb''b
b',;
Marin County O / Woo
email: OEM_GIS@MarinC
Date Printed: 10/19/23
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of la USDA, County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau omcu1
EMERGENCY
MANAGEMENT
0.6 Miles
n 6
N
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
253
One levee system exists in Kentfield and is located along Corte Madera Creek. The Corte Madera Creek Left Bank Levee is 0.7 miles long with an undocumented height. Figure 3.120 shows the Corte Madera Creek Left Bank Levee in Kentfield.
Figure 3.120: Levee in Kentfield
Source: U.S. Army Corps of Engineers, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
1ark 1
I
Stadium Way
- Ke ntfield
Co llege of M•rin
l<sntha ld Campu s- Ma rin
C ommunity Co lleg:-
, _
Acacia p..ve
Escalle
- Ke nlfol:J
Hal Bru,vn
Pari<
Marin C atho lie.
High &; iuofRoln3n Ca tho lr.
Ross ValE'y s-.,.,m
And Tennt. Club
1350 So
Elireo
Ltd P
Pa ss port
1-13a llh
Green brae
Red"ood l
., /
\
I
I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
254
Figure 3.121 shows the Greenbrae Levee system:
Figure 3.121: Greenbrae Levee System
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
La , pur
Communication
Facilities
Green brae
Levee
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Levee Centerline
Electric Power Facilities
Wastewater Facilities
Emergency Operations
Centers - Levee Inundation
Fire Stations
County of Marin, Calif!l[nia State Parks, Esri, HE
USDA, County of Maritr1 lifomia State Parks, E
1 omCEOI
EMERGENCY
MANAGEMENT
\
SartOuenun
Stat Pnso
Miles
in County OEM / Baker-Cohn
ii: llf.ttGIS@Marin ounty.org
P~ : 10/19/23
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
255
The McNears sea wall runs along Point San Pedro Road from roughly Marine Drive to the McNear Brickyard and is located along San Pablo Bay. The McNears sea wall is approximately
1.4 miles long with an undocumented height. Figure 3.122 shows the sea wall.
Figure 3.122: McNears Sea Wall in the San Pedro Hill Area Source: U.S. Army Corps of Engineers, 11/27/23
One levee system exists in Santa Venetia and is located along the South Fork of Galinas Creek.
The Santa Venetia Levee is 1.45 miles long with an undocumented height. Figure 3.123 shows the Santa Venetia Levee in Santa Venetia.
l ~<;>U·N· TY OF
~ ARIN
j;
a
~
lagoon
Poi nt S an
Pedro
S.1nRabfll
FbckQw,11)
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
256
Figure 3.123: Santa Venetia Levee in Santa Venetia
Source: U.S. Army Corps of Engineers, 11/27/23
Three levee systems exist in St. Vincent. Two of them, Marin County Levee 33 and Marin County Levee 24, are located along the north bank of Miller Creek. Marin County Levee 33 is
0.25 miles long with an undocumented height and Marin County Levee 24 is 0.2 miles long with an undocumented height. The third levee is the Las Galinas Valley Sanitary District Levee which extends along the north and east bank of Miller Creek before diverging north to the Hamilton Wetlands and west to Long Point. It is 3.63 miles long with an undocumented height.
Figure 3.124 shows the three levees in St. Vincent.
l ~<;>U·N· TY OF
~ ARIN
a
~
Estancia Wax
Santa V enetia -ti son l'ec!ro Rcl- -
v< ~01:\'3-(\
Sunny o~.,~
Dr
School
(Vaca nt Srtel
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
257
Figure 3.124: Marin Levee 33, Marin County Levees 33 and 24 and the Las Gallinas Valley Sanitary District Levee in St. Vincent
Source: U.S. Army Corps of Engineers, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
SamtV111:.-nfs
Equao::.trien
5:lmt Vinc.enfs Prcgram
School For Boys
~' Vincents-Dr R:lman G.:itholtc
. ..-.
Gallinas
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
258
Figure 3.125: Santa Venetia Levee System
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Legend
• Military and Civil
Defense Installations
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
Airports - Emergency Operations
Centers
Santa Venetia
Levee
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Levee Centerline
Levee Inundation
e
Da
ETJ/111
DIIICtOI
EMERGENCY
MANAGEMENT
/ Woody Baker-Cohn
MarinCounty.org
19/23 ~ N
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
259
Several levee systems exist around Bel Marin Keys and the Black Point area, but their failure does not present a risk to the communities.
Figure 3.126: Bel Marin Keys Levee System
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
llt
Marin Country
Military and Civil
Defense Installations
Electric Power Facilities
Emergency Operations
Centers
Fire Stations
County of Marin, california State Parks, Esri,
Bel Marin Keys
Levee
Hamlllon
Recreation
Facility
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Levee Centerline
- Levee Inundation
' \
\
\
omc101
EMERGENCY
MANAGEMENT
~ N
Management, EPA, N PS, USDA
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
260
Two levee systems are located around the Marin County Airport. The State Fish and Game Levee surrounds the Airport property and neighboring wetlands on three sides to the north, south, and east. The Gnoss Airport Levee consists of two sections that intersect the airport property. One section is 2.59 miles long with an undocumented height and the other section is
0.43 miles long with an undocumented height. Figure 3.127 shows the levee systems around the Marin County Airport.
Figure 3.127: Levees Around the Marin County Airport
Source: U.S. Army Corps of Engineers, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
Rush Creek
Rush
Vale)
r.\3morial
Park
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
261
Figure 3.128: Novato North Levee System
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Olompoh SI.al&
Historic Park
Legend
e Dams
Communication
Facilities
Airports
Hospitals and Medical
Facilities
Levee Centerline
- Levee Inundation
Novato North
Levee
ty.org
OlllCIOf
EMERGENCY
MllNAGEMENT
,;,•
0 nd Man<19. t, EPA, NPS, USDA
"
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
262
In 1982 a levee in Santa Venetia was breached by tidal elevations and flooded the neighborhood with 2-3 feet of water.
Over a million dollars-worth of levee damage on Novato Creek occurred in 2014 and 2017 and a heavy burden on stormwater pumping systems caused additional damage to pumping system components.
Over a million dollars-worth of levee damage on Novato Creek occurred in 2014 and 2017 and a heavy burden on stormwater pumping systems caused additional damage to pumping system components.
Impacts
Levee failure flooding would vary depending on which structure fails and the nature and extent of the failure and associated flooding. This flooding presents a threat to life and property, including buildings, their contents, and their use. Large flood events can affect lifeline utilities (e.g., water, sewerage, and power), transportation, jobs, tourism, the environment, agricultural industry, and the local and regional economies.
The overall impact to the community from levee breach or failure includes:
• Injury and loss of life;
• Commercial and residential structural damage;
• Disruption of and damage to public infrastructure;
• Health hazards associated with mold and mildew;
• Damage to roads/bridges resulting in loss of mobility; • Significant economic impact (jobs, sales, tax revenue) to the community; • Negative impact on commercial and residential property values; • Long dewatering periods;
• Significant disruption to students and teachers as temporary facilities and relocations would likely be needed.
•
Extent and Probability
The probability of future levee failures in the Marin County OA is largely unknown but may result from a large winter storm or seismic event.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
263
Table 3.14: Marin County OA Hazard Risk Assessment – Levee Failure Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Unlikely Negligible Moderate Medium High 9.00 City of
Belvedere Occasional Limited Moderate Medium Medium 10.00 Town of
Corte Madera Unlikely Limited Severe High Medium 11.00
Town of
Fairfax None None None None None 0.00
City of
Larkspur Unlikely Negligible Moderate Medium Low 7.00
City of
Mill Valley None None None None None 0.00
City of
Novato Occasional Negligible Weak Medium Low 7.00
Town of
Ross None None None None None 0.00
Town of
San Anselmo None None None None None 0.00
City of
San Rafael Unlikely Significant Severe High High 13.00
City of
Sausalito Occasional Negligible Weak Low Low 6.00
Town of
Tiburon Unlikely Negligible None None High 5.00
Bolinas
Public Utility
District
Unlikely Limited Extreme High Medium 12.00
Las Gallinas
Valley
Sanitary
District
Unlikely Significant Severe High High 13.00
North Marin
Water
District
Unlikely Significant Extreme High Medium 13.00
Southern
Marin Fire
District
None None None None None 0.00
Table 3.14: Marin County OA Hazard Risk Assessment – Levee Failure Source: Profiled Jurisdictions and Districts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
264
Vulnerability
The areas of the Marin County OA most vulnerable to levee failure are those with levees that could fail. Several unincorporated communities in Marin County are susceptible to levee failure:
A small area of Tamalpais Valley is protected from the Coyote Creek Levees (COYL) and could be susceptible to a levee failure. This area includes dozens of homes along with several commercial buildings and a section of Highway 1. Approximately 206 people and 105 buildings are at risk from a failure of the COYL levee, with a property value risk of around $59.4 million.
Approximately 557 people and 265 buildings are at risk from the levee on the southern bank of Coyote Creek, with a property value risk of around $156 million. The risk is considered to be low LSAC 4 (Levee Safety Action Classification) for both levees prior to overtopping and overtopping breach scenarios. The levee has an overtopping recurrence of 1/100 USACE with low life safety risk. Seepage has not been documented since the construction of a seepage barrier in 2005 (the levee was loaded 75% in 2008). Some uncertainty exists in the condition of culvert penetrations. Areas of oversteepened slope and erosion at the waterside levee toe are also moderate concerns. No loss of life is anticipated, and economic damages are anticipated to be low.
Two small areas of Strawberry are protected by levees and could be susceptible to levee failure.
The area protected by the Seminary Marsh Levee consists of several businesses adjacent to Highway 101. Approximately 325 people and 13 buildings are at risk from a failure of the Seminary Marsh Levee, with a property value risk of $20.9 million. The area protected by the Strawberry Marsh Levee consists of several homes and Strawberry Elementary School.
Approximately 488 people and 36 buildings are at risk from a failure of the Strawberry Marsh Levee, with a property value risk of around $17.2 million.
Part of the southern end of Kentfield is protected from Corte Madera Creek by the Corte Madera Creek Left Bank Levee and could be susceptible to a levee failure. This area includes a few dozen homes and the Marin General Hospital. Approximately 260 people and 104 buildings are at risk from a failure of the Corte Madera Creek Left Bank Levee, with a property value risk of around $40.3 million. The Levee was assessed in 2021 and the risk was determined to be low.
Numerous homes along with San Pedro Point Road and the McNears Brickyard are susceptible to a failure of the McNears sea wall. Approximately 604 people and 242 buildings in the unincorporated area and the City of San Rafael are at risk from a failure of the sea wall, with a total property value risk of around $169 million.
Part of the northern area of Santa Venetia is protected from the South Fork of Galinas Creek by the Santa Venetia Levee. There are several hundred homes in this area along with numerous pump stations and several medical facilities that could be susceptible to a levee failure.
Approximately 1,901 people and 676 buildings are at risk from a failure of the Santa Venetia Levee, with a property value risk of around $323 million.
The area of St. Vincent, which includes the St. Vincent School and the Las Galinas Valley Treatment Plant, is protected from Miller Creek and San Pablo Bay from Marin County Levee 33, Marin County Levee 24 and the Las Gallinas Valley Sanitary District Levee and could be susceptible to a levee failure. Approximately 8 buildings are at risk from a failure of both Marin County Levee 33 and Marin County Levee 24. Approximately 19 people and 9 buildings are at l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
265
risk from a failure of the Las Gallinas Valley Sanitary District levee, with a property value risk of around $9.47 million.
The Marin County Airport is protected by the State Fish and Game Levee and the Gnoss Levees, and airport facilities along with the access road could be susceptible to a levee failure.
The qualitative risk of the levees around the Airport is unknown.
Climate Change and Future Development Considerations
Climate change is expected to lead to an increase in the frequency and severity of major storm events, which can place added strain on levee systems. An increase in rainfall and runoff as a result of climate change will increase the potential for higher water levels in leveed areas across the Marin County OA, increasing the potential for a levee failure. Rising seas will lead to increased stress on the levees around the Marin County OA shoreline, particular during a major tidal event and potential tsunami. As development increases in the populated areas of the Marin County OA protected by its levees, particularly in coastal areas, the potential for significant impacts to residents and infrastructure will only increase.
3.3.8 SEA LEVEL RISE
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.
The Marin County OA MJHMP 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, 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.
Climate change adaptation is a key priority of the State of California. The 2013 State of California Multi- Hazard Mitigation Plan stated that climate change is already affecting California. The State has also seen increased average temperatures, more extreme hot days, l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
266
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.
Rising sea levels are considered a secondary effect of climate change due to warming ocean temperatures and melting glacial ice sheets into the ocean. The California coast has already seen a rise in sea level of four to eight inches over the 20th century due to climate change. Sea level rise impacts can be exacerbated during coastal storms, which often bring increased tidal elevations called “storm surge.” The large waves associated with such storm surges can cause flooding in low-lying areas, erosion of coastal wetlands, saltwater contamination of drinking water, disruption of septic system operations, impacts on roads and bridges, and increased stress on levees. In addition, rising sea levels result in coastal erosion as shoreline sediment is re-deposited back into the ocean. Evidence shows that winter storms have increased in frequency and intensity since 1948 in the North Pacific, increasing regional wave heights and water levels during storm events.
According to the 2017 “Rising Seas in California, An Update on Sea-Level Rise Science” report Marin County may experience impacts from Sea Level Rise over defined periods of time, to include long-term changes (second half of this century and beyond), and short- to mid-term projections (within the next two or three decades).
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
267
Figure 3.129: Marin County Sea Level Rise Susceptibility to Critical Facilities Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin OlllC(Of County EMERGENCY
Sea Level Rise MANAGEMENT
_,,J- _,~ ... -\. -
'-"'
•
Legend
• Dams Emergency Operations
Military and Ovil Centers
• Defense Installations Fire Stations
Communication Hospitals and Medical
Facilities Facilities
Electric Power Facilities Police / Sheriff Stations
Wastewater Facilities Schools
• Water Supply F<1cilities Sea Level Rise
Airports 1 ft Sea Level Rise
5 ft Sea Level Rise
•
•
•
•
IOI
116
------,_
•
•
•
•
0 J0---. .. -r-
---==~--- Miles
2.5 5
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 11/01/23
JI
County of Marin, California State Parks, Esri, HERE, Garmin, SilfeGraph, Geo Technologies, Inc, MEll/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, C...lifomia State Parks, Esri, HERE, Garmin, S...feGraph, FAO, METI/NASA, USGS, Burwu of Land Management, EPA, NPS 1"1
12 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
268
Location and Previous Occurrences
Past flooding, wildfire, levee failure, and drought disasters have been exacerbated by climate change in frequency of occurrence and intensity. Unlike earthquakes and floods that occur over a finite time period, climate change may be experienced as a compounding, long term hazard, the effects of which some communities may already be experiencing.
The 2018 State of California Multi-Hazard Mitigation Plan states 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 both snowmelt and rainwater running off sooner in the year. In addition to changes in average temperatures, sea level, and precipitation patterns, the intensity of extreme weather events is also changing. This data suggests that the effects of climate change have been occurring in the Marin County area. See Figure 3.130 for the historic and future change in average July temperatures across California.
Figure 3.130: Average July Temperatures in California
Source: California Climate Adaptation Strategy
1 ~<;>U·N· TY OF a ~ ARIN ~
42 1961 -90 2035-64 2070-99
40 38
36 34
236' 236' 244' 236"
50 60 70 80 90 100 110
.. F
Source: Dan Cayan et al 2009
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
269
Impacts
During the next few decades, scenarios project average temperature to rise between 1°F and
2.3°F in California. As such, temperatures across the Marin County OA, including in the unincorporated area, would be expected to rise, leading to increase in drought conditions that could lead to forest devastation and wildfires, and an increase in major flooding and associated debris flow events. These extreme weather events can cause additional injuries and fatalities and can cause worsened damage or destruction to homes and critical facilities and infrastructure across the County. Socioeconomic disruption can also occur across the County as a result of climate change.
Dealing with flooding from rain and upstream runoff is already complicated. Sea level rise will make it even more complicated by increasing the frequency and duration of flooding. When water temperature increases, warm water expands and takes up more space than colder water.
As the planet warms, the water in the ocean warms, expands, and elevates sea levels. The changing climate has also melted parts of the ice caps at the North and South Poles. As this ice melts and flows into the ocean, it increases the amount of water in the ocean and raises sea levels even more. Sea levels in San Francisco Bay have risen seven inches over the past century. Predictions of future sea level rise vary from 12 inches by 2030 to 60 inches by 2100.
The Bay Conservation and Development Commission (BCDC) recommends using 36 inches of sea level rise for planning purposes. Rising sea levels increase the upstream extent of tidal flooding, worsen creek overflow due to backwater effects of elevated high tides, and create larger, stronger waves which erode the shoreline and destroy sensitive marshes. Coastal flooding will have a large impact on cities and habitat.
A 36-inch increase in sea levels will greatly impact people’s lives throughout the Marin County OA, including in the unincorporated area. Daily high tides will inundate major thoroughfares, schools, retirement communities, private homes, shopping areas, bike paths, and stormwater detention ponds. Valuable marsh and mudflat habitat will be permanently flooded. Infrastructure will need to be armored, abandoned, or relocated. Shorelines will be eroded by increased wave erosion, threatening even more infrastructure. With sea level rise it is projected that more land along Marin’s coastline and bayside will be permanently inundated or subject to more regular flooding, while the frequency and intensity of storm events are anticipated to increase with climate change. Greater riparian flooding may also occur with sea level rise and future storm events, though modeling is necessary to better understand the extent of such hazards. As previously discussed best available sea level rise and future flood models indicate that by 2100 around 7,000 acres, 9,000 parcels, 10,000 buildings and 120 miles of roads throughout Marin County may be exposed to flooding due to future sea level rise and 100-year storm events. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
270
Extent and Probability
Table 3.15: Marin County OA Hazard Risk Assessment - Sea Level Rise Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Limited Extreme High High 16.00
City of
Belvedere
Highly
Likely Limited Extreme High High 16.00
Town of
Corte Madera Occasional Significant Weak High Medium 11.00 Town of
Fairfax None None None None None 0.00
City of
Larkspur
Highly
Likely Limited Extreme High High 16.00
City of
Mill Valley
Highly
Likely Limited Weak High Medium 12.00
City of Novato Occasional Limited Moderate High Medium 11.00 Town of Ross None None None None None 0.00
Town of
San Anselmo None None None None None 0.00
City of
San Rafael
Highly
Likely Significant Moderate High High 15.00
City of
Sausalito Likely Significant Severe High Medium 14.00
Town of
Tiburon
Highly
Likely Limited Extreme High High 16.00
Bolinas Public
Utility District Likely Extensive Severe High High 18.00 Las Gallinas
Valley
Sanitary
District
Likely Significant Moderate High High 14.00
North Marin
Water District Occasional Significant Moderate High Medium 12.00 Southern
Marin Fire
District
Likely Significant Extreme Medium Low 13.00
Table 3.15: Marin County OA Hazard Risk Assessment - Sea Level Rise Source: Profiled Jurisdictions and Districts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
271
Vulnerability
All residents in the Marin County OA, including in the unincorporated area, are susceptible to climate change, with effects being more prevalent in those with pre-existing health conditions and the elderly. Communities most vulnerable to the impacts of sea level rise in unincorporated Marin County include Muir Beach, Stinson Beach, Bolinas, Inverness, Pt. Reyes Station, East Shore, and Dillon Beach.
Coping with a changing climate presents opportunities for local health departments and partners in Marin County to consider policies, actions, and infrastructure design that will not just protect the public from climate change threats, but also establish health equity, resiliency, and sustainability. A critical step for building resilience is to improve capacity of communities to prepare, respond, and recover from climate-related health risks.
The most vulnerable assets in Marin County OA’s unincorporated communities in the near-term are Shoreline Highway through Almonte, Waldo Point Harbor houseboats and facilities, Greenbrae homes and facilities, and Paradise Cay homes and marina. The elevated homes on Greenbrae Boardwalk and floating homes in Waldo Point Harbor may be more adaptable in the near term than homes with solid foundations. In the medium-term, portions of Bel Marin Keys could face impacts, as would Santa Venetia homes, Tamalpais Valley homes, and the Greenwood Cove, Strawberry Circle, Strawberry Village Shopping Center, homes along Seminary Drive in Strawberry, and Kentfield creek side homes. In the long-term, Black Point and North Novato could anticipate damaging impacts. In the medium-term timeframe, regular high tide tidal flooding could adversely impact the same locations tidally flooded in the nearterm, though more severely. Storm surge flooding could be 10 inches with a 100-year storm surge, and extend further inland beyond the marshy areas of Mill Valley, Strawberry, San Rafael, St. Vincent’s, and North Novato. In the long-term (second half of this century and beyond), regular tidal flooding could adversely impact the same locations impacted in the nearand medium-terms (within the next two or three decades) and significant portions of what would have previously only flooded from the 100-year storm surge. The additional areas that would tidally flood at 60 inches of sea level rise are:
• Tamalpais Valley
• Mill Valley from the Richardson’s Bay shoreline up to and beyond Camino Alto between Miller and East Blithedale Avenues
• Mill Valley and Strawberry fronting US Highway 101 between Seminary Drive and Tiburon Boulevard
• Santa Venetia north of N. San Pedro Boulevard
• Cove Neighborhood, Tiburon
• Belvedere Lagoon neighborhood
• Paradise Cay
• Mariner Cove, Marina Village, Madera Gardens, and major retail centers lining US Highway 101
• Riviera Circle, Creekside, and Heatherwood neighborhoods, Larkspur • Interstate 580 and westward towards Andersen Drive in San Rafael and the community of California Park
• Marin Lagoon and Peacock Gap neighborhoods, San Rafael • Bel Marin Keys northern and southern lagoon areas
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
272
• Hamilton, Vintage Oaks, and pockets of development east of US Highway 101 at Rowland Boulevard and State Route 37 in Novato, and
• North Novato at US Highway 101 and Binford Road.
Bayside areas that could anticipate increased storm surge flooding are:
• Sausalito west of Bridgeway
• Marin City neighborhood
• Mill Valley east of East Blithedale Avenue at Alto Shopping Center • Las Gallinas and North San Pedro Boulevard, east of US Highway 101, San Rafael • Bayside Acres
• Country Club
• Kentfield
In their current conditions, the most vulnerable coastal Marin County OA infrastructure, in order of onset and flood depth, includes
Near term (ten years):
• Beaches, underground on-site wastewater treatment systems (OWTS), buildings, and streets in Stinson Beach west of Shoreline Highway
• Shoreline Highway between Stinson Beach and Bolinas, at Green Bridge over Lagunitas Creek in Pt. Reyes Station, the Walker Creek crossing in Marshall, and bridges on Middle Road and Valley Ford Lincoln School Road
• Beaches and beach front and downtown buildings and streets in Bolinas • Septic systems, beaches, marshes, and buildings along the eastern and western shores of Tomales Bay
• The water distribution pipe underneath Shoreline Highway and Sir Francis Drake • Boulevard serving many Inverness residents
• Intertidal rocky lands in Muir Beach and Duxbury Reef in Bolinas • Fire service facilities and tsunami evacuation routes in Stinson Beach • Recreational facilities at Dillon Beach Resort and Lawson’s Landing • Blufftop buildings in Muir Beach, Bolinas, and Dillon Beach may be vulnerable to accelerated erosion
Medium Term (thirty years):
• Olema-Bolinas Road, which is the only road to Downtown Bolinas • Additional buildings and streets in downtown Bolinas, including the historic district • Bolinas Public Utilities District lift station at the end of Wharf Road • Shoreline Highway in Pt. Reyes Station and East Shore, and Sir Francis Drake Blvd. in Inverness
• Along the east shore of Tomales Bay, homes on piers over the water are particularly vulnerable
Long Term (seventy years):
• Shoreline Highway along the East Shore
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
273
• Buildings in Inverness west of Sir Francis Drake Blvd • Downtown Bolinas up to Brighton Road, including the market, library, community center, gas station, museum, and other valued places
Along the bay shoreline, in the near-term timeframe, tidal flooding at 10 inches of sea level rise could reach 5,000 acres, 1,300 parcels, and 700 buildings, potentially impacting tens of thousands of residents, employees, and visitors. With an additional 100-year storm surge, the previously impacted acres, parcels, and buildings could face tidal and storm surge flooding. An additional 3,000 acres, 2,500 parcels, and 3,800 buildings could anticipate storm surge flooding across the Marin County OA. Eight miles of road could expect tidal flooding. Smaller public and private and marinas and boat launches along the bay in Strawberry, Bel Marin Keys, and Black Point could be flooded out and unusable. Storm surges can be powerful enough to damage and sink boats, including those belonging to the Southern Marin Fire Protection. Most concerning, however, is the potential inability of emergency professionals and vehicles to access people in or through flooded areas.
In this medium-term timeframe, tidal flooding at 20 inches of sea level rise could reach nearly 7,000 acres, 3,000 parcels, and 2,000 buildings in the Marin County OA, potentially impacting even more residents, employees, and visitors than in the near-term. With an additional 100-year storm surge, the previously impacted acres, parcels, and buildings could face tidal and storm surge flooding, and an additional 7,000 acres, 2,200 parcels, and 3,600 buildings in the Marin County OA could anticipate storm surge flooding. Most levees south of Novato are not designed to withstand this level of flooding and could be overtopped.
Eighteen miles of roadway, ten more miles than in the near-term, could expect tidal flooding.
Many of the impacted roads are the same as those impacted in the near-term, though much greater lengths could anticipate tidal flooding and flooding depths would increase. Storm surge flooding could reach a total of 44 additional miles of roadway. Water travel could experience similar outcomes as in the near-term, though the highest high tides and storms surges would cause even more damage than weathered twenty years earlier.
Pipelines under vulnerable roads, and lateral pipes to vulnerable properties, would become squeezed between rising groundwater and the confining roadway. This could cause pipes to bend and break and could even damage roadways. In the medium-term, impacts to the North Marin Water District service area would impact water service in Bel Marin Keys and unincorporated area around Novato. Vulnerable substations, electrical transmission towers and lines, and underground natural gas pipelines along the shoreline would be compromised by flooding and subsidence. Disruptions or failures in this network could also have far reaching impacts in transportation, sanitary service, stormwater management facilities, food storage, communications, and general public safety.
In the long-term timeframe, tidal flooding at 60 inches of sea level rise could reach nearly 7,000 acres, 8,000 parcels, and 9,000 buildings in the Marin County OA, potentially impacting hundreds of thousands of residents, employees, and visitors. In the long-term scenario, storm surge flooding could occur on nearly 13,500 acres hosting 12,600 parcels with 12,000 buildings in the Marin County OA, potentially impacting 200,000 residents, thousands of employees, and several million visitors.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
274
One-hundred miles of public and private roadways in the Marin County OA could be vulnerable to tidal exposure. Roads could degrade more quickly, or if flood waters are deep enough, become impassable. Lane miles could be more than double this figure. An additional 30 miles of roadway could be vulnerable at 60 inches of sea level rise and a 100-year storm surge.
Moreover, several park and rides, several hundred bus stops, and bus transit and SMART rail routes could flood. Breakdowns in the transportation network would have major impacts on the economy and daily life functions. In addition, significant safety hazards could cause injury or loss of life. Flooding at the Sewerage Agency of Southern Marin (SASM) and Novato Sanitary Wastewater Treatment Plants is a significant vulnerability that could arise, potentially disrupting hundreds of thousands of people.
By this time, much of the low-lying shoreline sanitary sewer and stormwater infrastructure could be flooded out. By the end of the century, sea level rise could have direct impacts to the Novato Atherton Avenue Fire Station. A few emergency shelters in Southern Marin communities could be vulnerable to tidal flooding, and several more could expect storm surge flooding and may not be available when needed most.
Beaches, estuaries, marshes, wetlands, and intertidal areas on the Marin County OA coast, including in the unincorporated area, are vulnerable to sea level rise and storms. Nearly all beaches except Dillon Beach and the federal portion of Stinson Beach, could be lost entirely in the long-term. Roughly 9,000 acres in the estuaries of Tomales Bay, Bolinas Lagoon, and Esteros Americano and San Antonio, 1,800 acres of wetlands and marshlands could be impacted to varying degrees across all of the scenarios in all of the communities. Sea level rise may push coastal habitats inland where possible, flooding tidal areas more frequently and inundating new inland areas with saltwater. The North Central California Coast and Ocean Vulnerability Assessment identified the five most vulnerable species to sea level rise as the Western snowy plover, black oystercatcher, black rail, California mussel, and red abalone.
On the bayside, the marshlands that buffer the shoreline communities from high tides and storm surges could begin to experience transitions in habitat, especially those in the Southern Marin County OA where they are typically bordered by urban development. Consequently, the waters here would get deeper and flood out the existing habitat, shifting high marsh to low marsh, low marsh to mud flat, and mud flats to open water. Without adequate light of shallow water, eelgrass beds would shrink. Collectively, these habitat shifts could have significant impacts on vulnerable species such as the salt marsh harvest mouse, Ridgway’s Rail, or the long-fin smelt.
A twenty-inch increase in sea level in the medium-term would continue to shrink the Southern Marin County OA, Tiburon Peninsula, and Pt. San Pedro marsh and tidal habitats.
Southern Marin County OA marshes may no longer exist by the end of the century, destroying the habitat of several shoreline birds and mammals. Northern Marin marshes would become increasingly tidally influenced, with tide water reaching US Highway 101 in Bel Marin Keys and North Novato up the Petaluma River. Typically freshwater marshes west of US Highway 101, for example, Sutton Marsh, could also expect damaging salinity impacts. Tidal marsh lands may increase in Northern Marin if they are not prevented from migrating inland. Approximately 1,358 acres on 30 agricultural parcels could be vulnerable to sea level rise and storm conditions.
Another 3,000 acres are public agency lands near Bel Marin Keys, Hamilton Field, and the Novato Sanitary District that are leased for agricultural use. Higher high tides could push brackish conditions inland, reducing grazing, manure spreading, and cultivation area. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
275
Loss of or compromised emergency services could be more devastating to communities with higher populations that fall into certain demographic categories. Communities with higher populations that fall into these categories include Marin City and the canal neighborhoods in the unincorporated area around the City of San Rafael. Marin County OA populations that are most vulnerable to the effects of sea level rise include:
• Low-income households
• Households in poverty
Climate Change and Future Development Considerations
The two major causes of global sea level rise are thermal expansion of warming oceans and the melting of land-based glaciers and polar ice caps. Climate change is affecting natural and built systems around the world, including the California coast. In the past century, average global temperature has increased about 1.4°F, and average global sea level has increased 7 to 8 inches. Sea level rise in the San Francisco Bay Area is projected to increase by eight inches MHW in 2050 and could reach 4.5 to eight feet by 2021 if greenhouse gas emissions aren’t reduced4
.
Figure 3.131: Projections of Sea Level Rise in the San Francisco Bay Area, 2000-2100 Source: 2019–2020 Marin County Civil Grand Jury, Climate Change: How Will Marin Adapt? While the Marin County OA shoreline already experiences regular erosion, flooding, and significant storm events, sea level rise will exacerbate these natural processes, leading to significant social, environmental, and economic impacts. The third National Climate Assessment cites strong evidence that the cost of doing nothing exceeds the costs associated with adapting to sea level rise by 4 to 10 times. Sea level rise will continue to affect the Marin County OA with increased tidal flooding and storm surge during severe weather events, and future along the Marin County OA shoreline will only amplify these impacts. Sea level can also lead to increased land subsidence and the potential of levee failure. The impacts of a tsunami would also be magnified with rising seas. Future development in the coastal areas of Marin County will put more people and property at risk from flooding as a result of sea level rise. Roads and utility infrastructure across the Marin County OA will continue to become inundated. 4 2017 Marin Shoreline Sea Level Rise Vulnerability Assessment. https://www.marincounty.org/- /media/files/departments/cd/planning/slr/baywave/vulnerability-assessmentfinal/final_allpages_bvbconsulting_reduced.pdf?la=en l ~ <;>U·N· TY OF
~ ARIN
a
~
Sea-Level Rise if Greenhouse Gas
Emissions Remain High
2000 2010 2020 2030 2040 2050 2060 2070 2080 2090
(Year)
Sea-Level Rise if Greenhouse Gas
Emissions Are Moderated
2000 2010 2020 2030 2040 2050 2060 2070 2080 2090
(Year)
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
276
3.3.9 SEVERE WEATHER – EXTREME HEAT
Extreme heat is defined as temperatures that hover 10 degrees or more above the average high temperature for the region and last for several weeks. A heat wave is an extended period of extreme heat, often with high humidity. When relative humidity is factored in, the temperature can feel much hotter as reflected in the Heat Index (see Figure 3.132):
Figure 3.132: Heat Index
Source: NOAA
Heat kills by taxing the human body beyond its abilities. In a normal year, about 1,300 Americans succumb to the demands of summer heat. Heat is the leading weather-related cause of mortalities in the US. In 2006, California reported a high of 204 heat related deaths, with 98 reported in 2017 and 93 deaths reported in 2018.
Location and Previous Occurrences
Extreme heat has the potential to impact all areas of the Marin County OA, though more predominantly in the lower elevations further away from the coast. In the unincorporated area this includes the Tamalpais Valley, Kentwood, Lucas Valley-Marinwood and Santa Venetia areas. Communities along the Pacific Ocean and Tomales Bay including Muir Beach, Stinson Beach, Bolinas, Inverness and Point Reyes Station tend to have cooler temperatures due to the ocean and bay breezes.
In the 40-year period from 1936 through 1975, nearly 20,000 people were killed in the United States by the effects of heat and solar radiation. In the heat wave of 1980, more than 1,250 people died. According to the 2018 California State Hazard Mitigation Plan, the worst single heat wave event in California occurred in Southern California in 1955, when an eight-day heat wave resulted in 946 deaths.
Impacts
Heat waves do not strike victims immediately, but rather their cumulative effects slowly take the lives of vulnerable populations. Heat waves do not cause damage or elicit the immediate 1 ~<;>U·N· TY OF a ~ ARIN ~
NOAA's National Weather Service
Heat lnd·ex
Temperature (OF)
80 82 84 86 88 90 94
40 80 81 83 85 88 91 9
45 80 82 84 87 89 93 1
l 50 81 83 85 88 91 95
~ 55 81 84 86 89 93 97 1
-0 60 82 84 88 91 95 100 .E 65 82 8E, 89 93 98 103 :::i :c 70 83 86 90 95 100 00 a, 75 84 88 92 97 10$ 109' ::,, :g 80 84 89 94 100 ., G)
Cl:'. 85 85 90 96
90 86 91 98
95 86 93 100
100 87 95 103 1
Likelihood ol Heat O is orders w ith Prolonged E x1rns ure or Streuou s Activity O c .. ution 0 E;,.1 re me c .. 1.11,on Oanger ■ Eictreme Ooinger 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
277
response of floods, fires, earthquakes, or other more “typical” disaster scenarios. While heat waves are obviously less dramatic, they are potentially more deadly. Heat emergencies are often slower to develop, taking several days of continuous, oppressive heat before a significant or quantifiable impact is seen. Heat waves do not strike victims immediately, but rather their cumulative effects slowly take the lives of vulnerable populations. Sickness can occur if someone has been in extreme heat for too long, or has over-exercised for his or her age or physical condition. Extreme heat can be more dangerous for older people, the very young, and people who are sick or overweight. See Figure 3.133 for a description of possible heat disorders by heat index level.
Figure 3.133: Heat Disorders by Heat Index Level
Source: National Weather Service (NWS)
Rural buildings without electricity, some mobile homes, or older homes that have not been retrofitted for AC, can become susceptible to extreme heat effects. The OA may open cooling centers as a result of heat or prolonged period of hot temperatures. When combined with low humidity, extreme heat can contribute to the start and spread of wildfires.
The NWS will issue a Heat Advisory, Watch, or Warning when the Heat Index is expected to have a significant impact on public safety. The expected severity of the heat determines whether advisories or warnings are issued. A common guideline for the issuance of excessive heat alerts is when the maximum daytime high is expected to equal or exceed 105°F and a nighttime minimum high of 80°F or above is expected for two or more consecutive days. The NWS office in Sacramento can issue the following heat-related advisory as conditions warrant.
Heat Advisory means that temperatures of at least 100°F or Heat Index values of at least 105°F are expected. Consider postponing or rescheduling any strenuous outdoor activities. If you must be outside, be sure to drink plenty of water and take frequent breaks in the shade. The young and elderly and those with medical conditions should use extra caution outdoors.
Excessive Heat Watch means that Heat Index values are expected to reach or exceed 110°F and not fall below 75°F for at least a 48 hour period. Plan to suspend all major daytime outdoor activities if a warning is issued. If you do not have air conditioning, locate the nearest cooling shelter or discuss staying with nearby family or friends who have A/C.
Excessive Heat Warning means that Heat Index values are expected to reach or exceed 110°F and not fall below 75°F for at least a 48-hour period, beginning in the next 24 hours. A warning may also be issued for extended periods with afternoon heat index values of 105°F-110°F. Refrain from outdoor activities of any nature during the warmest time of the day. Drink plenty of water and 1 ~ <;>U·N· TY OF a ~ ARIN ~
Heat • a : I
..
130°F or Extreme
higher Danger
105°- Danger 129° F
goo- Extreme
105° F Caution
80° - 90°F Caution
I Possible heat disorders for people in high risk groups Heatstroke risk extremely high with continued exposure.
Sunstroke, Heat Cramps and Heat Exhaustion likely, Heatstroke possible with prolonged exposure and/or physical activity.
Sunstroke, Heat Cramps and Heat Exhaustion possible with prolonged exposure and/or physical activity.
Fatigue possible with prolonged exposure and/or physical activity. 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
278
take frequent breaks if you must be outside. Stay indoors in an air-conditioned building as much as possible. Check on elderly family members if they are living alone.
Extent and Probability
The frequency, intensity, and duration of extreme heat events and heat waves are expected to rise as a result of climate change, with an increased number of extreme heat days and nights, increased temperatures over extreme heat days and greater duration of extreme heat events.
By the end of the century, most of the region will average six heat waves a year, with the average longest heat wave lasting ten days. Extreme heat events will also extend seasonally into spring and fall.
Table 3.16: Marin County OA Hazard Risk Assessment – Severe Weather, Extreme Heat
Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Moderate High Medium 15.00
City of
Belvedere
Highly
Likely Extensive Moderate High Medium 15.00
Town of
Corte Madera Likely Extensive Weak Medium Low 11.00
Town of
Fairfax Unlikely Significant Weak Medium Low 8.00
City of
Larkspur Likely Extensive Moderate High Medium 14.00
City of
Mill Valley Likely Extensive Moderate Medium Medium 13.00 City of
Novato Likely Extensive Weak Medium Medium 12.00
Town of
Ross Likely Significant Moderate Medium Medium 12.00
Town of
San Anselmo Likely Extensive Extreme High High 17.00
City of
San Rafael Likely Extensive Moderate High Low 13.00
City of
Sausalito Unlikely Negligible Weak Low Low 5.00
Town of
Tiburon
Highly
Likely Extensive Moderate High Medium 15.00
Bolinas
Public Utility
District
Unlikely Extensive Weak Low Low 8.00
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
279
Las Gallinas
Valley
Sanitary
District
Highly
Likely Negligible Weak High Low 10.00
North Marin
Water
District
Likely Extensive Weak Medium Medium 12.00
Southern
Marin Fire
District
Likely Significant Moderate High High 14.00
Table 3.16: Marin County OA Hazard Risk Assessment – Severe Weather, Extreme Heat Source: Profiled Jurisdictions and Districts
Vulnerability
Extreme heat can affect a range of key infrastructure from energy systems, water and wastewater treatment systems, the operation of government buildings, and public transit. While higher summer temperatures increase electricity demand for cooling, at the same time, they also can lower the ability of transmission lines to carry power, possibly leading to electricity reliability issues during heat waves. Increased temperatures also impact the efficiency of solar power infrastructure by increasing the surface temperature of solar panels, which reduces the voltage that panels can generate and thereby lowers efficiency. Although warmer winters will reduce the need for heating, modeling suggests that total U.S. energy use will increase in a warmer future. Extreme heat can also increase the risk of other types of disasters and exacerbate the urban heat island effect. Heat can exacerbate drought, and hot dry conditions can in turn create wildfire conditions. In cities, buildings, roads and infrastructure can be heated to 50 to 90 degrees hotter than the air while natural surfaces remain closer to air temperatures.
The heat island effect is most intense during the day, but the slow release of heat from the infrastructure overnight (or an atmospheric heat island) can keep cities much hotter than surrounding areas. People who are required to work outside during extreme heat are especially vulnerable to the effects of extreme heat. In California , between 2000-2017, 15,996 workers experienced heat related illness (Risk factors for occupational heat-related illness among California workers, 2000-2017 - PubMed (nih.gov). Animals, including livestock, poultry, and domestic pets are susceptible to extreme heat. For example, dogs and cats are in danger of heat stroke in temperatures of 110°F. The heat wave of 2006 resulted in more than 25,000 cattle, 700,000 fowl, and 15 reported heat-related pet deaths in California. Heat wave impacts on livestock and poultry can lead to financial losses in agriculture.
High temperature can be felt throughout the Marin County OA, though the lower elevations of the County are more vulnerable to higher temperatures than the higher elevations. People who live in the more urban areas of the County can be at greater risk to heat because concrete and asphalt store heat for longer and release it throughout the night. High temperatures can cause brownouts and increase the susceptibility of people to the effects of heat. Though crops in the Marin County OA are adaptable to heat, they can become vulnerable to prolonged periods of high temperatures.
Northern Marin County (roughly north of Point Reyes, Nicasio, and Lucas Valley-Marinwood to the northern County line) is likely to see greater increases in annual average maximum temperatures due to climate change at a faster rate than southern portions of the County. While l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
280
climate change induced extreme heat events will impact County residents in the future, extreme heat effects will be less severe in the County relative to other areas of the state, including the Central Valley, that already experience higher temperatures and more extreme heat events. In terms of overall level of impact to County residents and infrastructure, extreme heat due to climate change will be less of a concern compared to flooding, sea level rise, wildfire, and landslides, debris flows, and post-fire debris flows in most cases. However, extreme heat will have a relatively greater impact on certain populations. Marin County OA populations most vulnerable to the effects of extreme heat include:
• Low-income households
• Households in poverty
• Persons without access to transportation or telecommunications • Low-resources racial or ethnic minorities
• Outdoor workers
• Healthcare workers, first responders, and protective service occupations • Houseless population
• Children
• Persons with disabilities
• Persons with chronic health problems
• Senior community members
In extreme temperatures, air quality is also affected. Hot and sunny days can increase ozone levels, which in turn affects Nitrogen Oxides Control levels. In addition, greater use of heating and cooling of indoor spaces requires more electricity and, depending on the electricity source, can emit more of other types of pollution, including particulates. These increases in ozone and particulate matter can pose serious risks to people, particularly the same vulnerable groups directly impacted by heat mentioned above.
Climate Change and Future Development Considerations
The primary effect of climate change is warmer average temperatures. The annual average daily high temperatures in California are expected to rise by 2.7°F by 2040, 5.8°F by 2070, and
8.8°F by 2100 compared to observed and modeled historical conditions5 . At the current rate,
annual average temperatures in the Marin County region and Bay Area will likely increase by approximately 4.4 degrees by 2050 and 7.2 degree by the end of the century unless significant efforts are made to reduce greenhouse emotions according to California’s latest climate change assessment.
5 California Adaptation Planning Guide
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
281
Figure 3.134: Annual Average Temperatures in the San Francisco Bay Area, 2000-2100 Source: California Climate Change Assessment (Fourth Edition) As climate change accelerates in the 21st century, it is anticipated that extreme heat events will become more frequent and intense across the Marin County OA. There will be increased residential and business needs for cooling and addressing heat-related issues. Heat waves also tax the energy grid. Future development in the Marin County OA could exacerbate the impacts from heat related events, particularly in electricity provision and water delivery.
Increased temperatures will also lead to an increase in the occurrence and severity of wildfires across the Marin County OA as conditions become hotter and drier. Future development near the many open spaces around Marin Couty could expose more people and infrastructure to the threat of a major wildfire as a result of increasing temperatures.
3.3.10 SEVERE WEATHER – HIGH WIND/TORNADO
High Wind
High wind is defined as a one-minute average of surface winds 40 miles per hour or greater lasting for one hour or longer, or winds gusting to 58 miles per hour or greater regardless of duration that are either expected or observed over land. These winds may occur as part of a seasonal climate pattern or in relation to other severe weather events such as thunderstorms.
The Beaufort scale is an empirical measure that relates wind speed to observed conditions on land and is a common measure of wind intensity (see Figure 3.135). l ~<;>U·N· TY OF
~ ARIN
a
~
-.. 82
t
QI 80 .._
::,
~ 78 QI
C.
E 76
2l
;;'; 74
E
~ 72
~
~ 70 IO
iii
::, 68 C
C
<t 66
a) Annual time series
Historical • observed
Historical - modeled range
RCP4.S average
RCP8.5 average
RCP4.S range
RCP8.5 range
1960 1980 2000 2020 2040 2060 2080 2100
f 82
~ 80 ::,
~ 78 Q)
C.
E 76
2l
~ 74
E
~ 72
~
~ 70 re
ro
::, 68 C
C
<t 66
bl Time period summaries
Historical· observed AVG/MIN/MAX
Historical· modeled AVG/MIN/MAX
RCP4.S AVG/MIN/MAX
RCP8.5 AVG/MIN/MAX
tt=
MIN
1976-2005 2006-2039 2040-2069 2070-2100
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
282
Figure 3.135: Beaufort Wind Scale
Source: NOAA
Windstorms in the Marin County OA are typically straight-line winds. Straight-line winds are generally any thunderstorm wind that is not associated with rotation (i.e., is not a tornado). It is these winds, which can exceed 100 mph, which represent the most common type of severe weather and are responsible for most wind damage related to thunderstorms.
Location and Previous Occurrences
The entire Marin County OA, including the unincorporated area, is susceptible to storms and damage from wind. The coastal and mountainous areas are particularly susceptible to wind, although wind has caused damages throughout the county. High winds often occur with the onset of atmospheric river events. Figure 3.136 shows wind zones for the United States. The l ~<;>U·N· TY OF
~ ARIN
a
~
Beaufort
number
0 1
2 3
4 s
6 1
8 g
10 Oesaiptlon
calm
Ught air
Ugh breeze
Gentle breeze
Moderate breeze
Fre!;h breeze
51rong breeze
High wind, Moderate
gale, ear gale
Gale, Fr!'!~h gale
Strong gale
Storm, Whole gale
Violent storm
Hurricane
Wind speed Land conditions
kt$
<1
1-2
3 - 6
7- 10
11 - lS
16-20
21-26
27 - 33
m/h
<1 Clllm. Smo):~ rise-s ver lea Iv.
1-5 Wind mo on vislbl~ ins oke.
6 - ll Wind ell one posed skin. wves rustle.
2- lS Lc:a~cs end sm~ ller twie, in conH~nt mo1 iot1
20 - 28 Ous:t and loose paper rai:.ed. Sma11 branches bee in to move. 29-38 Branch!!S of a moder<!! e sire mo e. Sm<!! I •~ be11ln to s ~v. 3 ~_ 49 Laree branches in motion. Vh istlin1: lm1rd in overhead wires. Umbrella use hernme5 diffi cu lt. Emp~ plast.lc garbage can5 tip over. 50 _ 61
Wkoletree5 ln motion. Effo • ne~ed to ,,.,tk a11a ln!.t the wind. Swayln1 of skvscrapers mav be fel e:spe<la llv by people on ul)pet oors. 61 _ 74 Some twies broken from tree:s. e&rs veer on road. Proeress on foot is serlously lmpedtd.
Some branches break off tree:i;, and sonie sma ll rees blowo er. 41 - 47 75 - 88 COn.structlon/ empor11ry ~TiM nd l>Drrlc d~ blo "011«. D11m11ee toclr.::u~ ten!5 and canopies.
48-55 89 _ 1
02 rees are broken o or uprooted, sapllngs bent and de ormed. Poorly attached esphelt shl"£1ti end st11na1" in poor condi ion peel o·f roofs.
Wlde5pread vegetation damage. any roo • ng surfaces are damaged; 56 - 63 103 - U7 a~phalt tile~ that have curled up and/or ·,ac ure-d due o aa:e may bru away co.mple elv.
verv wldespre.id demaee o ~eee a on. !>ome wlr,dows mav brea : mobile l 64 l 118 homes end poor I constr1.1ct«l sh«ls end barns re de~ee<t. Debris mev be 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
283
Special Wind Region is an area of higher wind occurrence, primarily where down-slope mountain wind occurs.
Figure 3.136: Wind Zones in the US
Source: FEMA
The National Climatic Data Center (NCDC) provides a listing of all the high wind events to affect Marin County since 1950. Most high wind events occur between November and March. 12/27/2006 - One person died when gusty winds knocked a tree into a home in Lagunitas. More than 50 trees toppled in Point Reyes National Seashore, including a 150-foot Douglas fir that slammed into the picnic area at the Bear Valley Visitor Center in Olema. Winds in the National Seashore were estimated between 80-100 mph. Manaka’s Inverness Lodge burned to the ground in a fire triggered by a falling tree.
1/19/2010 - High winds brought an 18-inch diameter tree and power lines down along Lucas Valley Road about one-half mile east of Nicasio Valley Road blocking both lanes of traffic. l ~<;>U·N· TY OF
~ ARIN
a
~
·111-
~
/21-tAW;,ti,11+
Wl:ND ZONES lN THE UN IT.ED STATES*'
OTHER 00.NS!DERATIO,NS
~ ,~ 'WlodR'l'iJ!o!li
i\~-::;!3 ,., rh,mfieonc,,~p,lbl'c RcglOi;l
~ Wind S::iocd moosurilil1,1 crtlcna ll!l'(I 1»1'1$if1C'l"!t ,to ASCE 7-98 - J,s;ccol'l(li:J~
- 33 IOOt ,:llli'.M;! {lfll.d\"!
-~9ll'OC
WiN OZO·NES
1:=1 z:o--e.r
(130¾1
!=i ZONEII ~ (160 wl'ijll'IJ
Z·OllE."1 --- (200.mptit
- .:ZONl::,r\i
(15(1~}
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
284
1/20/2010 - Strong winds and saturated soil combined to knock over a 50-foot Douglas fir tree along Turnagain Road in Kentfield.
10/24/2010 – A tree knocked down a power line when it fell in Inverness Park near the intersection of Portola Avenue and Vallejo Avenue.
2/15/2011 – High winds knocked down more than a dozen power poles across Marin County. 1/21/2012 – High winds caused over 4,000 homes to lose power across Marin County. 2/6/2015 – High winds blew multiple trees down onto Bear Valley Road near Inverness, closing the road in both directions.
2017 - In Inverness, the boulevard was closed at Pierce Point Road because of fallen trees.
Nicasio Valley Road was closed between Sir Francis Drake Boulevard and Lucas Valley Road while crews removed fallen trees.
1/2023 – In Bolinas, extreme high winds estimated at close to 100 mph knocked down numerous trees across Mesa Road, closing the road several times, causing power outages and, in one case, injury.
Impacts
Straight-line winds may 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 snow storms. 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.
These winds may cause personal injury, damage crops, push automobiles off roads, damage roofs and structures, overturn mobile homes, tear roofs off of houses, topple trees, snap power lines, shatter windows, sandblast paint from cars, and cause secondary damage due to flying debris. Other associated hazards include utility outages, arcing power lines, debris blocking streets, dust storms, and an occasional structure fire. Due to the wildfire threat posed by trees falling or leaning on power lines as a result of high winds and other conditions, Pacific Gas and Electric began initiating Public Safety Power shutoffs (PSPS) events after the 2017 Northern California Wildfires and the 2018 Camp Fire (see wildfire profile) in order to prevent the start of wildfires. These PSPS events can have numerous impacts on residents who rely on electricity for cooling their homes, powering water pumps, keeping critical medical equipment operable and other needs.
In the Marin County OA, storms with strong winds knock down trees and power lines nearly every year and continue to slowly erode vulnerable coastal areas and critical inland ponds (i.e. reservoirs/dams, berms/levees around stormwater detention ponds, wastewater treatment/storage ponds). Although the entire OA is affected by wind, coastal areas tend to be impacted more frequently by the strongest winds (9+ on the Beaufort scale) than inland areas.
The Marin County OA’s coastal areas have small resident populations but large visiting populations, such as Muir Beach, Stinson Beach, and Bolinas that can be impacted by strong winds. Beachgoers and boaters would be particularly impacted by wind hazards. Tourism is a key part of the economy in Marin County, particularly in coastal communities, and thus there are potentially significant economic impacts of wind events. Some communities, such as Oceana Marin and Olema, rely on water and wastewater infrastructure that has potential to be impacted by coastal erosion, wind driving up wave elevations, and erosion from waves forming due to l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
285
wind over treatment and storage ponds. Inland critical ponds are also impacted by wind-driven wave erosion such as dams on drinking water reservoirs, and levees/berms containing stormwater retention and detention ponds. Across the county powerlines are potentially impacted by wind, potentially affecting commercial, industrial, and residential areas, and most years downed trees lead to temporary road closures.
Extent and Probability
The Marin County OA’s most damaging wind events tend to range between 7 and 11 on the Beaufort scale, or 30 to 60 knots. These wind strengths are characterized as high wind to violent storm. Thus, most years whole trees are put in motion and the ocean heaps up and white foam and spindrift form. Slight structural damage and uprooted trees can result occasionally. Wind events and associated damages are expected to continue to occur several times per year.
Table 3.17: Marin County OA Hazard Risk Assessment – Severe Weather; Wind and Tornado
Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Extensive Moderate High Medium 15.00
City of
Belvedere
Highly
Likely Extensive Moderate High Medium 15.00
Town of
Corte Madera Likely Negligible Weak Low Low 7.00
Town of
Fairfax Likely Limited Moderate Medium Medium 11.00
City of
Larkspur Likely Extensive Moderate High Medium 14.00
City of
Mill Valley
Highly
Likely Significant Moderate High Medium 14.00
City of
Novato Likely Extensive Weak Medium Medium 12.00
Town of
Ross Occasional Significant Moderate Medium Medium 11.00 Town of
San Anselmo Likely Extensive Extreme High High 17.00
City of
San Rafael Occasional Extensive Moderate Medium Medium 12.00 City of
Sausalito Likely Significant Moderate Medium Medium 12.00 Town of
Tiburon
Highly
Likely Extensive Moderate High Medium 15.00
1 ~<;>U·N· TY OF a
~ ARIN ~
I I I I I I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
286
Bolinas
Public Utility
District
Highly
Likely Extensive Moderate High High 15.00
Las Gallinas
Valley
Sanitary
District
Likely Negligible Weak Medium Medium 9.00
North Marin
Water
District
Likely Extensive Weak Medium Medium 12.00
Southern
Marin Fire
District
Likely Significant Moderate High Medium 13.00
Table 3.17: Marin County OA Hazard Risk Assessment – Severe Weather; Wind Source: Profiled Jurisdictions and Districts
Vulnerability
Areas of the Marin County OA, including the unincorporated area – coastal, mountainous and inland valleys where there are power lines, roads, and creeks/bridges, and ponded water for infrastructure (stormwater, wastewater, drinking water purposes), are particularly vulnerable to disruption due to wind damage, as are private structures with nearby trees. Certain locations are even more susceptible to damage due to building construction and the amount of tree canopy. Trees can fall on power lines, sparking wildfires and causing power outages. Trees can also fall on people and cars. People who live in homes with large tree branches over their roofs are particularly susceptible to high winds. Mobile home parks are vulnerable to high wind due to their light frame construction. Aviation vehicles, including small airplanes, are also susceptible to high winds and potential issues can arise when they are taking off and landing.
Specific building codes should be considered for construction in Special Wind Regions. The systems that are most vulnerable are those that wouldn’t be able to be fully repaired quickly should there be a catastrophic failure during an extreme wind event, such as a breach of a levee or dam due to wave erosion. Some examples of vulnerable facilities include:
• Oceana Marin Force Main Pump Station is 60 feet from the edge of a coastal bluff. • Coastal erosion rates up to 4.4 feet/year were anticipated in the Dillon Beach area (where Oceana Marin is located) according to a 2003 Cliff and Erosion Technical Background report prepared to support a Marin County Local Coastal Program update.
Although only a small community would be affected by the failure, it would be a long time before the critical water supply facility could be replaced. Additionally, the community has a sewer line potentially vulnerable to coastal erosion. • Wind driven waves could flood the Olema Domestic Water Pump Station which would cause electrical and water supply failure to 43 residents, 3 hotels, a church, and a campground.
• Stafford Dam’s (earthen) upstream face is subject to wind and wave action which has been eroding the gunite and welded wire reinforcement. A catastrophic failure could lead to inundation of the City of Novato and areas of the unincorporated County around it (see the subsection on Dam Failure for vulnerability analysis). l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
287
Tornado
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, and damage paths can be in excess of one mile wide and 50 miles long. The Enhanced Fujita Scale (see Figure 3.137) is commonly used to rate the intensity of tornadoes in the United States based on the damages that they cause.
Figure 3.137: Enhanced Fujita Scale
Source: NOAA
Tornadic waterspouts are tornadoes that form over water, or move from land to water. They have the same characteristics as a land tornado. They are associated with severe thunderstorms, and are often accompanied by high winds and seas, large hail, and frequent dangerous lightning.
1 ~<;>U·N· TY OF a ~ ARIN ~
.J. _________________ _
Enhanced Fujita Scale
. ~ • .... : '
.... - ·' . ......
EF-1
EF-2
EF-3
EF-4
65-85 mph winds
86-110 mph winds
111-135 mph winds
136-165 mph winds
166-200 mph winds
>200 mph winds
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
288
Figure 3.138: Waterspout Formation
Source: MarineInsights
Location and Previous Occurrences
Compared to the areas east of the Rocky Mountains, tornado occurrence over the western United States is much less frequent and even more rare across the Marin County OA due to its topography. A tornado in the Marin County OA would most likely begin as an off-shore waterspout that comes ashore off the coast and transitions into a tornado over lower-lying terrain, particularly in the area of Tomales Bay. Tornadoes could also form in the low-lying northerly parts of the OA near Sonoma County.
Table 3.18: shows a map of all tornado activity in the Marin County OA since 1973.
Column Definitions: 'Mag': Magnitude, 'Dth': Deaths, 'Inj': Injuries, 'PrD': Property Damage, 'CrD':
Crop Damage
Table 3.18: Tornados Activity in the Marin County OA
Location County/Zone St. Date Time T.Z. Type Mag Dth Inj PrD CrD TOMALES MARIN CO. CA 12/23/1996 10:00 PST Tornado F1 0 0 200.00K 5.00K Totals: 0 0 200.00K 5.00K
Table 3.18: Tornado Activity in the Marin County OA
Source: NOAA
From 1950 to 2020, there has been only one recorded tornado in the Marin County OA according to the National Weather Service. An EF-1 touched down in Tomales on December 23rd, 1996. This storm began over the ocean as a waterspout that moved in land. It destroyed a large barn and 10 large eucalyptus trees, and five telephone poles. It also ripped the roof off l ~<;>U·N· TY OF
~ ARIN
a
~
WATERSPOUTS AT SEA
IT'S NOT SEAWATER
INSIDE WATERSPOUTS
The clouds gather. and water condensation leads to a swirling mass of water droplets.
WIND VELOCITY
According to NOAA, an average waterspout is around SO meters in diameter. and its associated wind moves at 50 miles an hour.
I I
TORNADIC AND NONTORNADIC WATER
SPOUTS
A tornadic waterspout Is associated with
~~Y1~i~;ti~~~~~~Ti~fu~~~
Fair·weathe, waterspouts
need warm water to develop along the dark flat base of a line of growing cumulus clouds.
THE EARLIEST
WATERSPOUTS
In 1555, at the Grand Harbour of Valletta.
I I
CAN BE
DESTRUCTIVE
I I I I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
289
another house. A farmer was in the barn when it was blown over but he was not injured. There were over $200,000 in damages. At least two other waterspouts were reported as well as heavy rain and small hail in the Tomales Bay area. Larger and more destructive tornados have occurred just north of the Marin County OA in Sonoma County, including an EF 2 tornado near Petaluma in 1958 and an EF 1 tornado near Santa Rosa in 1996 that caused over $1 million in damages.
Impacts
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, broken gas lines, broken sewer and water mains, and the outbreak of fires. Agricultural crops and industries may also be damaged or destroyed. Access roads and streets may be blocked by debris, delaying necessary emergency response.
Extent and Probability
The Marin County OA would most likely experience an EF-0 or an EF-1 tornado, with little to moderate damage. The potential does exist for an EF-0 or an EF-1 tornado to cause injury and death.
While unlikely, a stronger EF-2 tornado does have the potential to occur in the Marin County OA and could cause considerable damages to buildings and infrastructure. Such a tornado could destroy mobile homes, tear roofs off well-constructed houses, shift the foundations of frame houses, and lift cars off the ground.
The probability of a tornado occurring in the Marin County OA is extremely rare.
Vulnerability
As with high winds, certain locations are more susceptible to damage due to building construction and the amount of tree canopy. Trees can fall on power lines and cause power outages and can also fall on people and cars. Power lines, transmission lines, and radio towers are all vulnerable to a direct hit from a tornado. A greater amount of property is vulnerable to damage from a tornado than a regular wind due to the higher wind speeds of tornado. Mobile home parks are vulnerable to tornadoes due to their light frame construction, as are industrial and commercial sites with loose materials. Aviation vehicles, including small airplanes, are also susceptible to tornadoes.
Climate Change and Future Development Considerations
It is anticipated that the atmospheric rivers that deliver storms to Northern California may intensify because of climate change. This increase in storm intensity may bring more intense winds and potential tornados to Northern California, including the Marin County OA. Significant wind events and tornadoes can topple trees, particularly those that may be saturated, or drought stressed as a result of climate change. An increase in fallen trees as a result of increased storms due to climate change can lead to an increase in power outages. Future development in any of the forested areas of the Marin County OA will increase the effects of severe wind events.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
290
3.3.11 TSUNAMI
Tsunamis consist of waves generated by large disturbances of the sea floor, which are caused by volcanic eruptions, landslides or earthquakes. Shallow earthquakes along dip slip faults are more likely to be sources of tsunami than those along strike slip faults. The West Coast/Alaska Tsunami Warning Center (WC/ATWC) is responsible for tsunami warnings. Tsunamis are often incorrectly referred to as tidal waves. They are actually a series of waves that can travel at speeds averaging 450 (and up to 600) miles per hour with unusual wave heights. Tsunamis can reach the beach before warnings are issued.
Location and Previous Occurrences
Tsunamis could occur in numerous areas of the Marin County OA. The California Department of Conservation updated the tsunami hazard maps for Marin County in 2022. Figure 3.139 shows all the tsunami inundation areas of the Marin County OA. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
291
Figure 3.139: Tsunami Inundation Zones in the Marin County OA Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
e Dams
a
~
Legend
• Military and Civil
Defense Installations
Communication
Facilities
Electric Power Facilities
Wastewater Facilities
e Water Supply Facilities
Airports
Marin County
Tsunami
DIIICIOI
EMERGENCY
MANAGEMENT
IOI
• • •
•
• •
•
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
Tsunami Inundation
•
0 Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/19/23
12 37
~ an
N
County of Marin, callfornia State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
292
Tsunami inundation zones extend into several unincorporated communities in Marin County which are shown below.
Figures 3.140 and 3.141 show the tsunami inundation zone in and around Inverness.
Figure 3.140: Tsunami Inundation Zone – Inverness Area
Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
0 '
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
293
Figure 3.141: Tsunami Inundation Zone – Inverness
Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
~ lnveme<;,;
'tlolunt-f!M
nr• Dep..1rtmc"t1!
lWl b·l11erntss
l-!br.:i,y
Poi11t Reye-s
StupwteCk5
f.fGrCJneJfi
Pork
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
294
Figure 3.142 shows the tsunami inundation zone south of Inverness.
Figure 3.142: Tsunami Inundation Zone – South of Inverness Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
Dr•k,,\,~0,
¼
~'p.
t ~
~~
°"'liJ"11l<N~
/✓ ~IW.'-"•
,-,
✓ ~
l
Tomares
Bay Ecological
Reserve
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
295
Figure 1.143 shows the tsunami inundation zone around Inverness Park and Point Reyes.
Figure 3.143: Tsunami Inundation Zone – Inverness Park and Point Reyes Source: California Department of Conservation, 11/27/23 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
296
Figure 3.144 shows the tsunami inundation zone around Reynolds and Marshall.
Figure 3.144: Tsunami Inundation Zone – Reynolds and Marshall Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
Morconi
Conference
Cen1er
Stare His1or,c
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
297
Figure 3.145 shows the tsunami inundation zone around McDonald and Blakes Landing.
Figure 3.145: Tsunami Inundation Zone – McDonald and Blakes Landing Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
McDonald
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
298
Figure 3.146 shows the tsunami inundation zone south of Tomales.
Figure 3.146: Tsunami Inundation Zone – South of Tomales Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
"}f
~
a
~
1/
/
/
,
/
'
,·
J.i
i/
/
I
!
!
I
!
,.
/
1 '
/
.'
.'
I
j '
,./
i:o-
-~~-
·,
\
·,.,
\
'.
\
I
\
'·, ·~ -~ ·,
7 -~.I'•, \
\ / \
/, ,•-.... ·,
(
\
1 ,.~
,.
i
r
/
,'
1 ·~
'
,
!,
I
\
\
\
'
... ,·-
:
I
,·
j
j
I
!
:
I
,'
;
!
,'
~/·
;
,.~·
1' '
.~·
,
(
/
,
, ,
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
299
Figure 3.147 and 3.148 shows the tsunami inundation zone in and around Dillon Beach.
Figure 3.147: Tsunami Inundation Zone – Dillon Beach Area Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
' ' ·, 1. ; ' . . ,. '
'!
' ,: ........
' ....... _
-,\, __
.. SU~r1oof
Hill
61m
·, .
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
300
Figure 3.148: Tsunami Inundation Zone – Dillon Beach
Source: California Department of Conservation, 11/27/23 Figure 3.149 shows the tsunami inundation zone around the northern Bolinas Lagoon.
Figure 3.149: Tsunami Inundation Zone – Bolinas Lagoon North Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
j
l
I
J ✓/
I
,,,
t ~--- .,o, ..... , . ..-
., ~ ,,../ "' ..
/
~·/ /
/
/ 1:-
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
301
Figures 3.150, 3.151 and 3.152 shows the tsunami inundation zone in and around Bolinas.
Figure 3.150: Tsunami Inundation Zone – Bolinas Area
Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
...
a
~
" i
,,
'¾,
., . .,;I,..,
;
..
1 . .,
6 "
#",#
... ;
'
Bolinas
Lagoon
Open Spore
Preserve
iJ:JJ, rJU!i
Loau1.H
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
302
Figure 3.151: Tsunami Inundation Zone – Bolinas Core
Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
1;e.ir:ice Jlwenue
C'.in)"()nRoacl
Bol•n,is
811(]tll(Jri
.1\-.if'n,.r-
!. Whad
Roa<l
,i1-- 1ir7r
'?r1 ,: 81-n.'
(1,:..·_.1
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
303
Figure 3.152: Tsunami Inundation Zone – Bolinas North
Source: California Department of Conservation, 11/27/23 Figure 3.153 and 3.154 shows the tsunami inundation zone in and around Stinson Beach.
Figure 3.153: Tsunami Inundation Zone – Stinson Beach Area Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
a
~
"
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
304
Figure 3.154: Tsunami Inundation Zone – Stinson Beach
Source: California Department of Conservation, 11/27/23 1 ~<?U·N· TY OF a ~ ARIN ~
p Q
o;;;rlr.<;011
BNch
P,>rl..,ng
Lu<
p •
• ;;::; ,,. - c, tmson Arenal Avenue - -l!cJ~~l /'} It.
Pc 51 o_rf<e
p
0 Stinton
6e,1,ti
'. vi~•tor •(PnH•r
p
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
305
Figure 3.155 shows the tsunami inundation zone in Muir Beach.
Figure 3.155: Tsunami Inundation Zone – Muir Beach
Source: California Department of Conservation, 11/27/23 rt;\ ~
.J'
, "" .,I ~ (
'
"~ \. \
Inn ,/'.... ..._\
f ......... .. \
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
306
Figure 3.156 and 3.157 shows the tsunami inundation zone in Tamalpais Valley.
Figure 3.156: Tsunami Inundation Zone – Tamalpais Valley South Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
l
i
a
~
Sh,,,,r...,. ~~• ' Ir (.•rrl
~·t~::: .L,·••· u• //
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
307
Figure 3.157: Tsunami Inundation Zone – Tamalpais Valley North Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
1 i
,
J
~~
a
~
. ..,, ,J&,-,J-•
'~ Ci)' .. "'1-.Js..--.ai;;...-.L.
J
l
f
I .. ~ I /' ,,,
/
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
308
Figure 3.158 shows the tsunami inundation zone in Marin City.
Figure 3.158: Tsunami Inundation Zone – Marin City
Source: California Department of Conservation, 11/27/23 Figure 3.159 shows the tsunami inundation zone in Manzanita.
Figure 3.159: Tsunami Inundation Zone – Manzanita
Source: California Department of Conservation, 11/27/23 U.N. TYOF a
ARIN ~~-~:~----~
,..
.,,,.,
/,',(Jt/1(1
iul/i,i
l,1. ::::.1:..,
----
••••• ••...... '~.,, :··t7~~.\'..,
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
309
Figure 3.160 and 3.1561 shows the tsunami inundation zone in Strawberry.
Figure 3.160: Tsunami Inundation Zone – Strawberry South Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
Ric r son
B rdg~
V.1/1:,
"'' '
a
~
~"' ,,.,1,,
ii.u·I
·,
.Arornb,:..ro
J:s rrm6
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
310
Figure 3.161 shows the tsunami inundation zone in the unincorporated area of the Tiburon Peninsula.
Figure 3.161: Tsunami Inundation Zone – Unincorporated Tiburon Peninsula Source: California Department of Conservation, 11/27/23 Figure 3.162 shows the tsunami inundation zone in Paradise Cay. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
311
Figure 3.162: Tsunami Inundation Zone – Paradise Cay
Source: California Department of Conservation, 11/27/23 l ~<;>U·N· TY OF
~ ARIN
.I
,/
, ..... ~~~- , ng ,1ou11tain
185m
a
~
Trimcl,1-d DI rW'
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
312
Figure 3.163: North Marin Tsunami Inundation Zones
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
,11
Olompal, State
Historic Park
e Dams
Communication
Facilities
Marin County
Airport-Gnoss
Field
Legend
North Marin
Tsunami
Fire Stations
Hospitals and Medical
Facilities 'al Police / Sheriff Stations
Schools
Electric Power Facilities
Airports
Emergency Operations
Centers
Tsunami Inundation
County of Marin, ca11tornia State Parks, Esri, HERE, Ga "'1arm Counh DfllctOI
EMERGENCY
MANAGEMENT
1.7 Miles
Bak -
nty.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
313
Figure 3.164: Santa Venetia Tsunami Inundation Zones
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Communiration
Facilities
Wastewater Facilities
Airports
Emergency Operations
Centers
Santa Venetia
Tsunami
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
CJ Building Footprints
- Tsunami Inundation
DfllctOI
EMERGENCY
MANAGEMENT
0.7 ••c:: •••• Miles
0 0.2 0.3
in County OEM·ifuWdy_tBaker-Cohn
ate
ail:
Printed
OEM_
:
GIS@Ma
10/19/23
'rl ~otrn\ly.org ~ N
ERE, Gannin, SafeGraph, Geo
, Esri, HERE, Garmin, SafeGrap
~og,~j/lffe"METI/NASA, USGS, Bureau of Land Management, EPA, NPS, ies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
314
Figure 3.165: Greenbrae Tsunami Inundation Zones
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
Aoun In
Blithedale
Summit
Communication
Facilities
Legend
Electric Power Facilities
Wastewater Facilities
Emergency Operations
Centers
Green brae
Tsunami
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
ail: OEM_
ate Printed: 1
DIIICUII
EMERGENCY
MANAGEMENT
~ N
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
315
Figure 3.166: Richardson Bay Tsunami Inundation Zones
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
• Military and Civil
Defense Installations
Communic.ation
Facilities
Electric Power Facilities
Wastewater Facilities
Airports
Rich a rd son Bay
Tsunami
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police / Sheriff Stations
Schools
- Tsunami Inundation
0.4 0.8
DIIICUII
EMERGENCY
MANAGEMENT
nty OEM / Woody BakerGIS@MarlnCounty,9)'.9"·,...
10/19/23 ,:,,-/
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
316
Figure 3.167: Tomales Bay Tsunami Inundation Zones
Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
lo
0 0
1) ""'
e.,
()
()
0 t>•
Legend
Fire Stations
Schools
D Building Footprints
0 Tsunami Inundation
[? .
" ~
o O
~
<ti"'
0 "
p
o.
Tamales Bay
Tsunami
DIIICIOI
EMERGENCY
MANAGEMENT
I>
"
~ 0
() .. _co 0
Cl
<::i,"
.,,
fll.l , •
I) t'arin County OEM / Woody Baker-Cohn
ema
0 11: [email protected] •
Date·'Printed:0 10/19/23 0 I'\ •
County of Marin, caltfornia State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NAs!?, USGS, Bureau of Land Management, EPA, NPS, USDA, Esri Community Maps Contributors, County of Marin, california State Parks, Esri, HERE'/'~rmin, Sares,/aph, GeoTechnologies, Inc, METI/NASA, USGS, 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
317
Figure 3.168: Bolinas – Stinson Tsunami Inundation Zones Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
, ...
a
~
Solinas - Stinson
Tsunami
DIIICUII
EMERGENCY
MANAGEMENT
Legend
e Dams
Communication
Facilities
Fire Stations
Hospitals and Medical
Facilities
Schools
D Building Footprints
- Tsunami Inundation
0 0.3 0.5 1
Miles
Marin County OEM / Woody Baker-C.ohn
email: [email protected]
Date Printed: 10/ 19/23
1 N
County of Marin, CaUfomla State Parits, Esrl, HERE, Garmin, SafeGraph, GeoTechnologles, Inc, METI/NASA. USGS, Bureau of Land Management. EPA, NPS, USDA, County of Marin, California Slate Parits, Esrl, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA. USGS, Bureau of Land Management, EPA, 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
318
Tsunamis have caused loss of life and damaged property in Hawaii, Alaska and the West Coast over the last hundred years. Over 80 tsunamis have been observed or recorded along the coast of California in the past 150 years. Since 1946, there have been five tsunamis known to have caused damage to ports and harbors in California with several impacting unincorporated Marin County:
In 1960, a tsunami caused by a magnitude 9.5 earthquake offshore from Chile resulted in minor inundation to the beach at Stinson Beach.
In 1964, a tsunami caused by a magnitude 9.2 earthquake offshore from Alaska resulted in 12 deaths in California and destroyed portions of downtown Crescent City. There was damage to Lawson’s Pier in Tomales Bay. A man drowned in Bolinas.
A 2006 tsunami (originating in the Kurile Islands region) caused approximately $20 million in damage to Crescent City harbor.
A 2010 tsunami (originating offshore from Chile) caused several million dollars in damage to ports and harbors in the state.
A tsunami in 2011 caused by a magnitude 9.0 earthquake offshore of Japan killed one person at the mouth of the Klamath River and caused up to $100 million damage to 27 ports, harbors, and marinas throughout the state.
Impacts
Community exposure to tsunamis in California varies considerably—some communities may experience great losses that reflect only a small part of their community and others may experience relatively small losses that devastate them. Among the incorporated communities and the unincorporated areas of the county are communities that have the highest number of people and businesses in the tsunami‐inundation zone. The communities of Belvedere and Sausalito have the highest percentages of people and businesses in this zone.
Extent and Probability
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. Tsunamis are a relatively infrequent occurrence in the Marin County OA.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
319
Table 3:19: Tsunami Hazard Risk Assessment
Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Limited Extreme Medium High 15.00
City of
Belvedere
Highly
Likely Significant Severe High High 16.00
Town of
Corte Madera Unlikely Limited Moderate Low Low 7.00
Town of
Fairfax None None None None None 0.00
City of
Larkspur Occasional Limited Extreme None High 11.00
City of
Mill Valley Unlikely Negligible Severe Medium Medium 9.00 City of
Novato Unlikely Negligible Weak None Low 4.00
Town of
Ross None None None None None 0.00
Town of
San Anselmo None None None None None 0.00
City of
San Rafael Unlikely Limited Moderate None Medium 7.00
City of
Sausalito None Limited Weak Low Low 5.00
Town of
Tiburon
Highly
Likely Limited Extreme Medium High 15.00
Bolinas
Public Utility
District
Occasional Limited Severe Low High 11.00
Las Gallinas
Valley
Sanitary
District
Unlikely Extensive Severe None Medium 10.00
North Marin
Water
District
Unlikely Negligible Extreme Low Low 8.00
Southern
Marin Fire
District
Likely Limited Moderate Low Low 8.00
Table 3.19: Marin County OA Hazard Risk Assessment - Tsunami Source: Profiled Jurisdictions and Districts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
320
Vulnerability
Some Marin County OA communities may be more vulnerable to tsunamis because of the location and quality of the built environment. Several unincorporated communities could be particularly susceptible to a tsunami:
Numerous shoreline homes, businesses, buildings and sections of Sir Francis Drake Boulevard along the west shore of Tomales Bay from Seahaven down through Inverness to Inverness Park lie in a tsunami inundation zone and could be susceptible to a tsunami. The downtown commercial district of Inverness, including the Post Office and several businesses, lie in a tsunami inundation zone and could be susceptible to a tsunami.
Numerous shoreline homes, businesses, buildings and sections of Highway 1 along the east shore of Tomales Bay from Bivalve to Hamlet and up Keys Creek south of Tomales lie in a tsunami inundation zone and could be susceptible to a tsunami. Low lying areas of Dillon Beach, including the main beach parking area and access road, lie in a tsunami inundation zone and could be susceptible to a tsunami.
Both the east and west sides of the Bolinas Lagoon lie in a tsunami inundation zone, including all of Highway 1 on the west side from Stinson Beach to the intersection of Olema Bolinas Road north of Bolinas. The northern end of Bolinas, including several homes, the Bolinas-Stinson Elementary School, and a section of Horseshoe Hill Road, lie in a tsunami inundation zone and could be susceptible to a tsunami. The community of Bolinas is particularly susceptible to a tsunami as it could essentially be isolated with access roads north and south becoming flooded in a tsunami. Most of the commercial center of Bolinas, including several businesses, residences, the College of Marin-Bolinas Campus and the Bolinas Library lie in a tsunami inundation zone and could be susceptible to a tsunami.
Most of Stinson Beach south of Highway 1, including Seadrift Road, Dipsea Road, and Calle del Aroyo lie in a tsunami inundation zone, and there are hundreds of homes and buildings in this area along with the Stinson Beach Fire Station #2 and the Water District office that could be susceptible to a tsunami. The commercial center of Stinson Beach, including several businesses, the entire beach area including access roads and parking lots, and a section of Highway 1 lie in a tsunami inundation zone and could be susceptible to a tsunami.
A section of Muir Beach up Redwood Creek that includes several homes and businesses, the Muir Beach Fire Station, and a section of Highway 1 lie in a tsunami inundation zone and could be susceptible to a tsunami.
A large section of Tamalpais Valley, including smaller sections to the north adjacent to and including the City of Mill Valley, lie in a tsunami inundation zone and could be susceptible to a tsunami pushing water up Coyote Creek. There are hundreds of homes, commercial buildings, the Southern Marin Fire Protection District Station #4 and part of Tamalpais Valley Elementary School that lie in this area. Most of the commercial core of Marin City, including the Gateway Shopping Center, the Martin Luther King Jr. Academy, the Marin City Fire Station, and numerous residences lie in a tsunami inundation zone and could be susceptible to a tsunami.
The Waldo Point community consisting of dozens of floating homes in Richardson Bay could be susceptible to a tsunami. The area around the intersection of Highways 1 and 101 including the highways themselves, the Commodore Heliport and several businesses lie in a tsunami inundation zone and could be susceptible to a tsunami.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
321
Both sides of the Strawberry Peninsula lie in a tsunami inundation zone and could be susceptible to a tsunami. There are dozens of homes in this area along with numerous commercial buildings, the Strawberry Point elementary school and a large section of Highway 101 that could be susceptible to a tsunami. There are also several homes in the northwest corner of Strawberry near Alto that lie in a tsunami inundation zone and could be susceptible to a tsunami.
The eastern side of the Tiburon Peninsula, where there are dozens of homes and buildings along with the Sanitary District #5 - Paradise Cove Treatment Plant, lies in a tsunami inundation zone and could be susceptible to a tsunami. Most of Paradise Cay lies in a tsunami inundation zone. There are dozens of homes in this area that could be susceptible to a tsunami.
The southwest side of Kentfield lies in a tsunami inundation zone and could be susceptible to a tsunami. There are dozens of homes and numerous businesses in this area along with the A.E.
Kent Middle School, the Anthony Bacich G. Elementary School, part of the parking lot for the Marin General hospital, and most of the College of Marin campus and part of Sir Francis Drake Boulevard. A small section of Greenbrae that consists of a few homes and a section of Sir Francis Drake Boulevard, along with a small Section of California City that consists of a few homes, lie in a tsunami inundation zone and could be susceptible to a tsunami. A large section of San Quentin lies in a tsunami inundation zone and could be susceptible to a tsunami.
There are dozens of homes along San Pedro Road in the unincorporated county south of the City of San Rafael that lie in a tsunami inundation zone and could be susceptible to a tsunami.
The McNear Brick Yard and parts of Point San Pedro lie in a tsunami inundation zone and could be susceptible to a tsunami.
Most of northern Santa Venetia along the Santa Venitia Marsh and the South Fork of Galinas Creek lies in a tsunami inundation zone and could be susceptible to a tsunami. There are several hundred homes in this area along with numerous pump stations and several medical facilities.
While most of Bel Marin Keys lies outside of a tsunami inundation zone, the far eastern side has several homes that lie inside a tsunami inundation zone and could be susceptible to a tsunami.
The Hamilton Wetlands PG&E substation could also be susceptible to a tsunami, as it lies on the fringe of a tsunami inundation zone.
Parts of the Black Point area close to the Petaluma River Marsh lie on the edge of a tsunami inundation zone and could be susceptible to a tsunami. There are several homes in this area that mostly lie at the end of cul de sacs.
The principal exposure to the Marin County OA will be people, buildings, and infrastructure located in the low-lying potential inundation areas. Especially at risk are visitors, hikers, campers, and non-residents who might be on the shore when the tsunami strikes.
Associated risks to tsunami include flooding, contamination of drinking water, ruptured tanks or gas lines, lack of ingress and egress, and the loss of vital community infrastructure.
Climate Change and Future Development Considerations
The biggest threat to tsunamis is sea level rise which is a direct result of climate change. Sea level rise can make tsunamis worse than they already are because higher sea levels allow for tsunamis to travel further inland and cause even more damage. Sea level rise results in more l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
322
vulnerable coastlines which make coastal communities even more vulnerable to an incoming tsunami as the natural buffer to absorb the energy of an incoming tsunami will cease to exist.
This is particularly true in the Marin County OA, where most of the developed population lies in an area vulnerable to sea level rise. Furthermore, it has been theorized that ocean warming, caused by climate change, can impact the tectonic plates that rest below large bodies of water.
Ultimately, this can result in more geological activities and worse tsunamis. Climate change has also affected ocean patterns, which could eventually lead to tsunamis distributing themselves across the ocean and impacting areas that are currently not susceptible to a tsunami. Tsunamis as a result of climate change and associated sea level rise will exacerbate the impacts of flooding in the lowland areas of the Marin County OA. Future development in these areas will expose more people and infrastructure to the effects of flooding in the Marin County OA as tsunami inundation areas expand with climate change. Development in marshland in the Marin County OA would expose additional people and infrastructure to flooding as marshlands act as a natural buffer to a tsunami. Flooding could be exacerbated in areas where levees could fail as a result of high wave heights associated with a more significant tsunami.
3.3.12 WILDFIRE
A wildfire is a fire that occurs in an area of combustible vegetation. The three conditions necessary for a wildfire to burn are fuel, heat, and oxygen. Fuel is any flammable material that can burn, including vegetation, structures, and cars. The more fuel that exists and the drier that fuel is, the more intense the fire can be. Wildfires can be started naturally through lightning or combustion or can be set by humans. There are many sources of human-caused wildfires including arson, power lines, a burning campfire, an idling vehicle, trains, and escaped controlled burns. On average, four out of five wildfires are started by humans. Uncontrolled wildfires fueled by wind and weather can burn acres of land and everything in their path in mere minutes and can reach speeds up to 15 miles per hour. On average, more than 100,000 wildfires burn 4 to 5 million acres of land in the United States every year. Although wildfires can occur in any state, they are most common in the Western states including California where heat, drought, and thunderstorms create perfect wildfire conditions.
Wildfires are of primary concern when they occur in the Wildland Urban Interface (WUI), which is defined as areas where homes are built near or among lands prone to wildfire. Even relatively small acreage fires may result in disastrous damages. Most structures in the WUI are not destroyed from direct flame impingement, but from embers carried by wind. The damages can be widely varying, but are primarily reported as damage to infrastructure, built environment, and injuries to people. WUI fires have unique chemistry due to the combination of natural and human-made fuels that are burned, which may lead to the formation or release of toxic emissions not found in purely wildland fires.
The pattern of increased damages is directly related to increased urban spread into historical forested areas that have wildfire as part of the natural ecosystem. Many WUI fire areas have long histories of wildland fires that burned only vegetation in the past. However, with new development, a wildland fire following a historical pattern may now burn these newly developed areas. WUI fires can occur where there is a distinct boundary between the built and natural areas or where development or infrastructure has encroached or is intermixed in the natural area. WUI fires may include fires that occur in remote areas that have critical infrastructure l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
323
easements through them, including electrical transmission towers, railroads, water reservoirs, communications relay sites or other infrastructure assets.
Consequently, wildland fires that burn in natural settings with little or no development are part of a natural ecological cycle and may actually be beneficial to the landscape. Century old policies of fire exclusion and aggressive suppression have given way to better understanding of the importance fire plays in the natural cycle of certain forest types.
Warning times are usually adequate to ensure public safety, provided that evacuation recommendations and orders are heeded in a timely manner. While in most cases wildfires are contained within a week or two of outbreak, in certain cases, they have been known to burn for months, or until they are completely extinguished by fall rains.
Wildfire poses the greatest risk to human life and property in the Marin County OA’s densely populated WUI, which holds an estimated 69,000 living units. Marin County is home to 23 communities listed on CAL FIRE’s Communities at Risk list, with approximately 80% of the total land area in the county designated as having moderate to very high fire hazard severity ratings.
The county has a long fire history with many large fires over the past decades, several of which have occurred in the WUI. To compound the issue, national fire suppression policies and practices have contributed to the continuous growth (and overgrowth) of vegetation resulting in dangerous fuel loads. The Community Wildfire Protection Plan (CWPP) provides a scientifically based assessment of wildfire threat in the WUI of the Marin County OA.
Fire protection in California is the responsibility of either the federal, state, or local government.
On federally owned land, or federal responsibility areas (FRA), fire protection is provided by the federal government, or in partnership with local agreements. In state responsibility areas (SRA), CAL FIRE typically provides fire protection. However, in some counties CAL FIRE contracts with county fire departments to provide protection of the SRA – this is the case in Marin County, where CAL FIRE contracts with Marin County Fire Department (MCFD). Local responsibility areas (LRA) include incorporated cities and cultivated agriculture lands, and fire protection is typically provided by city fire departments, fire protection districts, counties, and by CAL FIRE under contract to local government.
The MCFD is responsible for the protection of approximately 200,000 acres of SRA within the county and is the primary agency that handles wildland fires. MCFD also provides similar protection services to approximately 100,000 acres of FRA in the Golden Gate National Recreation Area (GGNRA), the Muir Woods National Monument, and the Point Reyes National Seashore.
Figure 3.169 indicates the federal responsibility areas, state responsibility areas and local responsibility areas in the Marin County OA.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
324
Figure 3.169: Federal, State and Local Responsibility Areas in the Marin County OA Source: Marin County OEM
The mix of weather, diverse vegetation and fuel characteristics, complex topography, and land use and development patterns in the Marin County OA are important contributors to the fire l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County
Fire Responsibility Areas
LRA /SRA/ FRA Responsibility Areas
FRA
0 Pelaluma 0
•
OlllCIOf
. . . EMERGENCY
MANAGEMENT
El Verano
Sonoma
San Pablo Bay
Wildlife Area
SRA
LRA
Marin County OEM / Woody Baker-Cohn
email: [email protected] ~ an
Date Printed: 08/08/23 N
County of Marin, (alifomia State Parks, Esrl, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 1(
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
325
environment. The MCFD Woodacre Emergency Command Center currently manages the data from four Remote Automated Weather Stations (RAWS) for predicting fire danger utilizing the National Fire Danger Rating System (NFDRS) during the fire season. The RAWS are located in Woodacre, Middle Peak, Barnabe, Big Rock and a new station will be coming online in Novato.
Marin County is bounded by the cool waters of the Pacific Ocean to the west, the San Francisco and Richardson Bays to the southeast, the San Pablo Bay to the east, and Sonoma County agricultural lands to the north. The combination of these large bodies of water, location in the mid-latitudes, and the persistent high pressure over the eastern Pacific Ocean results in several micro-climates. Weather in the OA consists of warm, dry summers and cool, wet winters. The climate in early fall and late spring is generally similar to the summer, and late fall is similar to winter. Spring is generally cool, but not as wet as the winter. While these general weather conditions are fairly representative of the typical Marin County weather, complex topography, annual variability of weather patterns, and less frequent and transient weather patterns are important to fire conditions.
In the late spring through early fall, the combination of frequent and strong high-pressure systems (known as the Pacific High) over California combined with the cool waters of the ocean/bays results in persistent fog and low clouds along the coast (including over southern Marin County near the San Francisco Bay). The fog often penetrates into the inland valleys of northern and central Marin County, especially during overnight hours. At the coastline, mist from fog can keep the land surfaces modestly moist while inland land surfaces above the fog or inversion are often very dry.
The Pacific High that persists from late spring through early fall over the eastern Pacific, combined with a thermal low pressure over the Central Valley of California, results in an almost continuous sea breeze. These winds usher in cool and moist air and can be strong (15 to 25 mph), especially over the ridge tops and through northwest to southeast lying valleys, including San Geronimo/Ross, Hicks, and Lucas Valleys. These westerly winds are usually highest in the afternoon, decrease in the evening, and are light overnight before increasing again in the late morning/early afternoon.
Occasionally in the summer and more often in the fall, the Pacific High moves inland and centers over Oregon and Idaho, while low pressure moves from the Central Valley of California to southern California and Arizona. The resulting north-to-south pressure gradient can be strong enough to retard the typical sea breeze and can even result in winds blowing from the land to the ocean (offshore winds). As the offshore winds move air from the Great Basin to the coastal areas of California, the air descends and compresses, which greatly warms and dries the air.
Under these “Diablo” wind conditions, temperatures in the Marin County OA can reach 100°F in the inland areas and even 80°F at the coast, and relative humidity can be very low. In addition, wind speeds can be high (20 to 40 mph) and gusty and are often much faster over the mountains and ridge tops such as Mt. Tamalpais, Loma Alta, and Mt. Burdell compared to lowlying areas. Wind speeds can be high over the ridges and mountains at all times of day under this “offshore” wind pattern and are often much slower or even calm at night in low-lying areas because nighttime cooling decouples the aloft winds from the surface winds. It is during these Diablo wind events that there is a high potential for large, wind-driven fires should there be an ignition. Historically, the largest and most destructive fires have occurred during these offshore (also known as Foehn) wind events including the Angel Island and the Vision fires. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
326
A few times per year in the summer and early fall, monsoonal flow from Mexico brings in moist and unstable air over central and northern California, which can result in thunderstorms with or without precipitation. With the otherwise dry summer conditions, the lightning can ignite fires.
These monsoonal flow patterns are usually only one to two-day events.
Beginning in late November and lasting through the end of March, the Pacific High moves south and weakens, allowing storms that originate in the Gulf of Alaska to move over California.
These storms bring precipitation and, at times, strong winds out of the south. Each storm usually results in one fourth inch to several inches of rain over a day or so. Near Mt. Tamalpais, rainfall amounts are enhanced by orographic lifting, resulting in higher rain amounts in the Kentfield and Fairfax areas compared to the rest of the county. Typically, after the first rain in November, the cool weather and occasional storm keeps the ground wet through late Spring.
However, in some years, significant rain does not occur until later in the year (e.g., early-to-late December) and there can be several weeks without any storms and rain. During storms, temperatures are usually mild.
When there are no storms over California, a land-breeze typically forms (i.e., winds blowing from the Central Valley to the Pacific Ocean). These winds can reach 30 mph, and travel through the southeast to northwest lying valleys, over low-lying ridges such as the Marin Headlands, and through the Golden Gate. These winds are usually highest in the mid-morning hours and decrease in the afternoon as the Central Valley warms during the day. The winds are associated with cold and modestly moist air.
In late February/early March through late April, the Pacific High strengthens and moves north, and storms impacting the county become less frequent. During this time of year there is often a low-pressure area over the desert in southwest California. The combination of the Pacific High to the north and low-pressure to the southwest results in strong winds blowing from the northwest to the southeast. Like the sea breeze, these winds bring in cool, moist air and are usually highest in the afternoon hours. Because of winter and spring rains, the land is wet and there is little danger of wildland fire despite the strong winds and only occasional precipitation.
There is often little coastal fog this time of year.
Vegetation, which is also known as fuel, plays a major role in fire behavior and potential fire hazards. A fuel’s composition, including moisture level, chemical make-up, and density, determines its degree of flammability. Of these, fuel moisture level is the most important consideration. Generally, live trees contain a great deal of moisture while dead logs contain very little. The moisture content and distribution of fuels define how quickly a fire can spread and how intense or hot it may become. High moisture content will slow the burning process since heat from the fire must first eliminate moisture.
In addition to moisture, a fuel’s chemical makeup determines how readily it will burn. Some plants, shrubs, and trees such as chamise and eucalyptus (both present in the Marin County OA) contain oils or resins that promote combustion, causing them to burn more easily, quickly, and intensely.
Finally, the density of a fuel influences its flammability; when fuels are close together but not too dense, they will ignite each other, causing the fuel to spread readily. However, if fuels are so close that air cannot circulate easily, the fuel will not burn freely. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
327
The Marin County OA has extensive topographic diversity that supports a variety of vegetation types.
Environmental factors, such as temperature, precipitation, soil type, aspect, slope, and land use history, all help determine the existing vegetation at any given location. In the central and eastern parts of the county, north facing slopes are usually densely wooded from lower elevations to ridge peaks with a mixture of mostly hardwood tree species such as coast live oak, California bay, Pacific madrone, and other oak species. Marshlands are also present throughout the county; once ignited marsh fires can be difficult to contain and extinguish.
Grasslands with a mixture of native and nonnative annual and perennial plant species occur most often in the northern and western parts of the county due to a combination of soil type, lower rainfall, and a long history of ranching. The southern and western facing slopes tend to have a higher percentage of grasslands, which in turn have the potential to experience higher rates of fire spread. Grassland fires are dangerous even without extreme fire weather scenarios due to the rapid rate of fire spread; in some cases, fires spread so quickly that large areas can burn before response resources are able to arrive.
In the west portion of the county closer to the coast, where precipitation is higher and marine influence is greater, most areas are densely forested with conifer species (i.e., Bishop pine, Douglas-fir, and coast redwood) and associated hardwood species. Chaparral vegetation also occurs in parts of the county, especially on steeper south and west facing slopes. This mix of densely forested areas mixed with chaparral results in higher fuel loads and potentially higher fire intensity. Expansion of the residential community into areas of heavier vegetation has resulted in homes existing in close proximity to dense natural foliage; these homes are often completely surrounded by highly combustible or tall vegetation, increasing the potential that wildland fires could impact them.
As part of the development of the CWPP, an updated vegetation map layer was created using the most recent vegetation information available from a variety of state and local data sources.
Vegetation distribution in the Marin County OA is characterized by approximately 20 different types of vegetation which have been classified into 15 fire behavior fuel models. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
328
Figure 3.170: Fuel Model Map for the Marin County OA
Source: Marin Community Wildfire Protection Plan, 2020
Insect infestations and plant diseases, such as California oak mortality syndrome (sudden oak death), are increasing and threaten to change the structure and overall health of native plant communities in Marin County. Sudden oak death has no known cure and is the biggest concern; this syndrome is caused by the fungus-like Phytophthora ramorum, which has led to widespread mortality of several tree species in California since the mid-1990s; the tanoak (Lithocarpus densiflorus) in particular appears to have little or no resistance to the disease. Sudden oak death has resulted in stands of essentially dead trees with very low fuel moistures.
Studies examining the impacts of sudden oak death on fire behavior indicate that while predicted surface fire behavior in sudden oak death stands seems to conform to a common fuel model already in use for hardwood stands, the very low moisture content of dead tanoak leaves may lead to crown ignitions more often during fires of “normal” intensity.
Two other plant diseases prevalent in the Marin County OA are pitch canker (which affects conifers such as Bishop pine and other pine species), and madrone twig dieback (which affects Pacific madrones). Pitch canker is caused by the fungus Fusarium circinatum (F. subglutinans, F. sp. pini), which enters the tree through wounds caused by insects. While some trees do recover, most infected trees are eventually killed by the fungus. Management of this disease largely focuses on containment to reduce the fungus spreading to other trees. Pitch canker is a l ~<;>U·N· TY OF
~ ARIN
Fuel Model
a
~
D 101 : Shoo, Sparse Ory Climate GraH
D 102: Law Load, Dry Climate Grus
D 104: Moderate Load, Dry Climate Grass
LJ 107: High Load. Dry Climate Cren
I=i 121 : Low Loed, Dry Climate Gre.ss-Shrub
Cl 141 : Low Load Dry Chmato Shrub
(:=) 142: Moderate lood Df"/ Chmate Shrub
145· H~h LoOO, Ory Climate Shrub
CJ 147. Very High Load. DryCC.rnatc Sh1ub
165· Very Hioh Load. Ory Climate Timber~Shn.Jb
1 tl1 -tow Lo AA Comp:w.:t Conifer Liner
18'2· I ow l,o;.d RroMtleaf I Iner
- 166: Moderat~ Load Broadleaf Litter
- 189: Very High Lo.ad Oroad!eaf Litter
- 91 : Urban.1
Developed
98: Open 'Nater
c::J 99. Bart:" G11)und
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
329
particular issue in the NPS lands of Pt. Reyes National Seashore, where many acres of young Bishop Pines that were seeded on the Inverness Ridge by the Mount Vision Fire of 1995 have been infected.
These dead and dying trees have created large swaths of land with dense and dry fuel loads.
Madrone twig dieback is caused by the native fungus Botryosphaeria dothidea and appears to be getting worse throughout the county due to drought effects on Pacific madrones. Three additional threats to trees common to the Marin County OA include:
• Bark and ambrosia beetles (Monarthrum dentiger and monarthrum scutellare), which target oak and tanoak trees. Sudden oak death may be exacerbating the effects of beetle infestations which prey on trees already weakened by this disease. • Root rot, caused by oak root fungus (Armillaria mellea), is primarily associated with oaks and other hardwoods but also attacks conifers. These fungal infestations cause canopy thinning and branch dieback and can kill mature trees. As with the beetle infestations, sudden oak death may be exacerbating the effects of root rot fungus in the county forests.
• Velvet-top fungus (Phaeolus schweinitzii) is a root rot fungus affecting Douglas-fir and other conifers, with the infection typically occurring through a wound.
Topography characterizes the land surface features of an area in terms of elevation, aspect, and slope. Aspect is the compass direction that a slope faces, which can have a strong influence on surface temperature, and more importantly on fuel moistures. Both elevation and aspect play an important role in the type of vegetation present, the length of the growing season, and the amount of sunlight absorbed by vegetation. Generally, southern aspects receive more solar radiation than northern aspects; the result is that soil and vegetation on southern aspects is warmer and dryer than soil and vegetation on northern aspects. Slope is a measure of land steepness and can significantly influence fire behavior as fire tends to spread more rapidly on steeper slopes. For example, as slope increases from 20 – 40%, flame heights can double and rates of fire spread can increase fourfold; from 40 – 60%, flame heights can become three times higher and rates of spread can increase eightfold.
The Marin County OA is topographically diverse, with rolling hills, valleys and ridges that trend from northwest to southeast. Elevation throughout the county varies considerably, with Mt.
Tamalpais’ peak resting at 2,574 feet above sea level and many communities at or near sea level. Correspondingly, there is considerable diversity in slope percentages. The San Geronimo Valley slopes run from level (in the valley itself) to near 70%. Mt. Barnabe has slopes that run from 20 to70%, and Throckmorton ridge has slopes that range in steepness from 40 – 100%.
These slope changes can make fighting fires extremely difficult.
In the WUI where natural fuels and structure fuels are intermixed, fire behavior is complex and difficult to predict. Research based on modeling, observations, and case studies in the WUI indicates that structure ignitability during wildland fires depends largely on the characteristics and building materials of the home and its immediate surroundings.
The dispersion of burning embers from wildfires is the most likely cause of home ignitions.
When embers land near or on a structure, they can ignite near-by vegetation or accumulated debris on the roof or in the gutter. Embers can also enter the structure through openings such as an open window or vent and could ignite the interior of the structure or debris in the attic. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
330
Wildfire can further ignite structures through direct flame contact and/or radiant heat. For this reason, it is important that structures and property in the WUI are less prone to ignition by ember dispersion, direct flame contact, and radiant heat.
Public Safety Power Shutoff (PSPS) Events
As a result of the 2017 Northern California Wildfires, the 2018 Camp Fire in Butte County and other wildfires caused by power line infrastructure, Pacific Gas & Electric (PG&E) began initiating Public Safety Power Shutoff (PSPS) events in their service areas (including Marin County) to help prevent the start of future wildfires. PG&E will initiate a PSPS if conditions indicate potentially dangerous weather conditions in fire-prone areas due to strong winds, low humidity, and dry vegetation. During these events, PG&E will proactively turn off power in high fire risk areas to reduce the threat of wildfires. The most likely electric lines to be considered for a public safety power outage will be those that pass through areas that have been designated by the California Public Utilities Commission (CPUC) High Fire-Threat District at elevated (Tier 2) or extreme risk (Tier 3) for wildfire. Customers outside of these areas could have their power shut off, though, if their community relies upon a line that passes through a high fire-threat area or an area experiencing severe weather. PG&E will consider numerous factors and analyze historical data to help predict the likelihood of a wildfire occurring, and closely monitoring weather watch alerts from the National Weather Service (NWS). These factors generally include, but are not limited to:
• A Red Flag Warning declared by the National Weather Service • Low humidity levels, generally 20 percent and below
• Forecasted sustained winds generally above 25 mph and wind gusts in excess of approximately 45 mph, depending on location and site-specific conditions such as temperature, terrain and local climate
• Condition of dry material on the ground and live vegetation (moisture content) • On-the-ground, real-time observations from PG&E's Wildfire Safety Operations Center and field crews
Pacific Gas & Electric Company (PG&E) operates a total of 1,179 miles of overhead electricity transmission and distribution lines in the Marin County OA. Overhead electricity lines and poles can be damaged or downed under severe weather conditions, particularly severe wind conditions, which increases the potential for wildfire ignition. 52 percent of PG&E’s overhead distribution lines and 41 percent of its overhead transmission lines are located in CPUCidentified High-Fire Threat Districts subject to elevated or extreme fire risk. PG&E is currently planning and implementing safety measures to prevent wildfires and reduce the impacts of Public Safety Power Shutoff (PSPS) events on communities in the Marin County OA and throughout California.
These measures include installing weather stations; installing high-definition cameras; installing sectionalizing devices on its overhead lines to separate the grid into smaller sections; hardening the system by installing stronger power poles, covering lines, and undergrounding lines in targeted areas; creating temporary microgrids to provide electricity during PSPS events; and enhancing existing vegetation management activities. From 2018 to July 2021, PG&E hardened three miles of overhead lines, installed 68 transmission and distribution sectionalizing devices, completed enhanced vegetation management on approximately 51 of overhead line miles, installed 28 weather stations, and installed 12 high-definition cameras in the Marin County OA. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
331
Location and Previous Occurrences
In the time before the county was settled, fire was a natural part of the ecosystem. Much of the vegetation in what is now the wildlands of Marin County depended on fire to renew itself by removing old, dead fuel in order to make room for healthy new vegetation and promote the growth of native plant species. Once the land was settled, business operators, landowners, and homeowners had an interest in protecting the natural assets of Marin County and their own investments. Uncontrolled fires had already burned large tracts in the past and valuable lumber, structures, and field crops had been destroyed. A series of fires that occurred in the late 1800s prompted the organization of the first fire departments in Marin County around the turn of the century.
Since then, national fire suppression policies and practices (among other factors) have contributed to the continuous growth (and overgrowth) of vegetation resulting in dangerous fuel density, or fuel loads. Combined with this fuel accumulation, people have been building homes closer and closer to wildlands, which is creating the WUI fire issues that are now present in many parts of Marin County and the country.
Figure 3.171: Wildfire Ignition Points in the Marin County OA Source: Marin Community Wildfire Protection Plan, 2020
Homes and structures located anywhere in and around the WUI are at a higher risk for exposure to wildland fire. Fire can spread rapidly throughout WUI areas through adjacent structures and/or vegetation, or by ember dispersion. Property owners in the WUI have a l ~<;>U·N· TY OF
~ ARIN
a
~
Legend
Fire Ignition Type
0 other
0 Structu re
e Vegetation
e Veh icle
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
332
responsibility to prepare their property for structure defense by providing adequate defensible space and complying with WUI building codes and ordinances. The WUI boundaries for Marin County were determined based on areas with high structure density and proximity to areas with a high density of burnable fuels.
Figure 3.172: WUI Boundary in the Marin County OA
Source: Marin Community Wildfire Protection Plan, 2020
Approximately 60,000 acres—18% of the county’s land area—falls within the wildland urban interface (WUI) where residences (i.e., homes and structures) are intermixed with open space and wildland vegetation. Within Marin County, there are 96,195 parcels and 106,679 living units; of these living units, an estimated 69,000 units are located in the WUI. A recent assessment by the Marin County Fire Department (MCFD) revealed that these living units within the WUI are valued at $59 billion (Marin County Fire Department, 2015). Because of the mix and density of structure and natural fuels combined with limited access and egress routes, fire management becomes more complex in WUI environments. In Marin County specifically, many of the access roads within the WUI are narrow and winding and are often on hillsides with overgrown vegetation, making it even more difficult and costly to reduce fire hazards, fight wildfires, and protect homes and lives in these areas.
To quantify the potential risk from wildfires, CalFire has developed a Fire Hazard Severity Scale which uses three criteria in order to evaluate and designate potential fire hazards in wildland l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
333
areas. The criteria are fuel loading (vegetation), fire weather (winds, temperatures, humidity levels and fuel moisture contents) and topography (degree of slope). In 2022, CalFire began the process of updating the 2007 map of the Fire Hazard Severity Zones (FHSZ) statewide. It is projected that the Very High Fire Severity Zone (VHFSZ) will grow significantly in the Mount Tamalpais watershed area between Mill Valley and Muir Beach, and in the area of Inverness and Marshall. Most of western Marin County that used to fall under the Moderate Fire Severity Zone (MFSZ) is projected to change to High Fire Severity Zone (HFSZ). As the new FHSZ maps are still pending final approval as of 2023, the Marin County OA has been advised by CalFire to use the 2007 FHSZ maps as current for wildfire analysis in the 2023 Marin County OA MJHMP. The updated FHSZ maps planned for final approval in 2024 will be used for wildlife analysis in the 2028 Marin County OA MJHM. Figure 3.173 shows the current 2007 map of the FHSZ for Marin County.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
334
Figure 3.173: Fire Hazard Severity Zones (FHSZ) in the Marin County OA Source: Marin OEM, CALFIRE
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / Full County DfllctOI
Fi re Severity EMERGENCY
MANAGEMENT
/
(
1 I
I
/
/
/
r---- _J
--·-----,./
Legend
Fire Severity Zone
Very High
High
Moderate
Non-Wildland/NonUrban
C Urban Unzoned
10 1
\
p
115
0 Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 09/27/23
121
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, (alifornia State Porks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 12 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
335
Figure 3.174: Marin County Wildfire Susceptibility to Critical Facilities Source: Marin County OEM
l ~<;>U·N· TY OF
~ ARIN
a
~
I
\
> (
I
I
I
/
I
• Dams Military and Ovll
Defense Installations
Communication
Facilities
Electric Power Fadlitles
Wastewater Facilities
• Water Supply Facilities
•
•
Legend
Airports
Emergency Operations
Center.;
Fire Stations
Hospitals and Medical
Fadhties
Police / She<iff Stations
SChools
Marin County
Fire
DIIICIOI
EMERGENCY
MANAGEMENT
101
• • •
•
•
•
Fire Severity Zone
Very High
High
Moderate
Non-Wildland/NonUrban
,---, Urban Unzoned
•
•
•
0 2.5
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/30/23
12 21
37 N
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, califomia State Parks, Esri, HERE, Garmin, SafeGraph, FAO, METI/NASA, USGS, Bureau of Land Management, EPA, NPS 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
336
As of 2007, several unincorporated communities in Marin County lie in moderate to very high wildfire hazard severity zones, which are shown below.
Figure 3.175 shows the fire hazard severity zones in and around Lagunitas, Forest Knolls and San Geronimo.
Figure 3.175: Fire Hazard Severity Zones – Lagunitas, Forest Knolls, San Geronimo and Woodacre Source: CalFire, 11/27/23
Figure 3.176 shows the fire hazard severity zones in and around Woodacre.
Figure 3.176: Fire Hazard Severity Zones –Woodacre
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
'\ \;
" ( \
l
,,. ,
I ., ·--,
\
' ' ·-.... ·,
.,\ '-, ,/
'I
f
·-"" ✓-
_ .........
\.
i
J
I
1-.1.-
°""'"1<,w.~ ....,,,. ·"·• .I
\ !
/ I ,
I \ ·--,/ I
'\ \
l
\ ' \
i \
\ "
', ...
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
337
Figure 3.177: Fire Hazard Severity Zones –Woodacre Area Source: CalFire
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / Wood acre Area
Fire •
omc101
EMERGENCY - MANAGEMENT
. Forest Knol ls agunitas ,
r
San _,..,..., Geron imo ,,. -,_
l.1,,...--i_.t
Gary Giacomini
Open Space
Legend
e Dams
Electric Power Facilities
Emergency Operations
Centers
Fire Stations
Schools
Fire Severity Zone
Very High
- High
Moderate
Sir Francis ora\<e eivd
I _,.,.~.,.wood acre
,> 0'
m r=:- 7
7 C ,.,__
l
Meadow
Country Club
l _J
J ,..1-
,,,~__, C ) IC
0.3 0.7 '1 -" U 3
••-===-••111111111111!1!,Miles , .... ,,.,,nr
Marin County OEM / WoodyL Bak1er-Cohn
email: [email protected] 1
Date Printed: 10/30/23 ,..,.r ~ N
le
'-i
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METJ/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA ' 7----" J
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
338
Figure 3.178 shows fire hazard severity zones in and around Nicasio.
Figure 3.178: Fire Hazard Severity Zones – Nicasio
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
tw
'c~
~~
l.
... r~,-, .,., c-
.-11, ii Y.-·I
r.,-,:.-
,,
i,,,: , .J F..: ..al
I. ~,•tr,.11 I ,h·.,
EJA.hull
-.1 • 1r,1r .-,
l,h,n -I 11 ..,. 1'1-•••
L L.L .. , \.'iJIIC!J Rd
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
339
Figure 3.179 shows the fire hazard severity zone in and around Tocoloma.
Figure 3.179: Fire Hazard Severity Zones – Tocoloma
Source: CalFire, 11/27/23
1 ~<?U·N· TY OF a
~ ARIN ~
... r,rn ,ir:i,1 -...
'I.:.iJJ
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
340
Figure 3.180 shows the fire hazard severity zones in and around Olema.
Figure 3.180: Fire Hazard Severity Zones – Olema
Source: CalFire, 11/27/23
Figure 3.181 shows the fire hazard severity zones in and around Point Reyes Station. l ~<;>U·N· TY OF
~ ARIN
a
~
--~----~--------~--~,------ ----------------------,
.I
I
\
\
\
\
\
f
1 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
341
Figure 3.181: Fire Hazard Severity Zones – Point Reyes Station Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
1 ' ¥:-,Y'
[llu~ Ro«"
j
' ': .tflp~(I~ ~·,#-YJ-=-~.~ •
,,
I ,,
\
"
j
I
I
\ .,.,.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
342
Figure 3.182 shows the fire hazard severity zones in and around Inverness Park.
Figure 3.182: Fire Hazard Severity Zones – Inverness Park Source: CalFire, 11/27/23
l ~ <;>U·N· TY OF
~ ARIN
r
j
a
~
I
.1
l
arrinelli
Ranch
(GGNRA)
~ "\ ~~~ .. ':S'C"r.
'.l;G' 1,.
\
~
~~ q_
°"~i,:
"o'-'"
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
343
Figures 3.183 and 3.184 show the fire hazard severity zones in and around Inverness.
Figure 3.183: Fire Hazard Severity Zones – Inverness
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
. .
.
.
.
--e
a
~
,:/..,.
---------~ / \)
E ,,
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
344
Figure 3.184: Fire Hazard Severity Zones – Inverness Area Source: CalFire
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / Woodacre Area
Fire
Seahaven
e omc101
EMERGENCY
• MANAGEMENT
Millerton
Communication
Facilities
Fire Stations
Schools
Legend
Invern ess
,6
High
Moderate
Non-Wildland/NonUrban
• Tamales Bay
And Misc
0 0.2 0.4
Tc _
(Fish
0.8 M iles
,ma, s Bay
,:;alt.
ser
Bi
Fire Severity Zone
- Very High
Marin County OEM / Woody Baker-Cohn
email:
Date Printed:
[email protected]
10/30/23 ~ N
County of Marin, California State Parks, Esri, HERE, Garmin, SafeGraph, Geo Technologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, NPS, USDA, County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, GeoTechnologies, Inc, METI/NASA, USGS, Bureau of Land Management, EPA, 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
345
Figure 3.185 shows the fire hazard severity zone in and around the Marconi/Marshall Area.
Figure 3.185: Fire Hazard Severity Zones – Marconi/Marshall Area Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
CI\ I
\
(
\ '~ :;!~
\
\
~ ,\ .. . ,,
...
\ __ ~
MmcorJ
cantt:trence
C'"..t:1"1tmSlah,
Hle:.ooc Pork
~ '- • ~ '}
··'
c,,,~G
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
346
Figure 3.186 shows the fire hazard severity zones in and around the McDonald/Blakes Landing area.
Figure 3.186: Fire Hazard Severity Zones – McDonald/Blakes Landing Area Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
7 \
,.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
347
Figure 3.187 shows the fire hazard severity zone in and around the Tomales area.
Figure 3.187: Fire Hazard Severity Zones – Tomales
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
I
j
l
J
I CA1
__ ,..,,.
'
"' i.:.. . t..:'
I
f
_., !J
I 1
f
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
348
Figure 3.188 shows the fire hazard severity zone in and around the Dillon Beach area.
Figure 3.188: Fire Hazard Severity Zones – Dillon Beach Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
'··-·· ···-·····--······--·'
.. Suiji:1"1:al
H5rn
'
'
'~'if~,u~II I
, ~ ___ .....
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
349
Figure 3.189 shows the fire hazard severity zones in and around the Dogtown area.
Figure 3.189: Fire Hazard Severity Zones – Dogtown
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
BoJ111 as R cl
ll <>lln_.•
lagoon
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
350
Figure 3.190 shows the fire hazard severity zones in and around the Bolinas area.
Figure 3.190: Fire Hazard Severity Zones – Bolinas
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
. .,-.. i~t,,_ ... · ..... __ ., m~
Bofinas
lagoon
Open Space
Preserve
Solinas
to9oot1
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
351
Figure 3.191 and Figure 3.192 shows the fire hazard severity zone in and around the Stinson Beach area.
Figure 3.191: Fire Hazard Severity Zones – Stinson Beach and Surrounding Area Source: CalFire, 11/27/23
Figure 3.192: Fire Hazard Severity Zones – Stinson Beach Source: CalFire, 11/27/23
1 ~<?U·N· TY OF a ~ ARIN ~~-~:~----~
""--............... io....... .........
\
,£_;;,i:;CJ11~<1.(.,~->,
q/.._f,
\ •••M••o,"'
'i
i
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
352
Figure 3.193 shows the fire hazard severity zone in and around the Muir Beach area.
Figure 3.193: Fire Hazard Severity Zones – Muir Beach
Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
a
~
Muir Beach
..... ~Drive
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
353
Figure 3.194 shows the fire hazard severity zones in and around Tamalpais Valley and Marin City.
Figure 3.194: Fire Hazard Severity Zones – Tamalpais Valley and Marin City Source: CalFire
l ~<;>U·N· TY OF
~ ARIN
a
~
Marin County / Mill Valley Area
Fire
OIRCf 01
EMERGENCY
MANAGEMENT
ea ows
Corte Madera
Mill Valley
Tamalpais Valley
Tamalpais
Valley
Legend
Communication
Facilities
Wastewater Facilities
Airports
Emergency Operations
Centers
Fire Stations
Hospitals and Medical
Facilities
Police/ Sheriff Stations
Schools
Fire Severity Zone
Very High
High
Moderate
Non-Wildland/NonUrban
LJ Urban Unzoned
0, a.itt
Marin City
0 0.3 0.6 1.1
Miles
Marin County OEM / Woody Baker-Cohn
email: [email protected]
Date Printed: 10/30/ 23
d.
County of Marin, california State Parks, Esri, HERE, Garmin, SafeGraph, GeoTechnologles, Inc, METJ/NASA, USGS, Bureau of land Management, EPA, NPS, USD 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
354
Figure 3.195 shows the fire hazard severity zone in and around the unincorporated area of the Tiburon Peninsula, including Paradise Cay.
Figure 3.195: Fire Hazard Severity Zone – Unincorporated Tiburon Peninsula and Paradise Cay Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
'ng Mountain
Open Space
Preserve
a
~
.,."i,,·'· .. ,-~-- -,--.\ u,
:~ /--.,._.-: .
. J Aln~1~•~;1.o,n
~
V ~,,.._,_
..... ,
lll"charris6tt
..
\
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
355
Figure 3.196 shows the fire hazard severity zone in and around San Quentin.
Figure 3.196: Fire Hazard Severity Zones – San Quentin
Source: CalFire, 11/27/23
Figure 3.197 shows the fire hazard severity zones in and around Lucas Valley and Marinwood.
Figure 3.197: Fire Hazard Severity Zones – Lucas Valley and Marinwood Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN e
I-
[
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
356
Figure 3.198 shows the fire hazard severity zones in and around the unincorporated area of Bel Marin Keys and Loma Verde.
Figure 3.198: Fire Hazard Severity Zone – Bel Marin Keys and Loma Verde Source: CalFire
l ~<;>U·N· TY OF
~ ARIN
a
~
idian Vall+?y College of Marin
Indian Valley
Campus - Marin
Community
College District
Electric Power Facilities
Emergency Operations
Centers
Fire Stations
Marin County / Novato South
Fire
Fire Severity Zone
Very High
e omcto1
EMERGENCY
• MANAGEMENT
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
357
Figure 3.199 shows the fire hazard severity zone around San Antonio and the Marin County airport.
Figure 3.199: Fire Hazard Severity Zone – San Antonio & Marin County Airport Source: CalFire, 11/27/23
l ~<;>U·N· TY OF
~ ARIN
l
!
_,,.,.,
a
~
GJamrnli
State Hiscoric
Par~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
358
Figure 3.200 shows the number of state and federal declared wildfire disasters in Marin County in relation to the rest of California.
Figure 3.200: Historic Wildfires in the Marin County OA 1919 - 1995 Source: Marin Community Wildfire Protection Plan
Throughout its history, Marin County has experienced many wildland fires. Figure 3.201 shows a map of large fires that have occurred in Marin County’s unincorporated WUI. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
359
Figure 3.201: Historic Wildfires in the Marin County OA 1973 - 2020 Source: Marin Community Wildfire Protection Plan
9/14/1904 – A wildfire burned 15,000-20,000 acres on Bolinas Ridge. 10/1917 – A wildfire burned 2,000 acres on a ridge near the unincorporated community of Inverness.
7/8/1913 – A wildfire started by a train or a discarded cigarette burned over 1,500 acres on Mount Tamalpais and threatened the City of Mill Valley. 9/17/1923 – September 1923 Wildfire
A wildfire started in the unincorporated community of Ignacio and threatened or destroyed thousands of homes around the unincorporated communities of Ignacio, Woodacre, Lagunitas, and Bolinas Ridge. Thirty-five homes were destroyed in Woodcare, leaving only five left standing. Large areas of timber and grazing land burned. Damage was estimated at $250,000. 9/27/1945 – The Mill Fire
Two brush fires merged together near the unincorporated community of Lagunitas and quickly spread across Bolinas Ridge coming within a quarter mile of the unincorporated community of Stinson Beach. The unincorporated community of Woodacre and the Town of Fairfax were threatened, with over 3,000 residents put on alert for evacuation. Over 18,000 acres burned. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
360
9/1965 – Chileno Valley Fire
Over 8,000 acres burned and several ranches were destroyed in a wildfire. 10/3-10/16/1995 – The Vision Fire
A wildfire started from an illegal campfire burned over 12,000 acres in Point Reyes National Seashore and destroyed 48 structures in the unincorporated community of Inverness.
Figure 3.202: 1995 Vision Fire
Source: Richard Blair
10/13/2008 – Angel Island Fire
A human-caused wildfire burned over 300 acres on Angel Island in Angel Island State Park. No structures were destroyed.
8/27/2019 – Spirit Fire
A wildfire started by arson burned 16 acres above the Sprit Rock Meditation Center near Woodacre.
10/24/2019 – Muir Fire
A 58-acre wildfire burned between the unincorporated communities of Muir Beach and Stinson Beach, closing Highway 1.
8/17/2020 – Woodward Fire
A wildfire burned over 700 acres in a remote area of Point Reyes National Seashore, causing evacuation warnings in the unincorporated community of Olema. 7/14/2021 – Dolcini Fire
A wildfire burned over thirty acres west of Novato.
9/6/2021 – Lucas Valley Wildfire
A wildfire started by a lawn mower burned over 40 acres, prompting evacuations in parts of the unincorporated communities of Lucas Valley and Marinwood.
As part of the CWPP, Ignition data for all authorities having jurisdiction were acquired and analyzed for 2002 through 2011 to evaluate ignition trends within the county. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
361
Impacts
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. Urban wildfires often occur in the WUI, where development has expanded into the rural areas. A wildfire in the WUI can result in major losses of property and structures. Also of significant concern to the planning area are the secondary impacts associated with a large burn area. Wildfires can have devastating effects on watersheds through loss of vegetation and soil erosion, which may impact the County by changing runoff patterns, increasing sedimentation, reducing natural and reservoir water storage capacity, and degrading water quality. These problems can be compounded by climate conditions.
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. In some cases, the economic impact of this loss of services may be comparable to the economic impact of physical damages or, in some cases, even greater. 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. Threats to healthcare, hazmat releases, ash deposition on properties (including schools), need for proper cleanup, and high costs of hazardous waste cleanup. Both environmental and economic losses occur from contamination of properties which grow produce, both for personal sustenance and commercial distribution.
Wildfires and subsequent smoke can have a negative impact on tourism and visitor use in the County. Wildfires can also cause major damage to power plants and power lines needed to distribute electricity to operate facilities.
Urban structural fires release toxic pollutants into air and water, cause injuries and deaths, mental/behavioral health issues, economic loss consequences of loss/damage to residences or places of business, displacement, cleanup costs to communities and governments, potential increased healthcare utilization due to injuries or chronic disease exacerbations, long term public health impacts including injuries to the response personnel.
There is also a mitigation opportunity. Even though smoke detectors are required in CA, there is no data on how many residential units in CA do not have a smoke detector, whether they have functioning smoke detectors, and whether residents are aware where to place them and how to maintain them. Conducting a rapid community assessment using established methods is one way to gather this information, which could be considered a mitigation action.
Poor air quality can result from wildfires. Sensitive individuals including the very young, elderly and those with respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) are at the greatest risk of developing aggravated symptoms such as coughing, watery and itchy eyes, headache, scratchy throat, and difficulty in breathing.
PSPS events can have numerous impacts on residents who rely on electricity for cooling their homes, powering water pumps, keeping critical medical equipment operating, and who have other critical needs. These impacts can become exacerbated during a period of higher temperatures, when community members are unable to cool their homes. PSPS events sometimes occur with little to no warning, and with no clear timeframe on how long the event may last, which presents a challenging situation for community members to be able to prepare for prolonged power outages.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
362
Extent and Probability
Wildfire threat can be defined as the result of an analysis of potential fire behavior and the likelihood of fire to occur relative to the assets (or communities) at risk. Recent research indicates that higher summer temperatures will likely increase fire severity in California. Future changes in fire frequency and severity are difficult to predict; however, regional climate change associated with elevated greenhouse gas concentrations could alter large weather patterns and produce conditions conducive to extreme fire behavior. A warmer climate will bring drier winters and higher spring temperatures. Combined with drought conditions, this leads to drier soils in early summer, drier vegetation, and an increase in the number of days in the year with flammable fuels, all which further raise the likelihood of fires.
The western U.S. is likely to continue its trend toward warmer and drier conditions, on average, with warmer spring and summer temperatures, reduced snowpack and earlier snowmelts, and longer, drier summer fire seasons. Models and observations, including reconstructions of fire and climate in the past; trends over the last few decades; and predictive models, predict that warming and drying conditions are likely to cause increased fire activity in the future.
Table 3.20: Marin County OA Hazard Risk Assessment – Wildfire Jurisdiction
Probability/
Likelihood
of Future
Events
Geographic
Extent
Magnitude/
Severity
Climate
Change
Influence
Significance Risk
Score
Marin County Highly
Likely Significant Severe High High 16.00
City of
Belvedere
Highly
Likely Limited Extreme Medium High 15.00
Town of
Corte Madera Occasional Significant Extreme High High 15.00 Town of
Fairfax
Highly
Likely Significant Severe Medium Medium 14.00
City of
Larkspur Likely Significant Extreme High High 16.00
City of Mill
Valley Likely Extensive Extreme High High 17.00
City of
Novato Likely Limited Weak Medium Medium 10.00
Town of
Ross Likely Extensive Severe Medium High 15.00
Town of
San Anselmo Likely Extensive Extreme High High 17.00
City of
San Rafael Likely Significant Severe High Medium 14.00
City of
Sausalito Occasional Limited Moderate High Medium 11.00 Town of
Tiburon
Highly
Likely Significant Severe High High 16.00
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
363
Bolinas
Public Utility
District
Occasional Extensive Severe High Medium 14.00
Las Gallinas
Valley
Sanitary
District
Likely Negligible Moderate Medium Medium 10.00
North Marin
Water
District
Occasional Extensive Extreme Medium High 15.00
Southern
Marin Fire
District
Occasional Extensive Severe High Medium 15.00
Table 3.20: Marin County OA Hazard Risk Assessment – Wildfire Source: Profiled Jurisdictions and Districts
Vulnerability
While the Cal Fire FHSZ maps are useful in examining potential fire hazard severity at the state level, the underlying data and methods used to develop the FHSZ maps can be improved upon by using local (and more recent) fuel characteristics and improved fire modeling methods. The Cal Fire FHSZ maps also do not take into account local perspectives and priorities regarding communities at risk and areas of concern.
To improve upon the currently available state-level fire hazard assessment information, an independent hazard, asset, risk assessment was performed to help identify and prioritize areas within the county that are potentially at a high threat from wildfire based on more recent fuels data, advanced modeling techniques, and local input. The assessment was performed by modeling potential fire behavior and the probability or likelihood that an area will burn given an ignition. Next, the fire modeling output was combined with areas of concern and assets at risk.
Composite maps were generated indicating relative potential fire hazards throughout the county.
Assets at risk are defined as structures and resources that can be damaged or destroyed by wildland fire. Assets in the Marin County OA include real estate (homes and businesses), all types of healthcare facilities, emergency communication facilities, transportation and utility infrastructure, watersheds, protected wildlands, tourist and recreation areas, and agricultural lands. In addition to providing a framework for protecting community members and providing for firefighter safety, the California Fire Plan identifies the following assets warranting consideration in pre-fire planning: watersheds and water; wildlife; habitat; special status plants and animals; scenic, cultural and historic areas; recreation; rangeland; structures; infrastructure; and air quality.
There are approximately 111,000 living units in the Marin County OA with a median home value of approximately $1 million. As many homes in the county are located in the WUI, if a major wildland fire were to result in the loss of many homes, it could have a short-term negative impact on the Marin County OA’s property tax base.
The Mt. Tamalpais watershed supplies central and southern Marin County with 75% of their fresh water. Given the area’s seasonal rainfall, any major wildfire impacting the heavily forested watershed will result in major silting and subsequent degradation of water quantity and quality in l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
364
the watershed. These watershed lands—as well as the lands managed by Marin County Open Space District (MCOSD), state parks, and NPS—are largely contiguous. They harbor several endangered, threatened, and special-status species, including the coho salmon and northern spotted owl.
The area is also part of a major migrating bird flyway and nesting area. The Marin County OA is also a major tourist destination. Major parks within Marin County include California State Parks (Mt. Tamalpais, Samuel P. Taylor, and China Camp), NPS’s Golden Gate National Recreation Area (GGNRA), Muir Woods National Monument, and Point Reyes National Seashore. The Point Reyes National Seashore and Muir Woods National Monument together attract 3.5 million visitors annually. The GGNRA, a majority of which resides within Marin County, attracts an additional 14.9 million visitors per year and contributes an estimated $365.2 million annually to the economy. A major wildfire affecting any of these parks could have negative impacts on the local economy for years after the event.
The Marin County OA’s agricultural land base includes nearly 137,000 acres of privately owned agriculturally zoned land and 32,000 acres of federally-owned land that is leased to agricultural operators. Agricultural operations include livestock and livestock products; aquaculture; field crops; fruit, vegetable, and nursery crops. The gross value of all agricultural production was approximately $101 million in 2014. To help protect people and property from potential catastrophic wildfire, the National Fire Plan identifies communities that are at high risk of damage from wildfire. These high-risk communities identified within the WUI were published in the Federal Register in 2001. In California, CAL FIRE has the responsibility for managing the list. With California's extensive WUI situation, the list of communities extends beyond just those adjacent to Federal lands; there are 1,329 communities currently on the California Communities at Risk List. The Marin County OA has 23 of these at-risk communities. A countywide assessment of the wildland fire threat undertaken by CAL FIRE revealed that nearly 313,000 acres (approximately 82% of the total land area of the county) are ranked as having moderate to very high fire hazard severity zone ratings.
Using the methodology described in the CWPP, a series of models of the hazards, assets, and risks were completed. One model was the average fire season flame length, with lengths above 8 feet possibly exhibiting the more extreme fire behavior and be relatively more hazardous from a fire suppression perspective. Rate of spread is defined as the rate of forward spread of the fire head expressed in feet per minute. The higher the rate of spread, the more difficult a fire is to suppress. A composite map of the flame length, rate of spread, and population density for the average fire season scenario is shown in Figure 3.203; orange and red show areas where more extreme fire behavior is likely given an ignition.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
365
Figure 3.203: Population Density, Flame Length, and Rate of Spread for the Average Fire Season in the Marin County OA
Source: Marin Community Wildfire Protection Plan, 2020 0 2.5 Legend
5 t Miles
Composite Map
Average Fire Season
10 11111 Very High Flame Le"glh, Rate of Spread, & Pop. Density == High Flame Lengtli, Rate of Spread, & Pop. Densrty 1111 Moderate Flame Len,gth, Rate •Of Spre.id, & Pop. Oensi UG .Pf ..
"'"
,nh
·)>
;;,c -< --<
z~
Cf)
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
366
Figure 3.204 shows areas of concern for the average fire season in the OA where fuel reduction and hazard mitigation efforts might be focused.
Figure 3.204: Areas of Concern for the Average Fire Season in the Marin County OA Source: Marin Community Wildfire Protection Plan, 2020
l ~<;>U·N· TY OF
~ ARIN
a
~
Areas of Concern
Relative Ranking
Average Fire Season
- V<>ryhigh
High
- Mod<>.rat<>.
N
A
0 2.5 5 Moles
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
367
Figure 3.205 shows areas of concern for the average fire season in the OA where fuel reduction and hazard mitigation efforts might be focused.
Figure 3.205: Areas of Concern for the Extreme Fire Season in the Marin County OA Source: Marin Community Wildfire Protection Plan, 2020
Unincorporated rural areas within the OA include the coastal communities of Muir Beach, Stinson Beach, and Bolinas; communities near Tomales Bay including Olema, Point Reyes Station, Inverness, Inverness Park, Marshall, Tomales, and Dillon Beach; and rural areas in the interior valleys including Nicasio, Lagunitas, Forest Knolls, San Geronimo, and Woodacre.
These communities are primarily situated within or adjacent to the WUI, with moderate to dense concentrations of structures. The Marin County OA has approximately 60,000 acres of WUI adjacent to 200,000 acres of watershed. Response times in these communities present significant challenges to keeping fires from directly impacting the communities and sub divisions (especially those within the SRA) as emergency fire access and evacuation egress is limited by narrow, winding roads lined with dense vegetation. Figure 3.206 shows the WUI boundary and population density in the OA.
l ~ <;>U·N· TY OF
~ ARIN
a
~
Areas of Concern
Relative Ranking
Extreme Fire Conditions
- VeryHigh
High
- Moderate
N
A
2.S
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
368
Figure 3.206: WUI Boundary and Population Density in the Marin County OA Source: Marin Community Wildfire Protection Plan, 2020
In the Marin County OA, cul-de-sacs generally service new housing developments and most of the smaller canyons, valleys, and hillsides. Some planned unit developments are served by privately- maintained roads, which create access issues (i.e., narrow paved widths and limited on-street parking). According to California Fire Code specifications, roadways that are considered hazardous in terms of fire access and protection are those with • less than 20 feet of unobstructed paved surface and 13.6 vertical feet; • dead-ends longer than 800 feet, and;
• cul-de-sac diameter less than 68 feet.
Driveways that are less than 16 feet wide or that do not have adequate turnaround space are also considered hazardous. A large number of roadways and driveways in many of the Marin County OA’s communities fall into one or more of the above categories.
Several communities in the Marin County OA lie partially or completely in a High and/or Very High FHSZ and could have a higher susceptibility to wildfire. They are highlighted below.
While most of Lagunitas, Forest Knolls San Geronimo and Woodacre lie in a Moderate FHSZ, the surrounding foothills lie in a High FHSZ. There are hundreds of homes in the High FHSZ along with the Woodacre PG&E substation that could have higher susceptible to wildfire. There are hundreds of homes and numerous businesses and critical facilities including the San l ~<;>U·N· TY OF
~ ARIN
a
~
Legend
G'l5 ll'A.II Boundary
Population Density j2010 total population/sq. mile)
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
369
Geronimo Community Center, San Geronimo Valley Elementary School, Lagunitas Elementary School, the Woodacre Fire Station and the Heartwood Charter School that lie in the Moderate FHSZ and could be susceptible to wildlife.
The area west and north of Inverness Park primarily lies in a High FHSZ. There are dozens of homes in this area that could have higher susceptibility to wildfire. There is a residential area north of Inverness Park with several dozen homes that lie in a Very High FHSZ and could have an even higher susceptibility to wildfire. Most of the core of Inverness lies in a High FHSZ but the outlying areas north lie in a Very High FHSZ. There are dozens of homes in both these areas that could have higher susceptibility to wildfire. The Inverness Fire Department, Inverness Elementary School and a Marin Emergency Radio Authority (MERA) antenna site lie in a High FHSZ area and could have higher susceptibility to wildfire. Populations from Inverness to Inverness Park are particularly susceptible to wildfire as there is essentially only one main road, Sir Francis Drake Boulevard, that could be used in an evacuation and in only one direction (south).
Most of Dogtown and the northern end of Bolinas lie in a High FHSZ. Several residences, the Bolinas PG&E substation and the Bolinas-Stinson Elementary School lie in this area and could have higher susceptibility to wildfire. Most of Bolinas, where there are dozens of homes, the Bolinas Community Center, the Bolinas Stinson School, the MERA antenna sites at Horseshoe Hill and Bolinas, the Bolinas Community Health Center and the Woodrat Water Treatment Plant lie in a Moderate FHSZ and could be susceptible to wildfire.
While most of Stinson Beach is in a Moderate FHSZ, the surrounding area to the south is in a High FHSZ. Several residences and businesses are in this area and could have higher susceptibility to wildfire. The downtown core of Stinson Beach along with the Stinson Beach Fire Department Stations #1 and #2 lie in a Moderate FHSZ just outside of the High FHSZ and could be susceptible to wildfire. The western end of Stinson Beach along Dipsea Road and Seadrift Road also lies in a Moderate FHSZ and includes dozens of homes that could be susceptible to wildfire.
Most of Muir Beach lies in a High FHSZ. This area includes dozens of homes, several businesses and the Muir Beach Community Center that have higher susceptibility to wildfire.
The Muir Beach Fire Department lies just outside the High FHSZ in a Moderate FHSZ and could be susceptible to wildfire.
Most of Tamalpais Valley and Marin City lie in a Very High FHSZ. There are thousands of homes and buildings in this area of Tamalpais Valley, along with a MERA antenna site, the Marin Horizon School, the Southern Marin Fire Protection District Station #4 and the Tamalpais Valley Elementary School that could have a very high susceptibility to wildfire. Populations in this area are particularly susceptible to wildfire due to the presence of numerous cul de sacs and windy secondary roads that could impede an evacuation. Numerous homes and critical facilities, including the Marin City Health and Wellness Center, the Bayside Martin Luther King Jr. Academy, and the Marin City Fire department lie in the Very High FHSZ of Marin City and could have a very high susceptibility to wildfire. The Very High FHSZ in Tamalpais Valley and Marin City is bordered to the east by a High FHSZ. Hundreds of homes and numerous businesses along with the Commodore Center Heliport lie in the High FHSZ and could have higher susceptibility to wildfire. The Mount Tamalpais School lies in the Moderate FHSZ and could be susceptible to wildfire.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
370
A small area in the north of Strawberry lies in a High FHSZ with a larger area that lies in a moderate FHSZ. There are several homes in this area that could have higher susceptibility to wildfire.
Most of the unincorporated area of the Tiburon Peninsula lie in a High FHSZ. There are dozens of homes in this area that could have higher susceptibility to wildfire. The eastern boundary of the peninsula lies in a Moderate FHSZ and has several homes that could be susceptible to wildfire.
The far northern and western side of Kentfield lie in a High FHSZ and are bordered to the immediate west by a Very High FHSZ. There are dozens of homes, numerous businesses, the Kentfield Hospital and part of the College of Marin that lie in this area and that have higher susceptibility to wildfire. A smaller part of Kentfield and part of Greenbrae and California City lie in a Moderate FHSZ. There are several homes along with part of the College of Marin that lie in this area and that could be susceptible to wildfire. All of San Quentin, including San Quentin State Prison, lies in a Moderate FHSZ and could be susceptible to wildfire.
While all of Sleepy Hollow lies in a Moderate FHSZ, it is bordered to the east, west, and south by areas of a High FHSZ. Dozens of homes along with the San Domenico School, Sleepy Hollow Villa Medical Facility and the Hidden Valley School that lie in this area could be susceptible to wildfire. Most of Los Ranchitos lies in a High FHSZ with a small part in a moderate FHSZ. There are dozens of homes in this area that could be susceptible to wildfire.
Most of Lucas Valley and Marinwood lie in a High FHSZ. There are hundreds of homes and critical facilities, including several medical facilities, Lucas Valley Elementary School, the Marin County Juvenile Complex, Lucas Valley School, the Marinwood Fire Department, Miller Creek School that lie in this area and have a high susceptibility to wildfire. There is a small section of Marinwood with several homes and part of the Mary E. Silveria Elementary School that lie in a Very High FHSZ and that could have an even higher susceptibility to wildfire. The far eastern end of Lucas Valley, which consists of several homes, lies a Moderate FHSZ and could be susceptible to wildfire.
All of the Saint Vincent area, which includes the Saint Vincent School, lies in a Moderate FHSZ and could be susceptible to wildfire. The Saint Vincent area is surrounded to the west, north and south by a High FHSZ.
Most of San Venetia is not in a FHSZ but the eastern foothills of the San Pedro Mountain Open Space Preserve are in a Moderate FHSZ. There are numerous homes and medical facilities along with the Marin School that lie in this area and that could be susceptible to wildfire. Part of the unincorporated community south of China Camp State Park lies in a Moderate FHSZ.
There are dozens of homes in this area that could be susceptible to wildfire. The southwest side of San Pedro Hill lies in a High FHSZ with a small part lying in a Moderate FHSZ. The McNear Brickyard and other industrial facilities lie in this area and could have an even higher susceptibility to wildfire.
The unincorporated residential area west of Novato lies mostly in a High FHSZ. There are hundreds of homes in this area that could have a high susceptibility to wildfire. The Loma Verde area, which includes dozens of homes and the Loma Verde Elementary School, also lies in a l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
371
High FHSZ and could have a high susceptibility to wildfire. This area is bordered to the south by a Very High FHSZ in the City of Novato.
Most of the Black Point-Green Point area lies in a High FHSZ. There are dozens of homes, several businesses, and the Novato Fire Protection District Station #62 that lie in this area and could have a high susceptibility to wildfire. A smaller section south of the Rush Creek Marsh Wildlife Area lies in a Moderate FHSZ. There are numerous homes and businesses in this area that could be susceptible to wildfire.
Numerous unincorporated communities in Marin County include all or part of a Moderate FHSZ and have no High or Very High FHSZ’s including Point Reyes Station, Olema, Nicasio, Tocoloma, Marshall, Tomales, Dillon Beach, Alto, Paradise Cay, and Bel Marin Keys. Hundreds of homes, numerous businesses, and several critical facilities lie in these communities and could be susceptible to wildfire. Critical facilities in these communities susceptible to wildfire include the Nicasio Fire Department, the Nicasio Elementary School, the Tocoloma PG&E substation, the MERA antenna site at Mt. Barnabe, the Olema PG&E substation, the Point Reyes National Seashore Headquarters and Fire Department, the Point Reyes Fire Station, the Marin County Sherrif’s Substation at Point Reyes, the CalTrans Point Reyes Maintenance Station, West Marin Elementary School, Tomales High School, Tomales Elementary School, Tomales Fire Station, MERA antenna site at Tomales and several medical facilities.
The Marin County Airport, the community of San Antonio, and the unincorporated County along the border of Sonoma County all lie in a Moderate FHSZ. There are numerous rural homes, businesses and buildings along with critical facilities including the Hicks Valley Fire Station, Laguna School, Lincoln School, Stafford Junction PG&E substation, MERA antenna site at Coyote Peak that lie in this area and could be susceptible to wildfire.
Marin County populations within the above-listed communities that are most vulnerable to the effects of wildfire include:
• Low-income households
• Households in poverty
• Persons living on single access roads
• Mobile homeowners
• Persons without access to transportation or telecommunications • Outdoor workers
• Healthcare workers, first responders, and protective service occupations • Houseless population
• Children
• Persons with disabilities
• Persons with chronic health problems,
• Senior community members, and
• Persons living alone.
See the Marin County CWPP for additional information on the susceptibility of the Marin County OA to wildfire.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
372
Climate Change and Future Development Considerations
Climate change can lead to an increase in wildfire events. Climate change has been a key factor in increasing the risk and extent of wildfires in the western United States. Changes in climate create warmer, drier conditions. Increased drought, and a longer fire season are boosting these increases in wildfire risk.
Figure 3.207: Trends in the Annual Number of Large Wildfires in the United States Source: Fourth Climate Change Assessment
As summer conditions in Northern California become hotter and drier due to climate change, the occurrence and severity of wildfires will only increase. The Marin County OA is particularly susceptible to these future impacts of climate change on wildfire, as the OA’s climate has generally been wet enough historically to avoid major wildfires. Extreme heat events and high wind events could cause electrical systems to become overloaded and fail, sparking wildfires.
An increase in wildfires as a result of climate change could lead to more significantly burned areas that could contribute to debris flows after a significant storm event. Future development in the WUI throughout the Marin County OA will expose more people and property to the impacts of a potentially significant wildfire. The growing number of people in the Marin County OA WUI can increase risk to life, property and public health as a result of a wildfire.
3.4 ADDITIONAL HAZARDS PROFILED
Additional non-natural hazards were identified as having some potential to impact the planning area. The sections below provide short profiles of each of these hazards, including qualitative discussion of their potential to impact Marin County. No formal risk assessment of these hazards was performed, and no mitigation initiatives have been developed to address them. l ~<;>U·N· TY OF
~ ARIN
a
~
g All Regions
~ \.,,,.",L~,1ln~1l11J 1984 1992 2000 2008
i ~ f """"'""''"c'"''' "'"
o o J'.j"
ill 1984 1992 2doo 2do8 f ; f ••• Plalrutol,mbia "'""
~ 01984 1992 2doo 2do8
o Basin and Range
I:~ 0 1....1;9;=84==;:::, =1:::;:9'9=2=;==20::;::'o=o ::::;==20;::: 1 08=
: f ••••'""" c,11rom1,
0 19'84 ' 1g92 ' 2doo ' 2do8
=~ Rocky Mountains
0 1~ I 19192 20'o0 2008
~ r rth,m P•to,
~ 19184 1992 2000 20'o8
-_f ~f o,th•m POio,
e>o I I I I I
•. I , .'.:l 1984 1992 2000 2008
:, ~. -:;_/' --1 ~ ! ( Mlro,a-N,w ""''° Mo,mt•••
• , ·I• ,, ~ , ~ o -
":-: • 1 - : ;~~ : 1i9;::: 84::::;:::=1::;:9'=2::::=20:o:0=2=0:08-
1., .=. ,.
al
0 ....
Warm Deserts
1992 2000 2008
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
373
3.4.1 AIR POLLUTION
Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere.
Household combustion devices, motor vehicles, industrial facilities and forest fires are common sources of air pollution. Pollutants of major public health concern and their effects on health and the environment include:
Ozone (O3)
• Respiratory symptoms
• Worsening of lung disease leading to premature death
• Damage to lung tissue
• Crop, forest and ecosystem damage
• Damage to a variety of materials, including rubber, plastics, fabrics, paint and metals PM2.5 (particulate matter less than 2.5 microns in aerodynamic diameter) • Premature death
• Hospitalization for worsening of cardiovascular disease • Hospitalization for respiratory disease
• Asthma-related emergency room visits
• Increased symptoms, increased inhaler usage
PM10 (particulate matter less than 10 microns in aerodynamic diameter) • Premature death & hospitalization, primarily for worsening of respiratory disease • Reduced visibility and material soiling
Nitrogen Oxides (NOX)
• Lung irritation
• Enhanced allergic responses
Carbon Monoxide (CO)
• Chest pain in patients with heart disease
• Headache
• Light-headedness
• Reduced mental alertness
Sulfur Oxides (SOX)
• Worsening of asthma: increased symptoms, increased medication usage, and emergency room visits
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
374
Lead
• Impaired mental functioning in children
• Learning disabilities in children
• Brain and kidney damage
Hydrogen Sulfide (H2S)
• Nuisance odor (rotten egg smell)
• At high concentrations: headache & breathing difficulties Sulfate
• Same as PM2.5, particularly worsening of asthma and other lung diseases • Reduces visibility
Vinyl Chloride
• Central nervous system effects, such as dizziness, drowsiness & headaches • Long-term exposure: liver damage & liver cancer
Visibility Reducing Particles
• Reduced airport safety, scenic enjoyment, road safety, and discourages tourism Toxic Air Contaminants (about 200 chemicals have been listed as toxic air contaminants) • Cancer
• Reproductive and developmental effects
• Neurological effects
Outdoor and indoor air pollution cause respiratory and other diseases and are important sources of morbidity and mortality.
The World Health Organization (WHO) shows that almost all of the global population (99%) breathe air that exceeds WHO guideline limits and contains high levels of pollutants, with lowand middle-income countries suffering from the highest exposures.
Air quality is closely linked to the earth’s climate and ecosystems globally. Many of the drivers of air pollution (i.e. combustion of fossil fuels) are also sources of greenhouse gas emissions.
Climate change–fueled wildfires and extreme heat are adding to the challenges of protecting public health. Policies to reduce air pollution, therefore, offer a win-win strategy for both climate and health, lowering the burden of disease attributable to air pollution, as well as contributing to the near- and long-term mitigation of climate change.
Mold and allergens from trees, weeds, and grass are also carried in the air, are exacerbated by climate change, and can be hazardous to health. Though they aren’t regulated and are less directly connected to human actions, they can be considered a form of air pollution. Pollen allergies are worsening because of climate change.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
375
135 million people or four out of ten U.S. residents live in counties with unhealthy levels of air pollution. Air monitoring shows that over 90 percent of Californians breathe unhealthy levels of one or more air pollutants during some part of the year. In the U.S., the Clean Air Act has been a crucial tool for reducing air pollution since its passage in 1970. The most effective way to control air pollution is to speed up the transition to cleaner fuels and industrial processes. By switching over to renewable energy sources such as wind and solar power, maximizing fuel efficiency in vehicles, and replacing more and more gasoline-powered cars and trucks with electric versions, air pollution can be limited at its source while also curbing the global warming that worsens so many of its worst health impacts.
Air Quality Index (AQI) & Health
Millions of people live in areas where air pollution can cause serious health problems. Local air quality can affect our daily lives. Like the weather, it can change from day to day. The Environmental Protection Agency (EPA) developed the Air Quality Index, or AQI, to make information available about the health effects of the five most common air pollutants, and how to avoid those effects.
The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. The AQI focuses on health affects you may experience within a few hours or days after breathing polluted air. EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide. For each of these pollutants, EPA has established national air quality standards to protect public health. Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country. https://www.airnow.gov/
https://airnow.gov/index.cfm?action=aqi_brochure.index
The purpose of the AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories: Note: Values above 500 are considered Beyond the AQI. Follow recommendations for the Hazardous category. Additional information on reducing exposure to extremely high levels of particle pollution is available here.
Each category corresponds to a different level of health concern. The six levels of health concern and what they mean are depicted in the figure below. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
376
Figure 3.208: Air Quality Index Concern Levels
Source: AirNow.gov
In the Bay Area, a certain amount of air pollution comes from industrial sources, such as refineries and power plants. But a greater percentage of harmful air emissions comes from cars and trucks, construction equipment, and other motor vehicles. In the wintertime, the largest single source of air pollution is residential wood burning. Ozone and fine particle pollution, or PM2.5, are the major regional air pollutants of concern in the San Francisco Bay Area. Ozone is primarily a problem in the summer, and fine particle pollution in the winter. Along the Marin County coast and in southern Marin County, clean air from the Pacific Ocean helps to keep air pollution at a minimum. Elsewhere in the Marin County OA, ozone only rarely becomes a concern, but the hilly terrain and colder winter temperatures can trap PM2.5 near the surface, resulting in air quality that exceeds health standards.
The Bay Area Air Quality Management District (BAAQMD) is the official air pollution control agency for the San Francisco Bay Area, which includes Marin County. They have issued numerous poor air quality advisories for Marin County over the years as a result of wildfires.
3.4.2 CRITICAL INFRASTRUCTURE/ UTILITY DISRUPTION
Critical Infrastructure and utility disruption is defined as the disruption of one or more of the physical structures, facilities, networks and other assets which provide services that are essential to the social and economic functioning of a community or society. Examples of infrastructure disruptions include building collapses, water main breaks, gas pipe ruptures, steam pipe explosions, communication system failures and related types of events. These disruptions can be caused by natural disasters such as a landslide or earthquake, by man-made disasters such as a train or major vehicle crash, or by acts of sabotage including terrorism. 1 ~<;>U·N· TY OF a ~ ARIN~
Air Quality Index
l~vcls of Health
concern
Good
Moderate
Unhealthy
Very Unhe.stthy
Ha23rdous
Numerical
Value
Oto50
51 to 100
Meaning
sk. cons dered sat!mctory :ind .:i r pc,llu on poses lfttl• or no Air qu3lity is 3ccept3ble; however, for some pollut3nts there m3y be 3 moder3te he3lth concern for 3 very sm3II number of people who ;ire unusu3lly sensitive to .1ir pollution.
151 to 200 Everyone m3y begin to experlen~ he.111h effects; members of sensitive groups may experience more senous heatth effects.
EH!@i+E Hnlth alert everyone m;sy· experience more serious hea~ effects. 301 to 500 Health_wamlngs of emergency conditions. The entire population Is more likely to be .Jffected.
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
377
Climate change is expected to heavily affect infrastructure through heatwaves, floods and droughts. Figure 3.208 shows critical infrastructure across the Marin County OA.
Figure 3.209: Marin County OA Critical Infrastructure
Source: Marin County
The availability of critical infrastructure and utilities are crucial for timely recovery after a disaster induced by natural hazards. Maintaining or quickly restoring road access, drinking water supply or healthcare can save lives. Very often disasters are exacerbated by poor infrastructure.
Preparing critical infrastructures, as well as the population, for long-term outages due to natural hazards is crucial. When critical infrastructure and utilities have a disruption, it can disproportionately affect socially vulnerable populations. For individuals stuck at home and who rely on timely medication or electrical devices, a situation can quickly become critical if road access and power supplies are damaged. The increasing complexity, interdependency and scale of infrastructure networks can make them more difficult to protect. While technological developments have improved the quality of essential services, this progress itself creates new vulnerabilities.
Beyond power outages caused by storms, wildfires and PSPS events, the Marin County OA has had no significant critical infrastructure or utility disruptions. Other critical infrastructure and utility disruptions across California and the United States have occurred, however, and could similarly occur in the Marin County OA including the 2011 Southwest power failure, the 2010 San Bruno PG&E gas line explosion, and the 2007 I-35 bridge collapse in Minneapolis, Minnesota.
l ~<;>U·N· TY OF
~ ARIN
a
~
CB1tfomit1 ctnc , rnnsm1H1en l 1n1P.s - 220 . ?67 kV
Smtlller than 110 kV
- 110 - 161\N
- 345-SOOIN
Marin County OA Critical Infrastructure
- UtJ1ty. PGE Mai10r Gae Line
[-1 Mann C1bos fTc,,,,,ns (OUIU ne)
~-;..
i>~ ..... ,., ,
::> " ~
et
10 1,577,791
,.
20~rn
~rnl
O!l, OUW\,ueaQ.C....l'ltt,:,,i"""""Cdi.rni.~ ,.~ &\. 1-E:Rt. ~ &11:0,~ f"o\O, ~ AA"-OSOS.6-<14t.aNM1<1~~NPS
s.-... m,
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
378
3.4.3 CYBER THREATS
A cyber threat is any circumstance or event with the potential to adversely impact organizational operations (including mission, functions, image, or reputation), organizational assets, or individuals through an information system via unauthorized access, destruction, disclosure, modification of information, and/or denial of service. A cyber threat is also the potential for a threat-source to successfully exploit a particular information system vulnerability. Cyber threats include:
Malware
Malware — or malicious software — is any program or code that is created with the intent to do harm to a computer, network or server. Malware is the most common type of cyberattack, mostly because this term encompasses many subsets such as ransomware, trojans, spyware, viruses, worms, keyloggers, bots, cryptojacking, and any other type of malware attack that leverages software in a malicious way. Types of malware include:
Ransomware: In a ransomware attack, an adversary encrypts a victim’s data and offers to provide a decryption key in exchange for a payment. Ransomware attacks are usually launched through malicious links delivered via phishing emails, but unpatched vulnerabilities and policy misconfigurations are used as well.
Fileless Malware: Fileless malware is a type of malicious activity that uses native, legitimate tools built into a system to execute a cyber attack. Unlike traditional malware, fileless malware does not require an attacker to install any code on a target’s system, making it hard to detect.
Spyware: Spyware is a type of unwanted, malicious software that infects a computer or other device and collects information about a user’s web activity without their knowledge or consent.
Adware: Adware is a type of spyware that watches a user’s online activity in order to determine which ads to show them. While adware is not inherently malicious, it has an impact on the performance of a user’s device and degrades the user experience.
Trojan: A trojan is malware that appears to be legitimate software disguised as native operating system programs or harmless files like free downloads. Trojans are installed through social engineering techniques such as phishing or bait websites.
Worm: A worm is a self-contained program that replicates itself and spreads its copies to other computers. A worm may infect its target through a software vulnerability or it may be delivered via phishing or smishing. Embedded worms can modify and delete files, inject more malicious software, or replicate in place until the targeted system runs out of resources.
Rootkit: Rootkit malware is a collection of software designed to give malicious actors control of a computer network or application. Once activated, the malicious program sets up a backdoor exploit and may deliver additional malware.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
379
Mobile Malware: Mobile malware is any type of malware designed to target mobile devices.
Mobile malware is delivered through malicious downloads, operating system vulnerabilities, phishing, smishing, and the use of unsecured WiFi.
Exploit: An exploit is a piece of software or data that opportunistically uses a defect in an operating system or an app to provide access to unauthorized actors. The exploit may be used to install more malware or steal data.
Scareware: Scareware tricks users into believing their computer is infected with a virus.
Typically, a user will see scareware as a pop-up warning them that their system is infected.
This scare tactic aims to persuade people into installing fake antivirus software to remove the “virus.” Once this fake antivirus software is downloaded, then malware may infect your computer.
Keylogger: Keyloggers are tools that record what a person types on a device. While there are legitimate and legal uses for keyloggers, many uses are malicious. In a keylogger attack, the keylogger software records every keystroke on the victim’s device and sends it to the attacker.
Botnet: Botnet is a network of computers infected with malware that are controlled by a bot herder. The bot herder is the person who operates the botnet infrastructure and uses the compromised computers to launch attacks designed to crash a target’s network, inject malware, harvest credentials or execute CPU-intensive tasks.
Denial and Distributed Denial of Service Attacks
A Denial-of-Service (DoS) attack is a malicious, targeted attack that floods a network with false requests in order to disrupt business operations.
In a DoS attack, users are unable to perform routine and necessary tasks, such as accessing email, websites, online accounts or other resources that are operated by a compromised computer or network. While most DoS attacks do not result in lost data and are typically resolved without paying a ransom, they cost the organization time, money and other resources in order to restore critical business operations.
The difference between DoS and Distributed Denial of Service (DDoS) attacks has to do with the origin of the attack. DoS attacks originate from just one system while DDoS attacks are launched from multiple systems. DDoS attacks are faster and harder to block than DOS attacks because multiple systems must be identified and neutralized to halt the attack.
Phishing
Phishing is a type of cyberattack that uses email, SMS, phone, social media, and social engineering techniques to entice a victim to share sensitive information — such as passwords or account numbers — or to download a malicious file that will install viruses on their computer or phone. Types of phishing include:
Spear Phishing: Spear-phishing is a type of phishing attack that targets specific individuals or organizations typically through malicious emails. The goal of spear phishing is to steal sensitive information such as login credentials or infect the targets’ device with malware. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
380
Whaling: A whaling attack is a type of social engineering attack specifically targeting senior or executive employees with the purpose of stealing money or information, or gaining access to the person’s computer in order to execute further cyberattacks.
SMiShing: Smishing is the act of sending fraudulent text messages designed to trick individuals into sharing sensitive data such as passwords, usernames and credit card numbers. A smishing attack may involve cybercriminals pretending to be your bank or a shipping service you use.
Vishing: Vishing, a voice phishing attack, is the fraudulent use of phone calls and voice messages pretending to be from a reputable organization to convince individuals to reveal private information such as bank details and passwords.
Spoofing
Spoofing is a technique through which a cybercriminal disguises themselves as a known or trusted source. In so doing, the adversary is able to engage with the target and access their systems or devices with the ultimate goal of stealing information, extorting money or installing malware or other harmful software on the device. Types of spoofing include:
Domain Spoofing: Domain spoofing is a form of phishing where an attacker impersonates a known business or person with fake website or email domain to fool people into the trusting them. Typically, the domain appears to be legitimate at first glance, but a closer look will reveal subtle differences.
Email Spoofing: Email spoofing is a type of cyberattack that targets organizations by using emails with forged sender addresses. Because the recipient trusts the alleged sender, they are more likely to open the email and interact with its contents, such as a malicious link or attachment.
ARP Spoofing: Address Resolution Protocol (ARP) spoofing or ARP poisoning is a form of spoofing attack that hackers use to intercept data. A hacker commits an ARP spoofing attack by tricking one device into sending messages to the hacker instead of the intended recipient. This way, the hacker gains access to your device’s communications, including sensitive data.
Code Injection Attacks
Code injection attacks consist of an attacker injecting malicious code into a vulnerable computer or network to change its course of action. Types of code injection attacks include:
SQL Injection: A Structured Query Language (SQL) Injection attack leverages system vulnerabilities to inject malicious SQL statements into a data-driven application, which then allows the hacker to extract information from a database. Hackers use SQL Injection techniques to alter, steal or erase application's database data.
Cross-Site Scripting (XSS): Cross Site Scripting (XSS) is a code injection attack in which an adversary inserts malicious code within a legitimate website. The code then launches as an infected script in the user’s web browser, enabling the attacker to steal sensitive information or impersonate the user. Web forums, message boards, blogs and other websites that allow users to post their own content are the most susceptible to XSS attacks. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
381
Malvertising: Malvertising attacks leverage many other techniques to carry out the attack.
Typically, the attacker begins by breaching a third-party server, which allows the cybercriminal to inject malicious code within a display ad or some element thereof, such as banner ad copy, creative imagery or video content. Once clicked by a website visitor, the corrupted code within the ad will install malware or adware on the user’s computer.
Identity-Based Attacks
Identity-based attacks are attacks on the behavior of an individual and are extremely hard to detect. When a valid user’s credentials have been compromised and an adversary is masquerading as that user, it is often very difficult to differentiate between the user’s typical behavior and that of the hacker using traditional security measures and tools. Types of identitybased attacks include:
Kerberoasting: Kerberoasting is a post-exploitation attack technique that attempts to crack the password of a service account within the active directory where an adversary masquerading as an account user with a service principal name requests a ticket, which contains an encrypted password, or Kerberos.
Man-in-the-Middle (MITM) Attack: A man-in-the-middle attack is a type of cyberattack in which an attacker eavesdrops on a conversation between two targets with the goal of collecting personal data, passwords or banking details, and/or to convince the victim to take an action such as changing login credentials, completing a transaction or initiating a transfer of funds.
Pass-the-Hash Attack: Pass the hash (PtH) is a type of attack in which an adversary steals a “hashed” user credential and uses it to create a new user session on the same network. It does not require the attacker to know or crack the password to gain access to the system.
Rather, it uses a stored version of the password to initiate a new session.
Silver Ticket Attack: A silver ticket is a forged authentication ticket often created when an attacker steals an account password. A forged service ticket is encrypted and enables access to resources for the specific service targeted by the silver ticket attack.
Credential Stuffing: Credential stuffing attacks work on the premise that people often use the same user ID and password across multiple accounts. Therefore, possessing the credentials for one account may be able to grant access to other, unrelated account.
Password Spraying: The basics of a password spraying attack involve a threat actor using a single common password against multiple accounts on the same application. This avoids the account lockouts that typically occur when an attacker uses a brute force attack on a single account by trying many passwords.
Brute Force Attacks: A brute force attack uses a trial-and-error approach to systematically guess login info, credentials, and encryption keys. The attacker submits combinations of usernames and passwords until they finally guess correctly.
Insider Threats
Insider threats are internal actors such as current or former employees that pose danger to an organization because they have direct access to the company network, sensitive data, and l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
382
intellectual property (IP), as well as knowledge of business processes, company policies or other information that would help carry out such an attack.
Internal actors that pose a threat to an organization tend to be malicious in nature. Some motivators include financial gains in exchange for selling confidential information on the dark web, and/or emotional coercion using social engineering tactics. On the other hand, some insider threat actors are not malicious in nature but instead are negligent in nature. To combat this, organizations should implement a comprehensive cybersecurity training program that teaches stakeholders to be aware of any potential attacks, including those potentially performed by an insider.
Supply Chain Attacks
A supply chain attack is a type of cyberattack that targets a trusted third-party vendor who offers services or software vital to the supply chain. Software supply chain attacks inject malicious code into an application in order to infect all users of an app, while hardware supply chain attacks compromise physical components for the same purpose. Software supply chains are particularly vulnerable because modern software is not written from scratch: rather, it involves many off-the-shelf components, such as third-party APIs, open-source code and proprietary code from software vendors.
DNS tunneling
DNS Tunneling is a type of cyberattack that leverages domain name system (DNS) queries and responses to bypass traditional security measures and transmit data and code within the network. Once infected, the hacker can freely engage in command-and-control activities. This tunnel gives the hacker a route to unleash malware and/or to extract data, IP or other sensitive information by encoding it bit by bit in a series of DNS responses. DNS tunneling attacks have increased in recent years, in part because they are relatively simple to deploy. Tunneling toolkits and guides are even readily accessible online through mainstream sites like YouTube.
IoT-Based Attacks
An IoT attack is any cyberattack that targets an Internet of Things (IoT) device or network. Once compromised, the hacker can assume control of the device, steal data, or join a group of infected devices to create a botnet to launch DoS or DDoS attacks. Given that the number of connected devices is expected to grow rapidly over the next several years, cybersecurity experts expect IoT infections to grow as well. Further, the deployment of 5G networks, which will further fuel the use of connected devices, may also lead to an uptick in attacks.
The Marin County OA has had several cybersecurity issues. More than $300,000 was stolen by fraudulent electronic transfers at the Marin County Civic Center, unwittingly approved by county financial gatekeepers in 2018. Marin County’s computer network has been hacked into and breached at least five times between July 2017 and August 2018. In addition, more than half of Marin’s cities — Corte Madera, Fairfax, Larkspur, Novato, Sausalito and Tiburon — have had their cybersecurity compromised including:
Town of Fairfax: In July 2016, Fairfax was victimized by a ransomware attack. An employee received an email with a malware program attached; and when the employee clicked on the attachment, the town’s servers were infected and became unusable. No ransom was paid, but the town was forced to use a previous backup in order to rebuild its systems. The Town lost data l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
383
for the day of the attack, since it had not yet been backed up. The Town suffered a similar breach in October 2014.
City of Novato: In 2017, Novato fell victim to a phishing attack. A city employee received an email purporting to be from a senior city official, requesting a wire transfer of funds. The employee initiated the wire transfer to the account specified by the hacker. The breach was reported to local law enforcement and the FBI. After the attack, the City strengthened its email security and implemented mandatory employee training to reduce its vulnerability to emailbased attacks.
City of Sausalito: In January 2018, Sausalito was the victim of a phishing attack in which a fake email, purporting to be from the city manager, was sent to a city employee. This employee complied with the fake email’s request for copies of the W-2 tax forms of all of the city’s employees and councilmembers. As a result, all these individuals were exposed to the risk of identity theft. The Sausalito breach was reported to the FBI. For two years after the attack, the city provided free credit monitoring services to all employees, at a cost of approximately $27,000. Nevertheless, three employees had fraudulent state tax returns filed in their names, although the attempts were unsuccessful because taxing authorities had been alerted.
Town of Tiburon: In 2019, Tiburon suffered a ransomware attack, also initiated by a fake email attachment opened by an employee. No ransom was paid, but the Town’s systems were largely disabled for more than three days. Most of its data was recovered using a backup, but the town discovered that one of its applications was not being backed up properly, so the town needed to rebuild much of that data by hand from paper records.
Town of Corte Madera: In 2019, Corte Madera suffered a direct attack. During a brief moment when a vendor intentionally disabled the town’s firewall for system updates, hackers were able to access its network and disable it using ransomware. No ransom was paid, but the system had to be restored from a backup.
City of Larkspur: In August 2019, Larkspur’s network was compromised in a direct attack. Four of its computers were reportedly accessed from one of the public computers in the Larkspur library. It is unknown what data may have been accessed.
Having a comprehensive cybersecurity strategy is vital. Organizations should secure their critical areas of risk, know their threats, be ready to respond quickly to a threat, monitor the criminal underground through hidden messaging platforms and dark web forums, utilize technology to stop sophisticated threats, and build a comprehensive cybersecurity training program.
3.4.4 OIL SPILLS
Oil spills can happen anywhere oil is drilled, transported, or used. They can happen in many different ways including when pipelines break, oil tanker ships sink, or drilling operations go wrong. Consequences to ecosystems and economies can be felt for decades following a large oil spill. Thousands of oil spills occur in U.S. waters each year. Most of these spills are small but can still cause damage, especially if they happen in sensitive environments, like beaches and wetlands. Large oil spills can be significant disasters. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
384
Where oil is spilled, what kinds of plants, animals, and habitats are found there, and the amount and type of oil, among other things, can influence how much harm an oil spill causes. Generally, oil spills harm ocean life in two ways:
Fouling or oiling: Fouling or oiling occurs when oil physically harms a plant or animal. Oil can coat a bird’s wings and leave it unable to fly or strip away the insulating properties of a sea otter’s fur, putting it at risk of hypothermia. The degree of oiling often impacts the animal’s chances of survival.
Oil toxicity: Oil consists of many different toxic compounds. These toxic compounds can cause severe health problems like heart damage, stunted growth, immune system effects, and even death. Our understanding of oil toxicity has expanded by studying the effects of the 2010 Deepwater Horizon oil spill.
Wildlife recovery, cleaning, and rehabilitation is often an important part of oil spill response.
However, wildlife is difficult to find and catch, oil spills can happen over wide areas, and some animals (like whales) are too big to recover. Unfortunately, it’s unrealistic to rescue all wildlife impacted during oil spills.
The U.S Coast Guard is primarily responsible for cleaning up oil spills, while NOAA provides scientific support to make decisions that protect people and the environment. There are different equipment and tactics that trained experts can use to contain or remove oil from the environment when a spill occurs:
Booms are floating physical barriers to oil, which help keep it contained and away from sensitive areas, like beaches, mangroves, and wetlands.
Skimmers are used off of boats and can “skim” oil from the sea surface. In situ burning, or setting fire to an oil slick, can burn the oil away at sea, and chemical dispersants can break up oil slicks from the surface.
Cleanup activities can never remove 100% of the oil spilled, and scientists have to be careful that their actions don’t cause additional harm.
Figure 3.209 shows the largest oil spills affecting United States waters from 1969-2017. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
385
Figure 3.210: Largest Oil Spills Affecting U.S. Waters 1969-2017 Source: NOAA
The Marin County OA has been impacted by oil spills. In 2007, an oil tanker colided with one of the San-Francisco Oakland Bay Bridge towers. It spilled 53,569 gallons of bunker fuel into San Francisco Bay. The tidal mechanics of San Francisco Bay caused the spill to spread rapidly, affecting a large area of the California North Coast, including the Golden Gate National Recreation Area, Ocean Beach and the Marin Headlands. More than 50 public beaches were closed, including Crissy Field, Fort Point, Baker Beach, China Beach and Kirby Cove. Beaches as far south as Pacifica, California were closed due to the spill. According to Federal and State natural resource trustee agencies, the spill is estimated to have killed 6,849 birds. Several fisheries in the Bay Area may have been affected by the spill, and the crab and sport fishing seasons were postponed by several weeks. As of the end of November 2007, State biologists had tested more than 1100 samples of fish, mussels and Dungeness crab in San Francisco Bay and coastal waters outside the Golden Gate. The tests found unsafe levels of contaminants in mussels from Rodeo Beach and the Berkeley pier. An estimated 1,079,900 recreational use days were also lost as a result of the spill. This includes general shoreline use as well as recreational fishing and boating. Total monetary damages were estimated at more than $70 million for oil spill cleanup.
In 1971, a spill occurred in the San Francisco Bay when two tankers collided and spilled 800,000 gallons of oil, threatening significant sensitive habitat inside and outside the Bay, including the Bolinas Lagoon.
On March 6, 2021, a steel shackle connecting a tugboat to the American Challenger, a 90-foot decommissioned vessel, failed in Bodega Bay, causing the American Challenger to drift into shore. A Coast Guard crew was monitoring it at the time and reported the commercial vessel grounded north of Dillon Beach, off Pt Reyes.
l ~<;>U·N· TY OF
~ ARIN
a
~
Million Gallons Spilled
Exxon Valdez - 1989 Largest Oil Spills
Affecting U.S. Waters
134.0 MG 01:iepwater Horizon
75.0 MG
Tank Barge UMTB 283 - 1988
•
•
1969 - Present
50.0 MG
10.0MG
1.0 MG
0.5MG
Tenyo Maru -1991
USS General M.C. Meigs - 1972 Ashland Petr~leum - 1988 \ Kalamazoo River - 2010 \
5 - 1985 Even relatively small oil spills can
cause major harm, depending on
location, season, environmental
sensitivity, and type of oil. The
following spills are examples:
MN Selendang Ayu - 2004. AK
MfT Athas I - 2004 - NJ/PA
MN Cosco Busan - 2007 - CA
MN New Carissa - 1999 - OR
Hawaiian Patriot - 1977
•
N
A
Oregon Standard - 1971
Puerto Rican - 1964
Santa Barbara - 1969/
Sansinena -1976
Citgo Refinery - 2006
Eagle otome - 2010
Apex Barges - 1990
Burmah Agate - 1979
N~r:
9 :a~:~: ~::/,
Tank Barge OM932 - 2008
Hurricane Katrina - 2005
Westchester - 2000
Chevron Main Pass Block41 -1970
Cape - 1996
go Merchant - 1976
kensack Estuary Tank Farm,
llen Oil Company - 1976
ro Savannah - 1990
Texaco Oklahoma - 1971
Reedy River - 1996
Amazon Venture - 1986
Deepwater Horizon• 2010
Epic Colocotronis - 1975
/ Vista Bella - 1991
lxtoc 1 - 1979 . . Hurricane Hugo- 1989
Santa Augusta - 1971 Zoe Colocotrom - 1973
MN Zanms - 197 4 eek Slip - 1978
Moms J. Berman - 1994
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
386
Officials representing the Marin County Sheriff’s Office of Emergency Services, the U.S. Coast Guard, the EPA, California Department of Fish and Wildlife, the National Oceanic and Atmospheric Administration, and state Office of Spill Prevention and Response, responded to the scene and attempted to contain the oil and other hazardous materials leaking from the vessel, ensuring debris and toxic substances did not stray into the surrounding Greater Farallones National Marine Sanctuary. About $2.3 million was spent on the initial response and costs related to the stranding, including oil booms, environmental assessments, shoreline surveys and Coast Guard costs, according to the Office of Spill Prevention and Response. The Environmental Protection Agency, Region 9, paid an estimated $1 million for the dismantling and disposal of the vessel.
Additional oil spills have impacted other areas of California:
In 1910, The Lakeview Gusher created the largest accidental oil spill in history, lasting 18 months and releasing an estimated 9 million barrels of crude oil. It occurred due to an eruption of hydrocarbons from a pressurized oil well in the Midway-Sunset Oil Field in Kern County, California.
In 1969, a blowout on an offshore platform off the coast of Santa Barbara, California, spilled over four million gallons of oil.
In 2021, a major oil spill occurred in Orange County, California, originating from an underwater pipe connected to the Elly platform about 4.5 miles offshore near Long Beach. The U.S. Coast Guard estimated that spill covered 8,320 acres of the ocean's surface, spilling approximately 24,696 gallons of oil.
Two of the most significant marine oil spills in American history, each of which was the largest oil spill into American waterways at the time, include:
In 1989, the Exxon Valdez oil tanker ran aground in the Prince William Sound in Alaska, spilling over 11 million gallons of oil.
On April 20, 2010, an explosion occurred on the Deepwater Horizon drilling platform in the Gulf of Mexico, killing 11 people. Before it was capped three months later, approximately 134 million gallons of oil had spilled into the ocean making it the largest marine oil spill in U.S. history. That is equivalent to the volume of over 200 Olympic-sized swimming pools.
While there is currently no oil drilling offshore of Northern California, including Marin County, the potential exists for new drilling to occur in the area in the future. Onshore drilling also does not occur in the Marin County OA. Currently, an oil spill affecting Marin County would most likely emanate from a ship accident as there are no oil pipelines in the Marin County OA.
Environmental, economic, and recreational impacts to the Marin County shoreline could be significant depending on the location of the spill and the tides.
3.4.5 PANDEMIC
A pandemic is a disease outbreak that spreads across countries or continents. It affects more people and takes more lives than an epidemic.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
387
An epidemic is when an infectious disease spreads quickly to more people than experts would expect. It usually affects a larger area than an outbreak.
An outbreak is when an illness happens in unexpected high numbers. It may stay in one area or extend more widely. An outbreak can last days or years. Sometimes, experts consider a single case of a contagious disease to be an outbreak. This may be true if it’s an unknown disease, if it’s new to a community, or if it’s been absent from a population for a long time.
The number of lives lost in a pandemic depends on:
• How many people are infected.
• How severe of an illness the virus causes (its virulence). • How vulnerable certain groups of people are.
• Prevention efforts and how effective they are.
The California Department of Public Health has identified several diseases that could contribute to an outbreak, epidemic or pandemic in California:
Animal Transmitted
These are diseases that are transmitted to humans by domestic or non-domestic animals.
Examples include:
• Brucellosis (undulant fever)
• Campylobacteriosis
• Cat scratch disease
• Cryptosporidiosis
• Escherichia coli (E. coli)
• Giardiasis
• Middle Eastern Respiratory Syndrome (MERS)
• Plague
• Psittacosis (ornithosis, parrot fever)
• Q Fever
• Rabies
• Ringworm
• Salmonellosis
• Toxoplasmosis
• Tularemia
Bloodborne
Viruses, bacteria and parasites that can be carried in blood and cause disease are known as bloodborne pathogens. Transmission of these diseases may be from direct blood contact, needle sticks, intravenous drug use, sexual behavior, insects or other vectors. Examples include:
• Tularemia
• Ebola
• Hepatitis C
• Malaria
Community-Acquired Infections
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
388
Community-acquired infections are infections that are contracted outside of a hospital (or are diagnosed within 48 hours of admission) without any previous health care encounter. Examples include:
• Adenovirus
• Bed Bugs
• Body Lice
• Campylobacteriosis
• Conjunctivitis (pink eye)
• Common cold viruses
• Enterovirus, non-polio
• Hand, foot, and mouth disease
• Head Lice (‘ukus)
• Impetigo
• Influenza (flu)
• Invasive Group A Streptococcus (necrotizing fasciitis) • Legionnaires’ Disease/Pontiac Fever
Foodborne
Foodborne diseases can be spread when food becomes contaminated with fecal matter containing bacteria, viruses, or parasites. This contamination can happen at a farm, manufacturing plant, restaurant, or home. Foodborne diseases usually result in gastrointestinal illness, which can include symptoms such as diarrhea, vomiting, nausea, stomachache, and fever. People who are ill with a foodborne disease can give the infection to others, so proper hygiene and hand washing practices are essential to limit the spread of disease. People experiencing gastrointestinal symptoms should not prepare or handle food for others. Examples include:
• Amebiasis
• Angiostrongyliasis (rat lungworm)
• Anisakiasis
• Botulism
• Brucellosis (undulant fever)
• Campylobacteriosis
• Cholera
• Ciguatera fish poisoning
• Cryptosporidiosis
• Cyclosporiasis
• Escherichia coli (E. coli)
• Giardiasis
• Listeriosis
• Norovirus
• Salmonellosis
• Scombroid
• Shigellosis
• Tularemia
• Typhoid Fever
• Vibriosis
• Yersinia enterocolitica
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
389
Influenza
Influenza is an infectious viral disease of birds and mammals commonly transmitted through airborne aerosols such as coughing or sneezing. Symptoms are chills, headache, fever, nausea, muscle pain and occasionally pneumonia. Flu pandemics in the late 19th and 20th centuries include:
• Russian flu
• 1918 Spanish flu
• Asian flu
• Hong Kong flu
• A/H1N1 or the swine flu.
Avian flu strains H5N1 and H7N9 caused human deaths but did not escalate to pandemic proportions.
Mosquito-Transmitted
Mosquitoes found in California are capable of spreading many diseases to humans and animals. Examples include:
• Malaria
• Yellow fever
• Dengue
• Chikungunya
• Zika
• Canine heartworm
• West Nile virus
• Other encephalitis viruses
Historically, California has experienced local transmission of malaria, western equine encephalomyelitis, St. Louis encephalitis, California encephalitis viruses, canine heartworm, and West Nile virus. Canine heartworm and West Nile virus continue to have frequent local transmission in California, with West Nile virus human cases numbering in the hundreds every year. With increased global travel, the potential exists for the introduction or reintroduction of many mosquito-borne diseases into California.
Waterborne Diseases
Diseases caused by micro-organisms transmitted in water can be spread while bathing, washing, drinking water, or eating food exposed to contaminated water. • Cholera
• Giardiasis
• Legionnaires’ Disease /Pontiac Fever
• Leptospirosis
• Typhoid Fever
Sexually Transmitted Disease
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
390
HIV/AIDS, chlamydia, gonorrhea, and syphilis are the predominant sexually transmitted infections.
• Chlamydia
• Genital warts
• Gonorrhea
• Hepatitis A, B, and C
• Herpes
• Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) • Human papillomavirus
• Syphilis
• Zika
Respiratory Viruses
Respiratory viruses are responsible for influenza-like illness. They can also cause the common cold. The virus that caused the Covid-19 pandemic is a respiratory virus. People at high risk (those with certain underlying conditions, the elderly, the very young, and pregnant women) can develop severe illness that results in hospitalization or death. The best protection is proper hygiene and avoiding contact with sick individuals. The best way for those who are infected to protect others is to cover their nose and mouth when sneezing and coughing, use good hand hygiene, and stay home from work or school.
• Adenovirus
• Coronaviruses
• Influenza
• Parainfluenza
• Parvovirus B19
• Respiratory Syncytial Virus
• Rhinovirus (Common Cold)
• Measles
• Pertussis (whooping cough)
Marin County, like the rest of the United States, was included in the March 2020 FEMA major disaster declaration for the COVID-19 coronavirus pandemic. Since March 2020, Marin County Public Health collected and analyzed information about COVID-19 impact in every community.
Figure 3.210 shows Marin County Covid-19 hospitalizations and Figure 3.211 shows Marin County Covid-19 cases, hospitalizations by demographic. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
391
Figure 3.211: Marin County Covid-19 Hospitalizations
Source: California Department of Public Health
Figure 3.212: Marin County Covid-19 Hospitalizations by Demographics Source: California Department of Public Health
l ~<;>U·N· TY OF
~ ARIN
a
~
LJl 0.6%
c::] 20.2%
~ 21.8%
=:::] 19.3%
0 8.0%
0 6.1%
10.6% 10.0%
4.3% 10.0%
10.8% 1 3.3%
c:::] 20.8% 7%
c:::J 20.S% - 18.2%
42.0%
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
392
The 1918 Spanish Flu also had impacts on the Marin County OA. San Rafael city officials took action before the disease hit the rest of Marin County. All unnecessary public gatherings in social halls and fraternal lodge were prohibited in San Rafael. Schools remained open but theaters were closed. The City of San Rafael passed an ordinance authorizing the arrest of people who failed or refused to wear gauze masks when appearing on the streets. Masks were considered a necessity and ultimately the rest of the Marin County OA public was mandated to wear them. By October 24, 1918, all Marin County schools had been closed and churches and lodges were ordered to postpone all planned meetings. The first death in Marin from the flu was reported that same day “when Seth Morby, of Kentfield was taken.” The Hotel Rafael in San Rafael was used to house flu patients. A resurgence of flu cases across the Marin County OA occurred throughout much of 1919. Several additional deaths occurred and emergency measures had to be reinstated before being lifted again later in the year.
Climate Change
Climate change is expected to have an impact on health hazards. Projected increases in hot days and extreme heat events will increase the risk of heat-associated deaths. Air quality impacts and drier conditions may exacerbate respiratory and cardiovascular conditions through greater concentrations of pollution and allergens. Prolonged droughts from climate change can also affect the quality of drinking water (Centers for Disease Control and Prevention, 2020).
The California 4th Climate Assessment finds that Bay Area public health is threatened by a number of climate related changes, including more extreme heat events, increased air pollution from ozone formation and wildfires, longer and more frequent droughts, and flooding from sea level rise and high-intensity rain events. Heat waves pose increased health risks due to urban heat islands and lack of local experience and cooling infrastructure (air conditioning) in bayside cities. These risks are compounded for low-income communities.
3.4.6 TRANSPORTATION SYSTEMS
Vehicle Accident
A vehicle accident occurs when a motor vehicle collides with another vehicle or object. Vehicle collisions can result in mass fatalities and property damage. A number of factors contribute to the risk of a collision including vehicle design, speed of operation, road design, road environment, driver skill, and impairment due to drugs or alcohol. There are numerous different types of vehicle collisions; of primary concern are the ones that result in a mass fatality and/or a hazmat incident. These incidents can occur due to a single vehicle accident, such as with a tour bus or a truck carrying hazardous materials, or due to a multi-vehicle accident. Multi-vehicle collisions generally occur on high capacity and high-speed routes such as freeways. The only interstate in the Marin County OA is Interstate 580 which connects Marin County to Contra Costa County via the Richmond-San Rafael Bridge. There are several major state highways that traverse the Marin County OA including Highways 101, 1 and 37. See figure 3.212 for a map of roadways in the Marin County OA.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
393
Figure 3.213: Marin County Highways
Source: Marin Convention and Visitors Bureau
Multi-vehicle accidents usually occur in low-visibility conditions. Marin County often experiences fog which can hamper visibility. Road hazards, including black ice and landslides, can cause multi-vehicle accidents in good visibility. On roads with high traffic volume, a chain-reaction crash can occur when motorists are unable to stop. Determining the cause of multi-vehicle accidents is often difficult. Multi-vehicle accidents are particularly deadly due to the heightened risk of injury and chances of a fire occurring. Multi-vehicle accidents can also overwhelm local responding units, making rescue more difficult. Accidents in remote areas can hamper the l ~<;>U·N· TY OF
~ ARIN
a
~
s, nd
-rt1J's
Tule EIII
Drak~s
&y ~
Pacific
Ocean
Gin Camp@
WU<ltat
(~/ "....,
--·
e O•c::::::i-==2,..s ___ s MIies
SONOMA
COUNTY
~ Mann •@iMIM'lhii
San Pablo
Bay
San
rancisco
Bay gel sland
tate Park
f.'::on BlhrBeldJPR"E-SID.,cl0<--10-1 ~ O ~ S.F. 1
)
~-------------------------------------.!!!!~End!!1'..,_ ft univ,~itvnf-'\ 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
394
ability to receive medical help. A mass fatality and/or hazmat incident could occur on any one of Marin County’s major highways.
In March 2006, a freak blizzard with two to four inches of slush caused a 28-car pileup on Highway 101 at the then Waldo Tunnel. Two people were killed and more than a dozen injured, and the northbound lanes were closed for 11 hours. The pileup scattered wreckage 350 to 400 feet along the road.
In December 2022, a Marin Transit bus overturned in rainy weather in San Rafael but there was only one person aboard.
Train Accident
A train accident is a violent and destructive crash involving a train. There are several different kinds of train accidents that can occur. A train can derail due to defects in or the compromising of track infrastructure, human error, mechanical or maintenance issues on the train itself, and/or from hitting another object such as a vehicle or another train. A train can also hit another object without derailing. Train accidents can be classified in terms of both cause and effect:
Classification of train accidents by cause:
Engineer/Conductor Error
• Passing signals at danger
• Excessive speed
Mishandling of the engine
• Failure to check brakes and safety systems
• Failure to stop at required positions
Controller Error
• Allowing two trains into the same occupied block section • Other Railway Personnel Error (shunters, porters, maintenance workers) • Accidental track obstruction
• Improper maintenance activities (leading to warped rails, damaged ties, faulty signals, etc.)
Mechanical Failure of Rolling Stock (Train Cars)
• Poor maintenance
• Poor design
• Undetected damage
• Overloading of or improperly secured freight
• Combustion fire
Civil Engineering Failure
• Track faults
• Bridge and tunnel collapses
• Poor track or junction layout
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
395
Non-Railway Personnel Error
• Accidental track obstruction
Deliberate Acts
• Deliberate track obstruction
• Intentional damage to track infrastructure or the train itself • Level crossing misuse
Natural Causes
• Track obstruction due to landslides, avalanches, floods, or felled trees • Fog or snow that can obscure signals or the position of a train • Wet leaves
Classification of Train Accidents by Effect:
Collision (any of which can cause a derailment)
• Head-on collision
• Rear collision
• Slanting collision
• Collision with buffer stops
• Collision with obstructions of the track
Derailment
• Plain track
• Curve
• Junction
Other
• Fires, explosions, and release of hazardous chemicals • People falling from trains
A train accident can cause significant loss of life and/or property and environmental damage depending on the severity of the accident and the type of materials involved. In addition to hazardous commodities being transported, fuel tanks on locomotives can also cause a fire and/or an environmental hazard.
The Sonoma-Marin Area Rail Transit (SMART) is the North Bay’s passenger rail service for Marin County. SMART is a Class 4 railroad. The current 45-mile system includes stations in Novato, San Rafael, and Larkspur. SMART’s system also includes a bicycle and pedestrian pathway along the rail corridor. SMART also provides freight service to North Bay businesses in Marin County on the same line. SMART Freight operates on the historic rail corridor constructed by Southern Pacific Railroad in the late 1800s and later utilized by Northwestern Pacific Railroad (NWP) beginning in 1914. See Figure 3.213 for a map of the SMART commuter and freight line.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
396
Figure 3.214: SMART Commuter and Freight Line
Source: SMART
There are currently 24 bridges in the segment of the SMART line from San Rafael to Santa Rosa in Sonoma County as well as 63 at grade crossings. A positive train control system was implemented for the length of the service corridor for customer and pedestrian safety.
The SMART commuter fleet consists of nine two-car Nippon Sharyo DMU trainsets. Each DMU car is powered by a Cummins QSK19-R diesel engine. Trains may be as long as station platforms provided there are cabs facing the outer ends. Each two-car train has room for over 300 passengers. Trains operate 19 round trips on weekdays at an average of 34.1 miles per hour. SMART freight trains do not transport hazardous materials and currently carry grain, food supplies and lumber.
On March 19th, 2023, a SMART freight train carrying corn tipped over in Sonoma County after heavy rainfall saturated the railroad tracks. Several cars derailed. There were no injuries.
On February 10th, 2023, a SMART commuter train hit a car in Novato, killing a woman. No passengers on the train were injured.
On September 17th, 2020, a SMART commuter train hit a car in San Rafael, injuring a woman.
No passengers on the train were injured.
A July 2016 fire aboard one of Toronto's Nippon Sharyo units revealed a design flaw in the engine's crankshaft that would result in premature wear. SMART delayed operations until the engines could be serviced to correct the problem.
B li&iil
MTNnOCJi:io COl'N1i
!ON0.\1.\
·coi.r.,·Tv
,\LOON
L'Ol,'NIY
;s.ArA
COLINl'Y
BRAZOS I FREIGHT L
(S ~'Ml,\\\
-lr.imm--::-::-
OCTOBE ·
!::...
CAPITOL I CO MMUTER
FREIGHT LINE
Sl.lLi\NO
COUNTY
COl\'TR/\ CO_SH
COUNI\
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
397
In December 2014, rains washed away some of the SMART train track beds near Petaluma in Sonoma County, but the trains were not running.
Airplane Accident
An airplane accident is an occurrence associated with the operation of an airplane where a person is fatally or seriously injured and where the aircraft sustains damage or loss. Airplane accidents can occur as a result of pilot error, mechanical issues associated with aircraft, terrorism, weather, or other human error. The majority of airplane accidents and fatalities occur before or during takeoff and during approach or landing.
There are two airports, two heliports and a seaplane base in Marin County, though none of them serve commercial flights. They are all private with the exception of the Gnoss Field Airport which is operated by Marin County Public Works.
Gnoss Field Airport - DVO
Novato, California
San Rafael Airport - CA35
San Rafael, California
San Rafael Private Heliport - 5CA3
San Rafael, California
Commodore Center Heliport - JMC
Sausalito, California
Commodore Center Seaplane Base - 22CA
Sausalito, California
There could be numerous different impacts from an airplane crash in the Marin County OA. The worst-case scenario would be if a large commercial aircraft were to crash in any heavily populated area of the OA resulting in a mass casualty incident and significant damage on the ground. The chances of this occurring are small. The most likely significant event would be a small to medium size airplane having an incident in a heavily populated area of the OA.
On July 8th 2023, a single-engine Cessna 172 plane crashed near San Rafael Airport. The plane’s tail hit power lines before the plane struck the ground. One person was killed.
On May 9th, 2022, a fixed-wing, single-engine Vans RV-10 plane crashed into a hillside near the Golden Gate Bridge. At the time of the crash, the area was surrounded by thick fog. Two people were killed.
On May 16th, 1946, a U.S. Army B-17 Flying Fortress aircraft crashed into White's Hill near Fairfax, California. Two people were killed and six seriously injured.
Ship Accident
A ship accident is a marine event that occurs directly in connection with the operation of a ship and results in loss of life, environmental damage, material damage to a ship, and/or the total loss of a ship. Ship accidents can occur as a result of a fire, explosion, collision, grounding/shoaling, contact, heavy weather damage, hull cracking, or hull defect that can result in the immobilization of main engines, penetration of the ship, extensive structural damage, l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
398
and/or a breakdown that necessitates towing assistance. A ship accident can occur with both cargo and passenger ships.
Since the closure of the Marinship shipyard, Marin County does not have a marine port. There are several ferry terminals in Marin County that cater to passenger vessels:
Larkspur Landing, also known as the Larkspur Ferry Terminal, serves the Golden Gate Ferry which travels to two locations in San Francisco.
The Tiburon Ferry Terminal serves the Golden Gate Ferry which travels to two locations in San Francisco and the Angel Island–Tiburon Ferry Company for ferry service to Angel Island State Park.
The Sausalito Ferry Terminal serves the Golden Gate Ferry and the Blue & Gold Fleet which both travel to San Francisco.
The Golden Gate Ferry has a fleet of four catamarans and three monohull vessels. The monohull vessels are named M.S. Marin, M.S. San Francisco, and M.S. Sonoma. The Marin can carry 750 passengers, and the San Francisco and Sonoma can carry 630 passengers each.
The catamarans are named the M.V. Del Norte, M.V. Golden Gate, M.V. Mendocino, and M.V.
Napa. The Del Norte has a capacity of 400 passengers while the other three vessels have a capacity of 450 passengers. The Blue & Gold Fleet operates a fleet of 21 vessels, the largest of which can hold approximately 450 people. The Angel Island Tiburon ferry operates three vessels, the largest of which can hold 400 people.
There are numerous public and private marinas and boating facilities in the Marin County OA along San Francisco Bay, Richardson Bay and Tomales Bay that serve smaller passenger watercraft and commercial fishing vessels.
The most significant maritime incident that could occur in the Marin County OA would be from a large ferry at full capacity having an incident in San Francisco or Richardson Bay or at one of the ferry terminals.
On November 23rd, 2018, a ferry carrying 53 passengers from Larkspur to San Francisco crashed into the dock at the San Francisco Ferry Terminal. Two people on board were injured.
Both the ferry and the San Francisco Ferry Building dock sustained damage in the crash. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
399
SECTION 4.0: MITIGATION STRATEGY
Mitigation projects that address the goals and objectives developed in the previous section were identified, evaluated, and prioritized. These actions form the core of the hazard mitigation plan. A capabilities assessment was conducted by Marin County and its participating jurisdictions, reviewing existing local plans, policies, and regulations for any other capabilities relevant to hazard mitigation planning. An analysis of their capability to carry out these implementation measures with an eye toward hazard and loss prevention was conducted.
The capabilities assessment required an inventory of each jurisdiction’s legal, administrative, fiscal and technical capacities to support hazard mitigation planning. After completion of the capabilities assessment, each jurisdiction evaluated and prioritized their proposed mitigations.
Each jurisdiction considered the social, technical, administrative, political, legal, economic, and environmental opportunities and constraints of implementing a particular mitigation action. This step resulted in a list of acceptable and realistic actions that address the hazards identified in each jurisdiction.
4.1 CHANGES IN DEVELOPMENT
Overall hazard vulnerability has remained unchanged over the past 5 years due to development and population changes. Marin County development and populations have increased in some cities and decreased in several others over the last 5 years. Overall vulnerability and risk reduction has been achieved through carefully planned development and application of the capabilities detailed in Section 4.3 CAPABILITY ASSESSMENT. 44 CFR Requirement §201.6(c)(3) [The plan shall include the following:] A mi�ga�on strategy that provides the jurisdic�on’s blueprint for reducing the poten�al losses iden�fied in the risk assessment, based on exis�ng authori�es, policies, programs, and resources, and its ability to expand on and improve these exis�ng tools.
§201.6(c)(3)(i) [The hazard mi�ga�on strategy shall include a] descrip�on of mi�ga�on goals to reduce or avoid long‐term vulnerabili�es to the iden�fied hazards. §201.6(c)(3)(ii) [The hazard mi�ga�on strategy shall include a] sec�on that iden�fies and analyzes a comprehensive range of specific mi�ga�on ac�ons and projects being considered to reduce the effects of each hazard, with par�cular emphasis on new and exis�ng buildings and infrastructure. All plans approved by FEMA a�er October 1, 2008, must also address the jurisdic�on’s par�cipa�on in the NFIP, and con�nued compliance with NFIP requirements, as appropriate. §201.6(c)(3)(iii) [The hazard mi�ga�on strategy shall include an] ac�on plan, describing how the ac�on iden�fied in paragraph (c)(3)(ii) of this sec�on will be priori�zed, implemented, and administered by the local jurisdic�on. Priori�za�on 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.
§201.6(c)(3)(iv) For mul�‐jurisdic�onal plans, there must be iden�fiable ac�on items specific to the jurisdic�on reques�ng FEMA approval or credit of the plan. §201.6(c)(4)(ii) [The plan shall include a] process by which local governments incorporate the requirements of the mi�ga�on plan into other planning mechanisms such as comprehensive or
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
400
Marin County is a county located in the northwestern San Francisco Bay Area. As of the 2020 census, the population was 262,231. Its county seat and largest city is San Rafael. Marin County is across the Golden Gate Bridge from San Francisco and is included in the San Francisco–Oakland–Berkeley, CA Metropolitan Statistical Area.
Unincorporated Marin County includes most of West Marin, which borders the Pacific Coast and is the most rural part of the county, with Golden Gate National Recreation Area and the Point Reyes National Seashore occupying much of the area and small communities mixed throughout. There are also pockets of unincorporated areas along the central, Highway 101 corridor and the San Francisco Bay shoreline. Altogether, there are 22 distinct communities within unincorporated Marin County.
According to the U.S. Census, the population in unincorporated Marin is 66,987. While population in both the unincorporated County and the County grew in the first half of the 2010s, since 2017 the population has decreased in both areas, with the most significant drop occurring in the most recent year. Between 2020 and 2021, the population in the unincorporated County decreased by 2.6%, over twice as much as in the County as whole (1.2%). The Association Bay Area of Governments (ABAG) projects that the population in the unincorporated County will grow by only 2% in the next two decades.
Based on 2021 data from the California Department of Finance (DOF), the unincorporated area of Marin has 24,778 single-family homes constituting 83% of the total housing stock, 4,452 multi-family homes comprising 15% of all housing, and 588 mobile homes, for a total of 29,818 homes. The beauty of the natural landscape helps define the character of the community, but it also presents risk of natural hazards that present challenges to locating and building new housing, which have been skillfully met in the 2023 update to Marin County’s Housing Element.
The Regional Housing Needs Assessment (RHNA) allocation for unincorporated Marin for the 2023-31 planning period has been determined by ABAG to be 3,569 housing units, including 550 units for extremely low income, 550 units for very low-income households, 634 units for low-income households, 512 units for moderate-income households, and 1,323 units for above moderate-income households.
Table 4.1 presents entitled projects and pending entitled projects in unincorporated Marin County.
Table 4.1: Unincorporated Marin County Future Growth Areas Development # of
Units
# of
Parcels
Project
Date Acres
Fire
Severity
Zone
Flood
Zone
North Knoll Rd/Saint Thomas Dr 59 2 N/A 3.7 NA NA
Pan Pac Ocean Site 32 4 N/A 16 NA NA
Strawberry Commercial 60 4 N/A 2 NA NA
Strawberry Rec District Site 46 1 N/A 2.3 NA NA
Strawberry Village Center 100 2 N/A 3.3 NA NA
Oak Manor Commercial Center 36 2 N/A 1.6 NA NA
Kentfield Commercial
Underutilized
71 12 N/A 2.4 Moderate AE
Sloat Garden Center 31 2 N/A 1.1 NA AO
Marin County Juvenile Hall 80 1 N/A 2.7 High NA
Marinwood Plaza 125 4 N/A 125 High NA
Office Building (Across from
Juvenile Hall)
58 1 N/A 2.32 High NA
1 ~<;>U·N· TY OF a
~ ARIN ~
I
I
I
I
I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
401
St. Vincents 680 3 34 NA NA
Marin Gateway Center 100 1 5 NA X02
MLK Academy School 63 1 6 High NA
825 Drake 74 1 Moderate NA
Atherton Corridor 147 4 7.4 Moderate NA
Black Point (Vacant) 58 1 14.5 Moderate NA
Buck Center Vacant Property 249 2 12.5 NA NA
Greenpoint Nursery 53 1 3.5 Moderate AE
Bernard Osher Marin Jewish
Community Center
49 4 1.6 Moderate NA
Cal Park 110 11 3.7 NA AE
Church of Jesus Christ 35 1 1.2 Moderate NA
McPhail School 33 3 1.1 NA AE
Old Gallinas Children Center 50 1 1.7 Moderate NA
San Quentin Adjacent Vacant
Property
230 1 7.7 NA NA
Office – Lagunitas (Upper
Floors and Rear Prop)
30 2 1.5 Moderate NA
San Domenico School 50 1 1.7 High NA
Sacramento/San Anselmo
Properties
64 4 2.1 Moderate –
NA
NA
Holiday Inn Mill Valley 72 1 2.4 NA AE
Jack Krystal Hotel Parcel Site 36 1 1.2 NA AE
Shoreline Unified School
District
44 2 2.2 Moderate NA
Olema Underutilized 36 4 3.6 Moderate –
NA
AE
Pt Reyes Coast Guard
Rehabilitation/Conversion
50 1 10 Moderate NA
Pt. Reyes County Vacant Site 37 2 1.9 Moderate NA
Shoreline Unified School
District
44 2 2.2 Moderate NA
Tomales (Vacant) 30 5 32 Moderate NA
Total 3,122 95
Table 4.1: Unincorporated Marin County Future Growth Areas Source: Marin County Department of Community Development
4.2 CHANGES IN PRIORITIES
The overall hazard mitigation priorities in Marin County and its participating jurisdictions have not changed since the 2018 MJHMP update. However, the strategies that support the overall county priorities have changed since the 2018 MJHMP and are reflected in the sections below.
There were many projects that were either ongoing day-to-day activities or were response related that were deleted from the 2018 MJHMP project list and not carried over to this plan update. Several actions were completed, and new projects were added to coincide with the changes in priorities, progress in local mitigation efforts and changes in development.
4.2.1 VULNERABILITY AND RISK REDUCTION
All new development occurring in the future growth area identified in Table 4.1 will provide hazard vulnerability and risk reduction for the county. This reduction will occur due to the anticipated improvements and investments implemented in the 2023 revisions to the Marin County General Plan. In addition, any new development will comply with the most up-to-date building codes and use the latest techniques, further reducing vulnerabilities throughout the County.
1 ~<;>U·N· TY OF a
~ ARIN ~
I
I
I
I
I
I
I
I
I
I
I
I
-
I I I
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
402
4.3 CAPABILITY ASSESSMENT
Capabilities are the programs and polices currently in place to reduce hazard impacts or that could be used to implement hazard mitigation activities. The capability assessment identifies the local planning mechanisms where information from the 2018 MJHMP is incorporated and where updated hazard mitigation information from this 2023 MJHMP will be incorporated once approved. The capability assessment is divided into four sections: regulatory, administrative and technical, fiscal, and outreach and partnerships.
4.3.1 REGULATORY CAPABILITIES
The legal and regulatory capabilities include existing ordinances and codes that affect the county’s or city’s physical or built environment. Examples of legal and/or regulatory capabilities can include: a jurisdiction’s building codes, zoning ordinances, subdivision ordnances, special purpose ordinances, growth management ordinances, site plan review, general plans, capital improvement plans, economic development plans, emergency response plans, and real estate disclosure plans. The table below lists regulatory mitigation capabilities, including planning and land management tools, typically used by local jurisdictions to implement hazard mitigation activities and indicates those that are in place.
Table 4.2: Legal and Regulatory Capabilities
Plans
Yes/No
Latest
Update
Does the plan/program address hazards?
Does the plan identify projects to include in the mitigation strategy?
Can the plan be used to implement mitigation actions?
Countywide Plan: Water
Resources, Environmental
Hazards, and Public Safety
Sections
Y
2023
Describes hazard areas and regulates current and future development based on known hazard areas.
Expansion and Improvement: The HMP will be informed
by referencing the Safety Element of the General Plan. The City will adopt the approved HMP as part of the General Plan Safety Element to meet the requirements of AB 2140.
Local Coastal Program Y
2023
Pursuant to the California Coastal Act, Marin County’s Local Coastal Program guides land use and development to
ensure protection of public access and other coastal
resources along Marin County’s Pacific coastline.
Expansion and Improvement: Included is a hazards
section with policies that guide development standards and project review for areas subject to hazards including
flooding, bluff retreat, earthquakes, and coastal erosion.
County Emergency
Operations Plan
Y
2018
This plan describes what the County’s actions will be during a response to all hazards. Includes annexes that describe in more detail the actions required of departments/agencies.
Further, this plan describes the role of the Emergency
Operation Center (EOC) and the coordination that occurs between the EOC and the local jurisdiction’s departments and other response agencies.
Expansion and Improvement: This plan may be used for
mitigation in that it describes risk and vulnerability in the county.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
403
Area Housing Authority
Organizational Emergency
Response Plan
Y
Enhances the Area Housing Authority’s ability to effectively respond to emergencies by establishing procedures and
assigning responsibilities.
Expansion and Improvement: This plan may be used for
mitigation in that it describes risk and vulnerability in the county.
Strategic Plan No
Capital Improvements Plan
Y
2021
The Capital Improvement Plan (CIP) was developed
through collaboration between Capital Project staff of
Public Works (DPW) and the County Administrator’s
office. Significant input was provided by multiple County departments, special districts, and enterprise funds of outside the general County General Funds. The CIP
presents the proposed funding for the fiscal year (FY) of 2021-2022 to improve four key areas. Facility
improvements, water resources, road infrastructure, and airports. Expansion and Improvement: CIP identifies
potential hazard mitigation projects.
Economic Development
Plan
Y
2022
The Marin County Economic Vitality Strategic Plan
outlines “Flagship Initiatives” that the County of Marin and community partners will pursue over the next 5 years.
Ultimately, the actions taken are intended to create a
dynamic economy, providing equitable access to good
jobs, opportunities for new business creation and a high quality of life for all Marin’s residents.
Expansion and Improvement: The plan has a strong
focus on the impact of Covid-19 on the local economy, so may be used to show how disasters impact Marin’s
businesses and workforce, but does not have mitigation
projects.
Continuity of Operations
Plan
N
Flood Safety Plan Y Plan addresses flood hazard response, not mitigation. It was created in 2018 and a 2023 update is in progress.
Engineering Studies for
Streams
Y
There are many existing studies on marinflooddistrict.org.
A study of Novato Creek is currently underway.
Expansion and Improvement: These studies do identify
potential hazard mitigation projects.
Open Space Management
Plan
Y
Marin County Parks holds numerous plans that guide
open space management: Strategic Plan, Road and Trail
Management Plan, Vegetation and Biodiversity
Management Plan, Inclusive Access Plan.
Expansion and Improvement: Some of these plans
contain guidance for mitigation projects and will be aligned with the MJHMP to describe developmental trends,
hazards, and potential development in hazard areas.
Regional Transportation
Plan (RTP)
Y
2021
The Transportation Authority of Marin (TAM) participates in the nine-county Metropolitan Transportation
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
404
Commission, which adopted Plan Bay Area 2050. The
plan outlines strategies spread across transportation,
housing, the economy and the environment that seek a
more equitable Bay Area.
Expansion and Improvement: The plan does outline
regional strategies for mitigation that may be used in
Marin.
Stormwater Management
Plan/Program
Y
2022
SWRP is a watershed-level resource planning document
covering the County and Marin’s 11 cities that describes watershed issues, identifies project opportunities with multiple benefits, and creates a prioritized list of project opportunities based on quantifying multiple benefits.
Expansion and Improvement: The Plan will be aligned
with the MJHMP in describing and developing mitigation
actions to address climate change and drought. Water
demand reduction strategies contained in the plan should be considered for inclusion as mitigation activities in the MJHMP.
Repetitive Loss Area
Analysis Y
On July 18, 2023, an expanded and updated multijurisdictional analysis was adopted by the County Board of Supervisors.
Community Wildfire
Protection Plan
Y
2020
CWPP addresses wildfire risk and mitigation measures to take throughout the county.
Expansion and Improvement: The plan can be used to
support and guide mitigation efforts.
Other special plans (e.g.,
brownfields redevelopment,
disaster recovery, coastal
zone management, climate
change adaptation)
Y
25 Community and area plans within Marin. Climate change adaptation policies and programs in Countywide Plan
Safety, Element/Environmental Hazards section. Policies and programs address sea level rise, flooding, extreme heat, wildfire, equitable safety planning for vulnerable populations.
Building Code, Permitting,
and Inspections Y/N Are codes adequately enforced?
Building Code Y
Yes, the Community Development Agency established a
code compliance program to ensure adherence with the
County’s law and regulations related to zoning,
construction, and environmental health.
Expansion and Improvement: Adherence to building
codes, including local codes, regulates growth and
controls land use patterns. Addressing known hazards, as codes are updated, results in lowered risk and potentially fewer losses.
Building Code
Effectiveness Grading
Schedule (BCEGS) Score
Y 3
Yes, codes are adequately enforced. The County’s score
is 3.
Fire department ISO rating: Y 3/3X
The County’s ISO Rating is 3/3x; to be rated a “3” the parcel must be within 1000-ft of a municipal fire hydrant and 5- miles from a fire station. If either of those criteria are not met, the parcel is 3x (the old 9). Furthermore, per the State, if the parcel is more than 5-miles from a fire station, the parcel is rated “10”. Yes, our codes are adequately
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
405
enforced.
Site plan review
requirements Y
Yes, this is adequately achieved.
Land Use Planning and
Ordinances Y/N
Is the ordinance an effective measure for reducing
hazard impacts?
Is the ordinance adequately administered and enforced?
County Code of Ordinances Y
The purpose of this code is to establish the minimum
requirements to safeguard the public health, safety, and general welfare through structural strength, means of
egress facilities, stability, access to persons with
disabilities, sanitation, adequate lighting and ventilation and energy conservation, and safety to life and property from fire and other hazards attributed to the built
environment; to regulate and control the demolition of all buildings and structures, and for related purposes.
Expansion and Improvement: Adherence to local
ordinances regulates growth and enforces standards.
Addressing known hazards, as codes are updated,
results in lowered risk and potentially fewer losses.
Zoning ordinance Y
2023
Zoning ordinances are regularly updated (last update
2023).
Yes, they are adequately administered and enforced.
Expansion and Improvement: Adherence to local
ordinances regulates growth and enforces standards.
Addressing known hazards, as codes are updated,
results in lowered risk and potentially fewer losses.
Subdivision ordinance Y
Yes, the ordinance is adequately administered and
enforced. It is regularly updated (last update 2023).
Expansion and Improvement: Adherence to local
ordinances regulates growth and enforces standards.
Addressing known hazards, as codes are updated,
results in lowered risk and potentially fewer losses.
Floodplain ordinance Y
Marin County Code 23.09 Floodplain Management.
Ordinance 3293 Sec 1, 1999
Expansion and Improvement: Adherence to local
ordinances regulates growth and enforces standards.
Addressing known hazards, as codes are updated,
results in lowered risk and potentially fewer losses.
Natural hazard specific
ordinance (stormwater,
steep slope, wildfire)
Hazards are addressed in the Development Code, Title
22. Regularly updated. Expansion and Improvement:
Adherence to local ordinances regulates growth and
enforces standards. Addressing known hazards, as
codes are updated, results in lowered risk and potentially fewer losses.
Flood insurance rate maps Y
Hard copies of the FEMA Flood Insurance Rate Maps
(FIRM) are maintained in the DPW Land Development
office. Electronic copies are available on MarinMap.org.
Expansion and Improvement: The maps can be used
to support and guide mitigation efforts.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
406
Elevation Certificates
Elevation Certificates are required for all new and
substantially remodeled structures. Hard copies of all
Elevation Certificates since 1982 are maintained in the DPW Land Development office.
Expansion and Improvement: The certificates can be
used to support and guide mitigation efforts.
Acquisition of land for open
space and public recreation
uses
Y
The County of Marin is committed to continuing to
preserve open space.
Expansion and Improvement: As a member of Together
Bay Area, the County has prioritized purchasing multiple open space properties to that may be used as open space preserves and recreation space.
Erosion or sediment
control program Y
Requires property owners to have effective Best
Management Practices in place to control pollutants in
runoff from certain earth-disturbing activities.
Expansion and Improvement: The program can be
used to support and guide mitigation efforts.
Table 4.2: Marin County Legal and Regulatory Capabilities Source: Marin County
Plans
Marin General Plan
California Government Code 65300 requires that every City and County in the state have a General Plan. The Marin General Plan, adopted in 2007, was prepared over a multiyear period that included an extensive public review process. The Marin General Plan was updated in 2015, with the Housing and Safety Elements updated in 2023. The Marin General Plan is the most important policy and planning document in the county and is used by virtually every department. The Marin General Plan is the County's statement of its vision for the future. The Marin General Plan contains policies covering every aspect of the County: land use (how land can be developed), circulation, noise, air quality, housing, open space and conservation, and health and safety.
Marin County specific goals and policies related to mitigation of natural hazards are as follows:
44 CFR Requirement §201.6(c)(4)(ii) [The plan shall include a] process by which local governments incorporate the requirements of the mi�ga�on plan into other planning mechanisms such as comprehensive or capital improvements, when appropriate. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
407
Table 4.3: County of Marin General Plan
Goal/Policy/
Program Explanation
Land Use Element
Goals
The requirements of the land use element are met in the following sections of the General Plan: water resources, community development, planning areas. The goals for these elements are:
To support healthy watersheds and provide clean and adequate water for wildlife and humans.
To utilize the Environmental Corridor Land Use Framework, coordinate with other jurisdictions, and map land use designations.
To establish land use policies for the seven planning areas.
Policies
Overall policies for land use are intended: to protect, improve, and restore resources, including, directing land use to appropriate areas, reducing impacts, establishing land use designations and categories, and setting land use standards.
Programs
Programs for land use include, setting standards, monitoring and assessing programs, coordinating with other jurisdictions, following best practices, maintaining urban, agricultural, and natural corridors, consider amending urban service areas preserve resources, consider sea level rise. Programs also include, updating plans, reviewing codes, and revising zoning maps.
Conservation and Open Space Element
Goal To sustainably manage and preserve open space and biological resources for the benefit of the environment and Marin residents.
Policy
Policies for Conservation and Open Space include; support efforts and continue to acquire open space, balance shoreline protection and access, protect natural resources, support vegetation and wildlife disease management, control non-native plants and species, and restrict use of toxic chemical substances in habitats.
Program
Conservation programs include mapping natural communities, developing monitoring programs, and partnering with local actors.
Open space programs include, coordinating with partners, establish compatible policies, inform and enforce, research, and acquire and protect lands.
Safety Element
Goals To reduce risk, increase safety, and bolster resilience in an equitable manner.
Policies
Policies in the Safety Element are to represent an inclusive, community-led approach to bolstering resilience. Furthermore, policies are evidence of an all-hazard informed, approach to protection, planning, and regulation.
Programs
Programs in the Safety Element include specific outreach and support to vulnerable populations, working with local leaders, coordinating with private and public partners, improving hazard information sharing with residents, improving infrastructure and systems to support/improve emergency response, and utilizing planning functions.
Public Facilities Element
Goal To provide adequate public facilities and services to accommodate the level of development planned by cities and towns and the County.
Policies
Policies to support the County’s Public Facility Element include requiring cost sharing, effective planning, discouraging privatization, and reducing demand on public facilities.
Programs
Programs include requiring fair share contributions, planning for service expansion, preparing naming and sponsorship guidelines, and reducing demand on public facilities.
Table 4.3: Marin County Goals and Policies
Source: Marin County General Plan
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
408
4.3.2 ADMINISTRATIVE AND TECHNICAL CAPABILITIES
The administrative and technical capability assessment identifies the personnel responsible for activities related to mitigation and loss prevention in Marin County. Many positions are full time and/or filled by the same person.
Table 4.4: Administrative and Technical Capabilities
Administrative Yes/No Is coordination effective?
Planning Commission
Y Administrative Services Division handles finance and
purchasing, budgeting, risk management, information
technology, and business licensing for the community.
The department may be responsible for implementing
mitigation actions related to the department’s scope.
Expansion and Improvement: Prioritize new initiatives
that support mitigation activities within the county.
Marin Operational Area
Hazard Mitigation Working
Group
Y The County participates in the Marin Operational Area Hazard Mitigation Working Group that meets quarterly to review and manage Hazard Mitigation projects and
programs. The Hazard Mitigation Committee is the
supporting branch of the disaster council.
Expansion and Improvement: Prioritize new initiatives
that support mitigation activities within the County.
Maintenance programs to
reduce risk (e.g., tree
trimming, clearing
drainage systems)
Y Many Flood Zones have creek and drainage
maintenance programs. These only cover a small portion
of creeks in the County, where residents formed a flood zone and where a project was initiated and right of way acquired by the Marin County Flood Control & Water
Conservation District. Under the guidelines of the 2020 Pacific Gas and Electric Wildfire Mitigation Plan, PG&E will assist with mitigation efforts by clearing trees.
Expansion and Improvement: The Marin Wildfire
Prevention Authority will provide funding and educational programs on best practices for prevention efforts. Brush clearance and controlled burns will assist with mitigation efforts.
Mutual aid agreements Y Fire, Law, PW, Water agencies, MHOAC Technical
Yes/No Has capability been used to assess/mitigate risk in the past?
Warning systems/services
(Reverse 911, outdoor
warning signals)
Y Utilizes the emergency warning systems through the EAS system as their primary warning capability. Utilizes the emergency warning systems through telephone, text, and
email notification utilizing reverse 911.
Expansion and Improvement: To ensure the
effectiveness of the emergency warning system and
proper community response, monthly LRAD testing, and
IPAWs drills are required.
Hazard data and
information
Y Yes, previous and new mitigation projects are informed by hazard data and information.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
409
Grant writing Y Yes
Hazus analysis N
Staff/Personnel Resources
Yes/No
Full
Time/
Part
Time
Is staffing adequate to enforce regulations?
Is staff trained on hazards and mitigation?
Is coordination between agencies and staff effective?
Chief Building Official Y/PT Yes
Expansion and Improvement: Integrate mitigation
actions and strategies into the Capital Improvements
Program and annual budgeting.
Planner(s), engineer(s) and
technical staff knowledge
of land development, land
management practices,
and natural hazards.
Y/FT Develops and maintains the General Plan, including the Safety Element.
Develops area plans based on the General Plan, to provide more specific guidance for the development of more specific areas.
Reviews private development projects and proposed capital improvements projects and other physical projects involving property for consistency and conformity with the General Plan.
Anticipates and acts on the need for new plans, policies, and Code changes.
Applies the approved plans, policies, code provisions, and other regulations to proposed land uses.
Expansion and Improvement: Provide opportunities for
continued education to staff to maintain knowledge of new code and regulatory requirements.
Engineer(s), Building
Inspectors/Code
Enforcement Officers or
other professional(s) and
technical staff trained in
construction requirements
and practices related to
existing and new
buildings.
Y/FT
Oversees the effective, efficient, fair, and safe
enforcement of the California Building Code
Expansion and Improvement: Provide opportunities for
continued education to staff to maintain knowledge of
new code and regulatory requirements.
GIS Coordinator Y/FT Yes
Community Development
Staff
Y/FT Develops and maintains the General Plan, including the Safety Element. Develops area plans based on the
General Plan, to provide more specific guidance for the development of more specific areas. Reviews private
development projects and proposed capital
improvements projects and other physical projects
involving property for consistency and conformity with
the General Plan.
Expansion and Improvement: Provide opportunities
for continued education to staff to maintain knowledge
of new code and regulatory requirements.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
410
Engineer(s), project
manager(s), technical staff,
equipment operators, and
maintenance and
construction staff.
Y/FT
Maintains and operates a wide range of local
equipment and facilities as well as providing assistance to members of the public. These include providing
sufficient clean fresh water, reliable sewer services,
street maintenance, storm drainage systems, street
cleaning, streetlights and traffic signals.
Expansion and Improvement: Provide opportunities
for continued education to staff to maintain knowledge
of new code and regulatory requirements.
Floodplain Administrator
Y/FT Reviews and ensures that new development proposals do not increase flood risk, and that new developments
are not located below the 100 year flood level. In
addition, the Floodplain Administrator is responsible for planning and managing flood risk reduction projects
throughout the unincorporated county.
Expansion and Improvement: Provide opportunities
for continued education to staff to maintain knowledge
of new code and regulatory requirements.
Emergency Management
Y/FT Maintains and updates the Emergency Operations Plan for the county. In addition, coordinates local response and relief activities within the Emergency Operation
Center, and works closely with local, state, and federal partners to support planning and training and to
provide information and coordinate assistance.
Expansion and Improvement: Develop a quarterly
countywide emergency management and hazard
mitigation coordination meeting.
Procurement Services
Manager
Y/FT Provides a full range of municipal financial services, administers several licensing measures, and functions as the county’s Procurement Services Manager.
Marin County Sheriff’s
Office Staff
Y/FT Yes, the Marin County Sheriff’s Office is
comprehensively staffed and trained on hazards. In
addition to field services, the responsibilities of the Sheriff’s Office include maintaining the county jail,
providing security to the Superior Court, operating a
countywide communications division, operating a
documentary services division consisting of records,
warrants, civil units, and more.
Expansion and Improvement: Proactively identify
opportunities to coordinate and collaborate with
neighboring jurisdictions to increase County and regionwide capabilities.
Marin County Fire Staff
Y/FT The Marin County Fire has responsibility for fire
suppression and emergency response in commercial,
residential, wildland / urban interface. The Marin County Fire supports implementation of mitigation actions that reduce the risk of wildfire.
The Marin County Office of Emergency Management, a
division of the County Fire Department, conducts
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
411
emergency preparedness activities for the community.
Mitigation activities related to emergency preparedness can be implemented by OEM in partnership with other
county partners.
Expansion and Improvement: Proactively identify
opportunities to coordinate and collaborate with
neighboring jurisdictions to increase County and regionwide capabilities.
Table 4.4: Marin County Goals and Policies
Source: Marin County General Plan
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
412
4.3.3 FISCAL CAPABILITIES
The fiscal capability assessment shows specific financial and budgetary tools available to Marin County such as community development block grants; capital improvements project funding; authority to levy taxes for specific purposes; fees for water, sewer, gas, or electric services; impact fees for homebuyers or developers for new development; ability to incur debt through general obligations bonds; and withholding spending in hazard-prone areas.
Table 4.5: Marin County Fiscal Capabilities
Financial Yes/No
Has the funding resource been used in past and for what type of activities?
Could the resource be used to fund future mitigation
actions?
Capital improvements
project funding Y Yes, Capital Improvements Project funding has been used in the past and can be used for future mitigation projects.
Authority to levy taxes for
specific purposes
Y
Post Prop 13 and Prop 218 the success in levying taxes
for mitigation projects has been significantly reduced.
Many flood-prone areas historically relied on special taxes to build out levee improvements and pump stations. In the last 20 years (a total of 4) special tax measures for flood mitigation projects have not passed. In March 2020, tax Measure C was passed. The measure will raise
approximately $20 million annually to fund wildland fire hazard mitigation efforts throughout the county. Marin
Wildfire Prevention Authority (MWPA) was formed to
serve as the governing body to manage the funds raised
through Measure C funds go to public outreach,
vegetation management, fire hazard assessments, among
other projects.
Fees for water, sewer, gas, or
electric services (water - fire
flow increase, sewer, more
research on G&E)
Y
Funding has not been used in the recent past for
mitigation, but could possibly fund future mitigation
activities. For example, some Special Districts are
considering potential projects with dual water storage and flood benefit utilizing water fees.
Impact fees for new
development Y
Road and transportation related impact fees are collected in connection with building permit issuance. These funds are not available for future mitigation.
Storm water utility fee
Y
Storm water fees have been used for mitigation projects in Flood Zone 9, including: bridge replacement, pump
stations, levee evaluations, and stormwater detention
basin construction. The Zone 9 fee expires in 2027. We
are following the work of other agencies after SB 231 to see if the County would pursue it again.
Incur debt through general
obligation bonds and/or
special tax bonds N
This approach has been taken in the 1980s for flood
mitigation in Novato creek, but not recently. They typically require voter approval to levy a special tax to pay back the bonds but those have not been successful in recent years.
Incur debt through private
activities N
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
413
Community Development
Block Grant
Y
The County has been administering the CDBG program
for 30+ years through a collaboration with the cities and towns. Funds are currently used to serve low-income
residents of Marin and address historical patterns of
segregation in our communities. Priorities for the use of funds are set through a Countywide Priority Setting
committee. Given the small amount of funds available,
less than $1.5 million countywide and many competing
needs, this may not be a viable source for mitigation
funds.
Other federal funding
programs Y
Yes, federal funding has been used for mitigation projects through Emergency Management Performance Grant and
the Hazard Mitigation Assistance Program.
State funding programs
Y
There have been several Department of Water Resources
grants in support of flood mitigation projects and there will likely continue to be in the foreseeable future.
The State Coastal Conservancy grants have funded sea
level rise adaptation.
Table 4.5: Marin County Fiscal Capabilities
Source: Marin County
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
414
4.3.4 OUTREACH AND PARTNERSHIPS CAPABILITIES
The outreach and partnerships capability assessment shows outreach and public education programs available to the County and the County partnerships utilized to promote those programs.
Table 4.6: Marin County Community Outreach
Outreach and Partnerships Yes/No Could the program/organization help implement future mitigation activities?
Local citizen groups or non-profit
organizations focused on
environmental protection, emergency
preparedness, access and functional
needs populations, etc.
Yes
Yes, these groups can assist with informing
project plans.
Expansion and Improvement: Proactively
identify opportunities to coordinate and
collaborate with neighboring jurisdictions to
increase County and region-wide capabilities.
Ongoing public education or
information program (e.g., responsible
water use, fire safety, household
preparedness, environmental
education)
Yes
Yes, these communities can assist with
informing project plans.
Expansion and Improvement: Proactively
identify opportunities to coordinate and
collaborate with communities to increase
educational opportunities.
Natural disaster or safety related school
programs
Yes
Yes, school partners can assist with informing
project plans.
Expansion and Improvement: Proactively
identify opportunities to coordinate and
collaborate with schools to increase
educational opportunities.
StormReady certification
Yes
Marin County is a StormReady community.
Expansion and Improvement: Proactively
identify opportunities to expand participation.
Firewise Communities certification
Yes
With over 80 Firewise Communities, Marin is
the fastest growing "Firewise USA" county in
the nation. These communities can assist with
informing project plans.
Expansion and Improvement: Proactively
identify opportunities to expand participation
and increase educational opportunities.
Community Rating System Yes Marin County is a Class 6 CRS community Public-private partnership initiatives
addressing disaster-related issues
Yes
Through Marin Voluntary Organizations Active
in Disasters, the County of Marin leverages
partnerships with public-private partners for
disaster related initiatives.
Expansion and Improvement: Proactively
identify opportunities to coordinate and
collaborate.
Table 4.6: Marin County Community Outreach
Source: Marin County
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
415
4.4 PARTICIPATION IN THE NATIONAL FLOOD INSURANCE PROGRAM Marin County has participated in the Regular Phase of the NFIP since March 1, 1982. Since then, the County has administered floodplain management regulations that meet or exceed the minimum requirements of the NFIP. Under that arrangement, residents and businesses paid the same flood insurance premium rates as most other communities in the country.
The Community Rating System (CRS) was created in 1990. Marin County has been in the CRS program since May 1, 2016. The program is designed to recognize floodplain management activities that are above and beyond the NFIP’s minimum requirements. CRS is designed to reward a community for implementing public information, mapping, regulatory, loss reduction and/or flood preparedness activities. On a scale of 10 to 1, Marin County is currently ranked Class Six community, which gives a 20% premium discount to individuals in the unincorporated Marin County Special Flood Hazard Area (SFHA), and a 10% discount to policyholders outside the SFHA.
Presently, the County manages its floodplains in compliance with NFIP/CRS requirements and implements a floodplain management program designed to protect the people and property of the County. Floodplain regulations are a critical element in local floodplain management and are a primary component in Marin County’s participation in the NFIP. As well, Marin County’s floodplain management activities apply to existing and new development areas, implementing flood protection measures for structures and maintaining drainage systems to help reduce the potential of flooding within the unincorporated Marin County.
As part of the County’s efforts to comply with NFIP, Marin County will make updates and revisions to these regulations periodically to ensure they are most effective at minimizing the threat of harm from flood events. These updates and revisions may be promoted by changes in local demographics, shifts in land use, changes to flood regimes such as frequency and intensity of flood events, and other factors that may warrant action. The County will also continue to incorporate any changes to the locations and designations of mapped floodplains into future planning documents, including future updates to this Plan.
The County will also explore opportunities to enforce or enhance County ordinances, building code, and other regulatory actions to address substantial improvements/substantial damage properties. Marin County will consider developing a Substantial Damage Management Plan.
The Marin County will continue to manage their floodplains in continued compliance with the NFIP. An overview of the Marin County’s NFIP status and floodplain management program is discussed in Table 4.7. Additional information on the Marin County’s CRS program follows.
The activities credited by the CRS program provide direct benefits to Marin County and its residents,
including:
• Enhanced public safety;
• A reduction in damage to property and public infrastructure; • Avoidance of economic disruption and losses;
• Reduction of human suffering; and
• Protection of the environment.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
416
The activities for which Marin County implements and receives CRS credits include:
310 Elevation Certificates – Marin County receives credit for creating Construction Certificate Management Procedures as well as to maintaining Post-FIRM elevation certificates. 320 Map Information Services – Marin County receives credit for providing map information to inquirers in all seven elements such as providing information from the FIRM necessary for flood insurance, notifying inquirers of the mandatory purchase of flood insurance for all federally backed loans, providing information regarding properties located in a floodway, sea level rise area, tsunami or dam inundation area, repetitive loss areas, and areas that should be protected such as wetlands and critical habitat.
330 Outreach Projects – Marin County has a robust outreach program and receives maximum credit for this Activity. The County mails out an annual brochure prior to the rainy season to properties in the Special Flood Hazard Area, Repetitive Loss Areas, Tsunami and Dam inundation areas and to local lenders, real estate brokerages and insurance companies. Marin County also receives credit for its social media outreach on Facebook, Twitter and NextDoor. 340 Hazard Disclosure – Marin County works with local real estate brokerages to encourage them to advise prospective home buyers of required disclosures and receives credit for this Activity.
350 Flood Protection Information – Marin County receives credit for Elements in this Activity by maintaining required information documents available in the Marin County Library catalog as well as documents that are pertinent to residents. The County also receives credit for maintaining a presence on the County Public Works website. 360 Flood Protection Assistance – Marin County receives credit for providing property protection advice. The County also provides information about available financing, such as grants and other funding sources, to all who inquire. County staff is also available to make site visits to assist residents.
370 Flood Insurance Promotion – Marin County receives credit for advising people about flood insurance.
410 Floodplain Mapping – Marin County receives credit for mapping special hazards such as tsunamis.
420 Open Space Preservation – Marin County receives credit for preserving open space, preserving the natural functions of open space, creating incentives for preserving open space and for maintaining low density zoning regulations.
430 Higher Regulatory Standards – Marin County receives credit for many of the elements under this Activity such as freeboard, foundation protection, providing local drainage protection, and administering floodplain management regulations. The County also receives credit for l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
417
creating, adhering, and enforcing a robust building code. The County also enforced the floodplain management provisions of our zoning, subdivision and building code ordinances. 440 Flood Data Maintenance – Marin County receives credit for maintaining digital Flood Rate Insurance Maps (FIRM). Electronic availability improves public access. Maintaining copies of previous version of the FIRMs provides a significant research tool and valuable service to the residents of Marin County.
450 Stormwater Management – Marin County receives credit for maintaining a Storm Water Management system via healthy erosion and sediment control requirements and water quality regulations. The County regulates development on a case-by-case basis to ensure that runoff is treated before it leaves the site. The County also ensures that stormwater runoff from a site will not exceed the pre-development runoff. The County promotes the use of onsite bio-retention areas or other treatment facilities have been provided to mitigate runoff and water quality. The County enforces regulations to minimize erosion from land disturbance due to construction. 502 Repetitive Loss – Marin County is a Category C community with greater than 50 repetitive Loss properties. The repetitive loss areas are mapped and can be viewed by the public on MarinMap.org. A notice is mailed to each property in the repetitive loss area to advise them of flood prevention measures, insurance requirements and availability, and available financial assistance.
510 Floodplain Management – Marin County receives credit for both its Floodplain Management Plan and its Repetitive Loss Area Analysis. The County has adopted the Marin County MultiJurisdictional Local Hazard Mitigation Plan and produces an annual progress report. Marin County participates in FEMA’s Home Elevation Program which is actively raising homes in the Special Flood Hazard Area.
520 Acquisition and Relocation – Marin County receives some credit for removing homes that have been demolished from the Special Flood Hazard Area.
530 Flood Protection – Marin County receives credit for elevating structures in the Special Flood Hazard Area above the Base Flood Elevation. Staff also provide information on other flood protection techniques such as barriers, wet floodproofing and dry floodproofing. Marin County participates in FEMA’s Home Elevation Program which is actively raising homes in the Special Flood Hazard Area.
540 Drainage Systems Maintenance – Marin County receives credit for removing debris from natural drainage channels and maintaining an active and ongoing maintenance program of problem site area. Marin County also has strong stream dumping regulations which includes outreach to the public.
610 Flood Warning and Response - Marin County receives credit for all of the Elements in the Flood Warning and Response Activity. These Elements include our flood threat recognitions system that identifies an impending flood, our emergency warning dissemination system that warns the public of impending flood, our flood response plan and operations, and coordination with critical facility operators. Marin County is also a registered Storm Ready Community and a Tsunami Ready Community. Marin County receives credit for annual outreach advising l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
418
residents of flood warning and safety precautions. The County organizes and participates in an annual flood exercise with the purpose of being prepared for an actual activation of the operations. Following an exercise, the County produces an After Action Report which includes lessons learned as a method to document and improve our flood warning and response procedures.
630 Dams: Credit is provided for a State Dam Safety Program.
Table 4.7: Participation in the National Flood Insurance Program (NFIP) NFIP Topic Source of Information Comments
Insurance Summary
How many NFIP policies
are in the community?
What is the total premium
and coverage?
State NFIP Coordinator or
FEMA NFIP Specialist
As 10/2/23 there are 1327 policies in
force. Total premiums $1,734,601.
Coverage is $406,7104,000.
How many claims have
been paid in the
community? What is the
total amount of paid
claims? How many of the
claims were for
substantial damage?
FEMA NFIP or Insurance
Specialist
As of 10/2/23 the total number of claims
was 773. Total amount of paid claims is
$10,173,472.49.
Since 1978, there have been 51
substantial damage claims.
How many structures are
exposed to flood risk
within the community?
*“flood risk” is defined as
the 1% annual chance flood
(100-year flood. Numbers
are from overlay of FEMA
SFHA and building stock
data.
Community Floodplain
Administrator (FPA)
There are 4536 buildings in the SFHA in
the unincorporated County
Describe any areas of
flood risk with limited
NFIP policy coverage
Community FPA and
FEMA Insurance
Specialist
None
Staff Resources
Is the Community
Floodplain Administrator
or NFIP Coordinator
certified?
Community FPA No
Is floodplain management
an auxiliary function?
Community FPA Yes
Provide an explanation of
NFIP administration
services (e.g., permit
review, GIS, education or
outreach, inspections,
engineering capability)
Community FPA Permits are reviewed for FEMA regulation
and compliance. GIS is used to ascertain
if property is in a flood zone. A final
inspection is performed to ensure
compliance. An annual outreach is
mailed to all properties in SFHA.
What are the barriers to
running an effective NFIP
program in the
community, if any?
Community FPA There are no barriers to running an
effective NFIP program.
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
419
Table 4.7: Participation in the National Flood Insurance Program (NFIP) NFIP Topic Source of Information Comments
Compliance History
Is the community in good
standing with the NFIP?
State NFIP Coordinator,
FEMA NFIP Specialist,
community records
yes
Are there any outstanding
compliance issues (i.e.,
current violations)?
no
When was the most recent
Community Assistance
Visit (CAV) or Community
Assistance Contact
(CAC)?
9/15/20
Is a CAV or CAC
scheduled or needed?
The next scheduled CAV will be October
19, 2023
Regulation
When did the community
enter the NFIP?
Community Status Book
http://www.fema.gov/
national-flood-insuranceprogram/national-floodinsurance-programcommunity-status-book March 1, 1984
Are the FIRMs digital or
paper?
Community FPA Marin County has both digital and paper
FIRMS
Do floodplain
development regulations
meet or exceed FEMA or
State minimum
requirements? If so, in
what ways?
Community FPA Marin County regulations meet and
exceed FEMA requirements in the
following: development limitations, higher
regulatory standards for freeboard,
foundation protection, and building codes.
Marin has adopted and enforces
international building Codes.
Provide an explanation of
the permitting process.
Community FPA,
State, FEMA NFIP
Flood Insurance
Manual
http://www.fema.gov/
flood-insurancemanual
Community FPA,
FEMA CRS
Coordinator, ISO
representative
CRS manual http://
www.fema.gov/library/
viewRecord.do?id=2434
Permit applications are received,
reviewed, and approved by professional
staff. Inspections are required at
foundation, close-in and at final. All
projects that will be constructed in the
SFHA will be subject to the provisions of
Marin County Code 24.04 Development
Code and 23.09 Floodplain Management
Code. The finished floor elevation of any
substantial remodel in the SFHA must be
at least 1 foot above the BFE.
Community Rating System (CRS)
Does the community
participate in CRS?
Community FPA, State,
FEMA NFIP
yes
What is the community’s
CRS Class Ranking?
Flood Insurance Manual
http://www.fema.gov/
flood-insurance-manual
Class 6
1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
420
Table 4.7: Participation in the National Flood Insurance Program (NFIP) NFIP Topic Source of Information Comments
What categoriesand
activities provide CRS
points and how can the
class be improved?
Marin receives credit in Series 310, 320,
330, 340, 350, 360, 370, 410, 420, 430,
440, 450, 510, 520. 530, 540, and 610.
Marin County could improve its class
ranking by doing more work in Activities
420, 430, 450, 520, and 630
Does the plan include
CRS planning
requirements
Community FPA,
FEMA CRS
Coordinator, ISO
representative
CRS manual http://
www.fema.gov/library/
viewRecord.do?id=2434
yes
Table 4.7: Participation in the National Flood Insurance Program (NFIP) Source: FEMA, Marin County
NFIP Insurance Coverage Details
Unincorporated Marin County joined the NFIP on March 1, 1982. NFIP insurance data provided by FEMA indicates that as of June 22, 2023, there were 1462 policies in force in the unincorporated Marin County with $1,994,164 in premiums, resulting in $452,421,500 of insurance in force.
There have been 889 closed paid losses totaling $10,360,625. Fifty-one (51) of the claims were considered substantial damage losses.
Of these losses, 572 parcels were in A or V zones, and 317 were in B, C, or X zones. Of the 889 claims, 736 were associated with pre-FIRM structures and 33 with post-FIRM structures.
As of October 19, 2023, there were ninety-three (93) repetitive loss structures in the unincorporated County. Five (5) were in X zones, one (1) was in an A 0.2% zones, one (1) was in an AH zone, three(3) were in AO zones , four (4) were in A zones, fifty-four (54) were in AE zones, fifteen (15) were in AE Floodway zones, and ten (10) were in VE zones. These repetitive loss structures account for $5,090,322 of the total losses in unincorporated Marin County. There were 11 severe repetitive loss properties in unincorporated Marin County totaling $1,152,259.
Repetitive Loss Structures
Repetitive Loss Residential Structures: 84
Repetitive Loss Non-Residential Structures: 9
Severe Repetitive Loss Residential Structures: 6
Severe Repetitive Loss Non-Residential Structures: 3
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
421
4.4.1 SUBSTANTIALLY IMPROVED OR SUBSTANTIALLY DAMAGED PROPERTIES The NFIP includes a requirement that new buildings and substantially improved buildings be constructed in ways that minimize or prevent damage during a flood. This requirement grew out of the recognition that there were large numbers of buildings already located in flood prone areas that would continue to be subject to damage.
The purpose of the substantially improved (SI) or substantially damaged (SD) requirements is to protect the property owner’s investment and safety, and, over time, to reduce the total number of buildings that are exposed to flood damage, thus reducing the burden on taxpayers through the payment of disaster assistance. The SI/SD requirements are triggered when the local official determines that the cost of repairing or improving a building in an SFHA equals or exceeds 50 percent of the building’s market value (excluding land value).
The Marin County Code 23.09 addresses Floodplain Management standards of construction.
The Marin County Construction Certificate Management Procedures, updated May 2023, describes of how the County implements the substantial improvement/substantial damage provisions of their floodplain management regulations.
The Department of Public Works, Land Development Division is responsible for the review, approval and inspection of all land development issues within the County of Marin including FEMA related administrative documents. Review, approval, and inspections of the structure associated with permits are conducted by both the Land Development Division of Public Works and the Building and Safety Division of the Community Development Department.
The following explains the management procedures for review of Elevation Certificates and all other required floodplain-related construction certificates including, but not limited to, Floodproofing Certificates, V Zone design certificates, and engineered flood opening certificates. These procedures outline the types of certificates required, the collection and review of all certificates, how corrections should be made, where the certificates are stored/archived, and how we make these certificates available to the public. (a) TYPES OF CERTIFICATES REQUIRED
When any new construction, substantial improvement or repair for a substantially damaged building is conducted in the Special Flood Hazard Area (SFHA) the Land Development Division of Public Works shall require an Elevation Certificate and any other floodplain-related certificates that are appropriate such as Floodproofing Certificate for Non-Residential Structures, V Zone design certificate, and certification of engineered flood openings for the development.
(a) & (b) WHEN CERTIFICATES ARE REQUIRED
The applicant shall submit an Elevation Certificate marked “construction drawings” with the building permit application. This Elevation Certificate shall be used to determine that the proposed design is in compliance with the Marin County Code 23.09. After the foundation is built and the elevation of the lowest floor is determined, another Elevation Certificate shall be submitted that is marked “building under construction.” This will document the elevation of surrounding grades and the lowest floor to ensure they comply with the approved plans before further construction is allowed. Once construction on the building is finished and all adjacent grading is finalized, a complete and correct “finished-construction” Elevation Certificate must be submitted by the applicant to show the “as-built” characteristics of the building. A “finishedl ~<;>U·N· TY OF ~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
422
construction” Elevation Certificate must be received, reviewed, and corrected (if necessary) before a final inspection can be scheduled. At this point, all other required certificates must also be submitted and reviewed.
Standard Operating Procedure: A final Elevation Certificate is required as a condition to be completed before the final inspection of the building permit. Prior to issuance a hold is placed on the permit pending the submittal of the Elevation Certificate to the Department of Public Works (DPW).
As part of the County’s efforts to comply with NFIP, Marin County and the Marin OA Hazard Mitigation Working Group will annually review and make updates and revisions to these regulations as necessary to ensure they are most effective at minimizing the threat of harm from flood events. These updates and revisions may be promoted by changes in local demographics, shifts in land use, changes to flood regimes such as frequency and intensity of flood events, and other factors that may warrant action. The County will also continue to incorporate any changes to the locations and designations of mapped floodplains into future planning documents, including future updates to this Plan.
The County will also explore opportunities to enforce or enhance County ordinances, building code, and other regulatory actions to address substantial improvements/substantial damage properties. Marin County will consider developing a Substantial Damage Management Plan. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
423
4.5 MITIGATION GOALS
The information developed from the risk assessment was used as the primary basis for developing mitigation goals and objectives. Mitigation goals are defined as general guidelines explaining what each jurisdiction wants to achieve in terms of hazard and loss prevention.
Hazard Risk Prioritization
Mitigation Goals & Objectives
Mitigation Project Identification
Mitigation Project Implementation
Goal statements are typically long-range, policy-oriented statements representing jurisdictionwide visions. Objectives are statements that detail how each jurisdiction’s goals will be achieved, and typically define strategies or implementation steps to attain identified goals. Other important inputs to the development of jurisdiction-level goals and objectives include performing reviews of existing local plans, policy documents, and regulations for consistency and complementary goals, as well as soliciting input from the public.
The following represents overarching strategic goals associated with the identification and eventual implementation of appropriate and meaningful hazard mitigation efforts in relation to prioritized hazards and threats confronting Marin County. These goals form the basis for specific supporting process objectives and are shown from the highest priority, at the top of the list, to those of lesser importance.
The establishment of hazard mitigation goals represents both individual and collective strategies that have been mutually agreed upon by the Steering Committee and have changed with the 2023 MJHMP update. Objectives were added to Goals 2 and 5. Eventually, these goals have been adopted by Marin County and its participating jurisdictions as the guiding policy behind local hazard mitigation efforts, in conjunction with other associated principles.
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 • A 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 44 CFR Requirement §201.6(c)(3)(i) [The hazard mi�ga�on strategy shall include a] descrip�on of mi�ga�on goals to reduce or avoid long‐term vulnerabili�es to the iden�fied hazards. 1 ~<;>U·N· TY OF a
~ ARIN ~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
424
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.
Goal 1: Minimize risk and vulnerability of the community to the impacts of natural hazards and protect lives and reduce damages and losses to property, economy, and environment in Marin County.
• Minimize economic and resource impacts and promote long-term viability and sustainability of resources throughout Marin County.
• Minimize impact to both existing and future development. • Provide protection for public health.
• Prevent and reduce wildfire risk and related losses.
Goal 2: Provide protection for critical facilities, infrastructure, utilities, and services from hazard impacts.
• Incorporate defensible space and reduce hazard vulnerability. • Develop redundancies in utilities and services.
• Enhance resilience through enhanced construction.
Goal 3: Improve public awareness, education, and preparedness for hazards that threaten our communities.
• Enhance public outreach and participation in the Alert Marin Emergency Notification System.
• Enhance public outreach, education, and preparedness program to include all hazards of concern.
• Increase public knowledge about the risk and vulnerability to identified hazards and their recommended responses to disaster events, including evacuation and sheltering options.
• Provide planning and coordination for "At-Risk" populations. • Provide planning and coordination for companion animals, livestock, and other animal populations.
• Increase community awareness and participation in hazard mitigation projects and activities.
Goal 4: Increase communities' capabilities to be prepared for, respond to, and recover from a disaster event.
• Improve interagency (local, state, federal) emergency coordination, planning, training, and communication to ensure effective community preparedness, response and recovery.
• Enhance collaboration and coordination of disaster-related plans, exercises, and training with local, state, and federal agencies, neighboring communities, private partners, and volunteers.
• Enhance the use of shared resources/Develop a strong mutual aid support system. • Create and maintain a fully functional, interoperable radio and communication system with all regional public safety partners.
Goal 5: Maintain FEMA Eligibility/Position the communities for grant funding. • Review hazard events and ongoing hazard mitigation projects annually. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
425
• Assess the need to pursue or adjust hazard mitigation projects after significant hazard events.
Goal 6: Reduce exposure to High Hazard Dams that pose an unacceptable risk to the public. • Improve alert and warning systems to provide residents downstream of a High Hazard Dam to receive timely warning to evacuation when threatened by potential or imminent dam failure.
• Enhance overall community preparedness to respond and evacuate a potential or imminent dam failure.
• Increase public awareness of the risk posed by High Hazard Dams and the potential for relocation of housing outside a possible inundation zone. • Prioritize High Hazard Dam Mitigation projects and programs.
4.6 HAZARD MITIGATION ACTIONS
The 2023 Marin County OA MJHMP was revised to reflect progress in local mitigation efforts.
Mitigation projects were selected for each hazard and for Marin County and its participating jurisdictions based off the hazard risk assessment. The projects are supported by the mitigation goals and objectives, and are ranked using the following criteria; approximate cost, timeframe of completion, whether the project requires Board of Supervisors regulatory action, and an assumption as to whether or not the project would be subject to CEQA or NEPA requirements.
Funding sources are identified for all projects. All projects consider new, future, and existing development. Project worksheets are used by the Planning Team and Steering Committee to describe criteria for each project.
4.6.1 PROGRESS IN LOCAL MITIGATION EFFORTS
This plan has been created as a “living” document with input from the population and professionals within Marin County and its participating jurisdictions. Based on the planning meetings and the progress monitored by the steering committee members, several mitigation 44 CFR Requirement §201.6(c)(3)(ii) [The hazard mi�ga�on strategy shall include a] sec�on that iden�fies and analyzes a comprehensive range of specific mi�ga�on ac�ons and projects being considered to reduce the effects of each hazard, with par�cular emphasis on new and exis�ng buildings and infrastructure. All plans approved by FEMA a�er October 1, 2008, must also address the jurisdic�on’s par�cipa�on in the NFIP, and con�nued compliance with NFIP requirements, as appropriate.
§201.6(c)(3)(iii) [The hazard mi�ga�on strategy shall include an] ac�on plan, describing how the ac�on iden�fied in paragraph (c)(3)(ii) of this sec�on will be priori�zed, implemented, and administered by the local jurisdic�on. Priori�za�on 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.
§201.6(c)(3)(iv) For mul�‐jurisdic�onal plans, there must be iden�fiable ac�on items specific to the jurisdic�on reques�ng FEMA approval or credit of the plan. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
426
actions were accomplished since the last planning cycle. Table 4.8 provides a brief description of the progress made in the local mitigation efforts and the plan for those mitigation actions that were not completed or are ongoing.
4.6.2 STATUS OF PREVIOUS MITIGATION ACTIONS
Table 4.8 summarizes the actions that were recommended in the previous version of the hazard mitigation plan and their implementation status at the time this update was prepared.
Table 4.8: Status of Previous Hazard Mitigation Actions Action Number / Name Completed Ongoing Not
Started
Still
Relevant
Included in
Updated
Action
Plan
(1) Seismic Retrofit of County-owned buildings not
current to code. West Marin Service Center, Point
Reyes Station
X N
(2) Seismic Retrofit of County-owned buildings not
current to code. Civic Center Roof Replacement X N
(3) Seismic Retrofit of County-owned buildings not
current to code. Tomales Fire Station- Replacement X N
(4) Seismic Retrofit of County-owned buildings not
current to code. 120 N. Redwood- Seismic
Assessment
X Y
(5) Seismic Retrofit of County-owned buildings not
current to code. Marin Center- Seismic Assessment
of the Veteran's Memorial Auditorium & Exhibit Hall
X Y
52 Follow all four phases of FEMA's How-to-Guide:
"Integrating Historic Property and Cultural Resource
Considerations Hazard Mitigation Planning"
X N
Acquire electric bikes and safety equipment for
official use during major disasters. X N
Arroyo Corte Madera del Presidio Riverine Flood
Risk Reduction project: Assist with reducing the
frequency and severity of flooding. Study completed
on 03/2022 with the best option to move forward with
a restoration project.
X N
Assess bulkheads surrounding Tomales Bay X Y
Azalea Ave Bridge Replacement project will replace
the original Azalea Bridge, to decrease flood
hazards.
Town of
Fairfax is
project
lead.
Bothin Marsh Restoration project. Thin-lift
placement of sediment from Coyote Creek into
Bothin Marsh.
X Y
Improve City of Novato Drainage Improvement
informed by study currently in process. Goal to
bypass high flows, increase storage, develop flood
barriers, daylighting drainages, and install pump
stations and/ or tide gates.
X Y
Conduct a comprehensive finished floor-elevation
inventory. Project to understand a Floor Elevation
Survey to determine the floor elevation of a
structure.
X N
Consider sea level rise adaptation from
Collaboration: Sea-level Marin Adaption Response
Team (C-SMART).
X Y
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
427
Table 4.8: Status of Previous Hazard Mitigation Actions Action Number / Name Completed Ongoing Not
Started
Still
Relevant
Included in
Updated
Action
Plan
Continue supporting the Sonoma County Water
Agency led Advanced Quantitative Precipitation
Information effort.
X Y
Corrillo Drive Pipe Rehabilitation was completed by
San Rafael in cooperation with flood zone 6. X N
Corte Madera Creek Flood Risk Management Project
will help to reduce the frequency of flooding by
enhancing natural stream functions. An HMGP
application for components in the channel that
reduce flood risk was submitted August 4, 2023
X Y
Cove Pump Station Improvements were completed
in 2022 and will assist with the updates to the pump. X N Coyote Creek Levee Improvements - a levee study
was completed, and a portion of the levee system
has a project underway for seepage mitigation. It is
in the design phase.
X Y
Crest Marin, Cardinal, and Shoreline Pump Station
Upgrades. A condition assessment for Crest Marin is
nearly complete.
X Y
Deer Island Basin Project to setback levees, restore
tidal wetlands, and increase tidal prism to reduce
sedimentation and flood risk. CEQA complete,
design underway.
X Y
Develop Renters and Homeowners Guides to Flood
Preparedness project outlining safety directives for
homeowners and renters during a potential flood
hazard.
X Y Y
Easkoot Creek Flood Flow Bypass Project. National
Park Service is working with FHWA and the Flood
District to identify and plan a potential overflow
channel from Easkoot Creek to the Ocean.
X Y
East Creek Outfall Modifications project is a
pavement rehabilitation project and potentially
include tide gates to reduce sunny day flooding of
Tiburon Blvd.
X Y
Encourage property owners in SFHAs to purchase
flood insurance. X Y
Establish additional local funding mechanisms for
increased flood and fire mitigation. X Y
Estancia Ditch and Pump Station improvement
project. All pump stations in Santa Ventia were
upgraded to the Trimble Unity systems. Additional
upgrades needed.
X Y
Flood Preparedness Pilot Program identifies
resources for flood preparedness on county website. X Y Gallinas Creek Geomorphic Dredge, currently in
design phase for the placement of 100,000 cubic
yards of dredge sediment
X Y
Initiate Community Plans for Adapting to Coastal
Hazards X Y
Karen Way Ditch Improvements is currently on hold X Y
Las Gallinas Levee Evaluation provides geotechnical
engineering service for the elevation and
assessment consistent with the Corps of Engineers
(USACE) Publication Number EM 1110-2-1913.
X N
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
428
Table 4.8: Status of Previous Hazard Mitigation Actions Action Number / Name Completed Ongoing Not
Started
Still
Relevant
Included in
Updated
Action
Plan
Levee Setback and Upgrade Project. Initiation of this
project depends on completion of a land exchange
through State Lands Commission. County is working
on surveying needed to support that exchange.
X Y
Lower Corte Madera Creek Improvements: Levee
evaluation completed in 2020 under a DWR grant
and a geomorphic dredge assessment in process to
be completed in 2023
Y
Lower Ryan Creek Pump Station Study and
Upgrades is currently on hold Y
Madrone Ave Bridge Replacement project will
reduce impacts from floods.
Town of
San
Anselmo is
project
lead.
Manzanita Modifications Project. Caltrans is working
on a project initiation document for December 2023
for sea level rise adaptation at the US 101/SR 1
between Manzanita and Marin City. County is
supporting this work through hydraulic studies.
X Y
Marin City Drainage Improvements Project, currently
in the planning phase of project. X Y
Marin County Structure Elevation Program provides
federal assistance to homeowners with costeffective projects. FEMA funding approved; 7 permits are being reviewed.
X Y
Marin County Watershed Program provides a
framework to integrate flood protection and
environmental restoration with public and private
partners to protect and enhance Marin’s watersheds.
X N
McInnis Park Wetland Restoration Project proposes
to restore subtidal and intertidal habitat at an 180-
acre are of diked wetlands.
X Y
Meadow Drive Interceptor and Ditch Upgrades.
Interim upgrades were made by adding an in-line
check valve to prevent tides from flooding Meadow
Dr. No funding (or local match) currently available
for full conceptual upgrades to proceed to design.
X Y
Mill Valley Comprehensive Flood Control & Drainage
Master Plan X N
Nokomis Ave Bridge Replacement project will assist
with the replacement of the Nokomis Ave Bridge,
with the hopes of reducing flood hazards.
Town of
San
Anselmo is
project
lead.
Novato Levee Study, completed in 2020 under a
DWR grant. X N
Pacheco Pond Project is currently on hold X Y
Protect and restore natural buffers. Two funded and
completed nature-based studies explored the
feasibility of these projects and follow up work is
now happening through the Stinson ARC project and
through pursuit of other grant opportunities.
X Y
Pump Station No. 1 Upgrade is currently on hold. X Y
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
429
Table 4.8: Status of Previous Hazard Mitigation Actions Action Number / Name Completed Ongoing Not
Started
Still
Relevant
Included in
Updated
Action
Plan
Pump Station No. 2 Upgrade, and interconnection to
Pump Station No. 1 is currently on hold. X Y
Pump Station No. 5 Upgrade on hold. X Y
Richardson Bay Shoreline Protection work is to be
integrated into future sea level rise adaptation
planning.
X Y Y
Ross Valley 10 Year Work Plan described technical
rationale for a suite of on-the-ground flood reduction
measures, spread watershed-wide, that work
together as a system to reduce flooding and seek to
restore the ecological health and function of Corte
Madera Creek and its tributaries
X N
Rush Creek Drainage Improvements is currently on
hold X Y
San Anselmo Flood Risk Reduction Project.
Construction of flood detention basin on Fairfax
Creek was substantially completed and the basin
operational in November 2022. The outfall pipe slide
gate can be operated manually and pending
installation of electrical paneling March 2023 for
electrical control operation. The project to remove
the building bridge in downtown San Anselmo is in
the final planning phase
X Y
Santa Venetia and Rafael Meadows Street Drain
Upgrades. Coordinating with County Engineering to
include drainage upgrades with road rehabilitation
projects. Labrea Way, vulnerable to recurrent
stormwater ponding, is currently in design.
X Y
Santa Venetia Pump Station No. 4 Upgrades on hold X Y
Santa Venetia Floodwall Project (Formerly the Santa
Veneita Timber-Reinforced Berm Improvement
Project)
X Y
Seismic Retrofit of County-owned buildings not
current to code. X Y
Seismic upgrades (bolting and anchoring pumps
and roof) to the Cove Pump Station building in
Tiburon.
X Y
Simmons Slough Flood Risk Reduction Project X N
Strawberry Levee Improvements will be incorporated
into sea level rise planning X Y Y
The Sycamore Ave Bridge Replacement project will
reduce the impact of flooding.
Town of
San
Anselmo is
project
lead and
federally
funded.
Tiburon Street Drainage Improvements Plan
identifies support to the town of Tiburon's storm
drainage, providing upgrades to the Cove
Stormwater pump station.
X Y
The upgrade Farmers, Cheda, and Lynwood pump
stations is currently on hold. X Y
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
430
Table 4.8: Status of Previous Hazard Mitigation Actions Source: Marin County
4.6.3 NEW MITIGATION ACTIONS
Based on the hazard profiles, threat assessment, capabilities assessment, community survey results, discussions among the Hazard Mitigation Planning Team members, and existing best practices, a set of potential mitigation actions was developed and then evaluated based on the following criteria:
• FEMA requires local governments to evaluate the monetary and non-monetary costs and benefits of potential mitigation actions. Although local governments are not required to assign specific dollar values to each action, they should identify the general size of costs and benefits.
• The Hazard Mitigation Planning Team may elect to include measures with a high cost or low benefits, but such measures should be clearly beneficial to the community and an appropriate use of local resources.
In addition, FEMA directs local governments to consider the following questions as part of the financial analysis:
• What is the frequency and severity of the hazard type to be addressed by the action, and how vulnerable is the community to this hazard?
• What impacts of the hazard will the action reduce or avoid? • What benefits will the action provide to the community? The Hazard Mitigation Planning Team also chose to review and revise the potential hazard mitigation actions with consideration for climate impact and social vulnerability. Projects and programs were assessed with consideration of these variables.
Prioritization
As part of the mitigation actions development and review, the Hazard Mitigation Planning Team also prioritized the actions. The prioritization efforts looked at the risks and threats from each hazard; lifesaving, life safety, property protection and lastly environmental protection; financial costs and benefits; technical feasibility; consideration for climate impact, and social vulnerability, and community values. Hazard Mitigation Planning Team members were asked to identify their priority actions using the following criteria.
Table 4.8: Status of Previous Hazard Mitigation Actions Action Number / Name Completed Ongoing Not
Started
Still
Relevant
Included in
Updated
Action
Plan
The West Creek Flood Wall Alternative Restoration
Project is currently on hold. X Y
The Winship Bridge Replacement project will reduce
the impact of flooding.
Town of
Ross is
the project
lead and
federally
funded.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
431
Implementation priority ratings were assigned as follows:
• High Priority - An action that meets multiple objectives, is linked to a high risk hazard, has benefits that exceed costs, and has a potential source of funding. Action can begin within the short term (1 to 5 years).
• Medium Priority - An action that meets multiple objectives, is linked to a high or medium risk hazard, has benefits that exceed costs, and is eligible for funding though no funding has yet been secured for it. Action can begin within the short term (1 to 5 years) once funding is secured.
• Low Priority - An action that will mitigate the risk of a hazard, has benefits that do not exceed the costs or are difficult to quantify, has no secured source of funding, and is not eligible for any known grant funding. Action can be completed in the long term (1 to 10 years). Low-priority actions may be eligible for grant funding from programs that have not yet been identified.
Table 4.9 lists the Current Hazard Mitigation Actions for Marin County. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
432
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-1
Develop a Vulnerable Communities
Index specific to Marin County,
aggregating economic, gender,
age, linguistic, ethnic, and racial
characteristics; geographic
locations; hazard impact; and
adaptive capacity.
All Hazards
1, 2, 3, 4, 5,
6 County of
Marin - CDA
New TBD Cost
General
Funds/Grants
HMPG, BRIC, CDC,
CDPH Public Health
Emergency
Preparedness
2-5 years
Medium Safety Element Action
CA Dept. of Public
Health - Community
Assessment for Public
Health Emergency
Response (CASPER)
MC-2
Develop a climate change
preparedness outreach program for
higher risk populations.
All Hazards
1, 3
County of
Marin – CDA,
OEM/Fire, Fire
Agencies
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium Safety Element Action
MC-3
Provide grants for alternative
housing to community members at
risk of climate change impacts.
All Hazards
1, 3
County of
Marin – CDA,
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
5+ years
Low Safety Element Action
MC-4
Mitigate by planning in advance for
climate change impacts and
incorporating lessons learned in
neighboring counties.
All Hazards
All goals
County of
Marin –
OEM/Fire,
CDA, DPW
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium Safety Element Action
MC-5
Develop a Property Rating System. All Hazards
1 County of
Marin - CDA
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium Safety Element Action
MC-6
Develop Resilience Hubs. All Hazards
1, 2, 4
County of
Marin – CDA
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium Safety Element Action
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
433
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-7
Focus improvements on the
transportation network for risk
reduction, especially informed by
new and emerging climate risk.
All Hazards
1, 2, 5
County of
Marin – CDA
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-8
Conduct study to identify natural
methods to limit coastal erosion
Land
Subsidence
1, 4, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-9
Conduct research on best natural
methods to mitigate erosion on
highways and roads and implement
planning and strategy stage.
Land
Subsidence
1, 4, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Low
MC-10
Conduct research on best natural
methods to mitigate erosion in and
around rivers and streams and
implement planning and strategy
stage.
Land
Subsidence
1, 2, 4, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Low
MC-11
Addition of vegetation in soil eroded
areas.
Land
Subsidence
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-12
Increase conventional storage that
is filled during high-flow periods
Drought,
Flooding
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/FMA,
DWR, HMGP, BRIC
5+ Years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
434
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-13
Provide multilingual outreach on
mitigation tactics to well-dependent
residents
Drought
1, 3
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-14
Conduct Outreach and acquire
grants to pass to rural communities
for installing Rainwater Harvesting
systems
Drought
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-15
Identify alternative water supplies
for times of drought; mutual aid
agreements with alternative
suppliers
Drought
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-16
Remove non-native plants and trees
from all County and City and Town
facilities, replace with drought
tolerant, native plants
Flooding,
Drought
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-17
Turn soil to increase infiltration rate
and pore space to absorb more
water
Flooding,
Drought
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-18
Encourage soil turning on private
land
Flooding,
Drought
1, 3, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
435
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-19
Install new HVAC systems at
schools and critical infrastructure
facilities
Heat
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-20
Implement non-AC solutions to cool
buildings - green roof and naturebased infrastructure systems Heat
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-21
Paint roofs with pigments to reduce
heat inside buildings
Heat
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-22
Outreach to communities at high
risk of heat impacts
Heat
1, 3, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-23
Establish policy for cooler homes /
Earthship homes
Heat
1, 4, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-24
Provide grants for high-risk
residents to improve and acquire
cooling mechanism in home.
Heat
1, 3, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
436
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-25
Provide alternative locations and
equitable response actions for
residents to seek cooler
environments (e.g., movie theaters)
via regional heat response plans
Heat
1, 3, 5
County of
Marin –
OEM/Fire
TBD Cost
General
Funds/Grants
HMPG, BRIC
0-2 years
Medium
MC-26
Establish additional and expand
functionality of heating, cooling
centers and resiliency hubs.
Heat
1, 3, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-27
Replace concrete sidewalks with
DG
Heat,
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-28
Implement green streets initiatives
in identified areas
Heat,
Flooding
1, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-29
Install green roofs on public
buildings supported by non-potable
water
Heat,
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-30
Conduct a whole county study on
what areas could benefit from more
shaded areas; a green streets
program.
Heat,
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
437
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-31
Conduct study on how much
concrete can be removed
Heat,
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-32
Implement countywide flood
monitoring system to inform
mitigation future projects
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Medium
MC-33
Conduct research on widening
storm channels and aged
infrastructure which has not been
climate change adapted and in need
of enhancements
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC,
BRIC technical
assistance
2-5 years
Low
MC-34
Widen storm channels in highdensity areas and urban settingsFlooding 1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
5-10 years
Low
MC-35
Develop policy to remove concrete
parking lots
Flooding
1, 4, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-36
Expand culverts in areas classified
as 100- or 500-year flood plain
Flooding
1, 2, 5
County of
Marin –
OEM/Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
5-10 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
438
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-37
Assess County and Town owned
parking lots to implement catch
basins
Flooding
1, 2, 5
County of
Marin –
OEM/Fire,
Cities and
Towns
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-38
Design creek restoration projects on
East and West Creek to improve
flood conveyance capacity
Flooding
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Medium
MC-39
Marin City Stormwater improvement
project to limit standing water and
flooding.
Flooding
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-7 years
High
MC-40
Research, design, and construct the
Santa Venetia Floodwall Project
Flooding
1, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC,
BRIC technical
assistance
5-10 years
Low
MC-41
Novato Bypass improvement project
to reduce flooding
Flooding
1, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-7 years
Low
MC-42
Corte Madera Creek Flood Risk
Management Project Phase 1,
Access Ramp and Granton Park
Pump Station
Flooding
1, 5
County of
Marin – DPW
New $4,104,227.00 bid +
contingency. 50%
reimbursed by DWR
Grant, 50% paid by
FCZ 9.
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
439
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-43
Develop Integrated Flood Modeling
System to New Weather Radars
Flooding
1, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-44
Apply below grade waterproofing
and implement other water-intrusion
mitigation measures to protect
facilities that are experiencing
increased levels of hydrostatic
pressure.
Flooding
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-45
Cardinal Rd Levee Upgrade -
Seepage Mitigation for a segment of
Coyote Creek Levee (~1,000 LF)
Flooding,
Sea Level
Rise
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-46
Conduct sea level rise vulnerability
analysis of County Flood Control
District-owned and operated flood
control assets
Flooding,
Sea Level
Rise
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-47
Harden the North San Pedro Road
Improvement at China Camp to
preserve the transportation corridor
through China Camp State Park.
Preserve the corridor for emergency
evacuations route and future sea
level rise.
Flooding,
Sea Level
Rise
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-48
Construct coarse-grained beach
marsh and shoreline edge
restoration to inhibit marsh and bay
coastal shoreline edge erosion due
to wind-wave erosion and SLR
Sea Level
Rise
1, 5
County of
Marin - DPW
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
440
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-49
Construct Corte Madera Creek
Flood Risk Management Project
Phase 1, Lower COM Restoration
Sea Level
Rise
1, 5
County of
Marin – DPW
New Cost Estimate
$3,000,000. 50%
eligible for
reimbursement by
DWR Grant, 50% to
be covered by FCZ 9
with additional
construction grant
funding being sought.
2-7 years
Medium
100% design, seeking
additional construction
funding
MC-50
Reduce impacts from Sea level rise
and protect natural storm barriers by
researching and restoring Tiscornia
Marsh and other wetlands and
marsh areas
Sea Level
Rise
1, 5
County of
Marin – OEM /
Fire, City of
San Rafael
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC,
BRIC technical
assistance
2-10 years
Medium
MC-51
Create offshore wetlands in low
lying areas susceptible to climate
driven sea level rise
Sea Level
Rise
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-52
Implement vegetation in coastal
areas to limit sea level rise and
storm surge
Sea Level
Rise
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-5 years
Low
MC-53
Enhance public awareness of
evolving flood risk hazards due to
sea level rise, both on county's
coast and bay side
Sea Level
Rise
1, 3, 5
County of
Marin – DPW,
OEM
New TBD Cost
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
2-5 years,
ongoing
Medium
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
441
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-54
Novato Baylands Resilience
Projects - including, Levee
Improvements, Setback Levee
Construction, Pump Station
Construction and Tidal Restoration
Sea Level
Rise
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
2-10 years
Low
MC-55
Geomorphic dredging of Tidal Flood
Control Channels and Thin-Lift
Marsh Augmentation for SLR
Resiliency
Sea Level
Rise
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
2-7 years
Low
MC-56
Southern Marin Levee
Improvements and New Levee
Construction with Associated
Pumping for Direct Coastal Flooding
Impacts
Sea Level
Rise
1, 2, 5
County of
Marin – DPW
New TBD Cost
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
2-7 years
High
MC-57
Complete designs and implement
wetland restoration project to protect
Bothin Marsh Open Space Preserve
and Bay Trail
Sea Level
Rise
1, 5
County of
Marin – Parks
New $25,000,000
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
15 years
Medium
Preliminary designs
completed
MC-58
Develop designs and implement
wetland resilience improvements
along shoreline of Bolinas Lagoon
Sea Level
Rise
1, 5
County of
Marin – Parks
New $15,000,000
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
15 years
Low
Letter Property and Pine
Gulch Creek
MC-59
Develop designs and implement
McInnis Marsh and Bucks Landing
wetland resilience features
Sea Level
Rise
1, 5
County of
Marin – Parks
New $35,000,000
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
15 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
442
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-60
Develop plan to prioritize high value
areas of potential wetland
expansion
Sea Level
Rise
1, 5
County of
Marin – Parks
New $500,000
General
Funds/Grants
FMA, DWR, HMGP,
BRIC
3 years
Low
MC-61
Research, Plan, and Construct
Tsunami Evacuation structures near
high-risk areas vulnerable to
tsunami inundation
Tsunami
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-10 years
Low
MC-62
Enhance public awareness of
mitigation approaches for tsunami,
including on bay side of county
Tsunami
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years,
ongoing
Medium
MC-63
Provide incentives to guide
development away from high-risk
areas
Tsunami
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-64
Plan for tsunami evacuation routes Tsunami
1, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-65
Put signage in place for evacuation
routes
Tsunami
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
High
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
443
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-66
Research, Analyze, and Harden
schools in tsunami inundation zones
Tsunami
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-10 years
Medium
MC-67
Harden piers and boat ramps to
withstand tsunami forces
Tsunami
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-68
Create barriers around public safety
water resources to mitigate tsunami
forces
Tsunami
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-69
Harden and lift critical infrastructure
in 1 and 3 feet for sea level rise
areas.
Sea Level
Rise,
Flooding,
Tsunami
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-10 years
Low
MC-70
Strengthen roads to withstand
natural hazards like fires and water
inundation. Reduce regulatory
impediments to road construction,
widening, and other improvements
by amending relevant sections of
Marin County Code Titles 22, 23,
and 24 to eliminate discretionary
permit requirements and replace
them with ministerial review to
ensure that both public and private
roads comply with codified
engineering standards
Wildfire,
Flooding
1, 2, 4, 5
County of
Marin – CDA,
DPW, Fire
Agencies
New TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-10 years
Low
Safety Element Activity
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
444
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-71
Review permit processes to ensure
that all applications for new
development comply with fire safety
and building code standards,
including but not limited to ensuring
the provision of adequate water
supply for fire suppression and fire
flow requirements.
Wildfire
1, 4, 5
County of
Marin – CDA,
Fire Agencies
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Medium
Safety Element Activity
MC-72
Electric signage for in VHFD and
HFD areas alerting residents on red
flag days
Wildfire
1, 3, 5
County of
Marin – OEM,
HHS
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-73
Amend Wildlands Urban Interface
(WUI) Regulations. Work with Marin
Fire agencies to prepare and adopt
WUI regulations for new
development and substantial
remodels to reduce fire hazards.
Track and update standards as the
areas of high and extreme fire
hazard areas are defined.
Wildfire
1, 4, 5
County of
Marin – CDA,
Fire agencies
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
Safety Element Activity
MC-74
Identify Areas with Insufficient
Evacuation Opportunities.
Wildfire
1, 5
County of
Marin – CDA,
Fire Agencies
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
Safety Element Activity
MC-75
Remove hazardous trees and
vegetation, including non-native
species throughout the High and
Very High Fire Danger Areas.
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-10 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
445
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-76
County-wide assessment of
hazardous trees and vegetation
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-77
Deploy additional AI cameras for fire
ignition and detection
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-78
Conduct research on impact of
wildfire smoke on southeastern
portion of the county
Wildfire
1, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Low
MC-79
Create green breaks in county in
VHFD and HFD Areas
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-80
Expand fuel management by
collaborating with land management
agencies
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-81
Encourage vegetation modification
at private residences
Wildfire
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
446
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-82
Conduct a county wide fuels study
to understand how different
vegetation would behave when
ignited
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-83
Conduct a vegetation study in high
and very high fire hazard areas
Wildfire
1, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-84
Implement culturally informed
(especially native tribal culture)
wildfire mitigation projects
Wildfire
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-85
Encourage fire resistant
construction and landscaping
Wildfire
1, 2, 3, 4, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-86
Exceed codes and standards for fire
resistant construction
Wildfire
1, 2, 3, 4, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
High
MC-87
Harden fire roads to withstand
impacts from natural hazards
Wildfire
1, 2, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
447
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-88
Conduct brush clearance around fire
roads
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-89
Provide grants to harden existing
structures against fires
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-90
Plant native fire-resistant vegetation Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-91
Conduct brush clearance around
evacuation routes
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-92
Deploy livestock to remove
vegetation
Wildfire
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-93
Collaborate with land management
agencies to manage vegetation in
open space and common space
areas
Wildfire
1, 2, 5
Co County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
448
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-94
Provide direct assistance to property
owners in need of vegetation
management to improve defensible
space
Wildfire
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-95
Retrofit any current roads, highways
and bridges to endure high
magnitude earthquakes in areas
with 0.55 or higher shaking intensity.
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-96
Establish policy for soft story homes Earthquake
1, 4, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-97
Research and assess current roads,
highways, and bridges probability to
endure a high magnitude
earthquake
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Low
MC-98
Replace or enhance water and
sewage pipes and joints within
areas vulnerable to liquefaction with
flex pipes or alternate infrastructure.
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-10 years
Low
MC-99
Retrofit all County and City and
Town facilities to withstand large
earthquakes.
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire, Cities and
Towns
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-10 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
449
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-100
Identify pre-1933 school buildings
and critical infrastructure
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-101
Retrofit all critical infrastructure to
resist severe earthquake shaking
above 0.55 intensity.
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-15 years
Low
MC-102
Expand community outreach to
Great Shakeout Drill – Use Shaker
trailer
Earthquake
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-103
Outreach to hospitals and other
critical care facilities on
infrastructure risk
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
MC-104
Conduct Research on impacts of
San Andreas Fault in West Marin
Earthquake
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Medium
MC-105
Provide outreach and education on
San Andreas Fault in West Marin
Earthquake
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Medium
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
450
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-106
Study dam spillways and
emergency spillways, specifically for
seepage and to reassess geological
assumptions
Dam
Inundation
1, 2, 5, 6
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-107
Widen dam spillways in areas where
dams may receive additional water
due to climate change
Dam
Inundation
1, 2, 5, 6
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
5-15 years
Low
MC-108
Harden dam spillway infrastructure
to prevent spillway failures during
controlled / emergency releases
Dam
Inundation
1, 2, 5, 6
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
5-15 years
Low
MC-109
Research effective methods to
strengthen wind load for existing
utilities and critical infrastructure
High Wind
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC, BRIC
technical assistance
2-5 years
Low
MC-110
Conduct geotechnical survey of
slope stability county wide
Debris Flow
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
MC-111
Seed and transplant fire resistant
and native plants and trees on
vulnerable sloped areas
Debris Flow
1, 2, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years
Low
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
451
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-112
Outreach and education to areas at
risk of debris flow
Debris Flow
1, 3, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-5 years,
ongoing
Medium
MC-113
Acquire land and or design new
codes for areas in high-risk
landslide areas and minimize new
construction via policy
recommendations
Debris Flow
1, 2, 4, 5
County of
Marin – OEM /
Fire
New TBD Cost
General
Funds/Grants
HMPG, BRIC
2-10 years
Low
MC-114
Marin County Structure Elevation
Program
Flooding
1, 2, 4, 5
County of
Marin - DPW
Existing, New $4M
General
Funds/Grants
(HMGP)
0-5 years
In progress
Provides federal
assistance to
homeowners with costeffective projects. FEMA
funding approved and 7
permits are being
reviewed
MC-115 Seismic Retrofit of County-owned
buildings not current to code.
Earthquake
1, 2, 5
County of
Marin - DPW
Existing
(2018)
TBD Cost
General
Funds/Grants
HMPG, BRIC
0-5 years
In progress
Staff also continue
gathering available
seismic assessment data
on County-owned (and
possibly leased sites in
the future) facilities. This
information will be
brought into an asset
management database,
which is in the early
stages of development,
and will support risk
assessment and work
plan development
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
452
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-116
Seismic Retrofit of County-owned
buildings not current to code. 120
N. Redwood- Seismic Assessment
Earthquake
1, 2, 5
County of
Marin - DPW,
CDA
Existing
(2018)
TBD Cost
General
Funds/Grants
HMPG, BRIC
0-5 years
In progress
Local hazard mitigation
by the States Office
MC-117
Seismic Retrofit of County-owned
buildings not current to code. Marin
Center- Seismic Assessment of the
Veteran's Memorial Auditorium &
Exhibit Hall
Earthquake
1, 2, 5
County of
Marin - DPW,
CDA
Existing
(2018)
TBD Cost
General
Funds/Grants
HMPG, BRIC
0-5 years
In progress
Completed assessment,
and HMGP grant secured
for upgrades. Seismic
retrofit work at the Exhibit
Hall completed in
November 2022. The
retrofit design work for
the Veterans' Memorial
Auditorium is complete.
Construction work
anticipated to run from
April 2023 thru January
2024.
MC-118 San Anselmo Flood Risk Reduction
Project.
Flooding
1, 2, 5
San Anselmo is
project lead
Existing
(2018)
$17.6M/ Flood Zone
9/
General
Funds/Grants (DWR,
HMGP application)
0-5 years
In progress
Construction of flood
detention basin on
Fairfax Creek was
substantially completed
and the basin operational
in November 2022.
Outfall pipe slide gate
can be operated
manually and pending
installation of electrical
paneling March 2023 for
electrical control
operation. The project to
remove the building
bridge in downtown San
Anselmo is in the final
planning phase
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
453
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-119
Arroyo Corte Madera del Presidio
Riverine (Corte Madera Creek)
Flood Risk Management Project
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$14M/Flood Zone 9:
General
Funds/Grants (DWR,
applications for
FEMA, NOAA)
0-5 years
In progress
Construction in progress
through 2023 - The Marin
County Flood Control and
Water Conservation
District (District)
proposed the Corte
Madera Creek Flood Risk
Management Project,
Phase 1 to reduce the
25-year flood risk along
Corte Madera Creek in
the Town of Ross and
unincorporated Kentfield
and to enhance natural
stream functions. An
HMGP application for
components in the
channel that reduce flood
risk was submitted
August 4, 2023
MC-120 Azalea Ave Bridge Replacement Flooding
1, 5 Town of Fairfax
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years Town of Fairfax is project
lead.
MC-121 Nokomis Ave Bridge Replacement Flooding
1, 5
Town of San
Anselmo
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years Town of San Anselmo is
project lead.
MC-122 Madrone Ave Bridge Replacement Flooding
1, 5
Town of San
Anselmo
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years Town of San Anselmo is
project lead.
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
454
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-123 Winship Bridge Replacement Flooding
1, 5 Town of Ross
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years Town of Ross is the
project lead.
MC-124 Sycamore Ave bridge replacement Flooding
1, 5
Town of San
Anselmo
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
Currently on hold. A
watershed study has
been scoped out, but not
enough funding has been
identified.
MC-125 Lower Corte Madera Creek
Improvements
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $2M/Flood Zone 9/
General
Funds/Grants (DWR)
0-5 years
In progress Currently on hold
MC-126
Continue supporting the Sonoma
County Water Agency led Advanced
Quantitative Precipitation
Information effort.
Flooding
1, 4, 5
County of
Marin - DPW
Existing
(2018)
$1.5M
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Working to expand storm
drainage improvement
planning into Nave
Gardens through a Flood
District funded study
currently underway
through 2023. The study
is looking at ways of most
effectively bypassing high
flows and potential
options such as
increasing storage,
building flood barriers,
daylighting drainages,
and installing pump
stations and/or tide gates.
Funding for future
improvements would
likely be sought through
FEMA HMGP.
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
455
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-127
Pacheco Pond Project - flood flow
diversion to wetlands to improve
water quality and habitat. Upgrade
title gages.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Annual outreach
conducted in October
MC-128
Deer Island Basin Project to setback
levees, restore tidal wetlands, and
increase tidal prism to reduce
sedimentation and flood risk.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $10M/ Flood Zone 1/
General
Funds/Grants
(SFBRA grant)
0-5 years
In progress
National Park Service is
working with FHWA and
the Flood District to
identify and plan a
potential overflow
channel from Easkoot
Creek to the Ocean.
MC-129 Rush Creek Drainage
Improvements
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
2-3 years
Low
During final design of the
levee upgrade in
February 2022, the
engineer’s updated
construction cost
estimate came in at
$12M, exceeding the
project’s available
funding for project design
and construction. The
District continues to track
opportunities for project
construction funding.
MC-130 The upgrade Farmers, Cheda, and
Lynwood pump stations
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
Low
Interim upgrades were
made by adding an in-line
check valve to prevent
tides from flooding
Meadow Dr. No funding
(or local match) currently
available for full
conceptual upgrades to
proceed to design.
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
456
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-131 City of Novato Drainage
Improvement
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
TBD Cost
General
Funds/Flood Zone 1/
FMA, DWR, HMGP,
BRIC
0-5 years
In progress Currently on hold
MC-132 Encourage property owners in
SFHAs to purchase flood insurance.
Flooding
1, 3, 5
County of
Marin - DPW,
OEM/Fire
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
Ongoing
In progress Currently on hold
MC-133
Easkoot Creek Flood Flow Bypass
Project. (National Park Service/
FHWA project being scoped
currently as part of parking lot work)
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress Currently on hold
MC-134
Santa Venetia Floodwall Project
(Formerly the Santa Venetia
Timber-Reinforced Berm
Improvement Project)
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$12 Million
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Coordinating with County
Engineering to include
drainage upgrades with
road rehabilitation
projects. Labrea Way,
vulnerable to recurrent
stormwater ponding, is
currently in design.
MC-135 Meadow Drive Interceptor and Ditch
Upgrades.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
Low
Currently in design phase
for the placement of
100,000 cubic yards of
dredge sediment. Goal to
support navigation and
storm drain outfall.
MC-136 Santa Venetia Pump Station No. 4
Upgrades on hold
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $3M/ Flood Zone 7
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
In 2021, County and
Parks staff received a
grant from the San
Francisco Bay
Restoration Authority
(SFBRA) Measure AA
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
457
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
Bay region wetlands
grant program. This grant
funding will allow the
McInnis Marsh
Restoration project to
continue work on final
design, compliance with
the California
Environmental Quality
Act (CEQA) and
permitting including the
proposed CSA 6 Gallinas
Creek geomorphic
dredge project. Note that
the proposed McInnis
Marsh Restoration project
is not currently funded for
implementation.
MC-137
Pump Station No. 2 Upgrade, and
interconnection to Pump Station No.
1 is currently on hold.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $3M
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Initiation of this project
depends on completion of
a land exchange through
State Lands Commission.
County is working on
surveying needed to
support that exchange.
MC-138 Pump Station No. 5 Upgrade Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $3M
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress Currently on hold
MC-139 Santa Venetia and Rafael Meadows
Street Drain Upgrades.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
In 2022 all pump stations
in Santa Venetia were
upgrade to Trimble Unity
System for alerts and
notifications to staff.
Funding for additional
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
458
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
upgrades not available at
this time.
MC-140 Gallinas Creek Geomorphic Dredge Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$3M/ County Service
Area 6/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Flood district is
supporting the Town of
Tiburon's storm drainage
master plan
implementation out by
designing the upgrade to
the Cove Stormwater
Pump Station
(construction completed,
Project 33 in 2018 LHMP)
to have capacity to
handle the increased
flows that would be
conveyed to the station
by the full buildout of the
Town's master plan.
MC-141 McInnis Park Wetland Restoration
Project
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress Currently on hold
MC-142 Levee Setback and Upgrade
Project.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Integrated into future sea
level rise adaptation
planning.
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
459
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-143 Pump Station No. 1 Upgrade Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $2M
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
On hold due to lack of
property owner
easements. Considering
a creek restoration
project instead.
MC-144 Estancia Ditch and Pump Station
improvement project
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$4M/ Flood Zone 7/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Coordinating with
Caltrans on a scheduled
2024 pavement
rehabilitation project to
potentially include tide
gates to reduce sunny
day flooding of Tiburon
Blvd.
MC-145 Tiburon Street Drainage
Improvements Plan
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
A levee study was
completed, and a portion
of the levee system has a
project underway for
seepage mitigation. It is
in the design phase.
MC-146 Karen Way Ditch Improvements Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost/ Flood
Zone 4/ General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Currently in the planning
phase of project.
MC-147 Strawberry Levee Improvements
Sea Level
Rise
1, 5
County of
Marin - DPW
Existing
(2018) $1M / Flood Zone 4/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Integrated into future sea
level rise adaptation
planning.
MC-148 West Creek Flood Wall Alternative
Restoration Project
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
5-10 years
In progress
The district is working
with the County's Parks
Department to evaluate a
potential pilot project for
thin-lift placement of
sediment from Coyote
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
460
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
Creek in Bothin Marsh. It
would require a Measure
AA grant to design,
permit, construct, and
monitor.
MC-149 East Creek Outfall Modifications
Project
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$10M/ Flood Zone 4/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
3 years
In progress
Caltrans is working on a
project initiation
document for December
2023 for sea level rise
adaptation at the US
101/SR 1 between
Manzanita and Marin
City. County is supporting
this work through
hydraulic studies.
MC-150 Coyote Creek Levee Improvements Flooding
1, 2, 5
County of
Marin - DPW
Existing
(2018) $40M/ Flood Zone 3/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress Currently on hold
MC-151 Marin City Drainage Improvements
Project
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Following the condition
assessment design will
proceed in 2024. After
construction of the crest
Marin improvements a
study of Cardinal and
shoreline pump stations
and associated drainage
is anticipated.
MC-152
Richardson Bay Shoreline
Protection work is to be integrated
into future sea level rise adaptation
planning.
Sea Level
Rise
1, 5
County of
Marin - DPW
Existing
(2018)
$150M
TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
5-10 years
In progress
County maintains a flood
preparedness webpage
with resources and
information for
landowners.
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
461
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-153 Bothin Marsh Restoration project Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$2.4 M
General
Funds/Flood Zone
3/Grants (SFBRA
application in
progress)
5-10 years
In progress
Ongoing through Local
Coastal Program update,
funded and completed,
nature-based adaptation
studies, and the Safety
Element update.
MC-154
Manzanita Modifications Project. To
support/supplement a Caltrans
project
Flooding,
Sea Level
Rise
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Funded through Ocean
Protection Council grant
and AARPA funds.
Ongoing Stinson Beach
Adaptation and
Resilience Collaboration
(Stinson ARC) project.
MC-155 Lower Ryan Creek Pump Station
Study and Upgrades
Flooding
1, 5
County of
Marin - DPW
Existing
(2018) $2.5M/ Flood Zone 3/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
5-10 years
In progress
Project has not started
due to lower community
priority. However, the
project has not been
abandoned and may be
completed in the next
year.
MC-156 Crest Marin, Cardinal, and Shoreline
Pump Station Upgrades.
Flooding
1, 5
County of
Marin - DPW
Existing
(2018)
$7.5M/ Floods Zone
3/
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
In progress
Two funded and
completed nature-based
studies explored the
feasibility of these
projects and follow up
work is now happening
through the Stinson ARC
project and through
pursuit of other grant
opportunities.
MC-157 Flood Preparedness Pilot Program Flooding
1, 3, 5
County of
Marin - DPW
Existing
(2018) Negligible cost
General funds
0-5 years
In progress In Progress
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
462
Table 4.9: Marin County Current Hazard Mitigation Actions No. Mitigation Action
Hazards
Mitigated/
Goals
Met
Jurisdiction/
Responsible
Agency
New,
Existing,
Completed,
Removed
Estimated Cost
and Potential
Funding Source
Timeline/
Priority Comments/Progress
MC-158
Consider sea level rise adaptation
from Collaboration: Sea-level Marin
Adaption Response Team (CSMART).
Sea Level
Rise
1, 4, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
Ongoing
In progress
MC-159 Initiate Community Plans for
Adapting to Coastal Hazards
Flooding,
Sea Level,
Rise,
Tsunami
1, 2, 3, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
Ongoing
In progress
MC-160
Develop Renters and Homeowners
Guides to Flood Preparedness
project
Flooding
1, 3, 5
County of
Marin - DPW,
OEM
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
0-5 years
Low
MC-161 Protect and restore natural buffers. Flooding
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
Ongoing
In progress
MC-162 Assess bulkheads surrounding
Tomales Bay
Flooding
(coastal)
1, 5
County of
Marin - DPW
Existing
(2018) TBD Cost
General
Funds/Grants/ FMA,
DWR, HMGP, BRIC
Ongoing
In progress
Table 4.9: Marin County Current Hazard Mitigation Actions Source: Marin County
I ~'?U ..N. TY OF
~ ARIN
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
463
4.7 PLAN INTEGRATION
For hazard mitigation planning, “integration” means that hazard mitigation information is used in other relevant planning mechanisms, such as general planning, capital facilities planning, emergency management, hazard specific planning, and that relevant information from those sources is also used in hazard mitigation. This section identifies where such integration is already in place from the 2018 MJHMP, and where the 2023 MJHMP will be used for further integration.
The Marin County Office of Emergency Management will be the central coordination point for maintaining this plan and will serve as a lead staff for grant project applications on the countywide projects selected for application under the Hazard Mitigation Assistance grant programs. Additionally, each participating jurisdiction applying for grant funds on its own will serve as lead staff for project implementation with assistance from the County and participating Steering Committee members as requested.
An important integration mechanism that is highly effective and low-cost is incorporation of the hazard mitigation plan recommendations and their underlying principles into other county, city and town plans and mechanisms. Where possible, plan participants will use existing plans and/or programs to implement hazard mitigation actions. Mitigation is most successful when it is incorporated into the day-to-day functions and priorities of government and development. As described in this plan’s capability assessment, Marin County and its jurisdictions 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:
• County, City and Town general and master plans - Integrates hazard mitigation through the consideration of hazards most likely to impact the County. These hazards are considered in the Safety Element, Housing Element and Open Space Element. • County, City and Town Emergency Operations Plans - Integrates hazard mitigation through the consideration of the Town’s planned response to hazards most likely to impact the Town.
• County, City and Town ordinances - Integrates hazard mitigation through the consideration of plans and policies outlined in the capability assessments in the jurisdictional annexes.
• Flood/storm water management/master plans - Integrates hazard mitigation through the consideration of strategies to reduce flood risk and storm water management for the protection of life and property.
• Community Wildfire Protection plan - Integrates hazard mitigation through the consideration of strategies to reduce fire hazard and the risk of catastrophic wildfires in the WUI, while promoting the protection and enhancement of the county’s economic assets and ecological resources.
• Capital improvement plans and budgets - Integrates hazard mitigation through the consideration of strategies for the development and funding a critical facilities and infrastructure.
• Other plans and policies outlined in the capability assessments in the jurisdictional annexes.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
464
• Other plans, regulations, and practices with a mitigation focus Steering Committee members involved in these other planning mechanisms will be responsible for integrating the findings and recommendations of this plan with these other plans, programs, etc., as appropriate. Implementation and 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
• 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. A few examples of incorporation of the MJHMP into existing planning mechanisms include:
1) As recommended by Assembly Bill 2140, each community should adopt (by reference or incorporation) this MJHMP into the Safety Element of their General Plans. Evidence of adoption (by formal, certified resolution) shall be provided to CalOES and FEMA 2) Integration of flood actions identified in this mitigation strategy with the actions and implementation priorities established in existing Flood Management Programs 3) Using the risk assessment information to update the hazards section in the County, City and Town Emergency Operations Plans
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 hazard mitigation plan.
4.8 FUTURE DEVELOPMENT TRENDS
Marin County’s abundance of natural, recreational, and scenic resources has supported a long history of open space preservation. Its rolling hills, expansive ranchlands, beaches, coastlines, and more are appreciated by both visitors and locals alike. This quote, from the Marin Independent Journal 1934 Editorial captures this sentiment:
"No community on earth is more favored than Marin with the wealth and beauty of potential playgrounds. If we don’t acquire some of these lands, the opportunity will surely slip away from us.”
In the 1960s, housing/transportation development proposals were underway throughout Marin County including for the Marin Headlands, outer coast, Tomales Bay area and more. Such proposals threatened Marin’s rural character and long heritage of family farming, sparking community activism which drew national attention. These efforts led to the employment of land use planning tools to ensure the County’s natural and agricultural areas remain protected in perpetuity. Establishment of the Point Reyes National Seashore in 1962, and a handful of other Federal/State Park units, ensured the protection of a large amount of the County’s most l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
465
cherished lands as publicly accessible open space. Additionally, the Marin Agricultural Land Trust, established in 1980, has placed agricultural conservation easements on over 60,000 acres of farmland, to ensure protection from development in perpetuity.
Furthermore in 1972 the California Coastal Commission was established as a regulatory agency whose mission is “To protect, conserve, restore, and enhance the environment of the California coastline”. Pursuant to the California Coastal Act of 1976, the agency is tasked with the protection of a variety of resources including public access, habitat, and water quality. The Commission issues Coastal Development Permits, until a local agency has a certified Local Coastal Program (LCP), with a land use plan and implementation plan.
West Marin’s coastal zone covers approximately 82,168 acres. Of this approximately 33,913 acres are owned and managed by the National Park Service, leaving 48.255 acres under County Jurisdiction subject to the LCP. This encompasses a handful of small communities along the Pacific Coast and Tomales Bay shorelines including Muir Beach, Stinson Beach, Bolinas, Inverness, Point Reyes Station, East Shore and Dillon Beach. New growth in these communities is limited by a variety of factors including few remaining undeveloped parcels; land use policies and plans which protect public access and natural resources; and environmental features such as the coast itself, Tomales Bay, and steep bluffs which naturally restrain development.
Development in the County over the last 5 years has been limited due to build out, and similarly future development is limited by these same constraints. For this reason, development related considerations to plan updates were not applicable to the planning process. Instead, the plan was revised to consider regional development trends and incorporation of new science such as potential climate change impacts.
Marin County has focused on sea level rise planning and climate action for several years.
Currently, the LCP is being updated to reflect the changing risks to coastal areas and develop appropriate policies and actions to avoid and minimize the risk of disaster and harm to its residents, infrastructure and coastal resources. Coastal Act policies Sections 30210, 30240, and 30251 dictate that new development shall be safe from hazards and recognize that shoreline protective devices such as seawalls may be appropriate in certain instances to serve coastaldependent uses or to protect existing structures or public beaches in danger from erosion.
However, shoreline protective devices must be designed to eliminate or mitigate the adverse impacts on the sand supply of surrounding natural shorelines. Other development-limiting Coastal Act policies include:
Section: 30210: Development shall not interfere with the public’s right of access to the sea including the use of beaches
Section 30240: Environmentally Sensitive Habitat Areas (ESHA) shall be protected.
Section 30251: The scenic and visual qualities of coastal areas shall be considered and protected as resources of public importance.
The 2040 population projection for Marin County is 277,087 (Department of Finance). In order to accommodate population growth over the next several years, Marin County and its incorporated cities have implemented a number of land use plans and development policies to direct growth away from hazardous conditions. For example, as required by state law, the County and each l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
466
incorporated city have a general plan with a safety element that identifies hazards affecting the County and incorporated cities. Likewise, the County and the incorporated cities have a number of planning policies, such as floodplain ordinances and building codes, restricting new development in hazard areas and/or increasing construction requirements in hazard areas.
In addition to steering away growth from hazard areas, Marin County and its incorporated cities have a history of aggressive growth management that seeks to limit growth overall and to direct it within the incorporated cities and urban areas of the unincorporated County.
The 2007 Marin Countywide Plan was last updated in 2015 to reflect the theme of planning for sustainable communities. Twelve principles support this theme including the preservation of natural assets and the protection of agricultural assets in order to minimize development in open space. The plan is divided into specific elements, each with goals, policies, and implementation programs. The Plan’s land use pattern reflects existing development potential shifted to a degree from environmentally constrained sites to more appropriate locations. Specific Countywide Plan policies which limit urban development through the protection of open space resources include:
• Biological Resources 1.1 Protect Wetland Habitats for Special-Status Species, Sensitive Natural Communities, and Important Wildlife Nursery Areas and Movement Corridors. • Biological Resources 1.2 Acquire Habitat
• Biological Resources 2.1 Include Resource Preservation in Environmental Review Biological Resources 2.2 Limit Development Impacts
• Biological Resources 3.1 Protect Wetlands
• Biological Resources 4.1 Restrict Land Use in Stream Conservation Areas • Biological resources 5.1 Protect the Baylands Corridor • Biological Resources 5.2 Limit Development and Access • Biological Resources 5.3 Leave Tidelands in Their Natural State • Air 4.m Focus Development in Urban Corridors
• Open Space 2.2 Continue to Acquire or Otherwise Preserve Open Space Countywide Open Space 2.4 Support Open Space Efforts Along Streams • Open Space 2.5 Support Open Space Efforts in the Inland Rural Corridor • Open Space 2.6 Support Open Space Efforts in the Coastal Corridor • Agriculture 1.1 Limit Residential Use
• Agriculture 1.2 Encourage Contractual Protection
• Agriculture 1.3 Preserve Agricultural Zoning
• Agriculture 1.4 Limit Non-Agricultural Zoning
• Agricultural 1.5 Restrict Subdivision of Agricultural Lands Within the Coastal, Inland Rural and Baylands Corridors
• Agriculture 1.6 Limit Non-Agricultural Development
• Additionally, the Plan includes policies to limit development in hazardous areas, including:
• Environmental Hazards 3.a Regulate Development in Flood and inundation Areas • Environmental Hazards 3.e Restrict Development in Flood Prone Areas • Environmental Hazards 4.1 Limit Fire Risks to Structures l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
467
Implementation tools such as the County Development Code are used to carry out Countywide Plan goals. Some of the policies and programs in the Countywide Plan will require rezoning of individual properties for consistency with land use designations and policies. Furthermore, many unincorporated communities are guided by community plans which may include customized building and site design standards, ridgeline and view corridor protection mechanisms, home size regulations and more.
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
468
SECTION 5.0: PLAN REVIEW, EVALUATION, AND
IMPLEMENTATION
The strategies presented are deemed appropriate and effective by recommendation of the Marin County OA Hazard Mitigation Steering Committee, senior management of local governments and public agencies, and individual organizations and groups that have participated in its creation, or reviewed the end product.
5.1 PLAN ADOPTION
Upon submission to the California Office of Emergency Services (CalOES) for review, and subsequent approval by the Federal Emergency Management Agency (FEMA), the Marin County OA MJHMP will be presented to local government for formal adoption. It will then be incorporated into local general plans for integration into organizational policy.
5.2 PLAN MONITORING AND PUBLIC ENGAGEMENT
The process of hazard mitigation does not end with the completion, approval, and adoption of the Marin County OA MJHMP. During the five-year lifespan the Marin plan, the County, cities, towns and special districts, along with community-based organizations will ensure that the mitigation goals and strategies identified are exercised and monitored under a collaborative and cooperative umbrella, and that the document itself is properly maintained.
The Marin County Office of Emergency Management, as lead coordinating agency for hazard mitigation planning within the Marin County OA, leads the Marin Operational Area Hazard Mitigation Working Group that meets quarterly to review and manage the plan, projects, and programs. The review will identify changing community priorities, updated or new planning documents and the progress or status of the mitigation actions as detailed in the mitigation strategy. Additional questions to complete the review will be considered as follows:
• Do the goals address current and expected conditions? • Are the goals and objectives consistent with changes in the local, state, and federal policy?
• Status updates on all mitigation actions?
• Have the hazards or risks changed?
• Are current resources appropriate for implementing the MJHMP? • Have the outcomes occurred as expected?
44 CFR Requirement §201.6(d)(3) A local jurisdic�on must review and revise its plan to reflect changes in development, progress in local mi�ga�on efforts, and changes in priori�es, and resubmit if for approval within 5 years in order to con�nue to be eligible for mi�ga�on project grant funding. §201.6(d)(5) [The plan shall include…] Documenta�on that the plan has been formally adopted by the governing body of the jurisdic�on reques�ng approval of the plan (e.g., City Council, County commissioner, Tribal Council). For mul�‐jurisdic�onal plans, each jurisdic�on reques�ng approval of the plan must document that it has been formally adopted. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
469
• Is the County and jurisdictions or districts participating in the plan implementation process as expected?
The Working Group is a subgroup of the Marin Disaster and Citizens Corps Council. During the five-year update cycle, the Marin Operational Area Hazard Mitigation Working Group will have quarterly update meetings with the Hazard Mitigation Planning Committee and local stakeholders to discuss revisions to the plan and progress updates for the hazard mitigation actions. Further, Marin OEM will host an annual one-day mitigation summit to increase engagement and enhance collaboration on the plan and projects. The summit will also have the goal to educate stakeholders on innovative approaches to mitigation, trends, and new plan requirements. Marin OEM, as the host, will seek subject matter experts, state and federal officials, and representatives from within the Marin OA to speak to mitigation and planning. The knowledge gathered and the coordination facilitated during the summit will be used to update the base plan and annexes.
Marin OEM has the capacity to lead the Working Group and Multi-Jurisdictional Planning with one coordinator assigned with direct maintenance of the plan, a department analyst assigned to support the coordinator with project and grant tracking, and a community preparedness coordinator assigned with conducting regular public outreach on the plan and education on mitigation. Community feedback and integration will continue through outreach events and OEM website, where residents and visitors are invited to provide feedback through a survey, available in English or Spanish.
Specific plan maintenance activities by the Marin County Office of Emergency Management and its participating jurisdictions/special districts may include:
• Hold quarterly update meetings with the Hazard Mitigation Planning Committee and local stakeholders to discuss revisions to the plan and progress updates for the hazard mitigation actions.
• Annual Hazard Mitigation Summit
• Holding public meetings after the first quarter and third quarter update meetings. • Maintaining the Marin County OEM Hazard Mitigation Website, which provides the public with the ability to access identified hazard impact maps, location address search capability, and a listing of hazard mitigation actions. • Monitoring of the Marin County and all participating jurisdiction mitigation project activities and dissemination of status reports.
• Generation of reports relative to plan status, project management, and revision updates to executive leadership.
• Preparations for the plan’s future revision and updating.
5.3 PLAN EVALUATION
Upon approval and adoption by Marin County and all participating jurisdictions, the prioritized mitigation strategies will be further developed for funding and implementation by the lead agencies. The plan describes the potential sources of hazard mitigation funding, and general procedures to obtain that funding.
The mitigation strategies represented and adopted within this plan are recommendations only and must be approved and funded in order to be implemented as official mitigation solutions.
Ultimately, it is the responsibility of jurisdictional and agency officials within the Marin County Operational Area to undertake project implementation based upon identified mitigation l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
470
strategies, funding availability, and local need when it arises. The Marin County Office of Emergency Management will meet with the Marin Operational Area Hazard Mitigation Working Group to evaluate the plan after each update meeting.
5.4 PLAN UPDATE
During the five-year update cycle, the Marin County Office of Emergency Management will be responsible for updating the MJHMP. This update process will begin in 2024 through quarterly update meetings by the Marin Operational Area Hazard Mitigation Working Group and local stakeholders. The Marin OEM will lead these meetings to discuss revisions to the plan and progress updates for the hazard mitigation actions. Additional plan update actions are described in 5.2 Plan Monitoring and Public Engagement. The Marin County Office of Emergency Management and all participating jurisdictions and special districts will continue to hold public meetings after the first quarter and third quarter update meetings annually and will continue to invite public participation in the update process via updated public surveys. l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
471
FIGURES AND TABLES INDEX
FIGURES
Figure 1.1: Map of Marin County...............................................................................................13 Figure 1.2: Fire Protection Districts in Marin County..................................................................21 Figure 1.3: School Districts in Marin County..............................................................................22 Figure 1.4: Muir Woods National Monument .............................................................................23 Figure 1.5: Marin County Parks and Public Lands.....................................................................24 Figure 1.6: Population of Marin County 1860-2020 ...................................................................25 Figure 1.7: Marin County Environmental Corridors....................................................................34 Figure 1.8: Marin County Habitat Types ....................................................................................35 Figure 1.9: Marin County Wetlands ...........................................................................................37 Figure 1.10: Marin County Watersheds .....................................................................................38 Figure 1.11: Marin County Geologic Units (East of San Andreas Fault).....................................44 Figure 1.12: Marin County Geologic Units (West of San Andreas Fault)....................................45 Figure 1.13: Marin County Mineral Resource Sites ...................................................................46 Figure 1.14: Marin County Average Precipitation 1895-2022.....................................................47 Figure 1.15: Marin County Average Temperature 1895-2022 ....................................................48 Figure 1.16: Diablo Wind Patterns.............................................................................................48 Figure 1.17: Historic Sites in Marin County ...............................................................................54 Figure 1.18: Generalized NRI Risk Equation.............................................................................55 Figure 1.19: Marin County NRI – Expected Annual Loss...........................................................62 Figure 1.20: Marin County National Risk Index Map..................................................................63 Figure 1.21: Marin County CDC Social Vulnerability Index Map................................................65 Figure 2.1: Marin County OEM MJHMP Website.......................................................................94 Figure 2.2: Marin County OA MJHMP Town Hall Meeting..........................................................95 Figure 2.3: Collecting community feedback on the MJHMP.......................................................96 Figure 2.4: Hazard Mitigation Plan Public Outreach Press Release ..........................................97 Figure 2.5: Hazard Mitigation Plan Survey ................................................................................98 Figure 3.1: Marin County Risk Assessment – Top Hazards Graphed ...................................... 111 Figure 3.2: NASA Global Temperature Change CO2 Gas .......................................................113 Figure 3.3: NASA Global Temperature Change 1884 to 2022 .................................................113 Figure 3.4: NASA Global Temperature Change Sea Level ......................................................114 Figure 3.5: Human Health Impacts from Climate Change........................................................115 Figure 3.6: Annual Mean Sea Level Trends.............................................................................117 Figure 3.7: California Climate Impact Regions ........................................................................118 Figure 3.8: Dams in and around the Marin County OA............................................................124 Figure 3.9: Marin County Dam Inundation Susceptibility to Critical Facilities...........................125 Figure 3.10: Phoenix Lake Dam Inundation Area ....................................................................127 Figure 3.11: Phoenix Lake Dam Inundation Area – Kentfield North .........................................128 Figure 3.12: Phoenix Lake Dam Inundation Area – Kentfield South ........................................129 Figure 3.13: Novato Creek/ Stafford Lake Dam Inundation Area .............................................130 Figure 3.14: Novato Creek Dam Inundation Area – Green Point and Bel Marin Keys..............131 Figure 3.15: Bon Tempe Dam Inundation Area........................................................................132 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
472
Figure 3.16: Bon Tempe Dam Inundation Area – Lagunitas-Forest Knolls-San Geronimo Area ...............................................................................................................................................133 Figure 3.17: Bon Tempe Dam Inundation Area – Point Reyes Station Area South...................134 Figure 3.18: Bon Tempe Dam Inundation Area – Point Reyes Station Area North and Inverness ...............................................................................................................................................134 Figure 3.19: Peters Dam Inundation Area ...............................................................................135 Figure 3.20: Peters Dam Inundation Area – Lagunitas-Forest Knolls Area ..............................136 Figure 3.21: Peters Dam Inundation Area – Point Reyes Station Area ....................................137 Figure 3.22: Alpine Dam Inundation Area................................................................................138 Figure 3.23: Alpine Dam Inundation Area – Point Reyes Station .............................................139 Figure 3.24: Lagunitas Dam Inundation Area ..........................................................................140 Figure 3.25: Seeger Dam Inundation Area ..............................................................................141 Figure 3.26: Seeger Dam Inundation Area – Point Reyes Station East ...................................142 Figure 3.27: Seeger Dam Inundation Area – Point Reyes Station West ..................................143 Figure 3.28: Big Rock Ranch Dam Inundation Area ................................................................144 Figure 3.29: Big Rock Ranch Dam Inundation Area East ........................................................145 Figure 3.30: Big Rock Ranch Dam Inundation Area West .......................................................146 Figure 3.31: Soulajule Dam Inundation Area ...........................................................................147 Figure 3.32: Soulajule Dam Inundation Area around Soulajule Dam .......................................148 Figure 3.33: Soulajule Dam Inundation Area – Walker Creek at Highway 1.............................149 Figure 3.34: Soulajule Dam Inundation Area – Walker Creek at Highway 1 and Tomales Bay . 149 Figure 3.35: Vonsen Dam Inundation Area..............................................................................150 Figure 3.36: Vosen Dam Inundation Area................................................................................151 Figure 3.37: Landslide Susceptibility Classes..........................................................................156 Figure 3.38: Mud Flow Areas ..................................................................................................157 Figure 3.39: Landslide Susceptibility in the Marin County OA .................................................158 Figure 3.40: Marin County Landslide Susceptibility for Critical Facilities Map..........................159 Figure 3.41: Landslide Susceptibility – Lagunitas, Forest Knolls, San Geronimo and Woodacre ...............................................................................................................................................160 Figure 3.42: Landslide Susceptibility – Nicasio and Tocoloma.................................................160 Figure 3.43: Landslide Susceptibility – Olema and Point Reyes Station..................................161 Figure 3.44: Landslide Susceptibility – Inverness....................................................................161 Figure 3.45: Landslide Susceptibility – Dillon Beach and Tomales ..........................................162 Figure 3.46: Landslide Susceptibility – Dogtown, Bolinas and Stinson Beach .........................162 Figure 3.47: Landslide Susceptibility – Southern Marin County...............................................163 Figure 3.48: Landslide Susceptibility – West Central Marin County.........................................164 Figure 3.49: Landslide Susceptibility – Novato West...............................................................165 Figure 3.50: Landslide Susceptibility – West Central Marin County.........................................166 Figure 3.51: Landslide Susceptibility – North Novato ..............................................................167 Figure 3.52: Landslide Inventory in the Marin County OA .......................................................168 Figure 3.53: Damage in Inverness from the January 1982 Storm............................................169 Figure 3.54: January 1982 Highway 101 Mudslide in Marin County ........................................169 Figure 3.55: February 2017 Landslide on Lucas Valley Road..................................................170 Figure 3.56: March 2023 Mudslide in Marin County ................................................................171 Figure 3.57: U.S. Drought Monitor for California (2023) ..........................................................177 Figure 3.58: U.S. Drought Monitor for California (2020) ..........................................................178 Figure 3.59: U.S. Drought Monitor for California (2016) ..........................................................179 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
473
Figure 3.60: Water Supply Conditions in California 2005-2018................................................179 Figure 3.61: Drought Impacts..................................................................................................181 Figure 3.62: 2022 Locations of Tree Mortality in the Marin County OA....................................182 Figure 3.63: Modified Mercalli Intensity Scale .........................................................................185 Figure 3.64: Mercalli Scale vs. Magnitude...............................................................................186 Figure 3.65: Soil Types ...........................................................................................................186 Figure 3.66: Earthquake Faults and Probability of Shaking in the Marin County OA ...............188 Figure 3.67: Marin County Earthquake Shaking Potential and Critical Facilities......................189 Figure 3.68: Uniform California Earthquake Rupture Forecast Version 3................................. 192 Figure 3.69: Population/Social Vulnerability to an Earthquake in California.............................195 Figure 3.70: Diagram of an Atmospheric River Event..............................................................198 Figure 3.71: FIRM Zones in the Marin County OA...................................................................199 Figure 3.72: The 100-year, 200-year and 500-year floodplains in the Marin County OA..........200 Figure 3.73: 100, 200, 500-Year Floodplains in the Marin County OA .....................................201 Figure 3.74: 100-Year Floodplain – Lagunitas .........................................................................202 Figure 3.75: 100-Year Floodplain – Forest Knolls Area............................................................203 Figure 3.76: 100-Year Floodplain – San Geronimo Area .........................................................203 Figure 3.77: 100-Year Floodplain – Woodacre Area ................................................................204 Figure 3.78: 100-Year Floodplain – Tocoloma .........................................................................204 Figure 3.79: 100-Year Floodplain – Nicasio.............................................................................205 Figure 3.80: 100-Year Floodplain –Nicasio East......................................................................206 Figure 3.81: 100-Year Floodplain –Olema...............................................................................206 Figure 3.82: 100-Year Floodplain – Point Reyes Station Area - South.....................................207 Figure 3.83: 100-Year Floodplain – Point Reyes Station Area - North .....................................208 Figure 3.84: 100-Year Floodplain – Inverness Park Area.........................................................209 Figure 3.85: 100-Year Floodplain – Inverness South...............................................................210 Figure 3.86: 100-Year Floodplain – Inverness .........................................................................211 Figure 3.87: 100-Year Floodplain – Reynolds and Marconi Area.............................................212 Figure 3.88: 100-Year Floodplain – Marshall Area...................................................................213 Figure 3.89: 100-Year Floodplain – Tomales Area...................................................................214 Figure 3.90: 100-Year Floodplain – Bolinas North ...................................................................215 Figure 3.91: 100-Year and 500-Year Floodplain – Bolinas and Stinson Beach West ...............216 Figure 3.92: 100-Year and 500-Year Floodplain – Stinson Beach............................................217 Figure 3.93: 100-Year and 500-Year Floodplain – Muir Beach ................................................218 Figure 3.94: 100-Year and 500-Year Floodplain – Tamalpais Valley Area................................218 Figure 3.95: 100-Year and 500-Year Floodplain – Alto and Strawberry....................................219 Figure 3.96: 100-Year and 500-Year Floodplain – Kentfield and Greenbrae............................220 Figure 3.97: 100-Year Floodplain – Marin City ........................................................................221 Figure 3.98: 100-Year Floodplain – Lucas Valley and Marinwood............................................222 Figure 3.99: 100-Year Floodplain – Saint Vincent....................................................................223 Figure 3.100: 100-Year and 500-Year Floodplain – Santa Venetia Area ..................................223 Figure 3.101: 100-Year and 500-Year Floodplain – San Pedro Hill Area..................................224 Figure 3.102: Novato Flooding - Marin County Landfill and Marin County airport...................225 Figure 3.103: Flooding in San Rafael Area..............................................................................226 Figure 3.104: 100-Year Floodplain – Bel Marin Keys...............................................................227 Figure 3.105: Stinson - Bolinas Area Flooding.........................................................................228 Figure 3.106: Flood Control Zones in the Marin County OA....................................................229 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
474
Figure 3.107: Damage in Inverness from 1982 Storm .............................................................231 Figure 3.108: Flooding in Marin City – 2019 Storm ................................................................. 232 Figure 3.109: Population/Social Vulnerability to Flooding in California ....................................240 Figure 3.110: Dissolution Sinkhole Formation .........................................................................241 Figure 3.111: Cover-Subsidence Sinkhole Formation..............................................................242 Figure 3.112: Cover-Collapse Sinkhole Formation ..................................................................242 Figure 3.113: Land Subsidence in California 2007-2018 with Marin County Cutout.................243 Figure 3.114: U.S. Rock types Susceptible to Water Dissolution .............................................244 Figure 3.115: Levee Failure Mechanisms................................................................................247 Figure 3.116: Marin County Levee System..............................................................................249 Figure 3.117: Levees in Tamalpais Valley................................................................................250 Figure 3.118: Levees in Strawberry.........................................................................................251 Figure 3.119: Tam Junction Levees.........................................................................................252 Figure 3.120: Levee in Kentfield..............................................................................................253 Figure 3.121: Greenbrae Levee System..................................................................................254 Figure 3.122: McNears Sea Wall in the San Pedro Hill Area...................................................255 Figure 3.123: Santa Venetia Levee in Santa Venetia ..............................................................256 Figure 3.124: Marin Levee 33, Marin County Levees 33 and 24 and the Las Gallinas Valley Sanitary District Levee in St. Vincent ......................................................................................257 Figure 3.125: Santa Venetia Levee System ............................................................................258 Figure 3.126: Bel Marin Keys Levee System...........................................................................259 Figure 3.127: Levees Around the Marin County Airport...........................................................260 Figure 3.128: Novato North Levee System..............................................................................261 Figure 3.129: Marin County Sea Level Rise Susceptibility to Critical Facilities ........................267 Figure 3.130: Average July Temperatures in California............................................................268 Figure 3.131: Projections of Sea Level Rise in the San Francisco Bay Area, 2000-2100 ........275 Figure 3.132: Heat Index........................................................................................................276 Figure 3.133: Heat Disorders by Heat Index Level..................................................................277 Figure 3.134: Annual Average Temperatures in the San Francisco Bay Area, 2000-2100 .......281 Figure 3.135: Beaufort Wind Scale..........................................................................................282 Figure 3.136: Wind Zones in the US .......................................................................................283 Figure 3.137: Enhanced Fujita Scale ......................................................................................287 Figure 3.138: Waterspout Formation.......................................................................................288 Figure 3.139: Tsunami Inundation Zones in the Marin County OA...........................................291 Figure 3.140: Tsunami Inundation Zone – Inverness Area.......................................................292 Figure 3.141: Tsunami Inundation Zone – Inverness ...............................................................293 Figure 3.142: Tsunami Inundation Zone – South of Inverness.................................................294 Figure 3.143: Tsunami Inundation Zone – Inverness Park and Point Reyes............................295 Figure 3.144: Tsunami Inundation Zone – Reynolds and Marshall ..........................................296 Figure 3.145: Tsunami Inundation Zone – McDonald and Blakes Landing ..............................297 Figure 3.146: Tsunami Inundation Zone – South of Tomales ...................................................298 Figure 3.147: Tsunami Inundation Zone – Dillon Beach Area ..................................................299 Figure 3.148: Tsunami Inundation Zone – Dillon Beach...........................................................300 Figure 3.149: Tsunami Inundation Zone – Bolinas Lagoon North ............................................300 Figure 3.150: Tsunami Inundation Zone – Bolinas Area ..........................................................301 Figure 3.151: Tsunami Inundation Zone – Bolinas Core ..........................................................302 Figure 3.152: Tsunami Inundation Zone – Bolinas North .........................................................303 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
475
Figure 3.153: Tsunami Inundation Zone – Stinson Beach Area ...............................................303 Figure 3.154: Tsunami Inundation Zone – Stinson Beach........................................................304 Figure 3.155: Tsunami Inundation Zone – Muir Beach ............................................................305 Figure 3.156: Tsunami Inundation Zone – Tamalpais Valley South..........................................306 Figure 3.157: Tsunami Inundation Zone – Tamalpais Valley North...........................................307 Figure 3.158: Tsunami Inundation Zone – Marin City ..............................................................308 Figure 3.159: Tsunami Inundation Zone – Manzanita..............................................................308 Figure 3.160: Tsunami Inundation Zone – Strawberry South...................................................309 Figure 3.161: Tsunami Inundation Zone – Unincorporated Tiburon Peninsula.........................310 Figure 3.162: Tsunami Inundation Zone – Paradise Cay .........................................................311 Figure 3.163: North Marin Tsunami Inundation Zones .............................................................312 Figure 3.164: Santa Venetia Tsunami Inundation Zones..........................................................313 Figure 3.165: Greenbrae Tsunami Inundation Zones...............................................................314 Figure 3.166: Richardson Bay Tsunami Inundation Zones.......................................................315 Figure 3.167: Tomales Bay Tsunami Inundation Zones ...........................................................316 Figure 3.168: Bolinas – Stinson Tsunami Inundation Zones ....................................................317 Figure 3.169: Federal, State and Local Responsibility Areas in the Marin County OA.............324 Figure 3.170: Fuel Model Map for the Marin County OA .........................................................328 Figure 3.171: Wildfire Ignition Points in the Marin County OA .................................................331 Figure 3.172: WUI Boundary in the Marin County OA.............................................................332 Figure 3.173: Fire Hazard Severity Zones (FHSZ) in the Marin County OA.............................334 Figure 3.174: Marin County Wildfire Susceptibility to Critical Facilities ....................................335 Figure 3.175: Fire Hazard Severity Zones – Lagunitas, Forest Knolls, San Geronimo and Woodacre ...............................................................................................................................336 Figure 3.176: Fire Hazard Severity Zones –Woodacre............................................................336 Figure 3.177: Fire Hazard Severity Zones –Woodacre Area....................................................337 Figure 3.178: Fire Hazard Severity Zones – Nicasio ...............................................................338 Figure 3.179: Fire Hazard Severity Zones – Tocoloma............................................................339 Figure 3.180: Fire Hazard Severity Zones – Olema................................................................. 340 Figure 3.181: Fire Hazard Severity Zones – Point Reyes Station............................................341 Figure 3.182: Fire Hazard Severity Zones – Inverness Park ...................................................342 Figure 3.183: Fire Hazard Severity Zones – Inverness............................................................343 Figure 3.184: Fire Hazard Severity Zones – Inverness Area ...................................................344 Figure 3.185: Fire Hazard Severity Zones – Marconi/Marshall Area........................................345 Figure 3.186: Fire Hazard Severity Zones – McDonald/Blakes Landing Area..........................346 Figure 3.187: Fire Hazard Severity Zones – Tomales..............................................................347 Figure 3.188: Fire Hazard Severity Zones – Dillon Beach .......................................................348 Figure 3.189: Fire Hazard Severity Zones – Dogtown.............................................................349 Figure 3.190: Fire Hazard Severity Zones – Bolinas ...............................................................350 Figure 3.191: Fire Hazard Severity Zones – Stinson Beach and Surrounding Area.................351 Figure 3.192: Fire Hazard Severity Zones – Stinson Beach ....................................................351 Figure 3.193: Fire Hazard Severity Zones – Muir Beach .........................................................352 Figure 3.194: Fire Hazard Severity Zones – Tamalpais Valley and Marin City .........................353 Figure 3.195: Fire Hazard Severity Zone – Unincorporated Tiburon Peninsula and Paradise Cay ...............................................................................................................................................354 Figure 3.196: Fire Hazard Severity Zones – San Quentin .......................................................355 Figure 3.197: Fire Hazard Severity Zones – Lucas Valley and Marinwood ..............................355 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
476
Figure 3.198: Fire Hazard Severity Zone – Bel Marin Keys and Loma Verde ..........................356 Figure 3.199: Fire Hazard Severity Zone – San Antonio & Marin County Airport .....................357 Figure 3.200: Historic Wildfires in the Marin County OA 1919 - 1995 ......................................358 Figure 3.201: Historic Wildfires in the Marin County OA 1973 - 2020 ......................................359 Figure 3.202: 1995 Vision Fire ................................................................................................360 Figure 3.203: Population Density, Flame Length, and Rate of Spread for the Average Fire Season in the Marin County OA..............................................................................................365 Figure 3.204: Areas of Concern for the Average Fire Season in the Marin County OA............366 Figure 3.205: Areas of Concern for the Extreme Fire Season in the Marin County OA............367 Figure 3.206: WUI Boundary and Population Density in the Marin County OA........................368 Figure 3.207: Trends in the Annual Number of Large Wildfires in the United States................372 Figure 3.208: Air Quality Index Concern Levels.......................................................................376 Figure 3.209: Marin County OA Critical Infrastructure .............................................................377 Figure 3.210: Largest Oil Spills Affecting U.S. Waters 1969-2017 ...........................................385 Figure 3.211: Marin County Covid-19 Hospitalizations ............................................................391 Figure 3.212: Marin County Covid-19 Hospitalizations by Demographics................................391 Figure 3.213: Marin County Highways ....................................................................................393 Figure 3.214: SMART Commuter and Freight Line..................................................................396 TABLES
Table 1.1: Marin County Population Changes 1860-2020..........................................................26 Table 1.2: Marin County Estimated Jurisdictional Population.....................................................26 Table 1.3: Marin County Estimated Jurisdictional Population Change 2010-2020 .....................27 Table 1.4: Marin County Population Age by Gender 2020 .........................................................28 Table 1.5: Marin County Population by Race or Ethnicity ..........................................................28 Table 1.6: Marin County Housing Stock.....................................................................................29 Table 1.7: Marin County Jurisdictional Housing Stock ...............................................................31 Table 1.8: Historic Sites in Marin County...................................................................................53 Table 1.9: NRI Risk Components and Factors...........................................................................56 Table 1.10: NRI Hazards and Marin County OA MJHMP Hazards.............................................57 Table 1.11: NRI Hazard Type Risk Index for Marin County ........................................................59 Table 1.12: NRI Highest-Risk Communities in Marin County.....................................................60 Table 1.13: Marin County Civilian Employed Population 16 Years and Over .............................67 Table 1.14: Marin County OA MJHMP Participants 2018 and 2023...........................................69 Table 2.1: 2023 Marin OA MJHMP Participating Jurisdictions ...................................................76 Table 2.2: Marin County OA MJHMP Steering Committee Members .........................................77 Table 2.3: Marin County OA MJHMP Preparative Consulting Planning Team Members ............78 Table 2.4: Marin County OA MJHMP Planning Team Members.................................................82 Table 2.5: Marin County OA MJHMP Planning Meetings...........................................................86 Table 3.1: Marin County OA MJHMP Hazard Identification and Comparison...........................101 Table 3.2: Marin County OA MJHMP Other Hazards Profiled ..................................................102 Table 3.3: State and Federal Declared Disasters in Marin County...........................................104 Table 3.4: Marin County Hazard Risk Assessment..................................................................108 Table 3.5: Hazard Magnitude and Severity Scale....................................................................109 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
477
Table 3.6: Marin County Hazard Risk Assessment – Top Hazards Scored ..............................110 Table 3.7: Hazard Ranked Dams in Marin County with Potential to Impact to the OA..............123 Table 3.8: Marin County OA Hazard Risk Assessment – Dam Failure .....................................153 Table 3.9: Marin County OA Hazard Risk Assessment – Debris Flow......................................173 Table 3.10: Marin County OA Hazard Risk Assessment – Drought..........................................183 Table 3.11: Marin County OA Hazard Risk Assessment – Earthquake.....................................193 Table 3.12: Marin County OA Hazard Risk Assessment – Flooding.........................................236 Table 3.13: Marin County OA Hazard Risk Assessment – Land Subsidence ...........................246 Table 3.14: Marin County OA Hazard Risk Assessment – Levee Failure................................. 263 Table 3.15: Marin County OA Hazard Risk Assessment - Sea Level Rise ...............................270 Table 3.16: Marin County OA Hazard Risk Assessment – Severe Weather, Extreme Heat......279 Table 3.17: Marin County OA Hazard Risk Assessment – Severe Weather; Wind...................286 Table 3.18: Tornado Activity in the Marin County OA...............................................................288 Table 3.19: Marin County OA Hazard Risk Assessment - Tsunami..........................................319 Table 3.20: Marin County OA Hazard Risk Assessment – Wildfire...........................................363 Table 4.1: Unincorporated Marin County Future Growth Areas................................................401 Table 4.2: Marin County Legal and Regulatory Capabilities.....................................................406 Table 4.3: Marin County Goals and Policies ............................................................................407 Table 4.4: Marin County Goals and Policies ...........................................................................411 Table 4.5: Marin County Fiscal Capabilities............................................................................413 Table 4.6: Marin County Community Outreach........................................................................414 Table 4.7: Participation in the National Flood Insurance Program (NFIP) ................................420 Table 4.8: Status of Previous Hazard Mitigation Actions..........................................................430 Table 4.9: Marin County Current Hazard Mitigation Actions.....................................................462 l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
478
ACRONYMS
Acronym Definition
ABAG Association Bay Area of Governments
AQI Air Quality Index
ARP Address Resolution Protocol
ASL American Sign Language
ATSDR Agency for Toxic Substances and Disease Registry
BAAQMD Bay Area Air Quality Management District
BCDC Bay Conservation and Development Commission
BCPUD Bolinas Community Public Utility District
BRIC Building Resilient Infrastructure and Communities
CA California
CAL FIRE California Department of Forestry and Fire Protection Cal OES California Office of Emergency Services
CAP Climate Action Plan
CASPER Community Assessment for Public Health Emergency Response - California Department of Public Health
CDA Community Development Agency
CDC Centers for Disease Control and Prevention
CDI Certified Deaf Interpreter
CEQA California Environmental Quality Act
CGS California Geological Survey
CIP Capital Improvement Plan
CMFD Central Marin Fire District
CNRA California Natural Resource Agency
CNRA California Natural Resource Agency
CNRA California Natural Resource Agency
CO Carbon Monoxide
COVID-19 Coronavirus Disease 2019
COYL Coyote Creek Left Bank Levee
CPUC California Public Utilities Commission
CRF Community Risk Factor
CRI Community Resilience Index
CRS Community Rating System
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
479
CRT Community Response Team
CSA County Service Area
C-SMART Sea-level Marin Adaption Response Team
CWPP Community Wildfire Protection Plan
DDoS Distributed Denial of Service
DMA Disaster Mitigation Act
DNS Domain Name System
DOF California Department of Finance
DoS Denial-of-Service
DPW Department of Public Works
DR Disaster Relief
DSOD Division of Safety of Dams - California Department of Water Resources DWR California Department of Water Resources
EAL Expected Annual Loss
EAS Emergency Alert System
EOC Emergency Operation Center
EOP Emergency Operations Plan
EPA Environmental Protection Agency
ESHA Environmentally Sensitive Habitat Areas
FD Fire Department
FEMA Federal Emergency Management Agency
FHSV Fire Hazard Severity Zones
FIRM Flood Insurance Rate Maps
FMA Flood Mitigation Assistance
FMP Flood Mitigation Plan
FPA Floodplain Administrator
FRA Federal Responsibility Areas
FY Fiscal Year
GGNRA Golden Gate National Recreation Area
GGNRA Golden Gate National Recreation Area
GIS Geographic Information System
Gov Government
GPAC General Plan Advisory Committee
H2S Hydrogen Sulfide
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
480
HFHSZ High Fire Severity Zone
HIRA Hazard Identification and Risk Assessment
HIV/AIDS Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome HLR Historic Loss Ratio
HMGP Hazard Mitigation Grant Program
IoT Internet of Things
IP Intellectual Property
IPAWS Integrated Public Alert and Warning System
ISEPA Identified Site Emergency Planning Application
LCP Local Coastal Program
LGVSD Las Gallinas Valley Sanitary District
LHMP Local Hazard Mitigation Plan
LRA Local Responsibility Areas
LRAD Long-Range Acoustic Device
LSAC Levee Safety Action Classification
Marin IJ Marin Independent Journal
MCEP Marin Climate Energy Partnership
MCFD Marin County Fire Department
MCOSD Marin County Open Space District
MCPIO Marin County Public Information Officers
MCSTOPP Marin County Stormwater Pollution Prevention Program MERA Marin Emergency Radio Authority
MERS Middle Eastern Respiratory Syndrome
MFHSZ Moderate Fire Severity Zone
MHOAC Medical/Health Operational Area Coordinator
MJHMP Multi-Jurisdictional Hazard Mitigation Plan
MMI Modified Mercalli Intensity
MMWD Marin Municipal Water District
MRZ Mineral Resource Zones
MV2040 Mill Valley General Plan 2040
Mw Scale Moment Magnitude Scale
MWPA Marin Wildfire Prevention Authority
NASA National Aeronautics and Space Administration
NCDC National Climatic Data Center
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
481
NFDRS National Fire Danger Rating System
NFIP National Flood Insurance Program
NID National Inventory of Dams
NIH National Institute for Health
NMWD North Marin Water District
NPR Northwestern Pacific Railroad
NR National Register of Historic Places
NRI National Risk Index
NWS National Weather Service
O3 Ozone
OA Operational Area
OEM Office of Emergency Management
OHP Office of Historic Preservation
OWTA On-Site Wastewater Treatment Systems
PD Police Department
PG&E Pacific Gas & Electric
PM10 Particulate Matter Less Than 10 Microns In Aerodynamic Diameter PSPS Public Safety Power shutoffs
PtH Pass the hash
PW Public Works
RAWS Remote Automated Weather Stations
RCD Resource Conservation District
RHNA Regional Housing Needs Assessment
SASM Sewerage Agency of Southern Marin
SFBRA San Francisco Bay Restoration Authority
SFHA Special Flood Hazard Area
SFHA Special Flood Hazard Areas - FEMA
SFHA Special Flood Hazard Area
SHMP State Hazard Mitigation Plan
SMART Sonoma Marin Area Rail Transit
SMFD Southern Marin Fire District
SOX Sulfur Oxides
SQL Structured Query Language
SRA State Responsibility Areas
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
482
SVI Social Vulnerability Index
TAM Transportation Authority of Marin
UCERF2 Uniform California Earthquake Rupture Forecast, Version 2 UCERF3 Uniform California Earthquake Rupture Forecast, Version 3 USACE U.S. Army Corps of Engineers
USGS United States Geological Survey
VHFHSV Very High Fire Severity Zone
WC/ATWC West Coast/Alaska Tsunami Warning Center
WHO World Health Organization
WUI Wildland Urban Interface
XSS Cross-Site Scripting
l ~<;>U·N· TY OF
~ ARIN
a
~
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
483
APPENDIX A: ADOPTION LETTERS
1 ~<;>U·N· TY OF a ~ ARIN~
December 1, 2022
CITY of BELVEDERE'
450 San Rafael Ave. • Belved ere, CA 94920-2336
Tel: 415/435-2611 • Fax: 415/ 435-8471
POLICE DEPARTMENT
Marin County Office of Emergency Services
1600 Los Gamos Drive
San Rafael, CA 94903
Re: Letter of Commitment as Participating Jurisdiction in Marin County Multi-jurisdictional Hazard Mitigation Planning
Dear State Hazard 'Mitigation Officer:
As the Federal Emergency Management Agency's (FEMA) Local Mitigation Plan requirements under 44 CFR §201 .6 specifically identify criteria that allow for multijurisdictional mitigation plans and that many issues are better resolved by evaluating hazards more comprehensively by coordinating at the county, regional , or watershedlevel, the City of Belvedere is submitting this letter of commitment to confirm that the City of Belvedere has agreed to participate in the Marin County's Multi-jurisdictional Hazard Mitigation Planning.
Furthermore, as .a condition of participation in the mitigation planning, the City.of..
Belvedere, agrees to meet the requirements for mitigation plans identified in 44 CFR §201 .6 and to provide such cooperation as i s necessary and in a timely manner to the Marin County to complete the plan in conformance with FEMA requirements.
The . City of Belvedere understands that it must engage. in the following planning_ process, as more fully described in FEMA's Local Mitigation Planning Handbook. including, but not limited to:
• Identification of hazards unique to the jurisdiction and not addressed in the master planning document; 1
• The conduct of a vulnerability analysis and an identification of risks, where they differ from the general planning area;
• The formulation of mitigation goals responsive to public input and development of mitigation actions complementary to those goals. A range of actions -must b_e identified specific for each jurisdiction; 2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
484
1 ~<;>U·N· TY OF a ~ ARIN ~
• Demonstration that there has been proactively offered an opportunity for participation in the planning process by all community stakeholders ( examples of participation include relevant involvement in any plannihg~ process, attending meetings, contributing research, data, or other information, commenting on drafts of the plan, etc.); and • Documentation of an effective process to maintain and implement the plan; and, • Formal adoption of the Multi-jurisdictional Hazard Mitigation Plan by~ the jurisdiction's governing body ( each jurisdiction must officially adopt the plan).
Therefore, with a full understanding of the obligations incurred by participating in the FEMA hazard mitigation plannir-ig process as a participant iA•a multi-jurisdictional plani, I, Robert Zadnik, City Manager, commit the City of Belvedere to the Marin County's Multijurisdictional Hazard Mitigation Planning effort.
This document is executed this 1 day of December 2022.
Robert-Zadnik
City Manager
City of Belvedere
( 415) 435-3838
2023 Marin County Operational Area
Multi-Jurisdictional Hazard Mitigation Plan
485
l ~ <;>U·N· TY OF
~ ARIN
a
~
SOLINAS COMMUNITY PUBLIC UTILITY DISTRICT
BCPUD BOX 390 270 ELM ROAD SOLINAS CALIFORNIA 94924 415 8681224 September 23, 2022
Sheriff Jamie Scardina
Marin County Sheriffs Office
1600 Los Gamos Drive, #200
San Rafael, California 94903
Re: "Statement of Intent to Paiticipate" as participating jurisdiction in Marin County MultiJurisdictional Local Hazard Mitigation Planning.