Portola City Council
June 10, 2026

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community. Since 2003, Connecting Point (originally the Nevada-Sierra Regional IHSS Public Authority) has been connecting people to In-Home-Support-Services and IHSS employment in Nevada, Sierra, and Plumas Counties. Representatives from Connecting Point were invited to be on the HMPC and provide input into the Plan development process, including input on the Draft LHMP. ➢ Red Cross - Red Cross, Gold Country Region, covers multiple counties including Plumas. The Red Cross mission is to prevent and alleviate human suffering in the face of emergencies. This involves providing relief to individuals and communities impacted by disasters, teaching life-saving skills, and supporting those in need through various services. These services include disaster relief, including providing shelter, food, and health services during emergencies. They also offer training in first aid, CPR, and other life-saving skills. Local Red Cross representatives were invited to be on the HMPC and review and provide comments on the Public Review Draft LHMP. ➢ Feather River College – Established in 1968, Feather River College is a small community college located in Quincy, California. Covering 256 acres, it serves as estimated 1,500 full time students.

Feather River College makes every effort to provide a safe and secure environment for all members of the college community, including providing students with information on hazard issues and disasters.

Representatives from Feather River College were invited to be on the HMPC and provide input into the Plan development process, including input on the Draft LHMP. ➢ Plumas County Unified School District - Plumas Unified School District, covering 2,613 square miles, serves the student and families in four distinct communities in rural Plumas County. PUSD serves over 1600 students in the 2,613 square miles through four elementary schools, three comprehensive high schools, and eight alternative education sites. The school locations range from Chester in the Lake Almanor north-west region, to Greenville in Indian Valley, to the county seat in Quincy in American Valley and to Portola in the East in Sierra Valley. The student population includes approximately: 78% Caucasian, 12.6% Hispanic, 1.2% Asian, 1.9% African American, and 6.3% other students. Representatives from PCUSD were invited to be on the HMPC and provide input into the Plan development process, including input on the Draft LHMP.

In addition to inviting the above groups to be part of the HMPC and LHMP development process, numerous other individuals, organizations, and agencies were included in the extensive outreach efforts conducted for the 2026 LHMP Update as described above. This includes news articles, newsletters, numerous Facebook Group postings and posting of LHMP posters and flyers in key locations throughout the County. All of these combined efforts provided notice of and an opportunity for participation by all groups in the 2026 Plumas County LHMP Update development process.

3.2.2. Phase 2: Assess Risks
Planning Steps 4 and 5: Identify the Hazards and Assess the Risks Foster Morrison led the HMPC in a research effort to identify, document, and profile all the hazards that have, or could have, an impact to the Plumas County Planning Area. Starting with the 2020/2019 LHMPs, natural hazards of concern were added, deleted, and modified for this LHMP Update. Data collection worksheets were developed and used in this effort to aid in determining hazards and vulnerabilities and where the risk varies across the Plumas County Planning Area. Geographic information systems (GIS) were used to display, analyze, and quantify hazards and vulnerabilities.

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The HMPC also conducted a capability assessment to review and document Plumas County’s and each participating jurisdictions’ current capabilities to mitigate risk and vulnerability to identified hazards. By collecting information about existing County/City/District programs, policies, regulations, ordinances, and emergency plans, the HMPC could assess those activities and measures already in place that contribute to mitigating some of the hazard risks and vulnerabilities. A more detailed description of the risk assessment process, methodologies, and results are included in Chapter 4 Risk Assessment.

NFIP Participation
Also addressed in the risk assessment and mitigation strategy of this 2026 LHMP is an assessment of the County’s and City of Portola’s floodplain management programs and participation in the NFIP, including a discussion of their continued compliance with NFIP requirements. However, it should be noted that this applies only to eligible NFIP communities. Participating special districts and agencies to this LHMP Update do not address their compliance with the NFIP as they are not eligible jurisdictions for purposes of the NFIP.

3.2.3. Phase 3: Develop the Mitigation Plan
Planning Steps 6 and 7: Set Goals and Review Possible Activities Foster Morrison facilitated brainstorming and discussion sessions with the HMPC that described the purpose and process of developing planning goals and objectives, a comprehensive range of mitigation alternatives, and a method of selecting and defending recommended mitigation actions using a series of selection criteria. This information is included in Chapter 5 Mitigation Strategy. Additional documentation on the process the HMPC used to develop the goals and mitigation strategy is in Appendix C.

Planning Step 8: Draft an Action Plan
Based on input from the HMPC regarding the draft risk assessment and the goals and activities identified in Planning Steps 6 and 7, a complete first draft of the LHMP Update was developed. This complete draft was provided for HMPC review and comment via a Dropbox web link. HMPC comments were integrated into the second public review draft, which was advertised and distributed to collect public input and comments. The HMPC integrated comments and issues from the public, as appropriate, along with additional internal review comments and produced a final draft for CAL OES and FEMA Region IX to review and approve, contingent upon final adoption by governing boards of all participating jurisdictions.

3.2.4. Phase 4: Implement the Plan and Monitor Progress Planning Step 9: Adopt the Plan
In order to secure buy-in and officially implement the LHMP Update, the Plan was adopted by the governing boards of each participating jurisdiction using the sample resolutions contained in Appendix D.

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Planning Step 10: Implement, Evaluate, and Revise the Plan The true worth of any mitigation plan is in the effectiveness of its implementation. Up to this point in the planning process, all of the HMPC’s efforts have been directed at researching data, coordinating input from participating entities, and developing appropriate mitigation actions and projects. Each recommended action includes key descriptors, such as a lead manager and possible funding sources, to help initiate implementation. An overall implementation strategy is described in Chapter 7 Plan Implementation and Maintenance.

Finally, there are numerous organizations within the Plumas County Planning Area whose goals and interests interface with hazard mitigation. Coordination with these other planning efforts, as addressed in Planning Step 3, is paramount to the implementation and ongoing success of this plan and mitigation in the Plumas County Planning Area and is addressed further in Chapter 7.

Implementation and Maintenance Process: 2020/2019 Plumas County/City of Portola LHMPs
The previous 2020 Plumas County and 2019 City of Portola LHMPs included a process for Plan maintenance and implementation of the mitigation strategy as well as formal updates to the LHMP. The 2020/2019 maintenance processes called for annual reviews, including a review of the status of mitigation strategy implementation and reviews after disasters. In addition, the 2020/2019 processes called for a formal plan update as required by DMA regulations every 5 years. With respect to the 2020/2019 LHMPs, Plumas County held an annual review in April of 2024 on their 2020 LHMP as part of the Plumas County Disaster Council agenda. This annual review focused on assessing and documenting progress on meeting LHMP goals and the status of mitigation action implementation. No other formal annual reviews were conducted on the 2020/2019 LHMPs ; although, both the County and City checked in on their LHMPs and potential mitigation actions post disaster to determine what funding might be available to implement priority projects. This 2026 LHMP Update, once approved and adopted, will meet the DMA formal 5-year update requirement for Plumas County and the City of Portola, as the previous participating jurisdictions.

In addition, the 2020 Plumas County LHMP was relied on and integrated into other planning mechanisms in the Plumas County Planning Area. Table 3-5 lists the planning mechanism the 2020 Plumas County LHMP was integrated into by unincorporated Plumas County. Specific to City of Portola, their jurisdictional annex addresses integration of their 2019 LHMP with other planning mechanisms.

Table 3-5 Unincorporated Plumas County -Incorporation of 2020 Plumas County LHMP into Other Planning Mechanisms
Planning Mechanism 2020
LHMP Was Incorporated
or Implemented Through
Details
General Plan Annual
Progress Report
LHMP was adopted by reference into the General Plan Safety Element. https://www.plumascounty.us/DocumentCenter/View/50845/PlumasCounty_2035 GP_2024-AnnualReport_4125

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Planning Mechanism 2020
LHMP Was Incorporated
or Implemented Through
Details
2021 Plumas County
Wildfires Long Term
Recovery Plan
The 2020 LHMP was referenced as a way in which to fund recovery and mitigation efforts. https://plumascounty.us/2964/2021-PLUMAS-COUNTY-WILDFIRESDIXIE-FIREPlumas County Regional Transportation Plan
The 2020 LHMP was referenced in terms of need for evacuation during hazard events. https://plumascounty.us/1900/Regional-Transportation-Plan Plumas County Community
Health Assessment
The Climate Change portion of the 2020 LHMP was referenced. Oct 2020 https://plumascounty.us/DocumentCenter/View/44000/PCPHA-Strategic-PlanUpdate-2022-PUBLIC-VERSION_121322?bidId= Plumas & Sierra Counties
Plan to address
Homelessness
This was adopted during the creation of the 2020 LHMP. The Plan to Address Homelessness references the wildfire hazard. June 2020
https://www.plumascounty.us/DocumentCenter/View/28278/Plumas-Sierra-FinalPlan-to-Address-Homelessness-061620_ADOPTED?bidId= Plumas County Housing
Study
This was adopted during the creation of the 2020 LHMP. The Housing Study references the wildfire hazard. June 2020 https://chpc.net/wpcontent/uploads/2024/05/Plumas_Housing_Report.pdf Sierra Valley Subbasin
Groundwater Sustainability
Plan Adoption
Portions of the Drought and Water Shortage section from the 2020 LHMP Update were referenced. https://www.sierravalleygmd.org/gsp-documents The plan implementation and maintenance process as set forth in the 2020/2019 LHMPs have been updated for this LHMP Update. The revised update implementation and maintenance process for the Plumas County 2026 LHMP Update is set forth in Section 7 of this Plan document. A strategy for continued public involvement for this update process is also included in Chapter 7.

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Chapter 4 Risk Assessment
44 Code of Federal Regulations (CFR) Requirement §201.6(c)(2): [The plan shall include] A risk assessment that provides the factual basis for activities proposed in the strategy to reduce losses from identified hazards. Local risk assessments must provide sufficient information to enable the jurisdiction to identify and prioritize appropriate mitigation actions to reduce losses from identified hazards.

As defined by the Federal Emergency Management Agency (FEMA), risk is a combination of hazard, vulnerability, and exposure. “It is the impact that a hazard would have on people, services, facilities, and structures in a community and refers to the likelihood of a hazard event resulting in an adverse condition that causes injury or damage.”
The risk assessment process identifies and profiles relevant hazards and assesses the exposure of lives, property, and infrastructure to these hazards. The process allows for a better understanding of a community’s potential risk to natural hazards and provides a framework for developing and prioritizing mitigation actions to reduce risk from future hazard events.

This risk assessment followed the methodology described in the FEMA publication Understanding Your Risks—Identifying Hazards and Estimating Losses (FEMA 386-2, 2002), which breaks the assessment down into a four-step process:

1. Identify Hazards;

2. Profile Hazard Events;

3. Inventory Assets; and

4. Estimate Losses.

Data collected through this process has been incorporated into the following sections of this chapter:
➢ Section 4.1 Hazard Identification identifies the natural hazards that threaten the Plumas County Planning Area and unincorporated Plumas County and describes why some hazards have been omitted from further consideration.
➢ Section 4.2 Plumas County Planning Area Assets Inventory and Growth and Development Trends identifies the populations; structures and values; critical facilities and community lifelines; cultural, historical, and natural resources; and economic and community activities of value. It also identifies past growth in the Plumas County Planning Area and reviews future development trends.

This information is not hazard specific and covers the entire Plumas County Planning Area and unincorporated Plumas County.
➢ Section 4.3 Hazard Profiles and Vulnerability Assessment provides an overview of each hazard, its location and extent, and discusses the risk, vulnerability, and impacts of each natural hazard to the Plumas County Planning Area and unincorporated Plumas County. The hazard profile also describes previous occurrences of hazard events and the likelihood of future occurrences. The vulnerability assessment evaluates the Plumas County’s exposure to natural hazards considering: populations;

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structures and values; critical facilities and infrastructure; natural, historic, and cultural resources; and future development trends, and where possible, estimates potential hazard losses. ➢ Section 4.4 Capability Assessment inventories existing mitigation activities and policies, regulations, plans, and programs that pertain to hazards and mitigation in the Plumas County Planning Area and unincorporated Plumas County and can affect net vulnerability. ➢ Section 4.5 Natural Hazard Summary summarizes the results of the risk assessment and whether a hazard is considered a priority for mitigation strategy planning.

This risk assessment covers the entire geographical extent of Plumas County (i.e., the Plumas County Planning Area) and unincorporated Plumas County. And as required by FEMA, this risk assessment for the Plumas County Planning Area also includes an evaluation of how the hazards and risks vary across the Planning Area.

This Local Hazard Mitigation Plan (LHMP) Update involved a comprehensive review and update of each section of the 2020 LHMP, as well as the relevant portions of the 2019 City of Portola LHMP. Information from the 2019 and 2020 LHMPs was used in this Update where valid and applicable. As part of the risk assessment update, new data was used, where available, and new analyses were conducted. Where data from existing studies and reports was used, the source is referenced throughout this risk assessment.

Refinements, changes, and new methodologies used in the development of this risk assessment update are summarized in Chapter 2 What’s New and are also detailed in this risk assessment portion of the Plan Update.

4.1 Hazard Identification
44 CFR Requirement §201.6(c)(2)(i): [The risk assessment shall include a] description of the type…of all natural hazards that can affect the jurisdiction.

The Plumas County Hazard Mitigation Planning Committee (HMPC) conducted a hazard identification study to determine the hazards that threaten the Planning Area. This section details the methodology and results of this effort.

Data Sources
The following data sources were used for this Hazard Identification portion of the plan:
➢ National Climatic Data Center Storm Events Database
➢ 2020 Plumas County Hazard Mitigation Plan
➢ 2013 Plumas County General Plan
➢ 2019 City of Portola Hazard Mitigation Plan
➢ 2023 State of California Hazard Mitigation Plan
➢ FEMA Disaster Declaration Database
➢ HMPC input

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4.1.1. Results and Methodology
Using existing hazards data and input gained through planning meetings, the HMPC agreed upon a list of hazards that could affect the Plumas County Planning Area. Hazards data from the California Office of Emergency Services (Cal OES), FEMA, California Department of Water Resources (CA DWR), the National Oceanic and Atmospheric Administration (NOAA), and many other sources were examined to assess the significance of these hazards to the Planning Area.

The following hazards in Table 4-1, listed alphabetically, were identified and investigated for this LHMP Update. As a starting point, the 2020 Plumas County LHMP Update, the 2019 City of Portola LHMP, and the 2023 California State Hazard Mitigation Plan were consulted to evaluate the applicability of new hazards of concern to the State to the Plumas County Planning Area. Building upon this effort, hazards from the past plans were identified, and comments explain how hazards were updated from the previous plans. Most hazards from the 2020 and 2019 plans were profiled in this LHMP Update, with the exception of pandemic. Compared to the 2020 Plumas County LHMP, avalanche was added to the Severe Weather:
extreme cold, freeze, and snow hazard, levee failure was placed inside the flood hazard, and agricultural hazards were added. Multiple hazards that were not profiled in the 2019 Portola LHMP were added, while none were dropped from consideration for this LHMP Update.

Table 4-1 Plumas County Hazard Identification and Comparison between 2020, 2019, and 2026 LHMPs
2026 Hazards 2020 Plumas County Hazards City of Portola 2019 LHMP
Comment
Ag Hazard: Severe
Weather/ Pests/Weeds
– – New hazard.
– Avalanche – This was added to a
Severe Weather hazard.

Climate Change Climate Change – This hazard was kept.

Dam Failure Dam Failure Dam Failure This hazard was kept.

Drought & Water
Shortage (w/tree
mortality)
Drought and Water Shortage – This hazard was kept.

Earthquake Earthquake Earthquake This hazard was kept.

Flood: 1%/0.2% annual
chance (w/levee failure)
Flood: 100/500-year Flood This hazard was kept and
levee failure was added.

Flood: Localized
Stormwater
Flood: Localized/Stormwater – This hazard was kept.

Haz Mat Transportation – – This is a new hazard.

Landslide, Mudslide, and
Debris Flow
Landslide, Mudslide, and
Debris Flows
– This hazard was kept.
– Levee failure – This was put into the
flood hazard.
– Pandemic – This hazard was dropped.

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2026 Hazards 2020 Plumas County Hazards City of Portola 2019 LHMP
Comment
Severe Weather: Extreme
Cold, Freeze, and Snow
(w/avalanche)
Severe Weather: Winter Storms
and Freeze
Winter and Extreme Cold This hazard was renamed
and avalanche was added.

Severe Weather: Extreme
Heat
Severe Weather: Extreme Heat Extreme Heat This hazard was kept.

Severe Weather: Heavy
Rains and Storms
Severe Weather: Heavy Rains
and Storms (winds, hail,
lightning)
Severe Weather This hazard was kept.

Severe Weather: High
Winds and Tornadoes
Severe Weather: High
Winds/Tornadoes
Severe Weather This hazard was kept.

Volcano Volcano - This hazard was kept.

Wildfire (w/smoke and air
quality)
Wildfire Wildfire This hazard was kept, and
smoke and air quality
subhazards were added.

Certain other hazards were excluded from consideration for this Plan Update. They are shown in Table 4-2.

Table 4-2 Plumas County – Excluded Hazards
Hazard Excluded Why Excluded
Coastal Flooding, Erosion, and
Sea Level Rise
The County is not on the coast.

Hurricane The County is not on the coast.

Tsunami The County is not on the coast.

Table 4-3 was completed by the County and HMPC to identify, profile, and rate the significance of identified hazards.

Note: Those hazards identified as a high or medium significance in Table 4-3 are considered priority hazards for mitigation planning. Those hazards that occur infrequently or have little or no impact in Plumas County were determined to be of low significance and not considered a priority hazard.

Significance was determined based on the hazard profile, focusing on key criteria such as frequency, extent, and resulting damage, including deaths/injuries and property, natural and cultural resources, and economic damage. The ability of a jurisdiction to reduce losses through implementation of existing and new mitigation measures was also considered as to the significance and priority of a hazard. This assessment was used to prioritize those hazards of greatest significance in the Plumas County Planning Area, enabling the County and participating jurisdictions to focus resources where they are most needed.

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Table 4-3 Plumas County Hazard Identification Assessment Hazard
Geographic
Extent
Likelihood of Future
Occurrences
Magnitude/
Severity Significance
Climate
Change
Influence
Ag Hazard: Severe Weather/
Pests/Weeds Extensive Highly Likely Critical Medium Medium Climate Change Extensive Likely Limited Medium --
Dam Failure Extensive Unlikely Critical High Medium
Drought & Water Shortage
(w/tree mortality) Extensive Likely Limited Medium High Earthquake Extensive Unlikely/Occasional Catastrophic Medium Low Flood: 1%/0.2% annual chance
(w/levee failure) Significant Occasional/Unlikely Critical High Medium Flood: Localized Stormwater Significant Highly Likely Negligible Medium Medium Hazardous Materials
Transportation Significant Occasional Critical Medium Low Landslide, Mudslide, and Debris
Flow Significant Likely Negligible Medium Medium
Severe Weather: Extreme Cold,
Freeze, and Snow (w/avalanche) Extensive Highly Likely Negligible Medium Medium Severe Weather: Extreme Heat Extensive Highly Likely Negligible Medium High Severe Weather: Heavy Rains
and Storms Extensive Highly Likely Limited Medium Medium Severe Weather: High Winds
and Tornadoes Extensive Highly Likely Limited Medium Low Volcano Extensive Unlikely Critical Low Low
Wildfire (w/smoke and air
quality) Extensive Highly Likely Catastrophic High
Medium
Geographic Extent
Limited: Less than 10% of planning area
Significant: 10-50% of planning area
Extensive: 50-100% of planning area
Likelihood of Future Occurrences
Highly Likely: Near 100% chance of
occurrence in next year, or happens
every year.

Likely: Between 10 and 100% chance of
occurrence in next year, or has a
recurrence interval of 10 years or less.

Occasional: Between 1 and 10% chance of
occurrence in the next year, or has a
recurrence interval of 11 to 100 years.

Unlikely: Less than 1% chance of
occurrence in next 100 years, or has a
recurrence interval of greater than every
100 years.

Magnitude/Severity
Catastrophic: More than 50 percent of property severely damaged; shutdown of facilities for more than 30 days; and/or multiple deaths Critical: 25-50 percent of property severely damaged; shutdown of facilities for at least two weeks; and/or injuries and/or illnesses result in permanent disability
Limited: 10-25 percent of property severely damaged; shutdown of facilities for more than a week; and/or injuries/illnesses treatable do not result in permanent disability
Negligible: Less than 10 percent of property severely damaged, shutdown of facilities and services for less than 24 hours; and/or injuries/illnesses treatable with first aid
Significance
Low: Minimal potential impact
Medium: Moderate potential impact
High: Widespread potential impact
Climate Change Influence
Low: Minimal potential impact
Medium: Moderate potential impact
High: Widespread potential impact

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4.1.2. Disaster Declaration History
One method used to identify hazards was the researching of past events that triggered federal and/or state emergency or disaster declarations in the Plumas County Planning Area. Federal and/or state disaster declarations may be granted when the severity and magnitude of an event surpasses the ability of the local government to respond and recover. Disaster assistance is supplemental and sequential. When the local government’s capacity has been surpassed, a state disaster declaration may be issued, allowing for the provision of state assistance. Should the disaster be so severe that both the local and state governments’ capacities are exceeded, a federal emergency or disaster declaration may be issued allowing for the provision of federal assistance.

The federal government may issue a disaster declaration through FEMA, the U.S. Department of Agriculture (USDA), and/or the Small Business Administration (SBA). FEMA also issues emergency declarations, which are more limited in scope and without the long-term federal recovery programs of major disaster declarations. The quantity and types of damage are the determining factors.

A USDA declaration will result in the implementation of the Emergency Loan Program through the Farm Services Agency. This program enables eligible farmers and ranchers in the affected county as well as contiguous counties to apply for low interest loans. A USDA declaration will automatically follow a major disaster declaration for counties designated major disaster areas and those that are contiguous to declared counties, including those that are across state lines. As part of an agreement with the USDA, the SBA offers low interest loans for eligible businesses that suffer economic losses in declared and contiguous counties that have been declared by the USDA. These loans are referred to as Economic Injury Disaster Loans. Disaster declarations for these programs are discussed in Section 4.3.6.

Based on the disaster declaration history provided in Table 4-4, Plumas County is among the many counties in California susceptible to disaster. Details on federal and state disaster declarations were obtained from FEMA and Cal OES and compiled in chronological order in Table 4-4. A review of state declared disasters indicates that Plumas County received 35 state declarations between 1950 and 2025. Of the 35 state declarations: 22 were associated with severe winter storms, heavy rains, or flooding; 8 were for fire; 2 were from pandemic, 1 was for drought; 1 was for freeze and severe weather conditions; and 1 was from economic disaster. A review of federal disasters shows 30 federal disaster declarations. Of these 30 federal declarations: 19 were associated with severe winter storms, heavy rains, or flooding; 6 for fire; 2 were from pandemic, 1 for drought; 1 was for seismic sea wave (which was declared for the entire State of California); and 1 was for hurricane (a nationwide declaration for Katrina evacuations). A summary of these events by disaster type is shown in Table 4-5.

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Table 4-4 Plumas County Federal and State Disaster Declarations, 1950-2025 Year Disaster Name Disaster Type Disaster Cause State Declaration # and Date
Federal
Declaration # and
Date
2023 California Severe
Winter Storms,
Straight-line
Winds, Flooding,
Landslides, and
Mudslides
Storms Storms 3/1/2023-
3/8/2023
DR-4699
4/3/2023
2023 California Severe
Winter Storms,
Straight-line
Winds, Flooding,
Landslides, and
Mudslides
Flood Storms 3/1/2023-
3/8/2023
EM-3592
3/10/2023
2021 California
Wildfires
Fire Fire 2021-04
7/16/2021
(Lava Fire)
7/16/2021
(Beckwourth
Complex)
8/6/2021
DR-4610
8/24/2021
2021 Dixie Fire Fire Fire 2021-03
7/23/2021
FM-5400
7/20/2021
2021 2021 Northeast
Wildfires
Fire Fire 2021-04
2021-03
8/6/2021
8/10/2021
(Monument
Fire)
–
2020 Bear Fire Fire Fire 2020-06
8/18/2020
FM-5363
9/9/2020
2020 California
Wildfires
Fire Fire – DR-4558
8/22/2020
2020 Covid-19 Pandemic Pandemic 2020-01
3/4/2020
DR-4482
3/22/2020
2020 Covid-19 Pandemic Pandemic 2020-01
3/4/2020
EM-3428
3/13/2020
2017 Severe Winter
Storms, Flooding,
Mudslides in
California
Flood Storms 2017-03
3/7/2017
DR-4308
4/1/2017
2017 Severe Winter
Storms, Flooding,
Mudslides in
California
Flood Storms 2017-01
1/23/2017
DR-4301
2/14/2017
2014 California
Drought
Drought Drought 2014-03
9/18/2014
–

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Year Disaster Name Disaster Type Disaster Cause State Declaration # and Date
Federal
Declaration # and
Date
2008 California
Wildfires
Fire Fire – EM-3287
6/28/2008
2007 Severe Freeze Freeze Freeze 2007-02
01/12/2007-
1/26/2007
–
2005/2006 Severe Storms,
Flooding,
Mudslides, and
Landslides in
California
Flood Storms 2006-01
1/12/2006
DR‐1628
2/3/2006
2005 Hurricane Katrina
Evacuations
Hurricane Hurricane – EM‐3248
9/13/2005
2001 Energy
Emergency
Economic Greed 1/1/2001 –
1999 California
Extreme Fire
Hazards
Fire Fire 99-05
8/26/1999
EM-3140
9/1/1999
1997 California Severe
Storms/flooding
Flood Storms 97-01
1/2/97‐1/31/97
DR‐1155
1/4/1997
1996 Torrential Wind
and Rains
Flood Storms GP 96-01
1/2/1996
–
1995 California Severe
Winter Storms,
Flooding,
Landslides, Mud
Flows
Flood Storms 95-03
03/12/95 –
03/24/95
DR-1046
3/12/1995
1995 1995 Severe
Winter Storms
Flood Storms 95-01, 95-02,
95-03, 95-04
1/6/95‐3/14/95
DR‐1044
1/13/1995
1993 California Severe
Storm, Winter
Storm, Mud &
Landslides,
Flooding
Flood Storms – DR-979
2/3/1993
1992 Late California
Severe Storm,
Winter Storm,
Mud &
Landslides,
Flooding
Flood Storms 93-01
2/12/92,
2/19/92
DR-979
2/25/1992
1992 1992 Late Winter
Storms
Flood Storms 93-01
1/7/93 - 2/19/93
DR-979
1/15/1992
1987 1987 Wildland
Fires
Fire Fire 9/10/1987,
9/3/1987
–
1986 California Severe
Storms, Flooding
Flood Storms 86-01
2/18‐86-3/12/86
DR‐758 2/21/1986

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Year Disaster Name Disaster Type Disaster Cause State Declaration # and Date
Federal
Declaration # and
Date
1980 April Storms Flood Storms 80-01–80-25
4/1/1980
–
1977 California
Drought
Drought Drought – EM-3023
1/20/1977
1970 California Severe
Storms, Flooding
Flood Flood 1/27/1970 -
3/2/1970
DR 283
2/16/1970
1969 California Severe
Storms, Flooding
Flood Storms 1/23/69, 1/25,69,
1/28/69, 1/29/69,
2/8/69, 2/10/69,
2/16/69, 3/12/69
DR-253
1/26/1969
1964 California Heavy
Rains & Flooding
Flood Storms 12/22/64,
12/23/64,
12/28/64, 1/5/65,
& 1/14/65
DR-183
12/24/1964
1964 Seismic Wave Other Other – DR-169
4/1/1964
1963 1963 Floods and
Rains
Flood Storms 2/7/63, 2/26/63,
2/29/63, &
4/22/63
DR-145
2/25/1963
1963 1963 Floods Flood Storms 2/14/1964 –
1960 1960 Widespread
Wildfires
Fire Fire 8/16/1960 –
1958 1958 April Storms
and Floods
Flood Storms 4/2/1958 DR-52
4/4/1958
1958 1958 February
Storms and
Floods
Flood Storms 2/26/1958 CDO 58-03
1955 1955 Floods Flood Flood 12/22/1955 DR-47
12/23/1955
1950 1950 Floods Flood Flood 11/21/1950 OCD 50-01
Source: Cal OES, FEMA. Retrieved April 2025.

Table 4-5 Plumas County – Federal and State Disaster Declarations Summary 1950-2025 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Drought 1 2014 1 1997
Economic 1 2001 0 –
Fire 8 1960, 1987, 1999, 2020 (twice),
2021 (three)
6 1999, 2008, 2020 (twice), 2021
(twice)

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Disaster Type State Declarations Federal Declarations
Count Years Count Years
Flood 22 1950, 1955, 1958 (twice), 1964,
1963, 1964, 1969, 1970 1980,
1986, 1993, 1992*, 1995
(twice*), 1996, 1997, 2006, 2017
(twice*), 2023 (twice*)
19 1950, 1955, 1958 (twice), 1963,
1964, 1969, 1970, 1986, 1992
(twice), 1995 (twice), 1997,
2006*, 2017 (twice*), 2023
(twice*)
Freeze 1 2007 0 –
Hurricane 0 – 1 2005
Pandemic 2 2020 (twice) 2 2020 (twice)
Seismic Sea Wave
(Tsunami)
0 – 1 1964
Totals 35 30
Source: Cal OES, FEMA. Retrieved April 2025.

Plumas County Disasters since 2019 City of Portola and 2020 Plumas County LHMP ➢ 2020 California Covid-19 Pandemic (2 state and 2 federal declarations) ➢ 2020 California Wildfires (federal declaration)
➢ 2020 Bear Fire (state and federal declaration)
➢ 2021 Northeast Wildfires (state declaration)
➢ 2021 Dixie Fire (state and federal declaration)
➢ 2021 California Wildfires (state and federal declaration) ➢ 2023 California Severe Winter Storms, Flooding, Landslides, and Mudslides (2 federal and 2 state declarations)
EOC Activations
It was noted that the County Emergency Operations Center (EOC) has been activated since the 2020 LHMP. This occurred during the following events:
➢ North Complex (Claremont, Bear, Sheep) – 8/14-9/26/2020 ➢ Dixie Fire – 7/14-8/30/2021
➢ Winter Storms – 2/21-7/10/2023
➢ COVID – 1/20/2020-5/11/2023

4.2 Plumas County Asset Inventory and Growth and Development Trends
As a starting point for analyzing the Plumas County Planning Area’s vulnerability to identified hazards, a variety of data was used to define a baseline against which all disaster impacts could be compared. If a catastrophic disaster was to occur in the Plumas County Planning Area, this section describes significant lands, assets, and other resources at risk. This section is broken into two parts:
➢ Asset Inventory – The assets inventory identifies the Plumas County Planning Area’s and unincorporated Plumas County’s total assets, including the people and populations: structures; critical

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facilities and infrastructure, and community lifelines; natural, historic, and cultural resources; and economic assets and community activities of value. This data is not hazard specific, but is representative of total assets within the Plumas County Planning Area and unincorporated Plumas County, potentially at risk to identified hazards as discussed in Section 4.3 Hazard Profiles and Vulnerability Assessment.
➢ Growth and Development Trends – A discussion of growth and development trends in the Plumas County Planning Area with a focus on unincorporated Plumas County, both current and future, is presented.

Data Sources
➢ 2019-2024 Plumas County Housing Element Background Report ➢ 2024 Plumas County Parcel/Assessor Data
➢ CalAtlas
➢ California Department of Conservation
➢ California Department of Finance E-1 Report
➢ California Department of Finance P-2 Report
➢ California Department of Fish and Wildlife Service
➢ California Department of Parks and Recreation Office of Historic Preservation ➢ California Department of Water Resources (CA DWR) Special Populations and Disadvantaged Community Mapping
➢ California Environmental Protection Agency (Cal EPA) Disadvantaged Communities ➢ California Environmental Quality Act (CEQA)
➢ California Natural Diversity Database
➢ Center for Disease Control (CDC) Social Vulnerability Index ➢ FEMA National Risk Index
➢ Hazus-MH 6.1
➢ National Environmental Policy Act (NEPA)
➢ Plumas County 2016 General Plan Land Use Element
➢ Plumas County 2035 General Plan Conservation Open Space Element ➢ Plumas County GIS
➢ Plumas County Intervention and Resource Center
➢ Plumas County Planning Department
➢ State of California Department of Conservation
➢ US Census Bureau
➢ US Fish and Wildlife Service

4.2.1. Assets Inventory
If a catastrophic disaster was to occur in the Plumas County Planning Area, this section describes populations, structures, critical facilities and infrastructure, and other key assets and resources at risk that comprise the existing built environment. Assets inventoried in this baseline assessment include:
➢ People and Populations
➢ Structures
➢ Critical Facilities and Infrastructure,
➢ Community Lifelines

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➢ Natural, Historic, and Cultural Resources
➢ Economic Assets and Community Activities of Value
Populations
Life safety is a priority issue for hazard mitigation planning. The people that work and recreate in the Plumas County Planning Area, and those that live and work in surrounding communities are also potentially at risk during a natural hazard event.

The estimated population of Plumas County (both incorporated communities and the unincorporated County) for January 1, 2024, was 18,841. Populations potentially at risk are described in the Table 4-6 based on California Department of Finance (DOF) estimates. The most recent estimates are dated 1/1/2024, which are shown in the table below.

Table 4-6 Plumas County Planning Area – Populations
Jurisdiction Population
City of Portola 2,098
Unincorporated Plumas County 16,787
Total 18,885
Source: Cal DOF E-1. 1/1/2024
Table 4-7 illustrates the pace of population growth in Plumas County dating back to 1940. Major growth in the County occurred in the 1970s, with other decades seeing small growth and small losses. There has been a recent downturn in population size since 2000. Details on population growth in the City of Portola is included in its respective annex to this LHMP Update.

Table 4-7 Plumas County Planning Area – Population Growth 1940-2024 Year Population Percent Increase
1940 11,548 –
1950 13,519 17.1%
1960 11,620 -14.0%
1970 11,707 0.7%
1980 17,340 48.1%
1990 19,739 13.8%
2000 20,824 5.5%
2010 20,007 -3.9%
2020 19,790 -1.1%
2024 18,885 -0.4%
Sources: 2019-2024 Plumas County Housing Element Background Report, California Department of Finance, US Census Bureau

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Vulnerable and Underserved Populations
Vulnerable populations include those who may be disproportionately affected by hazards or may need additional help or accommodation during a hazard event or disaster. The vulnerable and underserved populations discussion for the Plumas County Planning Area is based on the following sources:
➢ California Environmental Protection Agency (Cal EPA) Disadvantaged Communities ➢ Center for Disease Control (CDC) Social Vulnerability Index ➢ California Department of Water Resources (CA DWR) Special Populations and Disadvantaged Community Mapping
➢ FEMA National Risk Index
➢ Local Input
Note: These sources below show information for the Plumas County Planning Area and unincorporated Plumas County. Information on specific data for the incorporated jurisdictions can be found in their respective annexes to this Plan Update.

Cal EPA Disadvantaged Communities
Disadvantaged communities are defined by CalEPA as the top 25 percent of communities experiencing disproportionate amounts of pollution, environmental degradation, and socioeconomic and public health conditions according to the Office of Environmental Health Hazard Assessment’s CalEnviroScreen tool.

CalEPA is responsible for identifying disadvantaged communities for the purposes of the Cap-and-Trade funding program. This uses the CalEnviroScreen 4.0 Tool. Maps showing these areas in the Planning Area are shown on Figure 4-1.

Figure 4-1 Plumas County Planning Area – Cal EPA Disadvantaged Communities Source: Cal EPA, map retrieved 01/29/2025.

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Cal EPA has another way to track disadvantaged communities. California Climate Investments are funds (Greenhouse Gas Reduction Fund and appropriated by the Legislature) from the proceeds of the State’s Cap-and-Trade Program specifically targeted for investment in disadvantaged communities in California.

These funds must be used for programs that further reduce emissions of greenhouse gases. Senate Bill 535 directed that at least a quarter of the proceeds go to projects that provide benefit to disadvantaged communities and at least 10 percent of the funds go to projects located within those communities. Cal EPA has also mapped these communities. Those communities that fall inside this program in Plumas County are shown on Figure 4-2. As shown, these areas are very limited in Plumas County.

Figure 4-2 Plumas County SB 535 Disadvantaged Communities (2022) Source: Cal EPA, map retrieved 01/29/2025.

CDC Social Vulnerability Index
Every community must prepare for and respond to hazardous events, whether a natural disaster like a tornado or disease outbreak, or a human-made event such as a harmful chemical spill. A number of factors, including poverty, lack of access to transportation, and crowded housing may weaken a community’s ability to prevent human suffering and financial loss in a disaster. These factors are known as social vulnerability.

Social vulnerability refers to the potential negative effects on communities caused by external stresses on human health. Such stresses include natural or human-caused disasters, or disease outbreaks. Reducing social vulnerability can decrease both human suffering and economic loss. CDC Social Vulnerability Index (CDC SVI) uses 15 U.S. census variables to help local officials identify communities that may need support before, during, or after disasters.

The Agency for Toxic Substances and Disease Registry’s (ATSDR) Geospatial Research, Analysis & Services Program (GRASP) created databases to help emergency response planners and public health officials identify and map communities that will most likely need support before, during, and after a hazardous event. CDC SVI uses U.S. Census data to determine the social vulnerability of every census tract. Census tracts are subdivisions of counties for which the Census collects statistical data. The CDC

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SVI ranks each tract on 15 social factors, including poverty, lack of vehicle access, and crowded housing, and groups them into four related themes. Each tract receives a separate ranking for each of the four themes, as well as an overall ranking. Maps of the four themes are shown in the Plumas County Planning Area below. The overall SVI map is shown in Figure 4-3; the socioeconomic SVI for the Planning Area is shown in Figure 4-4; the household composition SVI is shown in Figure 4-5; the minority and language SVI is shown in Figure 4-6; and the housing and transportation SVI is shown in Figure 4-7. As shown on all of these maps, the County shows moderate changes across the County in social vulnerability.

Figure 4-3 Plumas County Planning Area – Overall Social Vulnerability Source: CDC Social Vulnerability Index – map retrieved 12/16/2024.

Level of Vulnerability Rating: Yellow – Low; Green – Low/Medium; Aqua – Medium/High; Blue – High; Grey Hatched – No Data; Grey – Not Available

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Figure 4-4 Plumas County Planning Area – Socioeconomic Status Vulnerability Source: CDC Social Vulnerability Index – map retrieved 12/16/2024.

Level of Vulnerability Rating: Faint Green – Low; Light Green – Low/Medium; Green – Medium/High; Dark Green – High; Grey Hatched – No Data; Grey – Not Available
Figure 4-5 Plumas County Planning Area – Household Composition and Disabilities Social Vulnerability
Source: CDC Social Vulnerability Index – map retrieved 12/16/2024.

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Level of Vulnerability Rating: Faint Orange – Low; Light Orange– Low/Medium; Orange – Medium/High; Dark Orange – High; Grey Hatched – No Data; Grey – Not Available
Figure 4-6 Plumas County Planning Area – Minority/Language Social Vulnerability Source: CDC Social Vulnerability Index – map retrieved 12/16/2024.

Level of Vulnerability Rating: Faint Purple – Low; Light Purple – Low/Medium; Purple – Medium/High; Dark Purple – High; Grey Hatched – No Data; Grey – Not Available

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Figure 4-7 Plumas County Planning Area – Housing/Transportation Social Vulnerability Source: CDC Social Vulnerability Index – map retrieved 12/16/2024.

Level of Vulnerability Rating: Faint Blue – Low; Light Blue – Low/Medium; Blue – Medium/High; Dark Blue – High; Grey Hatched – No Data; Grey – Not Available
California DWR Disadvantaged Community Mapping Tool
The State of California’s Proposition 1 Disadvantaged Community (DAC) Involvement Program is designated to ensure the involvement of DACs as well as Economically Distressed Areas and Underrepresented Communities, which DWR collectively refers to as DACs. The Cal DWR definition for a Disadvantaged Community is a community with an annual median household income (MHI) that is less than 80% of the Statewide annual MHI (PRC Section 75005(g)), and those census geographies with an annual MHI less than 60% of the Statewide annual MHI are considered “Severely Disadvantaged Communities”. Those areas in the Planning Area considered disadvantaged are shown in Figure 4-8.

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Figure 4-8 Plumas County Planning Area – Disadvantaged Areas Source: Cal DWR DAC Mapping Tool – retrieved 12/16/2024.

FEMA National Risk Index
Beginning in 2016, FEMA’s Natural Hazards Risk Assessment Program (NHRAP) started work on the National Risk Index (NRI) by adopting an established vision for a multi-hazard view of risk that combines the likelihood and consequence of natural hazards with social factors and resilience capabilities. The goal was to take a broad, holistic view and create a nationwide baseline of natural hazard risk.

A community’s susceptibility to natural hazards varies from location to location. The NRI is a dataset and online tool to help illustrate the United States communities most at risk for 18 natural hazards. It was designed and built by FEMA in close collaboration with various stakeholders and partners in academia; local, state, and federal government; and private industry. In the National Risk Index, risk is defined as the potential for negative impacts as a result of a natural hazard.

The risk equation behind the NRI includes three components (see Figure 4-9): a natural hazards component (Expected Annual Loss), a consequence enhancing component (Social Vulnerability), and a consequence reduction component (Community Resilience).

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Figure 4-9 National Risk Index Equation
Source: FEMA National Risk Index
Using these three components, composite Risk Index values and hazard type Risk Index values are calculated for each community (county and Census tract) included in the Index. Risk Index values form an absolute basis for measuring Risk within the NRI, and they are used to generate Risk Index percentiles and ratings across communities.

Data from the NRI for the Plumas County Planning Area is seen below. Figure 4-10 shows a summary map and score for the County. As shown, Plumas County’s Risk Index rating is Relatively Low. Figure 4-11 shows the expected annual loss map and score. As shown, Plumas County’s expected annual loss rating is Relatively Low. Figure 4-12 shows the social vulnerability map and score. As shown, Plumas County has a Relatively Low social vulnerability. Figure 4-13 shows the community resilience map and score. As shown, communities in Plumas County have a Relatively High ability to prepare for anticipated natural hazards, adapt to changing conditions, and withstand and recover rapidly from disruptions.

The Plumas County FEMA NRI Report is included in its entirety in Appendix H.

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Figure 4-10 FEMA National Risk Index – Summary Map and Score for Plumas County Source: FEMA National Risk Index, retrieved 01/09/2025.

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Figure 4-11 FEMA National Risk Index – Expected Annual Loss Map and Score for Plumas County
Source: FEMA National Risk Index, retrieved 01/09/2025.

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Figure 4-12 FEMA National Risk Index – Social Vulnerability Map and Score for Plumas County
Source: FEMA National Risk Index, retrieved 01/09/2025

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Figure 4-13 FEMA National Risk Index – Community Resilience Map and Score for Plumas County
Source: FEMA National Risk Index, retrieved 01/09/2025.

Local Input
In Plumas County, vulnerable populations groups primarily include seniors, children and students, large households, low income, homeless populations, people with disabilities, those with lack of or limited mobility, and those with limited access to public transportation services in the more rural areas for evacuations and other hazard response needs. There is also a seasonal farmworker population and a local student population which can create challenges during hazard events. The concept of Plumas County being vulnerable due to its location and status as a small, rural, and remote community was determined to be a major descriptor of the County’s underserved and vulnerable populations.

Plumas County noted that the County has two homeless day shelters (Quincy and Portola) that were recently funded for backup generators. The facilities are used for sheltering during times of cold, as these facilities are heated, but there was no air conditioning at these facilities. These are facilities operated by Plumas Crisis Intervention and Resource Center (PCIRC), a non-profit. Air conditioning has been added to these facilities.

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The PCIRC noted that a Point in Time count of homeless in the County is done in January of every odd calendar year. The 2025 data was still being processed due to changes in HUD guidelines, making the 2023 data the most recent fully available information. This can be seen in Table 4-8.

Table 4-8 Plumas County – 2023 Homeless Count
Homeless Type/Cause Number Percentage
Overall Count
Sheltered 58 43.28%
Unsheltered 76 56.72%
Total Homeless 134 100.00%
Count Subtypes
Chronically Homeless 13 9.70%
Veteran 3 2.23%
Domestic Violence Victim 5 3.37%
Felony Conviction 25 18.66%
COVID-19 0 0.00%
Fire 29 21.64%
Mental Health 9 6.72%
Eviction 35 26.12%
Drug Abuse 8 5.97%
Family Break Up 15 11.19%
Youth (18 to 24) 4 2.99%
Children (under 18) 18 13.43%
Male 76 56.72%
Female 49 36.57%
No Single Gender 0 0.00%
Transgender 0/1 0.00/0.75%
Questioning 0 0.00%
Source: Plumas County Intervention and Resource Center
Housing Element Special Populations
The County Planning Team noted that the Plumas County 2019-2024 Housing Element discusses special populations in the County. Discussions for seniors, those with disabilities, developmental disabilities, people experiencing homelessness, large households, female headed households, farmworkers, and students were included. These are discussed below.

Seniors
Many elderly individuals face challenges in securing affordable housing, given their fixed and often limited incomes. Physical disabilities and dependency needs further narrow their housing options while increasing

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the necessity for accessible healthcare and transportation. Despite Social Security and retirement benefits providing a guaranteed minimum income, many older adults still experience heightened poverty rates.

As of 2017, the American Community Survey estimated there were 4,364 seniors aged 65 years and over, living in unincorporated Plumas County, which represented over one-quarter of the total unincorporated County population, and approximately 6.8 percent of those 65 and older were below the poverty rate. When looking at senior household tenure, 87 percent of households were owner-occupied, and 13 percent were rented.

Disabled Citizens
As defined by the California Government Code, disabilities include physical and mental disabilities. A “mental disability” involves any mental or psychological disorder or condition, such as mental retardation, organic brain syndrome, emotional or mental illness, or specific learning disabilities that limit a major life activity. A “physical disability” includes any physiological disease, disorder, condition, cosmetic disfigurement, or anatomical loss of body functions. Physical disabilities include those that are neurological, immunological, or musculoskeletal in nature as well as those that involve the respiratory, cardiovascular, reproductive, genitourinary, hemic and lymphatic, or digestive systems and those involving the special sense organs, speech organs, skin, or endocrine system.

Cognitive difficulties and Ambulatory living difficulties are the most common forms of disability among residents ages 5 to 64 in Plumas County. Seniors aged 65 and above in unincorporated Plumas County are more likely to have either ambulatory difficulties or hearing difficulties. Persons aged 5–64 with a disability account for 1,975 individuals (10.0%) while persons aged 65 + with a disability account for 1,472 individuals (7.4%) residing in the County. The total sums to 3,447 individuals suffering from one or more disabilities (17.4%).

People with Developmental Disabilities
A developmental disability is a disability that occurs before an individual reaches 18 years of age, is expected to continue indefinitely, and constitutes a substantial disability for that individual. Developmental disabilities include mental retardation, cerebral palsy, epilepsy, autism, and disabling conditions closely related to mental retardation or requiring similar treatment. However, since data is collected by zip code, the exact number of developmentally disabled individuals is challenging to get an exact number. For 0-17 years-old, it’s estimated there are 87 individuals while the 18+ years-old account for estimated 126 persons.

Homeless Persons
Homeless individuals and families have the most immediate housing need of any special needs group. Their needs are difficult to meet because of the diversity and complexity of the factors that lead to homelessness.

California state law requires that housing elements estimate the need for emergency shelter for homeless people. The PCIRC offers homeless prevention and rapid re-housing programs, based on an evidencebased Housing First Model, utilizing available annual funding to those experiencing homeless in Plumas County.

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In 2019, the NorCal Continuum of Care Point-in-Time count identified 1,249 homeless people in Del Norte, Lassen Modoc, Plumas, Shasta, Sierra, and Siskiyou counties. In Plumas County specifically, the Pointin-Time count identified 53 homeless people, or 4 percent of the homeless population counted in the sevencounty region—11 had been experiencing chronic homelessness, and 24 were female, though only 5 of the women were unsheltered.

Large Households
Large families are defined by the US Census Bureau as households containing five or more persons. They are considered a special needs group because there is a limited supply of adequately sized housing to accommodate their needs. According to the 2012–2016 US Census American Community Survey, 366 households (4.9%) in unincorporated Plumas County included five or more persons. Of those, 154 (42.1%) were owner-occupied large households, and 212 (57.9%) were renter-occupied large households.

As of 2017, there was no shortage of housing for large families in Plumas County due to the availability of housing by bedroom size. There are 7,591 three-bedroom housing units, 1,611 four-bedroom units, and 166 units with five or more bedrooms, respectively comprising 48.2 percent, 10.2 percent, and 1.1 percent of all housing in the county. Since the population of Plumas County changes gradually and the average household size was 2.06 persons per household in 2017, it can be presumed that the current supply of housing is sufficient to accommodate large families.

Female Headed Households
Female-headed households are households headed by a single female parent with children under the age of 18 living at home. Single-parent households generally have lower incomes than two-parent households and often require special attention due to their need for affordable childcare, health care, housing assistance, and other supportive services. Additionally, female-headed households generally tend to have lower incomes and higher living expenses, often making the search for affordable, decent, and safe housing more difficult.

Poverty is typically an issue with female-headed households. As of the 2012–2016 American Community Survey, approximately 11% of households in unincorporated Plumas County were female-headed households with children, and 3% of households were female-headed households under the poverty level.

Farmworkers
Agricultural workers earn their primary income through permanent or seasonal agricultural labor. The number of persons employed in agriculture (including forestry, fishing and hunting, and mining), according to the USDA 2017 Census of Agriculture, there were 173 hired farm laborers and 211 unpaid farm laborers in Plumas County. This population represents nearly 10 percent of the job market in Plumas County in 2017.

Most farmworkers earn relatively low wages, and thus they fall into the extremely low– and very-lowincome categories. Housing opportunities for migrant farmworkers may include employee housing (i.e., dwelling units or manufactured homes) and other congregate living facilities as well as affordable multifamily or single-family rental units (Housing Element Program 20). Year-round farmworkers

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typically need affordable rental or ownership housing, which is available in the County’s existing residential zoning districts.

Students Residences
Feather River College (FRC) in Quincy is a public community college, which is fully accredited by the Western Association of Schools and Colleges, and offers two-year associate degrees, in addition to offering a four-year Bachelor of Science in Equine and Ranch Management. FRC, as of October 2019, operated the following student housing: On-Campus Dormitories – 64 apartments housing 160 students, the Meadows Apartments – 11 apartments housing 27 students, and the Pines Apartments – 25 rooms housing 46 students.

This inventory consists of 77 one-bedroom apartments, 19 two-bedroom apartments, and 4 studio apartments across the three locations.

The FRC resident housing capacity is set at 233 students; however, the college has added extra bunks to some of the larger rooms, increasing the overall capacity to approximately 250 students. While the unmet need for student housing is difficult to track, FRC estimates the resident housing needs gap to be approximately 70+ students. Based on a waitlist reaching 65 names during the summer of 2019, FRC was able to accommodate 25 additional students, leaving approximately 40 who could not be served with student housing. FRC received another 40+ inquiries about student housing during the summer of 2019, but these potential students never turned in an application after they learned about the waitlist.

Structures
Structures include buildings used for a variety of purposes and reflect the Plumas County Planning Area’s existing built environment. Depending on the nature and extent of a hazard event or disaster, all structures may be exposed to some level of risk, where certain buildings or concentrations of buildings are more vulnerable. This section captures the structures, and associated land and contents values, which comprise the Plumas County Planning Area’s and unincorporated Plumas County’s existing built environment.

Parcel and Structure Inventory and Assessed Values
An inventory of structures located within the Plumas County Planning Area and unincorporated County was developed utilizing data from the Plumas County Assessor’s Office. It is based on the 2024 Assessor’s data/Parcel layer provided by Plumas County Geographic Information Systems (GIS). This data represents best available data.

While conducting an inventory of structure assets within the Plumas County Planning Area is a key element of this asset inventory, understanding the total assessed value of structures and built environment is a starting point to understanding the overall value of identified assets in the Plumas County Planning Area.

When the total assessed values are combined with potential values associated with other community assets such as area populations, public and private critical infrastructure, historic and cultural resources, and natural resources, and other identified assets, the big picture emerges as to what is potentially at risk and vulnerable to the damaging effects of natural hazards within the Plumas County Planning Area.

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Methodology
The 2024 Plumas County Assessor’s data and County Parcel Layer was utilized as the basis for the inventory of assessed values for both improved and unimproved parcels within the Plumas County Planning Area. This data provides the land and improved values, and personal property values assessed for each parcel, along with key information such as property use. Other GIS data, such as jurisdictional boundaries, roads, streams, and area features, was also obtained from Plumas County and CalAtlas to support mapping and analysis of the existing built environment.

Data Limitations & Notations
Although based on best available data, the resulting information should only be used as an initial guide to overall values in the Plumas County Planning Area. In the event of a disaster, structures and other infrastructure improvements are at the greatest risk of damage. Depending on the type of hazard and resulting damages, the land itself may not suffer a significant loss. For that reason, the values of structures and other improvements are of greatest concern. Also, it is critical to note a specific limitation to the assessed values data within the Plumas County Planning Area, created by Proposition 13. Instead of adjusting property values annually, no adjustments are made until a property transfer occurs. As a result, overall property value information is likely significantly low and does not reflect current market, replacement, or true potential loss values for properties within the Plumas County Planning Area.

Another limitation to this data is found in the Williamson Act, also known as the California Land Conservation Act of 1965, that enables local governments to enter into contracts with private landowners for the purpose of restricting specific parcels of land to agricultural or related open space use. When the County enters into a contract with the landowners under the Williamson Act, the landowner agrees to limit the use of the land to agriculture and compatible uses for a period of at least ten years and the County agrees to tax the land at a rate based on the agricultural production of the land rather than its real estate market value. This further affects the County’s overall values for assessed taxable lands and structures.

Property Use Categories
The Plumas County Planning Area Assessor data included property use categories which provides detailed descriptive information about how each property is generally used, such as residential, commercial, or industrial. The property use codes were refined and categorized into the following property use categories and linked back to the Assessor data. The final property use categories for the Plumas County Planning Area include:
➢ Agricultural
➢ Commercial
➢ Federal Lands
➢ Government
➢ Industrial
➢ Institutional
➢ Miscellaneous
➢ Recreational
➢ Residential

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➢ ROW/Utilities
Once property uses were grouped into categories, the number of total and improved parcels, land, personal property, and improved (structure) values were inventoried for the Plumas County Planning Area by property use.

Estimated Content Replacement Values
The Plumas County Planning Area assigned property use categories were used to develop estimated content replacement values (CRVs) that are potentially at loss from hazards. FEMA’s standard CRV factors, derived from Hazus, were utilized to develop more accurate loss estimates for the total assets inventory and for all mapped hazard analyses. FEMA’s CRV factors estimate content values as a percent of improved structure value by property use. Table 4-9 shows the breakdown of the different property uses in the Plumas County Planning Area and their estimated CRV factors.

Table 4-9 Plumas County Planning Area – Content Replacement Factors by Property use Plumas County Property Use Categories Hazus Property Use Categories
Hazus Content
Replacement Values
Agricultural Agricultural 100%
Commercial Commercial 100%
Federal Lands Federal Lands 100%
Government Government 100%
Industrial Industrial 150%
Institutional Institutional 100%
Miscellaneous Miscellaneous 100%
Recreational Recreational 100%
Residential Residential 50%
ROW/Utilities ROW/Utilities 100%
Source: Hazus 6.1
Parcel and Structure Asset Inventory with Values Results Values associated with land and improved structures and personal property were identified and summed in order to determine total assessed values at risk in the Plumas County Planning Area. Together, the land and improved structure values make up the majority of assessed values associated with each identified parcel or asset. Improved parcel counts were based on the assumption that a parcel was improved if a structure value was present. CRVs were then added to the assessed values, as described below, to provide an estimate of total values at risk in the Planning Area.

Table 4-10 shows the total values or exposure for the entire Plumas County Planning Area broken out by jurisdiction. Table 4-11 shows the values for the unincorporated Plumas County broken out by property use. Tables showing the property use breakouts for the incorporated communities are included in their respective annexes to this LHMP Update.

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Table 4-10 Plumas County Planning Area – Total Parcels and Structures by Jurisdiction Jurisdiction Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola 1,643 1,021 $37,950,371 $151,251,034 $1,915,072 $94,642,209 $285,758,686 Unincorporated
Plumas County
24,234 13,427 $1,664,994,728 $3,202,945,278 $141,527,563 $1,734,158,622 $6,743,626,191 Grand Total 25,877 14,448 $1,702,945,099 $3,354,196,312 $143,442,635 $1,828,800,830 $7,029,384,876 Source: 2024 Plumas County Parcel/Assessor Data
Table 4-11 Unincorporated Plumas County – Total Parcels and Structures by Property Use Jurisdiction /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Agricultural 1,310 118 $70,282,817 $24,979,645 $2,766,527 $24,979,645 $123,008,634 Commercial 853 556 $78,599,880 $164,344,412 $32,275,885 $164,344,412 $439,564,589 Federal Lands 217 0 $0 $0 $0 $0 $0
Government 599 0 $124,956 $0 $0 $0 $124,956
Industrial 140 85 $10,733,621 $18,449,533 $33,550,208 $27,674,300 $90,407,662 Institutional 80 39 $2,145,116 $13,936,169 $196,380 $13,936,169 $30,213,834 Miscellaneous 26 0 $9,591 $0 $0 $0 $9,591
Recreational 519 91 $18,190,148 $25,212,673 $1,814,124 $25,212,673 $70,429,618 Residential 19,424 12,538 $1,484,908,599 $2,956,022,846 $70,924,439 $1,478,011,423 $5,989,867,307 ROW/Utilities 1,066 0 $0 $0 $0 $0 $0
Unincorporated
Plumas County
Total
24,234 13,427 $1,664,994,728 $3,202,945,278 $141,527,563 $1,734,158,622 $6,743,626,191 Source: 2024 Plumas County Parcel/Assessor Data
Critical Facilities and Infrastructure
For purposes of this plan, a critical facility is defined as:

Any facility, including without limitation, a structure, infrastructure, property, equipment or service, that if adversely affected during a hazard event may result in severe consequences to public health, safety, and the environment or interrupt essential services and operations for the community at any time before, during, and after the hazard event.

A critical facility is classified by the following categories: (1) Essential Services Facilities: (2) At-Risk Populations Facilities, and (3) Hazardous Materials Facilities.

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➢ Essential Services Facilities include, without limitation, public safety, emergency response, emergency medical, designated emergency shelters, communications, public utility facilities and equipment, and government operations. Sub-Categories include:
✓ Public Safety – Sheriff station and substations, California highway patrol stations, fire and rescue stations, emergency operations centers, and any facility deemed critical or leased by PG&E for the purposes of a community resource center during Public Safety Power Shutoff (PSPS) events. ✓ Emergency Response – Emergency vehicle and equipment storage and essential governmental work centers for continuity of government operations.
✓ Emergency Medical – Hospitals, emergency care, clinics, wellness centers, pharmacies, and ambulance services.
✓ Designated Emergency Shelters – Fairgrounds, memorial/veterans halls, and schools. ✓ Communication Sites and Facilities – Main broadcasting equipment and systems, cell towers, data transmission, and other emergency warning systems (hubs for telephone, television, cable, radio, and internet).
✓ Public Utility Plant and Substation Facilities – Equipment for treatment, generation, storage, pumping, and distribution (hubs for surface water, groundwater, wastewater, power, and fuel). ✓ Essential Government Operations – County Courthouse (public records, elections, government administration and risk management, information technology, and courts), jails, probation, building permitting and inspection services, Public Works (maintenance and equipment yards), Child Support Services, Assessor, and County Annex (public health, behavioral health, social services, and environmental health).
✓ Transportation Lifeline Systems – Airports, heliports, helipads, critical highways, critical roadways, bridges, railroads, and other transportation infrastructure.1 ➢ At-Risk Populations Facilities include, without limitation, pre-schools, public and private primary and secondary schools, before and after school care centers with 12 or more students, daycare centers with 12 or more children, group homes, and assisted living residential or congregate care facilities with 12 or more residents.
➢ Hazardous Materials Facilities include, without limitation, any facility that could, if adversely impacted, release hazardous material(s) in sufficient amounts during a hazard event that would significantly impact public health, safety, and the environment. For the purposes of this plan, those facilities storing threshold quantities of regulated substances subject to the California Accidental Release Response Plan (CalARP) program as specified in 19 CCR § 2770.5 are considered as meeting this criteria.

Critical facilities in the Plumas County Planning Area are shown on Figure 4-14. A summary of critical facilities in the Planning Area is shown in Table 4-12 and detailed in Table 4-13. Additional details of individual critical facilities can be found in Appendix G of this Plan Update. 1 Note: critical linear transportation routes and systems such as highways and roadways will be determined during any hazard-specific evacuation planning and, for those reasons, are not specifically identified in this plan.

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Figure 4-14 Plumas County Planning Area – Critical Facilities Table 4-12 Plumas County Planning Area – Critical Facilities by Jurisdiction and Critical Facility Category
Jurisdiction / Critical Facility Category Facility Count City of Portola
Essential Services Facilities 16
At Risk Populations Facilities 8
Hazardous Materials Facilities 0
City of Portola Total 24
Unincorporated Plumas County
Essential Services Facilities 829
At Risk Populations Facilities 33
Hazardous Materials Facilities 4
Unincorporated Plumas County Total 866
Unincorporated Butte County

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Jurisdiction / Critical Facility Category Facility Count Essential Services Facilities 4
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Unincorporated Butte County Total 4
Unincorporated Lassen County
Essential Services Facilities 34
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Unincorporated Lassen County Total 34
Unincorporated Sierra County
Essential Services Facilities 4
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Unincorporated Sierra County Total 4
Unincorporated Tehama County
Essential Services Facilities 2
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Unincorporated Tehama County Total 2
Grand Total 934
Source: Plumas County GIS
Table 4-13 Plumas County Planning Area – Critical Facilities by Jurisdiction and Critical Facility Category and Facility Type
Jurisdiction / Critical Facility Category Critical Facility Type Facility Count Portola
Essential Services Facilities
Emergency Medical 1
Essential Government Operations 3
Public Safety 2
Public Utility Plant and Substation Facilities 8
Transportation Lifeline Systems 2
Essential Services Facilities Total 16
At Risk Populations Facilities
Designated Emergency Shelter 1
Public Safety 1
School 6
At Risk Populations Facilities Total 8

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Jurisdiction / Critical Facility Category Critical Facility Type Facility Count Portola Total 24
Unincorporated Plumas County
Essential Services Facilities
Communication Sites and Facilities 495
Designated Emergency Shelter 3
Emergency Medical 11
Emergency Response 5
Essential Government Operations 14
Nursing, Congregate or Assisted Living 1
Public Safety 42
Public Utility Plant and Substation Facilities 119
Transportation Lifeline Systems 139
Essential Services Facilities Total 829
At Risk Populations Facilities
Nursing, Congregate or Assisted Living 2
School 31
At Risk Populations Facilities Total 33
Hazardous Materials Facilities
Hazardous Materials Facilities 3
Industrial 1
Hazardous Materials Facilities Total 4
Unincorporated Plumas County Total 866
Unincorporated Butte County
Essential Services Facilities
Public Utility Plant and Substation Facilities 4
Essential Services Facilities Total 4
Unincorporated Butte County Total 4
Unincorporated Lassen County
Essential Services Facilities
Communication Sites and Facilities 1
Public Safety 2
Public Utility Plant and Substation Facilities 31
Essential Services Facilities Total 34
Unincorporated Lassen County Total 34
Unincorporated Sierra County
Essential Services Facilities
Public Utility Plant and Substation Facilities 4
Essential Services Facilities Total 4
Unincorporated Sierra County Total 4
Unincorporated Tehama County
Essential Services Facilities
Public Safety 2
Essential Services Facilities Total 2
Unincorporated Tehama County Total 2

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Jurisdiction / Critical Facility Category Critical Facility Type Facility Count Grand Total 934
Source: Plumas County GIS
Community Lifelines
Assessing the vulnerability of the Plumas County Planning Area to natural hazards and disasters also involves reviewing and inventorying the community lifelines in place that could be affected. It is important to include these items in hazard discussions as the continuous operation of critical government and business functions is essential to human health and safety and/or economic security. Information on community lifelines include:
➢ Lifelines are the most fundamental services in the community that, when stabilized, enable all other aspects of society to function.
➢ FEMA has developed a construct for objectives-based response that prioritizes the rapid stabilization of Community Lifelines after a disaster.
➢ The integrated network of assets, services, and capabilities that provide lifeline services are used dayto-day to support the recurring needs of the community and enable all other aspects of society to function.
➢ When disrupted, decisive intervention (e.g., rapid re-establishment or employment of contingency response solutions) is required to stabilize the incident.

For this Plan, Community Lifelines includes the following (as defined by FEMA):
➢ Safety and Security – Law Enforcement/Security, Fire Service, Search and Rescue, Government Service, Community Safety
➢ Food, Hydration, Shelter – Food, Water, Shelter, Agriculture ➢ Health and Medical – Medical Care, Public Health, Patient Movement, Medical Supply Chain, Fatality Management
➢ Energy – Power Grid, Fuel
➢ Communications – Infrastructure, Responder Communications, Alerts Warnings and Messages, Finance, 911 and Dispatch
➢ Transportation – Highway/Roadway/Motor Vehicle, Mass Transit, Railway, Aviation, Maritime ➢ Hazardous Material – Facilities, HAZMAT, Pollutants, Contaminants ➢ Water Systems – Potable Water Infrastructure, Wastewater Management In the Plumas County Planning Area, these community lifelines are all in place and functional as part of regular government operations. It should also be noted that these community lifelines collectively include many of the individual components of other community assets inventoried for this LHMP including structures and critical facilities and infrastructure.

After the HMPC reviewed the list of hazards from Table 4-3, it was determined that most hazards that occur would not overwhelm the community lifelines in the Plumas County Planning Area. A matrix was put together in Table 4-14 for the hazards in the County. As shown, only earthquake, volcano, and wildfire are thought be able to (temporarily) overwhelm the community lifelines in the Plumas County Planning Area.

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Of the remaining hazards, only very extreme events of dam failure, flood, and hazardous materials transportation may have a chance of temporarily overwhelming community lifelines. Events associated with the remaining hazards would likely not overwhelm community lifelines.

Note: This inventory of community lifelines and hazard analysis only occurs in this overall asset inventory for Plumas County. To limit redundancy, it is not discussed further in the hazard profiles and vulnerability assessments in Section 4.3 below.

Table 4-14 Plumas County Planning Area – Hazards and their Potential to Overwhelm Community Lifelines
Hazard Potential to Overwhelm
Community Lifelines
Hazard Potential to Overwhelm
Community Lifelines
Severe Weather: Extreme
Cold, Freeze, and Snow
(w/avalanche)
Limited Earthquake High
Severe Weather: Extreme
Heat
Limited Flood: 1%/0.2% annual
chance (w/levee failure)
Moderate
Severe Weather: Heavy
Rains and Storms
Limited Flood: Localized Flooding Limited
Severe Weather: High
Winds and Tornado
Limited Hazardous Materials
Transportation
Moderate
Ag Hazard: Severe
Weather/ Pests/Weeds
Limited Landslide, Mudslide, and
Debris Flow
Limited
Climate Change Limited Volcano High
Dam Failure Moderate Wildfire (w/smoke and air
quality)
High
Drought & Water Shortage
(w/tree mortality)
Limited – –
Source: Plumas County Planning Team
Efforts to mitigate potential impacts to community lifelines are key to building resilience. These community lifelines connect to the sectors in the National Mitigation Framework and the Recovery Support Functions under the National Disaster Recovery Framework; the same agencies and departments that support these sectors also often support community lifelines and the recovery mission.

Specific information on these community lifelines in the Plumas County Planning Area and how they may be affected by a hazard event or disaster are discussed in more detail in each hazard section below as well as in each jurisdictional annex to this Base Plan.

Natural, Historical, and Cultural Resources
Assessing the vulnerability of the Plumas County Planning Area to disaster also involves inventorying the natural, historic, and cultural assets of the area. This step is important for the following reasons:
➢ The community may decide that these types of resources warrant a greater degree of protection due to their unique and irreplaceable nature and contribution to the overall economy.

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➢ If these resources are impacted by a disaster, knowing so ahead of time allows for more prudent care in the immediate aftermath, when the potential for additional impacts are higher. ➢ The rules for reconstruction, restoration, rehabilitation, and/or replacement are often different for these types of designated resources.
➢ Natural resources can have beneficial functions that reduce the impacts of natural hazards, such as wetlands and riparian habitat, which help absorb and attenuate floodwaters.

Natural Resources
Natural resources are important to include in cost/benefit analyses for future projects and may be used to leverage additional funding for mitigation projects that also contribute to community goals for protecting sensitive natural resources. Awareness of natural resource assets can lead to opportunities for meeting multiple objectives. For instance, protecting wetlands areas protects sensitive habitat as well as reducing the force of and storing floodwaters.

The Plumas County 2035 General Plan Conservation Open Space Element noted that Plumas County is located in an area of varying topography and slopes, with elevations ranging from approximately 1,800 feet in the Feather River Canyon to 8,300 feet near the summit of Mount Ingalls. With a majority of land associated with agricultural activities, forestry, or other managed resource uses, approximately 94% of the total County area, the primary land use in Plumas County is considered an open space use. Additionally, many of these lands are managed for a combination of resource values, including but not limited to recreation, mining, timber production, and cultural and historic resources.

Plumas County is comprised of a range of habitat types many of which influence the water quality and quantity of the Feather River Watershed. These habitats, or vegetation communities, provide food, shelter, movement corridors, and breeding opportunities for a variety of wildlife species, many unique to the Feather River Watershed and the larger Sierra Mountain region. Conifer (including Mixed Conifer) habitat types comprise approximately 72% of land coverage in the County and are habitats commonly found at higher elevations. Plants characteristic of this habitat includes a variety of pines and firs. As one gets farther away from the higher elevation Sierra regions of the County, the pines and firs give way to sagebrush, annual grasslands, and the freshwater emergent wetland habitat types more common at lower elevations.

Plumas County and the larger Feather River Watershed area contain a variety of aquatic habitats. Within the watershed, two types of fisheries are found: cold water river/stream species and warm water lake/ reservoir species. Historically, the watershed was habitat to Chinook salmon and steelhead. Special-status species are plants or animals that are legally protected under the State and/or federal Endangered Species Acts (ESAs) or other regulations, and species that are considered by the scientific community to be sufficiently rare to qualify for such listing. The California Department of Fish and Wildlife (CDFW) has documented habitat for over 90 different species of special concern in the County. These include several amphibians, such as the red-legged frog, bald eagles, osprey, several mammals, and plant/wildlife species associated with wetland habitats.

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Special Status Species
To further understand natural resources that may be particularly vulnerable to a hazard event, as well as those that need consideration when implementing mitigation activities, it is important to identify at-risk species (i.e., endangered species) in the Planning Area. An endangered species is any species of fish, plant life, or wildlife that is in danger of extinction throughout all or most of its range. A threatened species is a species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. Both endangered and threatened species are protected by law and any future hazard mitigation projects are subject to these laws. Candidate species are plants and animals that have been proposed as endangered or threatened but are not currently listed.

The California Natural Diversity Database, a program that inventories the status and locations of rare plants and animals in California, was queried to create an inventory of special status species in Plumas County.

A summary list of these species is found below in Table 4-15. Appendix E lists the name, federal status, state status, CDFW status, and the California Rare Plant rank of species in Plumas County.

Table 4-15 Plumas County Planning Area – Summary of Special Status Species Type Number
Animals - Amphibians 2
Animals - Birds 47
Animals - Fish 7
Animals - Insects 6
Animals - Mammals 26
Animals – Mollusks 11
Animals – Reptiles 2
Community – Aquatic 3
Community – Terrestrial 1
Plant – Bryophytes 2
Plants – Vascular 171
Source: California Natural Diversity Database. Retrieved January 2025.

Additionally, Plumas County has mapped critical habitat and endangered species in the County. This is shown on Figure 4-15.

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Figure 4-15 Plumas County Critical Habitat and Endangered Species

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Wetlands
Wetlands are habitats in which soils are intermittently or permanently saturated or inundated. Wetland habitats vary from rivers to seasonal ponding of alkaline flats and include swamps, bogs, marshes, vernal pools, and riparian woodlands. Wetlands are considered to be waters of the United States and are subject to the jurisdiction of the U.S. Army Corps of Engineers (USACE) as well as the CDFW. Where the waters provide habitat for federally endangered species, the U.S. Fish and Wildlife Service (FWS) may also have authority.

Wetlands are a valuable natural resource for communities providing beneficial impact to water quality, wildlife protection, recreation, and education, and play an important role in hazard mitigation. Wetlands provide drought relief in water-scarce areas where the relationship between water storage and streamflow regulation is vital and reduce flood peaks and slowly release floodwaters to downstream areas. When surface runoff is dampened, the erosive powers of the water are greatly diminished. Furthermore, the reduction in the velocity of inflowing water as it passes through a wetland helps remove sediment being transported by the water.

Fresh emergent wetland habitats occur in Plumas County on virtually all exposures and slopes, provided a basin or depression is saturated or at least periodically flooded. They are most common on level to gently rolling topography. They are found in various depressions or at the edge of rivers or lakes. Soils are predominantly silt and clay, although coarser sediments and organic material may be intermixed. In some areas organic soils (peat) may constitute the primary growth medium. Climatic conditions are highly variable and range from the extreme summer heat to winter temperatures well below freezing.

The FWS has maps of wetlands in the United States. Those wetlands that fall in Plumas County are shown on Figure 4-16. They are detailed in Table 4-16 and are shown separated by jurisdiction. More information on the locations of wetlands in Portola can be found in its respective annex to this LHMP Update.

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Figure 4-16 Plumas County Planning Area – Wetlands Locations Table 4-16 Plumas County Planning Area – Wetlands
Wetlands Area Type Wetlands Count Wetlands Area (in Acres) City of Portola
Freshwater Emergent Wetland 54 126.35
Freshwater Forested/Shrub Wetland 9 9.67
Freshwater Pond 1 0.18
Lake 0 0.0
Riverine 56 30.91
Non-Wetland* 1,643 3,324.21
City of Portola Total 1,763 3,491.32
Unincorporated Plumas County
Freshwater Emergent Wetland 7,077 43,290.38
Freshwater Forested/Shrub Wetland 7,571 11,795.93
Freshwater Pond 769 874.03

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Wetlands Area Type Wetlands Count Wetlands Area (in Acres) Lake 373 36,595.95
Riverine 18,236 14,995.44
Non-Wetland* 24,195 1,561,082.10
Unincorporated Plumas County Total 58,221 1,668,633.84
Grand Total 59,984 1,672,125.16
Source: USFWS October 2024 National Wetlands Inventory
* This category is all other "blank/no data" areas
Wetlands Natural and Beneficial Functions
Wetlands are often found in floodplains and depressional areas of a watershed. Many wetlands receive and store floodwaters, thus slowing and reducing downstream flow. Wetlands perform a variety of ecosystem functions including food web support, habitat for insects and other invertebrates, fish and wildlife habitat, filtering of waterborne and dry-deposited anthropogenic pollutants, carbon storage, water flow regulation (e.g., flood abatement), groundwater recharge, and other human and economic benefits.

Wetlands, and other riparian and sensitive areas, provide habitat for insects and other invertebrates that are critical food sources to a variety of wildlife species, particularly birds. There are species that depend on these areas during all parts of their lifecycle for food, overwintering, and reproductive habitat. Other species use wetlands and riparian areas for one or two specific functions or parts of the lifecycle, most commonly for food resources. In addition, these areas produce substantial plant growth that serves as a food source to herbivores (wild and domesticated) and a secondary food source to carnivores.

Wetlands slow the flow of water through the vegetation and soil, and pollutants are often held in the soil.

In addition, because the water is slowed, sediments tend to fall out, thus improving water quality and reducing turbidity downstream.

These natural floodplain functions associated with the natural or relatively undisturbed floodplain that moderates flooding, such as wetland areas, are critical for maintaining water quality, recharging groundwater, reducing erosion, redistributing sand and sediment, and providing fish and wildlife habitat.

Preserving and protecting these areas and associated functions are a vital component of sound floodplain management practices for the Plumas County Planning Area.

Farmlands
Williamson Act
The Williamson Act, also known as the California Land Conservation Act of 1965, enables local governments to enter into contracts with private landowners for the purpose of restricting specific parcels of land to agricultural or related open space use. When the County enters into a contract with the landowners under the Williamson Act, the landowner agrees to limit the use of the land to agriculture and compatible uses for a period of at least ten years, and the County agrees to tax the land at a rate based on the agricultural production of the land rather than its real estate market value. This affects the County’s

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overall values for assessed taxable lands. The County has designated areas as agricultural preserves within which the County will enter into contracts for the preservation of the land in agriculture. Locations from the most recent map (dated 2023) can be seen on Figure 4-17 for Plumas County.

Figure 4-17 Plumas County – Williamson Act Lands
Source: California Department of Conservation. Retrieved 04/22/2025.

State Inventory of Important Farmland
The Farmland Mapping and Monitoring Program was established in 1984 to document the location, quality, and quantity of agricultural lands and conversion of those lands over time. The program provides impartial analysis of agricultural land use changes throughout California. For inventory purposes, several categories were developed to describe the qualities of land in terms of its suitability for agricultural production. The State Department of Conservation utilizes the following classification system:
➢ The Prime Farmland category describes farmland with the best combination of physical and chemical features able to sustain long term agricultural production. This land has the soil quality, growing season, and moisture supply needed to produce sustained high yields. Land must have been used for irrigated agricultural production at some time during the four years prior to the mapping date. ➢ Farmland of Statewide Importance is farmland similar to Prime Farmland but with minor shortcomings, such as greater slopes or less ability to store soil moisture. Land must have been used for irrigated agricultural production at some time during the four years prior to the mapping date. ➢ Unique Farmland is farmland of lesser quality soils used for the production of the state’s leading agricultural crops. This land is usually irrigated but may include non-irrigated orchards or vineyards as found in some climatic zones in California. Land must have been cropped at some time during the four years prior to the mapping date.

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➢ Farmland of Local Importance is either currently producing crops or has the capability of production.

This farmland category is determined by each county’s board of supervisors and a local advisory committee.

The 2022 maps are the most recent versions. These lands are shown in Figure 4-18. The map does not show the full extent of the County; however, no important farmlands fall in the western and northwestern portions of the County.

Figure 4-18 Plumas County – Map of Important Farmlands 2022 Source: State of California Department of Conservation. Retrieved 04/22/2025.

Cultural and Historical Resources
Plumas County has a large stock of historically significant homes, public buildings, and landmarks. To inventory these resources, the HMPC collected information from a number of sources. The California Department of Parks and Recreation Office of Historic Preservation (OHP) was the primary source of information. The OHP is responsible for the administration of federally and state mandated historic preservation programs to further the identification, evaluation, registration, and protection of California’s

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irreplaceable archaeological and historical resources. OHP administers the National Register of Historic Places, the California Register of Historical Resources, California Historical Landmarks, and the California Points of Historical Interest programs. Each program has different eligibility criteria and procedural requirements.
➢ The National Register of Historic Places is the nation’s official list of cultural resources worthy of preservation. The National Register is part of a national program to coordinate and support public and private efforts to identify, evaluate, and protect historic and archeological resources. Properties listed include districts, sites, buildings, structures, and objects that are significant in American history, architecture, archeology, engineering, and culture. The National Register is administered by the National Park Service, which is part of the U.S. Department of the Interior. ➢ The California Register of Historical Resources program encourages public recognition and protection of resources of architectural, historical, archeological, and cultural significance and identifies historical resources for state and local planning purposes; determines eligibility for state historic preservation grant funding; and affords certain protections under the California Environmental Quality Act (CEQA). The Register is the authoritative guide to the state’s significant historical and archeological resources.
➢ California Historical Landmarks are sites, buildings, features, or events that are of statewide significance and have anthropological, cultural, military, political, architectural, economic, scientific or technical, religious, experimental, or other value. Landmarks #770 and above are automatically listed in the California Register of Historical Resources. ➢ California Points of Historical Interest are sites, buildings, features, or events that are of local (city or county) significance and have anthropological, cultural, military, political, architectural, economic, scientific or technical, religious, experimental, or other value. Points designated after December 1997 and recommended by the State Historical Resources Commission are also listed in the California Register.

Historical resources included in the programs above are identified in Table 4-17.

Table 4-17 Plumas County Planning Area – Historical Resources Resource Name (Plaque
Number)
National
Register
State
Landmark
California
Register
Point of
Interest
Date
Listed
City/
Community
Beckwourth Pass (336) X 8/8/1939 Chilcoot
Buck's Lake (197) X 6/20/1935 Quincy
Ch'ichu'yam-Bam (N2213) X 9/25/2003 Crescent Mills
Chinese American Cemetery,
Plumas County Memorial Park
(P770)
X 5/11/1992 Quincy
Drakesbad Guest Ranch (N2216) X 10/22/2003 Chester
Elizabethtown (231) X 6/20/1935 Quincy
James P. Beckwourth Ranch &
Trading Post (P183)
X 9/24/1970 Beckwourth
Jamison City, Eureka Mills,
Johnstown, and The Famous
Eureka Mine (196)
X 6/20/1935 Blairsden

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Resource Name (Plaque
Number)
National
Register
State
Landmark
California
Register
Point of
Interest
Date
Listed
City/
Community
Lakes Basin Petroglyphs (N85) X 5/6/1971 Gold Lake
Marysville-Carson City Trail
(P620)
X 8/16/1983 Plumas
National
Forest
Peter Lassen Marker (Site Of
Lassen Trading Post) (184)
X 6/20/1935 Greenville
Pioneer Grave (Grizzly Creek)
(212)
X 6/20/1935 Quincy
Pioneer Schoolhouse (625) X 1/13/1958 Quincy
Pioneer Ski Area of America,
Johnsville (723)
X 1/18/1960 Blairsden
Plumas-Eureka Mill, Jamison
Mines District (N249)
X 7/16/1973 Blairsden
Rabbit Creek Hotel Monument
(213)
X 6/20/1935 La Porte
Rich Bar (337) X 8/8/1939 Quincy
Site of American Ranch And
Hotel (479)
X 11/9/1950 Quincy
Site Of Plumas House (480) X 11/9/1950 Quincy
Spanish Ranch and Meadow
Valley (481)
X 11/9/1950 Quincy
Taylorsville Schoolhouse (P742) X 5/8/1991 Taylorsville Town Of Taylorsville (P318) X 9/12/1973 Taylorsville
Warner Valley Ranger Station
(N579)
X 4/3/1978 Chester
Source: California Department of Parks and Recreation Office of Historic Preservation. Retrieved 12/3/2024.

It should be noted that these lists may not be complete, as they may not include those currently in the nomination process and not yet listed. Additionally, as defined by the CEQA and the National Environmental Policy Act (NEPA), any property over 50 years of age is considered a historic resource and is potentially eligible for the National Register. Thus, in the event that the property is to be altered, or has been altered, as the result of a major federal action, the property must be evaluated under the guidelines set forth by CEQA and NEPA. Structural mitigation projects are considered alterations for the purpose of this regulation.

In addition to this, the County has its own inventory of historic buildings and places. These are shown on Figure 4-19, Table 4-17, and detailed in Appendix F.

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Figure 4-19 Plumas County – Historic Buildings and Places

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Economic Assets and Community Activities of Value
Assessing the vulnerability of the Plumas County Planning Area to natural hazards and disasters also involves inventorying the economic assets and community activities of value to the Plumas County Planning Area.

Economic Assets
After a disaster, economic resiliency is one of the major drivers of a speedy recovery. Each community has specific economic drivers. These include:
➢ Primary Economic Sectors
➢ Major employers
➢ Commercial Centers
In the County, this includes Pacific Crest Trail; Plumas Corporation; Sierra Pacific Industries; Collins Pines; Plumas County; City of Portola; High Sierra Music Festival; 4th of July activities throughout Plumas County; Fair; Mountain Biking events; Christmas activities; Land Trust; Recreation; Feather River College; PG&E; and Plumas Sierra Rural Electric Cooperative.

Plumas National Forest; Plumas Unified School District; Hospitals; Central Plumas Recreation District; Almanor Recreation District; Tourism;
More information on economic assets for the incorporated jurisdictions in the County can be found in the respective jurisdictional annexes to this Base Plan.

Community Activities of Value
Inventorying economic assets in the Plumas County Planning Area and their vulnerability to natural hazards and disasters also involves inventorying activities that have value to the community. This includes activities that are important to a community, like long-standing traditions such as a festival or fair. Some areas rely on seasonal industries to sustain them throughout the year. Many of these activities provide economic benefits to the Planning Area. A hazard event that cancels or shortens these can affect a community’s livelihood and can make disaster recovery more difficult or prolonged. This includes activities such as:
➢ Festivals and Fairs
➢ Sporting Events
➢ Tourism
In the County, this includes High Sierra Music Festival; 4th of July activities throughout Plumas County; Fair; Mountain Biking events; Christmas activities; and recreation events.

More information on community activities of value can be found in the respective jurisdictional annexes to this Base Plan.

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4.2.2. Growth and Development Trends
As part of the planning process, trends in growth and development, both current and future, were examined, both as a whole and in the context of hazard-prone areas, and how the changes in growth and development affect loss estimates and vulnerability over time. This discussion focuses on unincorporated Plumas County.

Land Use
The future use of land in the County is fundamental to attaining the vision of a balanced, self-sustaining community. A land use pattern which balances growth between rural and urban areas, as well as providing a balance between housing, employment, natural resources, and services in the County is a key element in maintaining the quality of life and unique character of the County. Descriptions of allowed uses for each classification are detailed in the Plumas County General Plan Land Use Element. Figure 4-20 is sourced from this section.

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Figure 4-20 Plumas County General Plan Land Use
Source: Plumas County 2016 General Plan Land Use Element

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Population Projections
As indicated in the previous section, Plumas County had been steadily growing from 1940 to 2020. Since then, the County has begun to lose population. Long term forecasts by the California Department of Finance project population in Plumas County continuing through 2070. Table 4-18 shows the population projections for the County Planning Area as a whole through 2070. As shown, populations are expected to shrink over time.

Table 4-18 Population Projections for the Plumas County Planning Area (incorporated and unincorporated), 2025-2070
2025 2030 2035 2040 2045 2050 2055 2060 2065 2070
Plumas
County
18,478 17,630 17,009 16,281 15,468 14,670 13,917 13,285 12,815 12,405 Source: California Department of Finance, P-2 Report
Development since 2020 Plan
The Plumas County Planning Building Department documented sought to track total building permits that were completed and issued a final certificate of occupancy issued since 2020 for unincorporated Plumas County residential, commercial, and industrial new construction, remodels and additions, garages and carports, and agricultural accessory structures including barns and outbuildings. Building permits documented under the ‘other’ category included things such as decks, porches, re-roofs, septic tanks and leachfields, wells, demolitions, electrical, wood stoves, HVAC, generators, sheds, solar, grading and drainage, and signage. A summary of this development is shown in Table 4-19. Development by known flood and fire hazard areas is shown in Table 4-20. All development in the identified hazard areas, including the 1% annual chance floodplains and high wildfire risk areas, were completed in accordance with the current and applicable development codes and standards in place at the time. Thus, with the exception of more people living in the area potentially exposed to natural hazards, this growth should not cause a significant change in vulnerability of the County to identified priority hazards.

Table 4-19 Unincorporated Plumas County Development 2020–2024 Summary Property Use 2020 2021 2022 2023 2024
Residential 121 115 121 150 157
Commercial 17 33 22 28 26
Industrial 0 1 0 0 2
Agricultural 7 5 9 6 8
Other Permits 634 550 682 691 779
Total 779 704 834 875 972
Source: Plumas County Building Department, January 2026

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Table 4-20 Unincorporated Plumas County Development in Hazard Areas since 2020 Property Use Moderate or
Higher Fire
Hazard Severity
Zones
1% Annual Chance
Flood
Landslide Potential
Areas
Other
Residential 291 25 0 0
Commercial 6 0 0 0
Industrial 0 0 0 0
Other 7 2 0 0
Total 304 27 0 0
Source: Plumas County Planning Department, August 2025
Summary by Year
➢ Moderate or Higher Fire Hazard Severity Zones
✓ 2020 – 37
✓ 2021 – 60
✓ 2022 – 66
✓ 2023 – 81
✓ 2024 – 60
➢ 1% Annual Chance Flood (Special Flood Hazard Area – 100-year floodplain) ✓ 2020 – 4
✓ 2021 – 8
✓ 2022 – 2
✓ 2023 – 8
✓ 2024 –5
Future Development Areas
It is important to review future development plans for the County. Future development should be sited in areas that are away from known hazard risks. If this is not possible, mitigation should be done to ensure that future development is protected against future hazard events and disasters.

Plumas County has multiple areas that are expected to see or may see development over the next 5 years.

These are listed below. Some of these have a narrative that follows the bulleted list. These are used as the basis for the GIS analysis below.
➢ CHP Station – This is a State/commercial facility. No narrative was available for this development area.
➢ Greenville Cy Hall Memorial Museum – This is a commercial museum property. No narrative was available for this development area.
➢ Greenville Rancheria Medical and Dental Clinic and Pharmacy – This is a medical/commercial facility.

A narrative about this facility follows this bulleted list. ➢ Plumas Charter School – No narrative was available for this development area. ➢ Plumas County Search and Rescue – No narrative was available for this development area.

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➢ Plumas District Hospital Skilled Nursing Facility – This is a medical/commercial facility. A narrative about this facility follows this bulleted list.
➢ Seneca Hospital – This is a medical/commercial facility. A narrative about this facility follows this bulleted list.
➢ Way Station – No narrative was available for this development area. ➢ Indian Valley Public Safety Center (Plumas County Sheriff Substation, Indian Valley Community Services District Fire Station, and Plumas District Hospital Ambulance) – This is an emergency services/commercial facility. A narrative about this facility follows this bulleted list. ➢ Meadow Edge Mobile Home Park – This is a residential single-family development. No narrative was available for this development area.
➢ North Star Navigation Center – Phase 2 – This is a residential multi-family development. A narrative about this facility follows this bulleted list.

In addition, though not mapped in the GIS analysis below, the County noted the following areas that may see development.
➢ 2024-2029 Housing Element Update Draft Regional Housing Need Allocation (RHNA) Vacant And Underutilized Sites List – multiple sites. A narrative about these follows this bulleted list.

Greenville Rancheria Medical Campus
On November 13, 2024, the Plumas County Zoning Administrator approved a special use permit amendment for the Greenville Rancheria of Maidu Indians of California to reestablish their Medical Campus in the Town of Greenville after the 2021 Dixie Fire destroyed the structure. The building involves the construction of a two-story, 16,200-square-foot outpatient medical, dental, pharmacy, and behavioral health facility and a 59-space parking lot on the parcels located at 408 and 410 Main Street, Greenville (APNs 110-062-007, 110-062-028, 110-062-029). As included in the construction document set, the proposed facility will have a reception and lobby area, waiting rooms, medical and dental exam and treatment rooms, behavioral health facilities, a pharmacy, administration and human resources offices, training and conference room space, a shipping and receiving area, employee break room, patient and staff restrooms, and several other supplemental rooms. The project will be able to serve up to a maximum of 25 patients a day with hours of operation Monday through Friday, 8:00 AM to 5:00 PM.

Plumas District Hospital Skilled Nursing Facility
On December 21, 2021, the Plumas County Zoning Administrator approved a special use permit for the construction of a new Plumas District Hospital skilled nursing facility in the Town of Quincy, located across the street from the existing hospital campus on Bucks Lake Road. The 22,507 square foot facility advanced construction activities in 2024 and is expected to be completed in summer 2025, consisting of two onestory buildings joined by a pedestrian bridge, and when fully operational, will host 36 beds with 24-hour nursing care and bring 79 livable wage jobs to Plumas County. Other functions include pharmaceutical service; dietary service space; activity programming space; common areas including lobby and reception, spa and salon, consult/family room, and restrooms; administrative offices; housekeeping; storage; employee dressing rooms; lockers; staff lounge; and parking.

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Seneca Healthcare District Hospital Replacement
On June 13, 2023, the Plumas County Board of Supervisors approved Resolution 2023-8812 and Ordinance No. 2023-1149 approving a Geneal Plan Amendment and Zone Change, including adopting the CEQA compliant Mitigated Negative Declaration (No. 685) for the Seneca Healthcare District Hospital property at 199 Reynolds Road, in the Town of Chester. The Seneca Healthcare District broke ground in 2024 and completed the underground infrastructure for the construction of a 45,000 square foot state-of-the-art healthcare hospital due to aging hospital facilities and the requirement of Sente Bill 1953 which mandated seismic safety standards for hospitals. The new hospital will typically have a staff of approximately 48 employees on site at peak hours and accommodate the District’s acute-care replacement hospital and an expanded skilled nursing facility, in addition to other amenities, as follows:
➢ 10-bed acute care, 2 of those with isolation capabilities ➢ 3-bed private emergency room and Trauma/procedure room ➢ 26-bed skilled nursing facility
➢ Imaging to include x-ray, CT scanner, ultrasound, and mobile MRI via trailer ➢ Operating room, procedure room, and 3-bed patient recovery ➢ Pharmaceutical services
➢ Laboratory services
➢ Dietary services – kitchen and dining
➢ Ambulatory surgery
➢ Physical therapy
➢ Occupational therapy
➢ Maintenance, materials management, laundry services
All spaces are sized to allow for improved workflow, updated and improved infrastructure, updated technology and medical equipment, and the Americans with Disabilities Act (ADA) accessibility per current code requirements. Additionally, the hospital will include a 3,000 square foot support services building and the approved plans allow for the construction of 10,000 square feet of housing for District employees and their families with up to ten 1,000 square foot residential units. To fund the construction, the District pursued USDA funding as well as a public bond measure (Measure B), which passed in the November 8, 2022, election, and philanthropic offerings by the community. Construction will continue into 2025, through 2026, with an anticipated timeframe to open of early 2027.

Indian Valley Public Safety Center
On April 13, 2023, Indian Valley Community Services District (IVCSD), applicant, submitted a special use permit application (Exhibit 1) to allow a public service facility use to construct the Indian Valley Public Safety Center facility (approximately 9,890-square-foot multi-use structure) for emergency services, including the IVCDS Fire Department Station, Plumas County Sheriff’s Substation, and Plumas District Hospital ambulance with sleeping quarters, in addition to other associated accessory structures on a 5.0- acre parcel zoned Periphery Commercial (“C-2”) located at 19646 Highway 89, Greenville, CA, APN 110- 330-007-000 (Exhibit 2).

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As shown on the site plan (Exhibit 3) dated February 20, 2025, the proposed facility would include a 4,560- square-foot drive-through truck bay, 5,070-square-foot main building, 260-square-foot shop, 700-squarefoot covered patio, 840-square-foot carport, and a 112-square-foot covered entry.

The existing fire house metal structure, with bays, shown on the site plan was placed on the property as a temporary fire house as a result of the destruction of the IVCSD fire house due to the 2021 Dixie Fire. The existing fire house would be kept on site for the storage of equipment.

The proposed 3,600-square-foot biomass building shown on the site plan may be relocated to another location in Greenville, but is shown to be analyzed, as it could possibly remain located on the subject parcel.

The Plumas District Hospital ambulance services would have personnel using the building twenty-four (24) hours per day, seven days per week, Monday through Sunday, and dependent on calls, the IVCSD Fire Department personnel may be using the building twenty-four (24) hours per day, seven days per week, Monday through Sunday. Other IVCSD staff would utilize the office space as a satellite office, with no public visits, to the primary public IVCSD office at 127 Crescent Street, Greenville. The Plumas County Sheriff’s Substation would be used intermittently seven days per week, Monday through Sunday.

The maximum number of staff on site at any given time would be as follows:
➢ Eight (8) IVCSD Staff
➢ Two (2) Sheriff Deputies
➢ Three (3) Staff for Plumas District Hospital Ambulatory Services Additionally, there are IVCSD Fire Department trainings held every Tuesday at a different fire station location throughout the District, which is a total of four (4) stations – Greenville, Taylorsville, North Arm Indian Valley, and Genesee. Therefore, on occasion, there would be a maximum of thirty (30) volunteer firefighters on site. For an intermittent total maximum number of staff on site of forty-three (43).

North Star Navigation Center – Phase 2
PCIRC, Plumas County’s homelessness and CE provider, broke ground in 2022 and completed construction of Phase 1 in 2024 on the County’s first emergency and transitional housing Navigation Center under the state’s Low Barrier housing model pursuant to Government Code Sec. 65660 – 65668 (Assembly Bill [AB] 101, Weiner, 2019). The parcel is 1 acre and is zoned “M-R” Multiple Family Residential. The NorthStar Navigation Center is an appropriate site for a year-round emergency shelter as the parcel has utility services, including water, sewer, and power. Furthermore, the site is located in Quincy in proximity to retail services, public transportation, medical facilities, and employment opportunities. A Low Barrier Navigation Center pursuant to Government Code Sec. 65660 – 65668 (AB 101, Weiner, 2019) means a Housing First approach, low-barrier, service-enriched shelter focused on moving people into permanent housing that provides temporary living facilities while case managers connect individuals experiencing homelessness to income, public benefits, health services, shelter, and housing. “Low Barrier” means best practices to reduce barriers to entry, and may include, but is not limited to: the presence of partners if it is not a populationspecific site, such as for survivors of domestic violence or sexual assault, women, or youth; pets; the storage of possessions; and privacy, such as partitions around beds in a dormitory setting or in larger rooms containing more than two beds, or private rooms. The North Star Navigation Center provides immediate

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emergency shelter and transitional housing services to the homeless, chronically homeless, transitioning offenders, the Housing and Disability Advocacy Program (HDAP) for seniors and/or disabled, and former foster youth in Plumas. The main building (Phase 1) includes a 27-bed capacity emergency shelter with congregate beds and non-congregate bedrooms for families, associated congregate and non-congregate bathrooms, day use room areas, a kitchen and dining room, administrative offices for staff, and storage.

More specifically, there are 12 beds in the bunkroom (7 male and 5 female) and three family rooms with a total 15 bed capacity. Ohana Village (Phase 2) will offer transitional housing that includes 26 detached cabins ranging in size from studio units (16 beds, one of which is accessible), 1 bedroom-units (16 beds, one of which is accessible), and 2 bedroom-units (8 beds, one of which is accessible). The 1- and 2-bedroom units will include half baths, while the studio units utilize a common building with congregate bathrooms that also have shower facilities for all Ohana Village units. A second common building will include Ohana Village resident dining and there is also a maintenance building and outdoor play area. Supportive service staffing includes a Navigation Center Manager, Housing Navigator, Behavioral Health Counselor, Alcohol and Drug Counselor, HDAP Disability Advocate, and Grief Recovery Specialist with the primary purpose to bring all activities in-house and on-site. Educational opportunities and trainings will be provided to North Star Navigation Center residents including money management, life skills, and workforce development skills. Expected outcomes include:
➢ Increasing access to emergency and transitional housing. ➢ Delivery of a comprehensive array of supportive services. ➢ Reducing the number of days of homelessness.
➢ Increasing access to permanent housing and housing stability. ➢ Developing a ‘systems change’ in how Plumas County addresses homelessness for its most vulnerable residents.

Sites from RHNA
The County provided the Initial Review Draft of the 2024-2029 Housing Element. It included the following tables (Table 4-21 through Table 4-24) where development may occur to accommodate Very Low Income and Low Income housing. Any of these sites could be used for future development.

Table 4-21 Vacant High-Density Sites to Accommodate the Very Low Income RHNA 1 Source: Plumas County Planning Department, August 2025. 1 The 32-unit realistic capacity of 1506 Peppard Flat Rd. as a vacant high-density site to accommodate a portion of the very low income RHNA assumes accommodating the acutely low- and
extremely low-income RHNA of 10 units.

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Table 4-22 Underutilized High-Density Sites to Accommodate the Very Low Income RHNA Source: Plumas County Planning Department, August 2025.

Table 4-23 Vacant High-Density Sites to Accommodate the Low Income RHNA Source: Plumas County Planning Department, August 2025.

Table 4-24 Underutilized High-Density Sites to Accommodate the Low Income RHNA Source: Plumas County Planning Department, August 2025.

GIS Analysis
Plumas County provided 13 future development areas which were used as the basis for the inventory of future development for unincorporated Plumas County. These were mapped in GIS. Figure 4-21 show the locations of the future development areas. Table 4-25 shows the details of the future development areas by acreage and parcel count.

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Figure 4-21 Unincorporated Plumas County – Future Development Areas

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Table 4-25 Unincorporated Plumas County – Future Development Areas by Parcels and Acres Future
Development
Status and
Type
Site / Map
ID and
Future
Development
Name
Total
Parcel
Count
Improved
Parcel
Count
Unimproved
Parcel Count
Total
Acres
Total
Improved
Acres
Total
Unimproved
Acres
Approved
Commercial

A - CHP
Station 1 0 1 5.00 0.00 5.00
B - Greenville
Cy Hall
Memorial
Museum
1 0 1 0.11 0.00 0.11
C - Greenville
Rancheria
Medical,
Dental Clinic,
and Pharmacy
1 0 1 1.58 0.00 1.58
D - Plumas
Charter
School
1 0 1 0.89 0.00 0.89
E - Plumas
County Search
and Rescue
1 1 0 4.50 4.50 0.00
F - Plumas
District
Hospital
Skilled
Nursing
Facility
1 0 1 4.12 0.00 4.12
G - Seneca
Hospital 1 0 1 11.80 0.00 11.80
H - Way
Station 1 0 1 0.28 0.00 0.28
I - Indian
Valley Public
Safety Center
1 0 1 5.00 0.00 5.00
Commercial
Total 9 1 8 33.28 4.50 28.78
Residential
J - Meadow
Edge Mobile
Home Park
1 1 0 42.74 42.74 0.00
K - North
Star
Navigation
Center - Phase
2 1 1 0 1.00 1.00 0.00
Residential
Total 2 2 0 43.74 43.74 0.00

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Future
Development
Status and
Type
Site / Map
ID and
Future
Development
Name
Total
Parcel
Count
Improved
Parcel
Count
Unimproved
Parcel Count
Total
Acres
Total
Improved
Acres
Total
Unimproved
Acres
Approved Total 11 3 8 77.02 48.24 28.78
Proposed
Commercial
L - Plumas
County
Courthouse
1 1 0 2.86 2.86 0.00
Commercial
Total 1 1 0 2.86 2.86 0.00
Proposed Total 1 1 0 2.86 2.86 0.00
Conceptual
Residential
M - Housing
Element
RHNA Site
1 1 0 3.64 3.64 0.00
Residential
Total 1 1 0 3.64 3.64 0.00
Conceptual Total 1 1 0 3.64 3.64 0.00
Grand Total 13 5 8 83.52 54.74 28.78
Source: Plumas County GIS

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4.3 Hazard Profiles and Vulnerability Assessment
44 CFR Requirement §201.6(c)(2)(i): [The risk assessment shall include a] description of the…location and extent of all natural hazards that can affect the jurisdiction. The plan shall include information on previous occurrences of hazard events and on the probability of future hazard events. 44 CFR §201.6(c)(2)(i): [The risk assessment shall include a] description of the…location and extent of all natural hazards that can affect the jurisdiction. The plan shall include information on previous occurrences of hazard events and on the probability of future hazard events. 44 CFR §201.6(c)(2)(ii): [The risk assessment shall include a] description of the jurisdiction’s vulnerability to the hazards described in paragraph (c)(2)(i) of this section. This description shall include an overall summary of each hazard and its impact on the community. 44 CFR §201.6(c)(2)(ii)(A): The plan should describe vulnerability in terms of the types and numbers of existing and future buildings, infrastructure, and critical facilities located in the identified hazard areas.
44 CFR §201.6(c)(2)(ii)(B): [The plan should describe vulnerability in terms of an] estimate of the potential dollar losses to vulnerable structures identified in paragraph (c)(2)(i)(A) of this section and a description of the methodology used to prepare the estimate. 44 CFR §201.6(c)(2)(ii)(C): [The plan should describe vulnerability in terms of] providing a general description of land uses and development trends within the community so that mitigation options can be considered in future land use decisions.

The hazards identified in Section 4.1 Hazard Identification, are profiled individually in this section. The Hazard Profiles set the stage for the Vulnerability Assessment, where the vulnerability is quantified, as data allows, for each of the identified hazards.

Hazard Profiles Methodology
Each hazard is profiled in the following format:
➢ Hazard/Problem Description—This section gives a description of the hazard and associated issues followed by details on the hazard specific to the Plumas County Planning Area and unincorporated Plumas County. Where known, this includes information on the hazard extent, location, seasonal patterns, speed of onset/duration, and magnitude and/or any secondary effects. ➢ Past Occurrences—This section contains information on historical incidents, including impacts where known. Hazard research, historical incident worksheets and other input from the Hazard Mitigation Planning Committee were used to capture information on past occurrences. ➢ Likelihood of Future Occurrence—The frequency of past events is used in this section to gauge the likelihood of future occurrences. Where possible, frequency was calculated based on existing data. It was determined by dividing the number of events observed by the number of years on record and multiplying by 100. This gives the percent chance of the event happening in any given year (e.g., three droughts over a 30-year period equates to a 10 percent chance of experiencing a drought in any given year). The likelihood of future occurrences is categorized into one of the following classifications:
✓ Highly Likely—Near 100 percent chance of occurrence in next year or happens every year. ✓ Likely—Between 10 and 100 percent chance of occurrence in next year or has a recurrence interval of 10 years or less.

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✓ Occasional—Between 1 and 10 percent chance of occurrence in the next year or has a recurrence interval of 11 to 100 years.
✓ Unlikely—Less than 1 percent chance of occurrence in next 100 years or has a recurrence interval of greater than every 100 years.
➢ Climate Change—This section contains the effects of climate change (as applicable). The possible influence of climate change on the hazard is discussed.

Vulnerability Assessment Methodology
With the Plumas County Planning Area’s hazards identified and profiled, a vulnerability assessment was conducted to describe the vulnerability and impact that each hazard would have on the Plumas County Planning Area and specific to each jurisdiction. The vulnerability assessment quantifies, to the extent feasible using best available data, assets at risk to identified hazards and estimate potential losses. This section focuses on the vulnerabilities of the Plumas County Planning Area as a whole and specific to unincorporated Plumas County. The vulnerability assessment is done in the following format:
➢ General Vulnerability Discussion – An assessment of the vulnerability of the Plumas County Planning Area to each hazard is provided in addition to the estimate of the risk of future occurrence.

This is followed by a general discussion of the hazard and its vulnerability on the Plumas County Planning Area and unincorporated Plumas County. Vulnerability is measured in general, qualitative terms and is a summary of the potential impact based on past occurrences, spatial extent, and damage and casualty potential. It is categorized into one of the following classifications:
✓ Extremely Low—The occurrence and potential cost of damage to life and property is very minimal to nonexistent.
✓ Low—Minimal potential impact. The occurrence and potential cost of damage to life and property is minimal.
✓ Medium—Moderate potential impact. This ranking carries a moderate threat level to the general population and/or built environment. Here the potential damage is more isolated and less costly than a more widespread disaster.
✓ High—Widespread potential impact. This ranking carries a high threat to the general population and/or built environment. The potential for damage is widespread. Hazards in this category may have occurred in the past.
✓ Extremely High—Very widespread with catastrophic impact. ➢ Local Concerns – This includes information on how the unincorporated Plumas County is uniquely affected by or vulnerable to each hazard. Information contained in this section also supports the resulting mitigation strategy for the unincorporated County. Local concerns sections specific to each of the other participating jurisdictions are included in their jurisdictional annexes to this plan. ➢ Assets at Risk – A discussion of the assets at risk follows. This includes sections on: People and Populations, as well as Structures (including Critical Facilities and Infrastructure; and Natural, Historic, and Cultural Resources). These are discussed in specific terms for mapped hazards, and in more general terms for those hazards that are unmapped.
✓ FEMA NRI Hazard Vulnerability – For each hazard in the FEMA NRI in Plumas County, the relevant portions of the hazard analysis done by FEMA is presented. This includes the Hazard Risk Index Rating, Expected Annual Loss Values, Exposure Values, and the Historic Loss Ratio Rating.

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➢ Impacts – A discussion on hazard impacts is included. Impacts describe how each hazard can affect the County and its assets. The type and severity of impacts reflect both the potential magnitude of the hazard and the vulnerability of the asset.
➢ Future Conditions/Future Development – A discussion of how future conditions will influence or affect the hazard over time is included here and considers factors related to climate change, changes in population patterns, and changes in land use and development. This section also discusses future development plans relative to each hazard as well as mitigating measures that should be considered in the development process. Future conditions and future development is addressed specifically for mapped hazards, and in more general terms for those hazards that are unmapped.

Existing Built Environment and Assets at Risk
Vulnerability can be quantified in those instances where there is a known, identified hazard area, such as a mapped floodplain. In these instances, the numbers and types of assets subject to the identified hazard can be counted and their values tabulated. Other information can be collected in regard to the hazard area, such as the location of critical facilities, historic structures, and valued natural resources. Together, this information conveys the impact, or vulnerability, of the Plumas County Planning Area and unincorporated Plumas County to that hazard.

The vulnerability assessment identified six hazards in the Plumas County Planning Area for which specific geographical hazard areas have been defined and for which sufficient data exists to support a quantifiable vulnerability analysis. These six hazards are:
➢ Dam Failure
➢ Earthquake
➢ Flood: 1%/0.2% (w/levee failure)
➢ Hazardous Materials Transportation
➢ Landslide, Mudslides, and Debris Flows
➢ Wildfire (w/smoke and air quality)
These hazards were analyzed using GIS, Plumas County data, and hazard data.

The vulnerability and potential impacts from the nine priority hazards that do not have specific mapped areas nor the data to support additional vulnerability analysis are discussed in more general terms. These include:
➢ Agricultural Hazards (severe weather/pests/weeds)
➢ Climate Change
➢ Drought and Water Shortage (w/tree mortality)
➢ Flood: Localized/Stormwater
➢ Severe Weather: Extreme Cold, Freeze, and Snow (w/avalanche) ➢ Severe Weather: Extreme Heat
➢ Severe Weather: Heavy Rain and Storms
➢ Severe Weather: High Winds and Tornadoes
➢ Volcano

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Power Outages/Failure: A Common Vulnerability of all Hazards An additional impact or vulnerability common to most all hazards is power outage or power failure. The US power grid crisscrosses the country, bringing electricity to homes, offices, factories, warehouses, farms, traffic lights and even campgrounds. According to statistics gathered by the Department of Energy, major blackouts are on the upswing. Over the past two decades, blackouts impacting at least 50,000 customers have increased 124 percent. The electric power industry does not have a universal agreement for classifying disruptions. Nevertheless, it is important to recognize that different types of outages are possible so that plans may be made to handle them effectively. Electric power disruptions can be generally grouped into two categories: intentional and unintentional.

Intentional Disruptions
There are four types of intentional disruptions:
➢ Planned: Some disruptions are intentional and can be scheduled based maintenance or upgrading needs.
➢ Unscheduled: Some intentional disruptions must be done "on the spot." in response to an emergency. ➢ Demand-Side Management: Some customers (i.e., on the demand side) have entered into an agreement with their utility provider to curtail their demand for electricity during periods of peak system loads.
➢ Load Shedding: When the power system is under extreme stress due to heavy demand and/or failure of critical components, it is sometimes necessary to intentionally interrupt the service to selected customers to prevent the entire system from collapsing, resulting in rolling blackouts.

The California Independent System Operator (CAISO) is tasked with managing the power distribution grid that supplies most of California, except in areas served by municipal utilities. CAISO is thus the entity that coordinates statewide flow of electrical supply. CAISO uses a series of stage alerts to the media based on system conditions. The alerts are:
➢ Stage 1 – reserve margin falls below 7 percent
➢ Stage 2 – reserve margin falls below 5 percent
➢ Stage 3 – reserve margin falls below 1.5 percent
Rotating blackouts become a possibility when Stage 3 is reached. Rotating outages and/or blackouts such as those experienced in 2000/2001 and 2006 can occur due to losses in transmission or generation and/or extremely severe temperatures that lead to heavy electric power consumption. Key California events include the following:

On January 17, 2001, CAISO declared a Stage 3 Emergency and notified the then Governor’s Office of Emergency Services that PG&E was dropping firm load of 500 megawatts (MW) in Northern California leading to rolling blackouts. Cal OES, in turn, issued an Electrical Emergency Message to all Emergency Services Agencies to prepare for rolling blackouts. This scenario was repeated the following day, January 18, 2001, and again on March 19, 2001.

A July 2006 heat storm event affected the entire state as well as most of the West, producing record energy demand levels in California. The State was able to avoid rotating outages due to a combination of favorable

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factors that included no major transmission outages, lower than typical generator outages, significant customer response to pleas for energy conservation, high imports from the Pacific Northwest despite unusually high loads, outstanding cooperation among western control area operators, and prompt response to fires that potentially threatened major interties. However, the event brought to light the vulnerability of the electric distribution system, as over 3,500 distribution transformers failed, leaving over two million customers without power at various times over the ten-day event, many for several hours and a small minority for up to three days.

In 2020, the state battled both extreme heat and wildfires. As a result of extreme heat, the CAISO declared a Stage 3 emergency. PG&E initiated rotating outages in August at the request of California's grid operator.

The outages, which impacted 220,000 customers, occurred during periods of high heat. These rolling blackouts lasted less than a week.

Unintentional Disruptions
Unintentional or unplanned disruptions are outages that come with essentially no advance notice. This type of disruption can be the most problematic. The following are categories of unplanned disruptions:
➢ Accident by the utility, utility contractor, or others ➢ Malfunction or equipment failure
➢ Equipment overload (utility company or customer)
➢ Reduced capability (equipment that cannot operate within its design criteria) ➢ Tree contact other than from storms
➢ Vandalism or intentional damage
➢ Weather, including lightning, wind, earthquake, flood, and broken tree limbs taking down power lines ➢ Wildfire that damages transmission lines
Public Safety Power Shutoff
A new intentional disruption type of power shortage/failure event has recently occurred in California. In recent years, several wildfires have started as a result of downed power lines or electrical equipment. This was the case for the Camp Fire in 2018. As a result, California’s three largest energy companies (including PG&E), at the direction of the California Public Utilities Commission (CPUC), coordinated to prepare all Californians for the threat of wildfires and power outages during times of extreme weather. To help protect customers and communities during extreme weather events, electric power may be shut off for public safety in an effort to prevent a wildfire. This is called a PSPS.

PSPS are another tool that PG&E uses to help eliminate and minimize ignitions caused by objects coming in contact with electrical circuits and causing fires. Severe weather, such as high winds, low humidity, and dry vegetation are some of the key elements to trigger a PSPS event in high fire threat areas (Tier 2 & Tier 3). By proactively shutting off power in areas that are very prone and susceptible to catastrophic wildfires, PG&E can help minimize the chance of a fire caused by electrical infrastructure. PG&E doesn’t take lightly the shutting off power to residents, business, and critical customers and has a strict protocol for these actions.

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Public Safety Power Shutoff for Plumas-Sierra Rural Electric Cooperative (PSREC) PSREC may be affected by PSPS events. PSREC provides power to areas in Plumas County. During the summer, PG&E will de-energize electric lines that pass through high fire-threat areas. NV Energy has a similar program, though they call their outages Public Safety Outage Management (PSOM). These shutoffs will affect both distribution and transmission lines. The goal is to reduce the risk of fire during high-fire risk times such as high winds, low humidity levels and red flag warnings declared by the National Weather Service.

Although PSREC does not buy power from PG&E, PSREC’s main transmission feed is from PG&E through the Feather River Canyon, where this feed transports power to PSREC members. Since PSREC relies on this transmission feed, these public safety power shutoffs will impact members. PSREC will strive to keep the impact of these shutoffs as minimal as possible to members.

A backup feed that comes to members from NV Energy is able to help support PSREC’s system. However, this back-up isn’t always available and could be de-energized for an NV Energy PSOM at the same time as a PG&E PSPS. When available during peak hours, it may not be enough, so rolling blackouts may need to be implemented. PSREC asks members to conserve when they are on a backup feed to prevent disruptions to service for all members.

It is likely that, in the event of PSPS and PSOM events, electric power will be out for one to a few days.

Because these events will be triggered by PG&E and NV Energy’s assessment of weather conditions and fire risk, PSREC cannot reliably predict the timing or duration. Residents or businesses who can’t be without power should consider a professionally installed generator that meets local code requirements.

Public Safety Power Shutoff Criteria for PG&E
The Wildfire Safety Operations Center (WSOC) monitors fire danger conditions across PG&E’s service area, including PSPS conditions. These factors include:
➢ A Red Flag Warning declared by the National Weather Service ➢ Low humidity levels generally 20% 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 fuel on the ground and live vegetation (moisture content) ➢ On-the-ground, real time observations from PG&E’s WSOC and field observations from PG&E crews The most likely electric lines to be considered for shutting off for safety will be those that pass through areas that have been designated by the CPUC as at elevated (Tier 2) or extreme (Tier 3) risk for wildfire (seen on Figure 4-22). This includes both distribution and transmission lines. The specific area and number of affected customers will depend on forecasted weather conditions, and which circuits PG&E needs to turn off for public safety. Although a customer may not live or work in a high fire-threat area, their power may also be shut off if their community relies upon a line that passes through an area experiencing extreme fire danger conditions. This means that any customer who receives electric service from PG&E should be prepared for a possible PSPS. PSPS events, while preventative in nature, can cause a variety of issues related to the lack of power to those impacted by the PSPS. For the Plumas County Planning Area, a

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significant concern is the impact to their communication systems as well as on other critical infrastructure and services. PSPS events also cause concerns for certain vulnerable populations. As seen on Figure 4-22, Plumas County has areas inside the Tier 2 and Tier 3 areas, as well as areas outside of them.

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Figure 4-22 State of California Tier 2 and 3 Areas

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PG&E noted that extreme weather threats can change quickly. When possible, PG&E will provide customers with advance notice prior to turning off the power, as well as updates until power is restored.

Timing of notifications (when possible) are:
➢ Approximately 48 hours before power is turned off
➢ Approximately 24 hours before power is turned off
➢ Just before power is turned off
➢ During the public safety outage
➢ Once power has been restored
Power outages that affect Plumas County residents do happen, though these outages are becoming less frequent and are not sustained as long as past years. This is due to PG&E’s hardening and undergrounding projects along with its enhanced vegetation management practices. During these outages, PG&E provides contacts and tools to assist the residents and officials with current outage information for planning purposes.

PG&E works with county officials to assist and help mitigate outages affecting the residents of Plumas County.

When a PSPS is forecasted, PG&E will notify County Emergency Management Agencies so they may monitor and make any plans they see needed. Customers affected will also get notified so they may also take steps to plan and make arrangements they deem necessary for the event. PG&E will support the customers with Community Resource Centers (CRC) near the affected areas of the PSPS and offer other programs to qualified customers. PG&E will also work with the public safety agencies in the area to help mitigate any other issues related to the PSPS event. PG&E offers many tools to help assist the agencies in monitoring and planning for these events. The County noted that there have been events in the past where wildfires have not occurred, but wildfire conditions were high. During these times of high winds, high temps, and high wildfire risk, a PSPS occurred in the County. These are also discussed in the City of Portola’s respective annex to this Base Plan.

October 9–November 1, 2019: The 2019 California power shutoffs, described as massive PSPS events, included Plumas County among approximately 30 counties affected by PG&E, Southern California Edison (SCE), and San Diego Gas & Electric (SDG&E). Multiple events occurred during this period, but the exact number specific to Plumas County is not isolated in the source.

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Figure 4-23 Plumas County – 2019 PSPS Events
l
It should be noted that “customers” in PG&E vernacular refer to both households or business addresses.

October 2020: A PSPS event impacted 1,855 customers in Plumas County, as part of a broader event affecting 41,000 customers across multiple counties.

In October of 2021, the CPUC began a mapping application to show areas affected by PSPS. These are shown on Figure 4-24, and each event is discussed below.

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Figure 4-24 Plumas County Planning Area – PSPS Events since October 2021 Source: California Public Utility Commission PSPS Dashboard. Retrieved 4/22/2024.

October 11, 2021: A PSPS event was reported, with potential impacts in Plumas County, specifically in the Bucks Lake area and a portion of the Feather River Canyon. The source does not confirm the exact number of customers affected but notes 25,000 customers across 20 counties were impacted.

August 2021: A potential PSPS event was expected to affect 778 customers in Plumas County, as part of a broader event impacting 39,000 customers across 16 counties.

February 22, 2024 – Seneca Health noted a PG&E Power Failure - Hospital on Emergency Generator power. The CT machine was out of service due to power outage. Stroke and trauma patients had to be diverted. Power out at 1550 and Restored at 1700.

March 29, 2024 – at 11:23 PM Liberty Utilities had a power outage. The outage lasted for 2 days. Plumas County OES opened a warming shelter on March 30th.

April 6, 2024 – Seneca Health noted a PG&E Power Outage from 0009 – 0330. The Hospital was on emergency power and CT was disrupted due to outage.

April 29, 2024 – At 11:23 PM Liberty Utilities’ customers lost power. They supply power to a portion of Portola and Sierra Valley. Liberty Utilities receives its power from Nevada Energy. Nevada Energy lost power. Unknown what broke.

October 17–20, 2024: A PSPS event affected 658 customers in Plumas County, with specific areas like Little Grass Valley Reservoir, Bucks Lake, Haskins, and Feather River Canyon noted.

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November 5, 2024: A PSPS watch was issued for Plumas County, with potential outages in areas east of Highway 70, including Storrie, as part of a 12-county event affecting 15,000 customers. It’s unclear if this watch resulted in an actual shutoff.

PG&E has started to underground more power lines to reduce wildfire risks. The most recent map for Plumas County showing this progress is included in Figure 4-25.

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Figure 4-25 Plumas County – PG&E Undergrounding
Source: PG&E – January 2025.

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It was also noted that PG&E is working to enhance its power network with Enhanced Powerline Safety Settings (EPSS) capable lines. EPSS are advanced safety settings. They allow PG&E powerlines to automatically turn off power within one-tenth of a second. This can happen when there is a hazard, like a tree branch falling into a powerline, which can cause a fire. These settings are in high fire-risk and surrounding areas. These have not yet been installed in and near the Plumas County area, as PG&E focuses on other very high fire hazard areas in its service territory first. It is thought these EPSS capable lines will eventually come to the Plumas County Planning Area.

Climate Change and Power Outages/Failures (Energy Shortage) Changing climate is expected to bring more frequent and intense natural disasters. Key climate parameters are starting to move outside of historically observed variability at a rate that makes historical data a poor predictor of future climate. For example, the warmest years on record in California occurred in 2014, 2015, 2016, and 2019. 2022 - 2025 were remarkably hot years as well. In addition, the 2016-2017 year broke the record as the wettest ever recorded in the northern Sierra Nevada Mountains. Recent years, including the 2023 storms, have also seen heavy precipitation, further compounded by atmospheric river events.

Changes in temperatures, precipitation patterns, extreme events, and sea level rise have the potential to decrease the efficiency of thermal power plants and substations, decrease the capacity of transmission lines, render hydropower less reliable, spur an increase in electricity demand, and put energy infrastructure at risk of flooding.

With climate warming, higher costs from increased demand for cooling in the summer are expected to outweigh the decreases in heating costs in the cooler seasons. Hotter temperatures in California will mean more energy (typically measured in “cooling‐degree days”) needed to cool homes and businesses both during heat waves and on a daily basis, during the daytime peak of the diurnal temperature cycle. During future heat waves, historically cooler coastal cities (e.g., San Francisco and Los Angeles) are projected to experience greater relative increases in temperature, such that areas that never before relied on air conditioning will experience new cooling demands.

Secondary impacts of energy shortages are most often felt by vulnerable populations. For example, those who rely on electric power for life-saving medical equipment, such as respirators, are extremely vulnerable to power outages. Also, during periods of extreme heat emergencies, the elderly and the very young are more vulnerable to the loss of cooling systems requiring power sources.

Additional impacts from power disruption can also affect remote areas. This can affect evacuation messaging and coordination difficulties, and a reduction in firefighting capabilities due to lack of water access in more remote areas (especially for those on wells).

Hazard Profiles and Vulnerability Assessment by Hazard
The following sections provide the hazard profile and vulnerability assessments for each of the hazards identified in Section 4.1 Hazard Identification. The severe weather hazards are discussed first to paint the picture of the Plumas County’s Planning Area’s climate and hazard environment which often lead to other hazards such as flood and wildfire. The remainder of the hazards follow alphabetically.

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Data Sources
In general, information provided by the County, participating jurisdictions, and the HMPC is integrated into this section with information from other data sources. The data sources listed below formed the basis for this Hazard Profiles portion of the plan. Where data and information from these studies, plans, reports, and other data sources were used, the source is referenced as appropriate throughout this risk assessment. ➢ 2014 California Natural Resources Report
➢ 2017 California Adaptation Planning Guide
➢ 2020 US Census Bureau Average Household Size
➢ 2021 California Climate Adaptation Study (and Draft 2024 Climate Adaptation Study) ➢ 2023 State of California Hazard Mitigation Plan
➢ 2023 US Census American Community Survey Average Household Size ➢ American Society of Civil Engineers
➢ Bureau of Land Management
➢ Cal Adapt – Extended Drought Scenarios
➢ CAL FIRE
➢ CAL FIRE (FHSZ SRA 2024, FHSZ FRA 2007)
➢ CAL FIRE (LRA 2025)
➢ Cal-Adapt
➢ Cal-Adapt – Number of Extreme Heat Days by Year
➢ Cal-Adapt – Precipitation: Decadal Averages Map
➢ Cal-Adapt – Temperature: Decadal Averages Map
➢ Cal-Adapt 2017/2023
➢ Cal-Adapt Climate Projections
➢ California Climate Adaptation Strategy
➢ California Department of Conservation’s Farmland Mapping and Monitoring Program ➢ California Department of Public Health
➢ California Department of Water Resources
➢ California Department of Water Resources 2012-2016 California Drought: Historical Perspective ➢ California Department of Water Resources Best Available Maps ➢ California Department of Water Resources Division of Safety of Dams ➢ California Division of Mines and Geology
➢ California Geological Survey
➢ California Invasive Plant Council
➢ California Natural Resource Agency
➢ California Office of Emergency Services
➢ California Public Utilities Commission
➢ California’s Adaptation Planning Guide: Understanding Regional Characteristics ➢ Center for Western Weather and Water Extremes
➢ Chapman, K., Gold, M.B., Boatwright, J., Sipe, J., Quitoriano, V., Dreger, D., and Hardebeck, J., 2016, Faulting, damage, and intensity in the Canyon dam earthquake of May 23, 2013: U.S.

Geological Survey Open-File Report 2016-1145, 49 p., http://dx.doi.org/10.3133/ofr20161145 ➢ Climate Change and Health Profile Report – Plumas County ➢ Design-Magnitude Avalanche Mapping and Mitigation Analyses ➢ DSOD/Cal OES/NID Dam Status 1/25

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➢ Feather River Bulletin, Wednesday January 29, 1997
➢ FEMA 03/02/2005 DFIRM
➢ Federal Emergency Management Agency – DFIRM 1/20/2016 ➢ Federal Emergency Management Agency – Disaster Declaration Database ➢ Federal Emergency Management Agency – National Flood Hazard Layer ➢ Federal Emergency Management Agency – Wind Zones in the United States ➢ Federal Emergency Management Agency: Building Performance Assessment: Oklahoma and Kansas Tornadoes
➢ Fire and Resource Assessment Program
➢ Geology Open File Report 84-52 (1994)
➢ Hazus-MH 6.1
➢ Intergovernmental Panel on Climate Change
➢ KCRA News Report
➢ Multi-Hazard Identification and Risk Assessment, FEMA 1997 ➢ National Aeronautics and Space Administration
➢ National Avalanche Center
➢ National Center for Atmospheric Research
➢ National Climate Assessment
➢ National Climatic Data Center Storm Events Database.
➢ National Drought Mitigation Center
➢ National Earthquake Information Center
➢ National Flood Insurance Program
➢ National Hazardous Materials Routes Registry
➢ National Integrated Drought Information System
➢ National Inventory of Dams
➢ National Levee Database
➢ National Oceanic and Atmospheric Administration
➢ National Oceanic and Atmospheric Administration Storm Prediction Center ➢ National Oceanic and Atmospheric Administration’s National Climatic Data Center ➢ National Park Service
➢ National Performance of Dams Program
➢ National Weather Service
➢ National Weather Service HeatRisk
➢ National Weather Service XMAC site
➢ Plumas County 2014 LHMP
➢ Plumas County Agriculture Commissioner
➢ Plumas County Agricultural Commissioner Reports
➢ Plumas County Drought Plan
➢ Plumas County Drought Task Force
➢ Plumas County Fire Safe Council
➢ Plumas County General Plan Water Resources Element
➢ Plumas County Road Department
➢ Plumas County Volunteers Active in Disasters
➢ Plumas Eureka Community Services District
➢ Public Policy Institute of California
➢ Sierra Avalanche Center

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➢ Sierra Neveda Photos
➢ Sierra Valley Groundwater District
➢ Smoke Impacts CA: 2020 Lessons – 2021 Actions
➢ State of California Department of Conservation Farmland Mapping and Monitoring Program ➢ The Storm of ’86 by Robert Moon, Feather River Publishing, Quincy, CA 1986 ➢ Susceptibility to Deep-Seated Landslides map – CSG Map Sheet 58 (05/2011) ➢ University of California, Berkeley’s Department of Environmental Science, Policy, and Management ➢ US Army Corps of Engineers
➢ US Department of Agriculture
➢ US Department of Agriculture – Farm Service Agency Secretarial Disasters Declarations ➢ USDOT Pipeline and Hazardous Materials Safety Administration’s Office of Hazardous Materials Safety
➢ US Drought Monitor
➢ US Farm Service Agency
➢ US Fish and Wildlife Service
➢ US Forest Service
➢ US Geological Survey – A Sight “Fearfully Grans” – Eruptions of Lassen Peak California, 1914 to 1917
➢ US Geological Survey Bulletin 1847
➢ US Geological Survey Open File Report 2015‐3009
➢ US Geological Survey Earthquake Intensity Zonation and Quaternary Deposits, Miscellaneous Field Studies Map 9093, 1977
➢ US Geological Survey Emergency Assessment of Post-Fire Debris Flow Hazards ➢ US Geological Survey Fact Sheet 2014-3120
➢ US Geological Survey National Earthquake Information Center ➢ US Geological Survey Open File Report 2015‐3009
➢ US Geological Survey Publication 2014-3120
➢ US Geological Survey: Volcanic Ash: Effect & Mitigation Strategies. ➢ Vaisala National Lightning Detection Network
➢ Western Regional Climate Center

4.3.1. Severe Weather: General
Severe weather is generally any destructive weather event, but usually occurs throughout the Plumas County Planning Area as temperature extremes, localized storms that bring heavy rain and strong winds, and other extreme weather events. NOAA’s National Climatic Data Center (NCDC) has been tracking severe weather since 1950. Their Storm Events Database contains data on the following: all weather events from 1993 to current (except from 6/1993-7/1993); and additional data from the Storm Prediction Center, which includes tornadoes (1950-1992), thunderstorm winds (1955-1992), and hail (1955-1992). This database contains 785 severe weather events that occurred in Plumas County between January 1, 1950, and July 31, 2024. Table 4-26 summarizes these events.

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Table 4-26 NCDC Severe Weather Events for Plumas County 1950-7/31/2024* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Astronomical Low Tide 2 1 0 0 0 $0 $0
Blizzard 3 0 0 0 0 $0 $0
Cold/Wind Chill 3 0 0 0 0 $0 $0
Debris Flows 21 0 0 0 0 $2,000 $0
Dense Fog 9 0 0 0 0 $1,000 $0
Dense Smoke 1 0 0 0 0 $0 $0
Drought 2 0 0 0 0 $50,000 $0
Excessive Heat 5 0 0 0 0 $0 $0
Flash Flood 3 0 0 0 0 $0 $0
Flood 12 0 0 1 0 $3,140,000 $0
Freezing Fog 1 0 0 0 0 $0 $0
Hail 10 0 0 0 0 $100 $5,000
Heat 2 0 0 0 0 $0 $0
Heavy Rain 60 0 0 0 0 $1,000 $0
Heavy Snow 330 1 0 0 0 $220,000 $0
High Wind 88 0 0 1 0 $2,245,500 $0
Ice Storm 1 0 0 0 0 $0 $0
Lightning 1 0 0 0 0 $0 $0
Strong Wind 4 0 0 0 0 $63,300 $0
Thunderstorm Wind 2 0 0 0 0 $675,000 $0
Wildfire 14 1 0 3 0 $22,775,000 $0
Winter Storm 150 0 0 0 0 $150,000 $0
Winter Weather 61 0 0 0 0 $0 $0
Total 785 3 0 5 0 $29,322,900 $0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of Plumas County The NCDC table above summarizes severe weather events that occurred in Plumas County. Only a few of the events actually resulted in federal and state disaster declarations. It is further interesting to note that different data sources capture different events during the same time period, and often display different information specific to the same events. While the HMPC recognizes these inconsistencies, they see the value this data provides in depicting the County’s “big picture” hazard environment.

As previously mentioned, most all of Plumas County’s federal and state disaster declarations have been a result of severe weather. For this Plan Update, severe weather is discussed in the following subsections:
➢ Severe Weather: Extreme Cold, Freeze, and Snow (w/avalanche) ➢ Severe Weather: Extreme Heat
➢ Severe Weather: Heavy Rains and Storms

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➢ Severe Weather: High Winds and Tornadoes

4.3.2. Severe Weather: Extreme Cold, Freeze, and Snow (w/Avalanche) Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Plumas County Planning Area and unincorporated Plumas County. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; likelihood of future occurrence; and how climate change can affect or influence this hazard.

Hazard/Problem Description
Separate hazard descriptions and locations and extents are shown below for cold and freeze, as well as for snow and avalanche.

Extreme Cold and Freeze
According to the National Weather Service (NWS) and the Western Regional Climate Center (WRCC), extreme cold often accompanies a winter storm (and snow event) or is left in its wake. Prolonged exposure to cold can cause frostbite or hypothermia and can be life-threatening. Infants and the elderly are most susceptible. Pipes may freeze and burst in homes or buildings that are poorly insulated or without heat.

Freezing temperatures can cause significant damage to the agricultural industry. The effects of freezing temperatures on agriculture in Plumas County are discussed further in Section 4.3.6 Agricultural Hazards.

In 2001, the NWS implemented an updated Wind Chill Temperature index (shown in Figure 4-26), which is reproduced below. This index was developed to describe the relative discomfort/danger resulting from the combination of wind and temperature. Wind chill is based on the rate of heat loss from exposed skin caused by wind and cold. As the wind increases, it draws heat from the body, driving down skin temperature and eventually the internal body temperature.

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Figure 4-26 Wind Chill Temperature Chart
Source: National Weather Service
It should be noted that the WRCC and NWS maintain data on weather normal and extremes in the western United States. Each of these data sources maintain data in slightly different ways. Data from the WRCC stopped being collected in April of 2016. NWS covers the entire time period to present. Therefore, both data sets are shown below. WRCC and NWS data for extreme cold and freeze for the County is summarized below.

Plumas County—WRCC Quincy Station Weather Station, Period of Record 1895 to 2016 According to the WRCC, in Plumas County monthly average minimum temperatures from November through April range from the low-20s to upper-40s. The lowest recorded daily extreme was -28°F on January 8, 1937. In a typical year, minimum temperatures fall below 32°F on 166.9 days with 1.5 days falling below 0°F. Table 4-27 shows the record low temperatures by month for western Plumas County.

Average daily temperatures for Plumas County are shown in Figure 4-27.

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Figure 4-27 Plumas County— Quincy Station (WRCC) Daily Temperature Averages and Extremes
Source: Western Regional Climate Center
Table 4-27 Plumas County – Quincy Station (WRCC) Record Low Temperatures 1895 to 2016 Month Record Low Date Month Record Low Date
January -28 1/8/1937 July 23 7/1/1912
February -19 2/13/1949 August 20 8/31/1910
March 0 3/20/1952 September 15 9/28/1972
April 12 4/6/1982 October 6 10/27/1917
May 20 5/7/1984 November -3 11/12/1985
June 25 6/4/1950 December -24 12/12/1972
Source: Western Regional Climate Center
Plumas County—NWS Quincy Station Weather Station, Period of Record 1895 to 2025 According to the NWS, monthly average minimum temperatures in the coldest months (December through February) range from the mid to upper-20s. The lowest recorded daily extreme was -24°F on December 12, 1972. Figure 4-28 shows the average daily low temperatures and extremes for the County. Table 4-28 shows the record low temperatures for the County.

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Figure 4-28 Plumas County – Quincy Station (NWS) Daily Temperature Averages and Extremes, 1991-2020
Source: National Weather Service XMAC site. Retrieved 3/12/2025 Table 4-28 Plumas County – Quincy Station (NWS) Record Low Temperatures 1895 to 2025 Temperature Date
-24.0° 12/12/1972
-24.0° 1/20/1937
-22.0° 12/9/1972
-22.0° 1/7/1937
-20.0° 1/21/1937
-20.0° 1/9/1937
-19.0° 1/3/1950
-19.0° 1/25/1949
-18.0° 1/24/1949
-16.0° 2/5/1989
Source: National Weather Service XMAC site. Retrieved 3/12/2025 Location and Extent of Extreme Cold and Freeze
Extreme cold and freeze events occur on a regional basis. Extreme cold can occur in any location of the County. All portions of the County are at risk to extreme cold, with the upper elevations at greater risk.

Extreme cold can affect agricultural products in the County. Freeze damages reduce the values of

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agricultural crops (discussed further in Section 4.3.6). While there is no scale (i.e. Richter, Enhanced Fujita) to measure the effects of freeze, temperature data from the County from the WRCC indicates that there are 166.9 days that fall below 32F. Freeze has a slow onset and can generally be predicted in advance for the County. Freeze events can last for hours (in a cold overnight), or for days to weeks at a time. Figure 4-29 and Figure 4-30 show the probabilities in the County of freeze for both spring and fall. Note: there are no National Weather Service XMAC freeze probabilities, so only the WRCC is captured below.

Figure 4-29 Plumas County – Spring Freeze Probabilities Source: Western Regional Climate Center

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Figure 4-30 Plumas County – Fall Freeze Probabilities
Source: Western Regional Climate Center
Snow and Avalanche
Plumas County is located in the Sierra Nevada region of the State of California. Severe weather affects all areas of Plumas County but differs significantly by region. Throughout areas of the County there are significant variations in the average temperature and amount of precipitation received due to topography.

Snowfall in the Sierras increases with elevation. The lower foothills rarely receive any measurable snow.

Middle elevations receive a mix of snow and rain during the winter. Above about 6,000 ft., the majority of precipitation falls as snow. It is not unusual, in some locations, to have ten feet of snow on the ground for extended periods. Figure 4-31 shows the average maximum measured snow depth in the Sierra Nevada for the month of March (the month of greatest average snow depths).

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Figure 4-31 Average Maximum Snow Depths of Sierra Nevada Mountains in March Source: http://www.sierranevadaphotos.com. This image is no longer available publicly. It was retrieved for the 2020 Plumas County LHMP Update.

It should be noted that the WRCC and NWS maintain data on weather normal and extremes in the western United States. Each of these data sources maintain data in slightly different ways. Data from the WRCC stopped being collected in April of 2016. NWS covers the entire time period to present. Therefore, both data sets are shown below. WRCC and NWS data for snowfall for the County is summarized below.

Plumas County—WRCC Quincy Station Weather Station, Period of Record 1895 to 2016 According to the WRCC, average snowfall of the County is 55.1 inches, as shown in Figure 4-32. The highest annual snowfall fell in 1952, when 167.2 inches fell. Highest monthly snowfall accumulation came in January of 1916, when 133.0 inches fell. Average snow depths in January through March can be significant. This can be seen in Figure 4-33.

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Figure 4-32 Plumas County—Snowfall Averages and Extremes Source: Western Regional Climate Center
Figure 4-33 Plumas County—Snow Depth Averages and Extremes Source: Western Regional Climate Center

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Plumas County—NWS Quincy Station Weather Station, Period of Record 1895 to 2025 Table 4-29 shows historical data of the highest daily snowfall on March 23, 1907, when 36.0 inches fell.

The maximum snow depth came on January 29th of 1916, with a depth of 58.0 inches. This can be seen in Table 4-30. Monthly average snowfall (from 1991 to 2020) is shown on Figure 4-34. Note: While the overall period of record for this NWS station is 1895 to 2025, not all data is recorded for those dates.

Snowfall is covered from November of 1895 to April 2025. Snow depth is covered from November of 1900 to April of 2025.

Table 4-29 Plumas County –Quincy Station (NWS) Highest Daily Snowfall 1895 to 2025 Snowfall in Inches Date

36.0 3/23/1907

34.0 1/30/1968

30.0 10/30/1909

30.0 12/22/1908

26.0 2/27/1955

24.0 1/18/1955

24.0 1/12/1952

24.0 1/13/1911

24.0 1/11/1911

24.0 1/14/1910
Source: National Weather Service XMAC site. Retrieved 3/12/2025 Table 4-30 Plumas County – Quincy Station (NWS) Maximum Snow Depth 1895 to 2025 Snow Depth in Inches Date

58.0 1/29/1916

54.0 1/30/1916

53.0 1/15/1952

52.0 1/14/1952

52.0 1/31/1916

51.0 1/16/1952

50.0 1/17/1952

49.0 2/3/1937

48.0 1/18/1916

48.0 1/17/1916
Source: National Weather Service XMAC site. Retrieved 3/12/2025

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Figure 4-34 Plumas County –Quincy Station (NWS) Average Daily Snowfall 1991 to 2020 Source: National Weather Service XMAC site. Retrieved 3/12/2025 According to the Sierra Avalanche Center, avalanches occur when loading of new snow increases stress at a rate faster than strength develops, and the slope fails. Avalanches are a rapid down-slope movement of snow, ice and debris triggered by ground shaking, sound, or human or animal movement. Avalanches consist of a starting zone where the ice or snow breaks loose, a track which is the grade or channel the debris slides down and a run-out zone where the snow is deposited. This can be seen in Figure 4-35.

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Figure 4-35 Avalanche Zones
Source: Sierra Avalanche Center
Critical stresses develop more quickly on steeper slopes and where deposition of wind-transported snow is common. The vast majority of avalanches occur during and shortly after storms. This hazard generally affects a small number of people, such as snowboarders, skiers, and hikers who venture into backcountry areas during or after winter storms. Roads and highway closures, damaged structures, and destruction of forests are also a direct result of avalanches.

Location and Extent of Snow and Avalanche
Snowfall can affect almost all areas of the County. Depending on the elevation of any given area, severe snowstorms are some of the most common extreme weather events that occur in Plumas County. Some winter storms are accompanied by strong winds, creating blizzard conditions with blinding wind-driven snow, severe drifting and dangerous wind chills. There is no scale (i.e. Richter, Enhanced Fujita) to measure the effects of snowfall other than snow depths. Heavy snow has a slow to moderate onset and can generally be predicted in advance for the County. Snow events can last for hours or for days, and snow can stay on the ground for weeks to months at a time.

Avalanche affects only certain areas of the County. The combination of steep slopes, abundant snow, weather, snowpack, and an impetus to cause movement to create an avalanching episode. Avalanche

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hazards exist in many of the steeply sloped areas of Plumas County, where combinations of the above criteria occur. The two primary factors impacting avalanche activity are weather and terrain. Large, frequent storms deposit snow on steep slopes to create avalanche hazards. Additional factors that contribute to slope stability are the amount of snow, rate of accumulation, moisture content, wind speed and direction and type of snow crystals. Topography also plays a vital role in avalanche dynamics. Slope angles between 30 to 45 degrees are optimal for avalanches. The risk of avalanches decreases on slope angles below 30 degrees. At 50 or more degrees they tend to produce sluff or loose snow avalanches that account for only a small percentage of avalanche deaths and property damage annually. The HMPC noted that Genesee (and approximately 20 homes) are in an area affected by avalanche.

Speed of onset of avalanche is short, as is the duration of each event. Most avalanches occur during and shortly after storms between January and March. A scale of avalanche danger has been created for North America. This can be found in Table 4-31.

Table 4-31 North American Public Avalanche Danger Scale Danger Level Travel Advice Likelihood of Avalanche Avalanche Size or Distribution.
5 – Extreme Avoid all avalanche terrain Natural and humantriggered avalanches certainLarge to very large avalanches in many areas
4 – High Very dangerous avalanche conditions.

Travel in avalanche terrain not
recommended
Natural avalanches likely;
human-triggered avalanches
very likely
Large avalanches in many
areas; or very large
avalanches in specific areas
3 – Considerable Dangerous avalanche conditions.

Careful snowpack evaluation, cautious
route-finding and conservative
decision making essential
Natural avalanches possible;
human-triggered avalanches
likely
Small avalanches in many
areas; or large avalanches in
specific areas; or very large
avalanches in isolated areas
2 – Moderate Heightened avalanche conditions on
specific terrain features. Evaluate
snow and terrain carefully; identify
features of concern
Natural avalanches unlikely;
human-triggered avalanches
possible
Small avalanches in specific
areas; or large avalanches in
isolated areas
1 – Low Generally safe avalanche conditions.

Watch for unstable snow on isolated
terrain features
Natural and humantriggered avalanches
unlikely
Small avalanches in isolated
areas or extreme terrain
Source: National Avalanche Center
Past Occurrences
Disaster Declaration History
The County has had no past federal and one past state disaster declarations for extreme cold and freeze.

There were no disasters from snow or from avalanche. Table 4-32 shows the dates of the disaster declarations. More information on USDA disaster declarations (2016, twice in 2022, 2023) from cold and freeze can be found in Table 4-51 in the Past Occurrences in Section 4.3.6.

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Table 4-32 Plumas County – Federal and State Disaster Declarations for Freeze 1950-2025 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Freeze 1 2007 0 –
Source: Cal OES, FEMA
NCDC Events
The NCDC data shows 549 extreme cold, freeze, and snow incidents for Plumas County since 1993.

Information for these events is shown in Table 4-33. The NCDC has no recorded events of avalanche.

Table 4-33 NCDC Cold and Freeze Events for Plumas County 1950-7/31/2024* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Blizzard 3 0 0 0 0 $0 $0
Cold/Wind Chill 3 0 0 0 0 $0 $0
Freezing Fog 1 0 0 0 0 $0 $0
Heavy Snow 330 1 0 0 0 $220,000 $0
Ice Storm 1 0 0 0 0 $0 $0
Winter Storm 150 0 0 0 0 $150,000 $0
Winter Weather 61 0 0 0 0 $0 $0
Total 549 1 0 0 0 $370,000 $ 0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of Plumas County Hazard Mitigation Planning Committee Events
The HMPC noted past events. These are separated for cold and freeze, snow, and avalanche.

Cold and Freeze Events
These section separates events since the 2019/2020 LHMPs and those before 2019.

Events since 2019/2020 LHMP
The County noted the following notable events since the 2019 and 2020 LHMPs:
➢ 2022
✓ On the 1st-2nd of January, temperatures dropped down to 6º and 7º. ✓ On September 14th, Plumas County had its first frost of the year. ✓ On the 20th of November, temperatures dropped to 15º. ➢ 2023
✓ In January, temperatures dropped to 11º-15º on the 21st, 30th, and 31st. ✓ In February, Temperatures reached 15º on the 16th and the 22nd.

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✓ A cold event on June 21 caused temperatures to drop to 37º and frost was seen. ➢ 2024
✓ A cold event on June 18 caused temperatures to decrease to 33º causing a freeze event.

Events before 2019
Many events occurred, but not specific events causing damages could be recalled.

Snow Events
These section separates events since the 2019/2020 LHMPs and those before 2019.

Events since 2019
➢ 2020 – Jan 14-16. 12.75’ of snow. Mar 16. 21.75' of snow ➢ 2021 – In the month of December 6.75” of snow fell on the 16th. Following this, the 25- 29 received 35” (or almost 3 ft.) of snow
➢ 2022 – On November 9th, 5” of snow fell in Plumas County. ➢ February of 2023 – between the days of the 23rd and 28th, 40.75” of snow fell, causing blizzard conditions on the 28th.
➢ March of 2023 – Snow occurred in the County as part of an atmospheric river storm event. A strong winter storm impacted Plumas County from February 26 through March 4, 2024. Rain, strong winds and multiple feet of snow occurred with this storm. Blizzard conditions were widespread with a total snow accumulation of 1 to 10 feet. Snow levels dropped as low as 1,500 feet over the weekend, with a significant accumulation. Visibility on roads was poor. Downed trees and power outages occurred throughout Plumas County. Outages ranged from less than an hour to 96 hours. Portola was impacted the most with over 4 feet of snow and power outages for 4 days. Liberty Utilities supplies power to a portion of Portola and Sierra Valley. Liberty Utilities receives its power from Nevada Energy. The damage was down a steep hill with no easy access. Nevada Energy did not keep linemen on 24/7 during this event. Once Nevada restored their power, Liberty linemen were on top of getting the power restored. A Damage Tracking document provided by the County indicated that several parties did have major damage to their residences where the weight of the snow cracked their walls, there was ice dam destruction to roofs, and minor flooding in basements. All parties affected advised the County that they are still able to live in the structures. This caused flooding in areas of the County. This is discussed in the Past Occurrences of Section 4.3.11.
➢ 2024 – In March, after multiple inches of rain had already fallen, 13.75” fell on the 3rd and 7.25” fell the next day, totaling to 21” of snowfall. In May, late snowfall impacted the county with 2.25” falling.

Events before 2019
HMPC also noted the following events:
➢ Extreme snow events have included up to 60 inches of snow in Quincy and 45 inches of snow in Chester in one month. Two notable snow seasons occurred in 1951-1952, and 1992-1993. During these years the Chester area received a total of 362 inches of snow in 1951-52 and 295 inches in 1992-93.

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Figure 4-36 Community of Chester 1951-1952 Snow Event
Source: Plumas County

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Figure 4-37 1993 Storm Damage of Store in Quincy
Source: KCRA News Report

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Figure 4-38 Community of Chester 2001 Snow Event
Source: Plumas County
➢ On June 12 to 14 of 1981, there were freezes each day in Quincy. A member of the HMPC from Viera Ranch noted that the freeze killed their garden.
➢ Between March 28 and April 7 of 1982, there was high snowfall in the Quincy area. A member of the HMPC from Viera Ranch noted that power was out by March 31, with roads and schools closed in the area.
➢ The winter of 1989 featured many cold weather incidents and heavy snows. A member of the HMPC from Viera Ranch noted that from January 1 to 3, 46 inches of snow fell. Lows in Quincy from February 5 to February 8 were -8°F, -15°F, -14°F, and -18°F, respectively. ➢ The winter of 1990 also featured many cold weather incidents and heavy snows. A member of the HMPC from Viera Ranch noted that from February 15 to 18 46 inches of snow fell. Lows in Quincy from December 21 and 22 were -5°F and -8°F, respectively. ➢ On June 15, 1992, a late freeze hit. It killed gardens and crops in the area. ➢ A member of the HMPC from Viera Ranch noted from December 28 of 1992 to January 9 of 1993 over six feet of snow fell in Quincy.
➢ A member of the HMPC from Viera Ranch noted on February 20 and 21 of 1994, 23 inches of snow fell near Quincy. June 20-24 of that yar also saw lows around 32°F. ➢ A member of the HMPC from Viera Ranch noted the from January 4-6 of 1995, 13 inches of snow fell. Between the 7th and the 15th, 27.85 inches of rain fell as well. This caused flooding in Quincy.

Snow fell again in March, and on the 22nd and 23rd, 41 inches of snow fell, cancelling schools and knocking out power. June 16th of 1995 of that year also saw 2.5 inches of snow! ➢ A member of the HMPC from Viera Ranch noted 19 inches of snow fell between April 5th and 8th of 1999.

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➢ A low of 8°F was seen on February 15th of 2001.
➢ A member of the HMPC from Viera Ranch noted heavy snows between January 7th and 11th of 2005.

Power was out in the Quincy area on January 11th. Events of frost were noted between June 3rd and 6 th of 2005.
➢ June 7
th of 2007 saw frost, with damages to gardens and crops in the area reported. ➢ Frost was noted on June 18th, 2014.

Avalanche Events
Historically, avalanches occur within the steeply sloped portion of the County between the months of January and March, following snowstorms. Past occurrences of avalanche in the County include:
➢ The HMPC noted that near Grizzly Ridge in Genessee, avalanches occur with regularity. These have blocked Indian Creek and Little Grizzly Creek and/or Grizzly Creek. There are 4 homes in the area that have their ingress and egress routes blocked. There are numerous avalanche chutes on the northeast and north faces of Grizzly Ridge in the Genesee Valley area. These can be seen in Figure 4-39. The Tower & Lind chutes are active annually, with multiple small to moderate falls per year. The Tower does deliver stream-blocking falls to Little Grizzly Creek (observed by a member of the HMPC in 1983 and 1993). The Lind chute, while very active, does not extend to Indian Creek. The Hairpin chute reportedly blocked Indian Creek in 1952 and 1963 (as reported by members of the HMPC). It last sent snow to Indian Creek in 1995, without blocking the creek. The less active chutes are becoming more overgrown with vegetation with overall reductions in last 30 years in snowfall/avalanches to keep clear.

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Figure 4-39 Plumas County – Grizzly Ridge Avalanche Chutes

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➢ An avalanche occurred in the winter of 2012 near Sloat. No injuries or deaths were reported. Timber stock in the avalanche area was damaged, though no damage estimates were available. ➢ CalTrans had an avalanche in 2023 on SR70 in the Feather River Canyon within the Butte County section of the highway, but the risk factors are similar to Plumas County along that portion of SR70.

Likelihood of Future Occurrence
Highly Likely—Extreme cold, freeze, snow, and avalanche are likely to continue to occur annually in the Plumas County Planning Area, especially in the eastern portion of the County. In a typical year, minimum temperatures fall below 32°F on 166.9 days in Plumas County. Snow falls in the County every year.

Avalanches occur every year (though many go unreported as they occur in undeveloped areas). This equates to a likelihood of future occurrences being considered highly likely.

It is likely that climate change will decrease the chance of future occurrence as well as future impacts. More information on climate change and extreme cold, freeze, snow, and avalanche can be found in the next section. More information on future impacts can be found in the Future Conditions/Future Development section of the Vulnerability Assessment below.

Climate Change and Extreme Cold, Freeze, Snow, and Avalanche According to the 2021 California Climate Adaptation Study (CAS) as well as the 2024 Draft CAS, freezing spells are likely to become less frequent in California as climate temperatures increase. If emissions increase, freezing events could occur only once per decade in large portion of the State by the second half of the 21st century. According to a California Natural Resources Report in 2014, it was determined that while fewer freezing spells would decrease cold related health effects, too few freezes could lead to increased incidence of disease as vectors and pathogens do not die off. Snow and avalanche are expected to decline due to reduced snow and snowpack.

Vulnerability Assessment
Vulnerability—Medium
Extreme cold, freeze, snow, and avalanche events happen in the Plumas County Planning Area each year.

It can impact key assets in the Planning Area. The whole of the Planning Area has some measure of vulnerability to extreme cold, freeze, snow, and avalanche.

An assessment of a community’s vulnerability to this hazard begins with an understanding of local exposure to unincorporated Plumas County. This is included in the Local Concerns section below. After that, vulnerability is discussed in multiple sections that detail how this hazard can affect both the entire Plumas County Planning Area as well as the unincorporated portions of Plumas County. How the hazard affects the other participating jurisdictions can be found in their respective annexes to this LHMP Update. These sections below include assets at risk, impacts, and how future development can be affected by this hazard.

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Local Concerns (unincorporated Plumas County)
The unincorporated County has specific concerns regarding this hazard. These concerns form a portion of the basis for the mitigation strategy and mitigation actions that seek to reduce risk and vulnerabilities to this hazard.

The varying elevations in the County, in part, determine the extent to which a given area is affected by freeze and cold. The agricultural industry is especially vulnerable to extreme temperatures. Freezing temperatures can cause significant loss to crops. Historically, extreme cold and freeze have caused losses to agricultural crops and have resulted in several USDA disaster declarations including the ones noted above in the Past Occurrences section.

The Plumas County Planning Area does experience snowfall on a seasonal basis, and portions of the County receive an abundance of snow, mostly between the months of November through March. Winter snowstorms in the County, including strong winds and blizzard conditions, can result in localized power and phone outages and closures of streets, highways, schools, businesses, and nonessential government operations. During periods of heavy snow there is also an increase in the number and severity of traffic accidents. People can become isolated in their homes and vehicles and are unable to receive essential services. During times of isolation, individuals and communities become isolated and must depend upon themselves in early stages of an emergency. Snow removal costs can impact budgets significantly. Heavy snowfall during winter can lead to flooding or landslides during the spring if the area snowpack melts too quickly and can also create numerous challenges for emergency responders.

Heavy snow events occur on an annual basis in the higher elevations of the County. Snow removal is an ongoing issue in the upcountry areas of the County. Snow removal is constant during the snowiest months, within the County and other agencies providing snow removal on public roads. Individuals and road associations are a primary snow removal resource for all the private roads. Impacts to the County as a result of winter snowstorms include damage to infrastructure, utility outages, road closures, traffic accidents, and interruption in business and school activities. Also, of concern as described below is the impact to populations with additional needs such as the elderly, low-income individuals, and those requiring the use of medical equipment should the power go out. Delays in emergency response services can be of significant concern during large storm events. Further, there are economic impacts associated with areas prone to heavy snow.

There have been many extreme snow events that have occurred in Plumas County, most notably in the high elevation regions such as Chester and La Porte. However, lower elevation areas such as Quincy are also susceptible to extreme snow events. Seneca Road, the first part of the road, has been impacted by avalanches during heavy snow (this is County Road 306).

The HMPC noted that Genesee (and approximately 20 homes) are in an area affected by avalanche.

Local concerns for Portola and the Special Districts can be found under the Local Concerns heading in each respective jurisdictional annex to this LHMP Update.

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Assets at Risk
Assets at risk from extreme cold, freeze, snow, and avalanche include people and populations; structures; critical facilities and infrastructure; and natural, historic, and cultural resources. These are discussed in the following sections for the Plumas County Planning Area and unincorporated Plumas County.

Additionally, for each hazard in the FEMA NRI in Plumas County, the relevant portions of the hazard analysis done by FEMA is presented below. This includes the Hazard Risk Index Rating, Expected Annual Loss Values, Exposure Values, and the Historic Loss Ratio Rating. These are presented for the Plumas County Planning Area as a whole.

People and Populations
All populations within the Plumas County Planning Area are vulnerable to extreme cold, freeze, and snow, but this hazard generally affects people spending large amounts of time outside to a greater extent.

Prolonged exposure to cold can cause frostbite or hypothermia and can be life-threatening. Snow can cause transportation issues for people, including vulnerable populations. Vulnerable populations to cold, freeze, and snow include the unhoused; individuals who exercise or train outdoors; outdoor workers; individuals that lack the resources to afford heat; and the young, old, or medically fragile individuals that are more susceptible to cold related impacts. In addition to vulnerable populations, pets and livestock are at risk to freeze and cold. Populations in the County are much less vulnerable to avalanche.

Structures
Structures in the Plumas County Planning Area have some measure of risk from extreme cold and freeze.

Buildings in the upper elevations of the County can be affected directly by freeze; pipes that feed buildings can be damaged during periods of extreme cold and cause water damage and other related impacts to a structure. Structures can also be damaged by downed trees during freeze and winter storm and snow events.

Structures can also be damage by excessive snow loads (as seen above in Past Occurrences). Structures in the Plumas County Planning Area have some measure of risk from avalanche. Buildings in the upper elevations of the County can be affected directly by avalanche events. However, most of these events occur away from structures in the Plumas County Planning Area.

Critical Facilities and Infrastructure
Winter storms typically involve snow and ice, occasionally accompanied by high winds, cold temperatures, and avalanche, which can cause downed trees and power lines, power outages, accidents, and road closures.

Transportation networks, communications, and utilities infrastructure are the most vulnerable physical assets in the County. Depending on the facility type and function, critical facilities and infrastructure may be affected directly by freeze and extreme cold and winter weather events. Damage to pipes that feed buildings can be damaged during periods of extreme cold. Other equipment may also be affected.

Infrastructure such as roads, highways, and bridges can become slippery, causing accidents and road closures. Depending on the facility type and function, critical facilities and infrastructure may be affected directly by avalanche events. Infrastructure such as roads, highways, and bridges can be blocked during these events.

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Natural, Historic, and Cultural Resources
Depending on how low the temperatures go and the duration of an extreme cold, freeze, snow, or avalanche event, natural resources in the Plumas County Planning Area may be affected. During periods of freeze and heavy snow, trees in the Planning Area may be damaged. This is especially true if a freeze occurs during a winter storm with winds and precipitation. Other natural resources like wildlife may be at risk during a period of freeze. While it is rare for buildings to be affected directly by freeze, damages to pipes that feed historic buildings can be damaged during periods of extreme cold and cause additional impacts to the structures.

FEMA NRI Hazard Vulnerability Assessment
FEMA’s NRI provides additional data on Plumas County’s vulnerability to Extreme Cold, Freeze, and Snow (with avalanche). The NRI contains data and analysis for 18 separate natural hazards. The NRI hazards related to Plumas County’s Extreme Cold, Freeze, and Snow (with Avalanche) hazards are:
avalanche, cold wave, ice storm, and winter weather. As shown in Table 4-34, while avalanches, cold waves, and ice storms are expected to cause no expected annual losses and are given no historic loss ratio, winter weather could cause a total of $29,230 in expected annual losses, with a rating of very low. Winter weather has a relatively low rating for social vulnerability and a relatively high community resilience, with a risk index score of 35.8 out of 100. According to the NRI, there have been 297 events on record between the years 2005-2021, with an average of 16.5 events per year.

Table 4-34 Plumas County Planning Area – Avalanche, Cold Wave, Ice Storm, and Winter Weather Vulnerability Ratings from FEMA NRI
NRI Hazard Hazard Risk Index
Rating
Expected Annual
Loss Values
(total)**
Exposure Value
(total)***
Historic Loss Ratio
Rating
Avalanche – $0 $0 –
Cold Wave 0 $0 $0 No rating
Ice Storm – $0 $0 –
Winter Weather 35.8 $29,230 $237,469,807,133 Very low
Source: FEMA NRI Report
*Hazard Risk Index is calculated using data for only a single hazard type, and reflects a communities expected annual loss value, community risk factors, and the adjustment factor used to calculate the risk value. **Expected annual loss represents the average economic loss in dollars resulting from natural hazards each year. ***Exposure is a natural hazard consequence factor that is the representative value of buildings, populations, or agriculture potentially exposed to a natural hazard occurrence.

Additional information on the FEMA NRI can be found in Section 4.2 and Appendix H.

Impacts from Severe Weather: Extreme Cold, Freeze, Snow, and Avalanche Extreme cold, freeze, and snow can affect critical facilities and infrastructure, down trees, break pipes, and can be a life safety issue. Transportation networks, communications, and utilities infrastructure are often the most vulnerable physical assets in the Plumas County Planning Area. Infrastructure such as roads and utilities are at risk to freezing temperatures and snow, causing failures and hazardous road conditions.

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When extreme cold is coupled with high winds and freezing storms, power lines may be downed, resulting in power outages and an interruption of utilities and critical services. During periods of extremely low or prolonged cold temperatures, other impacts to the Planning Area include can include interruption in business and school activities.

The elderly, the young, and those experiencing medical issues are often more vulnerable to temperature extremes, but anyone can be affected. Exposure to cold temperatures can cause hypothermia and frostbite.

Those exercising or recreating outdoors, outdoor workers, and the unhoused may be at a higher risk.

The most significant impacts from snow avalanches are the closure of transportation corridors, which can isolate populations and interrupt commodity flows. Avalanches tend to occur independently of other types of hazards, although it is possible for avalanches to be triggered by severe weather and earthquakes. There may be occasions where avalanches contribute to the presence of other hazards, such as flash floods resulting from mountainside erosion. Avalanches might cause erosion on sloped terrain, thereby increasing the likelihood of future landslides. In addition, debris deposited in a river or stream because of avalanches might alter its flow and contribute to flooding later.

Impacts to identified assets at risk to this hazard and the overall vulnerability of the County may be affected in the future by climate change (which was discussed in the hazard profile section above), changes in population patterns, and changes in land use and development. The influencing effects of these factors on this hazard are discussed further in the Future Conditions/Future Development discussion below.

Future Conditions/Future Development
This section provides a discussion of how future conditions will influence or affect the hazard over time and also discusses future development relative to each hazard.

Future Conditions
Future conditions may be affected by climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development. Findings on these factors for Plumas County include the following:
➢ Climate change is unlikely to exacerbate extreme cold, freeze, snow, and avalanche and their associated impacts to the County.
➢ The population of Plumas County is expected to slowly shrink as time progresses. Future population growth should be considered, as having more or less people in a community affects the overall hazard vulnerability to the County. Changes in populations patterns should also be considered. Especially vulnerable individuals to this hazard include older adults, children, outdoor workers, those below the poverty line and the unhoused. Planning for population changes will help to decrease the County’s overall vulnerability. Changes in population and population patterns may or may not increase the impacts and vulnerability of the County to this hazard depending on the location and nature of population growth and continued planning for future hazard conditions. ➢ Land use planning should be proactive to address future hazard conditions. County building codes are in effect to reduce this risk and should be updated as necessary to continue to address future freeze, extreme cold, and heavy snow conditions. In addition, structures should be built away from avalanche

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prone areas. Due to adherence to protective building codes, changes in land use and development will likely not increase the impacts and associated vulnerabilities of the County to this hazard.

Future Development
Future development built to code should be able to withstand extreme cold, freeze, and heavy snow. Future development should be built away from avalanche zones. Current building codes provide such provisions for new construction. Older buildings and infrastructure should be evaluated to ensure that extreme cold and freeze will not cause negative impacts. Future development considerations should be ongoing and proactive. Ensuring that comprehensive land use planning is conducted, regulatory requirements such as building codes are followed, and varying needs for different demographic groups that reside within the County are considered can help make for a more resilient community.

4.3.3. Severe Weather: Extreme Heat
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Plumas County Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; likelihood of future occurrence; and how climate change can affect or influence this hazard.

Hazard/Problem Description
According to information provided by FEMA, 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. Heat kills by taxing the human body beyond its abilities. In a normal year, about 175 Americans succumb to the demands of summer heat. 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.

Recently in California, records were set across the state during a July 2024 heat event. 2024 was considered the hottest on record. Extreme heat can also affect the agricultural industry. Extreme heat as it affects agriculture in Plumas County is discussed further in the agricultural hazards discussion in Section 4.3.6.

Heat disorders generally have to do with a reduction or collapse of the body’s ability to shed heat by circulatory changes and sweating or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds a level at which the body can remove it, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body’s inner core begins to rise, and heat-related illness may develop. Elderly persons, small children, those on certain medications or drugs, and persons with weight and alcohol problems are particularly susceptible to extreme heat.

Location and Extent
Extreme heat events occur on a regional basis. Extreme heat can occur in any location of the County. All portions of the County are at risk to extreme heat. Extreme heat occurs throughout the Planning Area primarily during the summer months. The WRCC and NWS maintain data on weather normal and extremes in the western United States. Each of these data sources maintain data in slightly different ways. Data from

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the WRCC stopped being collected in April of 2016. NWS covers the entire time period to present.

Therefore, both data sets are shown below. WRCC and NWS data for the County is summarized below.

Plumas County — WRCC Quincy Station, Period of Record 1896 to 2016 According to the WRCC, in Plumas County, monthly average maximum temperatures in the warmest months (May through October) range from the low-70s to the upper-80s. The highest recorded daily extreme was 110°F on both August 9, 1981, and September 5, 1988. In a typical year, maximum temperatures exceed 90°F on 45.3 days. Figure 4-40 shows the average daily high temperatures and extremes for the County. Table 4-35 shows the record high temperatures for the County.

Figure 4-40 Plumas County – Quincy Station (WRCC) Daily Temperature Averages and Extremes 1943 to 2016
Source: Western Regional Climate Center. Retrieved 3/19/2025 Table 4-35 Plumas County – Quincy Station (WRCC) Record High Temperatures 1943 to 2016 Month Record High Date Month Record High Date
January 74° 1/23/1918 July 109° 7/21/1994
February 80° 2/17/1920 August 110° 8/09/1981
March 85° 3/13/1910 September 110° 9/05/1988
April 89° 4/21/2006 October 98° 10/22/1988
May 100° 5/24/1992 November 86° 11/09/1990
June 105° 6/17/1895 December 76° 12/14/1921
Source: Western Regional Climate Center

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Plumas County—NWS Quincy Station, Period of Record 1895 to 2025 According to the NWS, monthly average maximum temperatures in the warmest months (May through October) range from the mid-70s to the low 90s. The highest recorded daily extreme was 111°F on August 6, 1994, and July 31, 1994. Figure 4-41 shows the average daily high temperatures and extremes for the County. Table 4-28 shows the record low temperatures for the County.

Figure 4-41 Plumas County – Quincy Station (NWS) Daily Temperature Averages and Extremes, 1991-2020
Source: National Weather Service XMAC site. Retrieved 3/12/2025 Table 4-36 Plumas County – Quincy Station (NWS) Record High Temperatures 1895 to 2025 Temperature Date
111.0° 8/6/1994
111.0° 7/31/1994
110.0° 8/7/1990
110.0° 9/5/1988
109.0° 8/9/1981
109.0° 7/11/2002
109.0° 7/21/1994
109.0° 8/8/1981
108.0° 8/3/1993
108.0° 8/12/1992
Source: National Weather Service XMAC site. Retrieved 3/12/2025

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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. Heat waves do not generally cause damage or elicit the immediate response of floods, fires, earthquakes, or other more “typical” disaster scenarios. While heat waves are obviously less dramatic, they are potentially deadlier. According to the 2018/2023 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.

The NWS has in place a system to initiate alert procedures (advisories or warnings) when extreme heat is expected to have a significant impact on public safety. The expected severity of the heat determines whether advisories or warnings are issued. The NWS HeatRisk forecast provides a quick view of heat risk potential over the upcoming seven days. The heat risk is portrayed in a numeric (0-4) and color (green/yellow/orange/red/magenta) scale which is similar in approach to the Air Quality Index (AQI) or the UV Index. This can be seen in Table 4-37.

Table 4-37 National Weather Service HeatRisk Categories Category Level Meaning
Green 0 No Elevated Risk
Yellow 1 Low Risk for those extremely sensitive to heat, especially those without effective cooling and/or adequate hydration
Orange 2 Moderate Risk for those who are sensitive to heat, especially those without effective cooling and/or adequate hydration
Red 3 High Risk for much of the population, especially those who are heat sensitive and those without effective cooling and/or adequate hydration
Magenta 4 Very High Risk for entire population due to long duration heat, with little to no relief overnight Source: National Weather Service
The NWS office in Sacramento or Reno can issue the following heat-related advisory as conditions warrant. ➢ Heat Advisories are issued during events where the HeatRisk is on the Orange/Red threshold (Orange will not always trigger an advisory)
➢ Excessive Heat Watches/Warnings are issued during events where the HeatRisk is in the Red/Magenta output
Past Occurrences
Disaster Declaration History
There have been no FEMA or Cal OES disasters related to extreme heat, as shown in Table 4-4. There have been no USDA disaster declarations for extreme heat.

NCDC Events
The NCDC data shows 7 extreme heat incidents for Plumas County since 1993. Information for these events are shown in Table 4-38.

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Table 4-38 NCDC Extreme Heat Events in Plumas County 1993 to 7/31/2024* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Excessive Heat 5 0 0 0 0 $0 $0
Heat 2 0 0 0 0 $0 $0
Total 7 0 0 0 0 $ 0 $ 0
Source: NCDC
*Deaths, injuries, and damages are for the entire event, and may not be exclusive to the County.

Hazard Mitigation Planning Committee Events
These section separates events since the 2019/2020 LHMPs and those before 2019.

Events since 2019/2020 LHMP
A member of the HMPC from Viera Ranch searched through records kept by the Ranch, and found the following extreme heat events:
➢ 2020 – In the month of June, from the 22nd to the 29th, high temperatures reached 101º to 104º. June 29 saw 101ºF. In the month of July, from the 15th to the 17th, temperatures reached 102º to 103ºF. In August 9th and 10th, temperatures reached 102º to 103ºF. ➢ June 2021 – In the second half of the month of June, temperatures reached as high as 103º-108º, the highest being on the 28th.
➢ July 6-9, 2021 – Seneca Health noted excessive heat during these days caused in influx of additional patients. Temperatures reached 103º-106ºF.
➢ August 29th of 2021 saw temperatures reached up to 101º F. ➢ September 9th and 10th of 2021 saw temperatures reached 101º- 102º F. ➢ 2022 - In January, temperatures reached odd heights, up to 60º-61º on the 13th, 28th, and 30th. In July, between the 27th and 30th, temperatures reached up to 101º-105ºF. In early September, the 5th-8th, temperatures reached up to 101º-105ºF.
➢ 2023 – In July, throughout various days between the 2nd and 22nd, temperatures reached 101º-106ºF.

In August, the heat trend continued from the 12th to the 16th, with temperatures reaching 103º-105ºF.

Seneca Health noted excessive heat during these days caused an influx of additional patients. ➢ 2024 - In July, from the 5th to the 20th, temperatures ranged from 101º-105º.

Events before 2019
A member of the HMPC from Viera Ranch searched through records kept by the Ranch, and found the following extreme heat events:
➢ 1999 – From July 6th to 10th, high temperatures ranged from 100°F to 103°F. On October 9th, daytime highs were at 92°F.
➢ 2002 – Multiple days saw very high temperatures. This includes July 9th – 104°F; July 10th – 108°F; July 11th – High 109°F; 8/14/2002 – 105°F; 8/15/2002 – 104°F; 8/16/2002 – 101°F. ➢ 2003 – Multiple days saw very high temperatures. This includes June 28th – 102°F, July 14th to 23rd – 100°F to 108°F, and July 28th to 30th – 102°F to 105°F.

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➢ 2006 – Multiple days saw very high temperatures. This includes June 20th to 24th – 101°F to 103°F, and July 17th to 25th – 100°F plus highs.
➢ 2007 – Multiple days saw very high temperatures. This includes July 4th to 6th – 101°F to 101°F. ➢ 2015 – Multiple days saw very high temperatures. This includes June 24th to 27th – 105°F to 108°F, and June 30th to July 2nd – 101°F to 105°F.
➢ 2016 – Multiple days saw very high temperatures. This includes July 14th – 102°F, July 23rd to 30th – 101°F to 108°F, and August 13th to 21st – 102°F to 107°F. ➢ 2017 – Multiple days saw very high temperatures. This includes June 19th to 23rd – 101°F to 106°F, and July 30th to August 2nd – 102°F to 110°F.
➢ 2018 – Multiple days saw very high temperatures. This includes July 18th – 101°F, July 19th – 103°F, July 25th – 102°F, July 26th – 104°F, and August 7th to 10th – High 10°F each day.

Likelihood of Future Occurrence
Highly Likely—Temperature extremes are likely to continue to occur annually in the Plumas County Planning Area. Temperatures at or above 90°F are common most summer days in the western portion of the County.

It is likely that climate change will increase the chance of future occurrence as well as future impacts. More information on climate change and extreme heat can be found in the next section. More information on future impacts can be found in the Future Conditions/Future Development section of the Vulnerability Assessment below.

Climate Change and Extreme Heat
Climate change and its effect on extreme heat in the County has been discussed by three sources:
➢ California Climate Adaptation Strategy (CAS) – 2021
➢ Climate Change and Health Profile Report –Plumas County ➢ Cal-Adapt
Climate Adaptation Strategy
The 2021 CAS (as well as the 2024 Draft CAS), citing a California Energy Commission study, states that “over the past 15 years, heat waves have claimed more lives in California than all other declared disaster events combined.” This study shows that California is getting warmer, leading to an increased frequency, magnitude, and duration of heat waves. These factors may lead to increased mortality from excessive heat, as shown in Figure 4-42.

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Figure 4-42 California Historical and Projected Temperature Increases – 1961 to 2099 Source: Dan Cayan; California Climate Adaptation Strategy As temperatures increase, California and Plumas County will face increased risk of death from dehydration, heat stroke, heat exhaustion, heart attack, stroke and respiratory distress caused by extreme heat. According to the 2021 CAS report (as well as the 2024 Draft CAS) and the 2023 State of California Hazard Mitigation Plan, by 2100, hotter temperatures are expected throughout the state, with projected increases of 3-5.5°F (under a lower emissions scenario) to 8-10.5°F (under a higher emissions scenario). These changes could lead to an increase in illnesses and deaths related to extreme heat in Plumas County.

Climate Change and Health Profile Report – Plumas County The Climate Change and Health Profile Report (CCHPR) noted for Plumas County that increased temperatures manifested as heat waves and sustained high heat days directly harm human health through heat-related illnesses (mild heat stress to fatal heat stroke) and the exacerbation of pre-existing conditions in the medically fragile, chronically ill, and vulnerable. Increased heat also intensifies the photochemical reactions that produce smog and ground level ozone and fine particulates (PM2.5), which contribute to and exacerbate respiratory disease in children and adults. Increased heat and carbon dioxide enhance the growth of plants that produce pollen, which are associated with allergies. Increased temperatures also add to the heat load of buildings in urban areas and exacerbate existing urban heat islands adding to the risk of high ambient temperatures.

Cal-Adapt
Cal Adapt also noted that overall temperatures are expected to rise substantially throughout this century.

During the next few decades, scenarios project average temperature to rise between 1 and 2.3°F; however, the projected temperature increases begin to diverge at mid-century so that, by the end of the century, the temperature increases projected in the higher emissions scenario (Representative Concentration Pathways (RCP) 8.5) are approximately twice as high as those projected in the lower emissions scenario (RCP 4.5).

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These projections also differ depending on the time of year and the type of measurement (highs vs. lows), all of which have different potential effects to the state's ecosystem health, agricultural production, water use and availability, and energy demand. Future temperature estimates from Cal-Adapt for the Plumas County Planning are shown in Figure 4-43. It shows the following:
➢ The upper chart shows the number of days in a year when daily maximum temperature is above the extreme heat threshold of 98.5°F. Data is shown for Plumas County under the RCP 8.5 scenario in which emissions continue to rise through 2050 and maintain that trend into 2100. ➢ The lower chart shows the number of days in a year when daily maximum temperature is above the extreme heat threshold of 98.5 °F. Data is shown for Plumas County under the RCP 4.5 scenario in which emissions show continued rise throughout 2050 with continued increasing patterns into 2100.

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Figure 4-43 Plumas County – Future Temperature Estimates in Low and High Emission Scenarios
Source: Cal-Adapt – Number of Extreme Heat Days by Year. Retrieved 2/10/2025.

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Vulnerability Assessment
Vulnerability—Medium
Extreme heat happens in Plumas County each year. Extreme heat may overload demands for electricity to run air conditioners and other utilities in homes and businesses during prolonged periods of exposure and presents health concerns to individuals outside in the temperatures. Extreme heat may also be a secondary effect of droughts or may cause drought-like conditions in a temporary setting. For example, several weeks of extreme heat increases evapotranspiration and reduces moisture content in vegetation, leading to higher wildfire vulnerability for that time period even if the rest of the season is relatively moist. Extreme heat, when combined with wind, can also lead to PSPS events in the County. Extreme heat also contributes to poor air quality during extended events.

Vulnerable populations are at the greatest risk to the effects of extreme heat. The Public Health Alliance has developed a composite index to identify cumulative health disadvantages in California. Factors such as those bulleted above were combined to show what areas are at greater risk to hazards like extreme heat.

The whole of the Planning Area has some measure of vulnerability to extreme heat. An assessment of a community’s vulnerability to this hazard begins with an understanding of local exposure to unincorporated Plumas County. This is included in the Local Concerns section below. After that, vulnerability is discussed in multiple sections that detail how this hazard can affect both the entire Plumas County Planning Area as well as the unincorporated portions of Plumas County. How the hazard affects the other participating jurisdictions can be found in their respective annexes to this LHMP Update. These sections below include assets at risk, impacts, and how future development can be affected by this hazard.

Local Concerns (unincorporated Plumas County)
The unincorporated County has specific concerns regarding this hazard. These concerns form a portion of the basis for the mitigation strategy and mitigation actions that seek to reduce risk and vulnerabilities to this hazard.

The County noted that extreme heat can cause crop damages. These can be substantial if extreme heat occurs during periods of plant susceptibility to heat. Extreme heat contributes to PSPS and wildfire issues in the County. Heat domes have settled over the County in the past, which has caused the County to open cooling centers. The County is also worried about the effects on vulnerable populations. It was also noted that extreme heat contributes to unhealthy air quality.

Local concerns for Portola and the Special Districts can be found under the Local Concerns heading in each respective jurisdictional annex to this LHMP Update.

Assets at Risk
Assets at risk from extreme heat include people and populations; structures; critical facilities and infrastructure; and natural, historic, and cultural resources. These are discussed in the following sections for both the Plumas County Planning Area and unincorporated Plumas County.

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Additionally, for each hazard in the FEMA NRI in Plumas County, the relevant portions of the hazard analysis done by FEMA is presented below. This includes the Hazard Risk Index Rating, Expected Annual Loss Values, Exposure Values, and the Historic Loss Ratio Rating. These are presented for the Plumas County Planning Area as a whole.

People and Populations
All populations within the Plumas County Planning Area are vulnerable to extreme heat, but it generally affects people spending large amounts of time outside or without means of cooling indoor structures.

During extended periods of high temperatures, extreme heat may overload the demands for electricity to run air conditioners and can present health concerns to individuals. When interruptions in power occur during extreme heat, the risk of heat related illnesses and deaths increase. Extreme heat is a significant concern to vulnerable populations. The unhoused; individuals who exercise or train outdoors; outdoor workers; individuals that lack the resources to afford heat; and the young, old, or medically fragile individuals that are more susceptible to heat related impacts. In addition to vulnerable populations, pets and livestock are at risk to extreme heat conditions.

Structures
Extreme heat normally does not generally impact structures, but individuals working in structures may be affected during periods of extended heat, especially in structures that might not be equipped with air conditioning or other means of cooling. In the Plumas County Planning Area, extreme heat has caused interruptions to power in the past. Also depending on the structure, sensitive contents such as IT equipment can be impacted, especially if a power outage occurs.

Critical Facilities and Infrastructure
Depending on their type and function, critical facilities and infrastructure can also be affected by extreme heat. Interruptions in power caused by extreme heat can lead to system failures. Schools without air conditioning may have to close or operate on a reduced schedule.

Natural, Historic, and Cultural Resources
Park areas and natural resource assets in the Plumas County Planning Area may be vulnerable during periods of extreme heat. These include turfed areas; landscapes, trees, wildlife and habitat areas, and wetlands and marsh lands. Recently, trees were lost in areas of Plumas County that were weakened by drought and extreme heat. Extreme heat may also cause drought-like conditions, contributing to other issues. For example, several weeks of extreme heat increases evapotranspiration and reduces moisture content in vegetation, leading to higher wildfire vulnerability in the region for that time period, even if the rest of the season is relatively moist. Historic and cultural resources are not expected to be affected by extreme heat.

FEMA NRI Hazard Vulnerability Assessment
FEMA’s NRI provides additional data on Plumas County’s vulnerability to Extreme Heat. The NRI contains data and analysis for 18 separate natural hazards. The NRI hazard related to Plumas County’s

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Extreme Heat is a heat wave. As shown in Table 4-39, heatwaves could cause a total of $8,162 in expected annual losses, with a historic loss rating of very low. Heat wave has a relatively low rating for social vulnerability and relatively high community resilience, with a risk index score of 23.8 out of 100.

According to the NRI, there have been 11 events on record between the years 2005-2021, with an average of 0.7 events per year.

Table 4-39 Plumas County Planning Area – Heat Wave Vulnerability Ratings from FEMA NRI
NRI Hazard Hazard Risk Index
Rating
Expected Annual
Loss Values
(total)**
Exposure Value
(total)***
Historic Loss Ratio
Rating
Heat Wave 23.8 $8,162 $237,469,807,133 Very low
Source: FEMA NRI Report
*Hazard Risk Index is calculated using data for only a single hazard type, and reflects a communities expected annual loss value, community risk factors, and the adjustment factor used to calculate the risk value. **Expected annual loss represents the average economic loss in dollars resulting from natural hazards each year. ***Exposure is a natural hazard consequence factor that is the representative value of buildings, populations, or agriculture potentially exposed to a natural hazard occurrence.

Additional information on the FEMA NRI can be found in Section 4.2 and Appendix H.

Impacts from Severe Weather: Extreme Heat
The County experiences temperatures in excess of 100°F during the summer and fall months. The temperature moves to 105-110°F in rather extreme situations. Health issues are the primary concern with this hazard with vulnerable populations at greater risk, although economic impacts can also be an issue.

Air quality can also be an issue during extreme heat.

During these times, drought conditions may worsen, and the Planning Area may see an increase in dry fuels contributing to wildfires. For example, several weeks of extreme heat increases evapotranspiration and reduces moisture content in vegetation, leading to higher wildfire vulnerability for that time period even if the rest of the season is relatively moist. Also power outage and PSPS events may occur during these times as well. Drought is discussed further in Section 4.3.9 and wildfire in Section 4.3.15.

Impacts to identified assets at risk to this hazard and the overall vulnerability of the County may be affected in the future by climate change (which was discussed in the hazard profile section above), changes in population patterns, and changes in land use and development. The influencing effects of these factors on this hazard are discussed further in the Future Conditions/Future Development discussion below.

Future Conditions/Future Development
This section provides a discussion of how future conditions will influence or affect the hazard over time and also discusses future development relative to each hazard.

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Future Conditions
Future conditions may be affected by climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development. Findings on this for Plumas County include the following:
➢ Climate change is likely to exacerbate future extreme heat conditions and associated impacts and vulnerability of the County.
➢ Future population growth should be considered, as having more or less people in a community affects the overall hazard vulnerability to the County. Population is expected to decrease for Plumas County and, as such, the vulnerability to this hazard may decrease. However, certain growing vulnerable populations such as the senior citizens population continues to rise within the communities of the County. Along with this, low income and the unhoused population are at risk to extreme heat which can put strain on emergency services and shelters. Changes in population and population patterns may or may not increase the impacts and vulnerability of the County to this hazard depending on the location and nature of growth and continued planning for future hazard conditions. ➢ Land use planning should be proactive to address future hazard conditions. County building codes are in effect to reduce this risk and should be updated as necessary to continue to address future extreme heat conditions. Due to adherence to protective building codes, changes in land use and development will likely not increase the impacts and associated vulnerabilities of the County to this hazard.

Future Development
Future development in the County will take extreme heat into account. Backup generators are currently in use at many County facilities, and additional generators and backup power sources are being sought for other locations. One way to reduce the negative impacts of an extreme heat event is to develop a comprehensive heat response plan that combines individual strategies into an integrated approach.

Components of such a plan might include forecasting and monitoring, education and awareness, and heat wave preparedness and response.

In addition to a comprehensive heat response plan, local officials can help areas adapt to extreme heat in the short-term by improving the resilience of infrastructure. Transportation planners can protect or modify roads, bridges, and other structures—for example, by using materials that are more resilient and heat tolerant—to help these systems withstand higher temperatures and reduce service disruptions. They can also implement energy efficiency and conservation efforts to reduce stress on electricity systems during heat waves and help avoid power outages.

Future development considerations should be ongoing and proactive. Ensuring that comprehensive land use planning is conducted, regulatory requirements such as building codes are followed, and varying needs for different demographic groups that reside within the County are considered can help make for a more disaster resilient community.

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4.3.4. Severe Weather: Heavy Rains and Storm
Hazard Profile
This hazard profile contains multiple sections that detail how this hazard can affect the Plumas County Planning Area. These sections include a hazard/problem description; description of location and extent; past occurrences of this hazard; likelihood of future occurrence; and how climate change can affect or influence this hazard.

Hazard/Problem Description
Storms in the Plumas County Planning Area occur throughout the Planning Area and are generally characterized by heavy rain often accompanied by strong winds and sometimes lightning and hail.

Approximately 10 percent of the thunderstorms that occur each year in the United States are classified as severe. A thunderstorm is classified as severe when it contains one or more of the following phenomena:
hail that is three-quarters of an inch or greater, winds in excess of 50 knots (57.5 mph), or a tornado. Heavy precipitation in the Plumas County area falls mainly in the fall, winter, and spring months.

Cloudburst storms can be expected in the spring, summer, and fall. Cloudburst storms, sometimes lasting as long as 6 hours in the study areas, are high intensity storms that can produce floods characterized by high peak flows, short-duration flood flows, and small runoff volume. In small drainage basins such as Portola Tributary, cloudbursts can produce peak flows substantially larger than those of general rainstorms.

Separate hazard descriptions and locations and extents are shown below for heavy rains and storms, hail, and lightning.

Heavy Rain and Storms
The NWS reports that storms and thunderstorms result from the rapid upward movement of warm, moist air. They can occur inside warm, moist air masses and at fronts. As the warm, moist air moves upward, it cools, condenses, and forms cumulonimbus clouds that can reach heights greater than 35,000 ft. As the rising air reaches its dew point, water droplets and ice form and begin falling the long distance through the clouds towards earth's surface. As the droplets fall, they collide with other droplets and become larger.

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

The County and the rest of California can also be affected by a phenomenon known as an atmospheric river.

According to the NOAA, atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow. This can be seen in Figure 4-44.

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Figure 4-44 Atmospheric Rivers
Source: NOAA
Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding. These events can disrupt travel, induce mudslides and cause catastrophic damage to life and property. A well-known example is the "Pineapple Express," a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.

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

While atmospheric rivers are responsible for great quantities of rain that can produce flooding, they also contribute to beneficial increases in snowpack. A series of atmospheric rivers fueled the strong winter storms that battered the U.S. West Coast from western Washington to southern California from Dec. 10– 22, 2010, producing 11 to 25 inches of rain in certain areas. These rivers also contributed to the snowpack in the Sierras, which received 75 percent of its annual snow by Dec. 22, the first full day of winter. Another example of this happened in 2022. Multiple atmospheric river storms occurred in the County and the rest of California. This can be seen in Figure 4-45. This also happened in the 2023 as well as in 2024, which can be seen in Figure 4-46 and Figure 4-47, respectively.

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Figure 4-45 2022 Atmospheric River Events
Source: Center for Western Weather and Water Extremes. Retrieved 12/18/2024.

Figure 4-46 2023 Atmospheric River Events
Source: Center for Western Weather and Water Extremes. Retrieved 12/18/2024.

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Figure 4-47 2024 Atmospheric Rivers
Source: Foxweather.com. Retrieved 12/18/2024.

Short-term, heavy storms can cause both widespread flooding as well as extensive localized drainage issues.

In addition to the flooding that often occurs during these storms, strong winds, when combined with saturated ground conditions, can down very mature trees.

Location and Extent of Heavy Rains and Storms
Heavy rains in Plumas County vary by season and location. Plumas County is located in the Northern portion of the Sierra Nevada region and has significant topographic variation, which causes it to experience a more severe and geographically variable winter climate (discussed in more detail in Section 4.3.2). The highest precipitation amounts are seen in the Western portion of the county where there is an orographic lift that forces air from low elevations to a higher elevation, quickly cooling down the air and raising the relative humidity to 100%. Under the right conditions orographic lifts create rain shadows where high amounts of precipitation are found on the crests of mountain ranges, but as the air descends to the leeward side of the mountain it warms and dries. In Plumas County the leeward side of the mountains represents the Eastern portion of the county where precipitation typically averages around two inches in the wettest months of the year. Areas west of the mountains, however, experience much higher precipitation levels.

For example, Bucks Creek averages nearly 12 inches per month in December and January as shown on Figure 4-48. Most of these rains occur during the winter months, as discussed below.

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Figure 4-48 Plumas County Average Annual Precipitation
Source: Plumas County GIS
There is no scale by which heavy rains are measured – usually it is measured in terms of rainfall amounts.

Magnitude of storms is measured often in rainfall and damages. The speed of onset of heavy rains can be short, but accurate weather prediction mechanisms often let the public know of upcoming events. Duration of thunderstorms in California is often short, ranging from minutes to hours. This can cause localized flooding, which is discussed in more detail in Section 4.3.12.

The WRCC and NWS maintain data on weather normal and extremes in the western United States. Each of these data sources maintain data in slightly different ways. Data from the WRCC stopped being collected in April of 2016. NWS covers the entire time period to present. Therefore, both data sets are shown below.

WRCC and NWS data for the County is summarized below.

Plumas County—WRCC Quincy Station Weather Station, Period of Record 1895 to 2016 According to the WRCC, average annual precipitation in Plumas County is 40.15 inches per year. The highest recorded annual precipitation is 68.87 inches in 1909; the highest recorded precipitation for a 24- hour period is 6.50 inches on March 18, 1907. The lowest recorded annual precipitation was 22.15 inches in 1949. Average monthly precipitation for Plumas County is shown in Figure 4-49. Daily average and extreme precipitations are shown in Figure 4-50.

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Figure 4-49 Plumas County—WRCC Monthly Average Total Precipitation Source: Western Regional Climate Center, www.wrcc.dri.edu/. Retrieved 4/12/2025.

Figure 4-50 Plumas County—WRCC Daily Average and Extreme Precipitation Source: Western Regional Climate Center, www.wrcc.dri.edu/. Retrieved 4/12/2025.

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Plumas County—NWS Quincy Station Weather Station, Period of Record 1895 to 2016 According to the NWS, average annual precipitation in Plumas County is 41.7 inches per year. Average monthly precipitation for Plumas County is shown in Figure 4-51. The highest recorded precipitation for a 24-hour period is 9.0 inches on December 31, 2004. One day extreme precipitations are shown on Table 4-40.

Figure 4-51 Plumas County— Quincy Station (NWS) Monthly Average Total Precipitation 1991 to 2020
Source: National Weather Service XMAC site. Retrieved 4/12/2025.

Table 4-40 Plumas County – Quincy Station (NWS) 24 Hour Rainfall Extremes from 1895 to 2025
Rainfall in Inches Date

9.00 12/31/2004

6.71 10/25/2021

6.50 3/18/1907

6.10 10/13/1962

5.33 12/22/1964

5.32 2/24/1904

5.30 3/17/1907

5.25 12/11/1937

5.17 12/11/1937

5.05 11/23/2024
Source: National Weather Service XMAC site. Retrieved 4/12/2025.

The NOAA Storm Prediction Center tracks thunderstorm watches on a county basis. Figure 4-52 shows thunderstorm watches in Plumas County and the United States for a 20-year period between 2004 and 2023.

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Figure 4-52 Plumas County – Average Thunderstorm Watches per Year (2004 to 2023) Source: NOAA Storm Prediction Center. Retrieved 3/5/2025.

Hail
Hail can occur throughout the Planning Area during storm events, though it is rare in the County. Hail is formed when water droplets freeze and thaw as they are thrown high into the upper atmosphere by the violent internal forces of thunderstorms. Hail is sometimes associated with severe storms within the Plumas County Planning Area. Hailstones are usually less than two inches in diameter and can fall at speeds of 120 miles per hour (mph). Severe hailstorms can be quite destructive, causing damage to roofs, buildings, automobiles, vegetation, and crops.

The NWS classifies hail by diameter size, and corresponding everyday objects to help relay scope and severity to the population. Table 4-41 indicates the hailstone measurements utilized by the NWS.

Table 4-41 Hailstone Measurements
Average Diameter Corresponding Household Object
.25 inch Pea
.5 inch Marble/Mothball
.75 inch Dime/Penny
.875 inch Nickel

1.0 inch Quarter

1.5 inch Ping-pong ball

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Average Diameter Corresponding Household Object

1.75 inch Golf-Ball

2.0 inch Hen Egg

2.5 inch Tennis Ball

2.75 inch Baseball

3.00 inch Teacup

4.00 inch Grapefruit

4.5 inch Softball
Source: National Weather Service
Location and Extent of Hail
Hail events can occur in any location of the County. All portions of the County are at risk to hail. Hail tends to be rare in California. There is no scale in which to measure hail, other than hail stone size as detailed above. The speed of onset of hail can be short, but accurate weather prediction mechanisms often let the public know of upcoming events. Duration of thunderstorms that can cause hail in California is often short, ranging from minutes to hours. Hail events last shorter than the duration of the total thunderstorm. The NWS tracks hail events. Figure 4-53 shows the average days each year where hail of greater than 1" in diameter occurred during a 20-year period from 1986 to 2015 (the most recent data available).

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Figure 4-53 Plumas County – Average Hail Days per Year (1986 to 2015) Source: National Weather Service. Retrieved 4/23/2025.

Lightning
Lightning can occur throughout the County during storm events. Lightning is defined by the NWS as any and all of the various forms of visible electrical discharge caused by thunderstorms. Thunderstorms and lightning are usually (but not always) accompanied by rain. Cloud-to-ground lightning can kill or injure people by direct or indirect means. Objects can be struck directly, which may result in an explosion, burn, or total destruction. Or damage may be indirect when the current passes through or near an object, which generally results in less damage.

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

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

However, a large minority of flashes carry positive charge to earth. These positive flashes often occur during the dissipating stage of a thunderstorm's life. Positive flashes are also more common as a percentage

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of total ground strikes during the winter months. This type of lightning is particularly dangerous for several reasons. It frequently strikes away from the rain core, either ahead or behind the thunderstorm. It can strike as far as 5 or 10 miles from the storm in areas that most people do not consider to be a threat (see Figure 4-54). Positive lightning also has a longer duration, so fires are more easily ignited. And, when positive lightning strikes, it usually carries a high peak electrical current, potentially resulting in greater damage.

Figure 4-54 Cloud to Ground Lightning
Source: National Weather Service
Location and Extent of Lightning
Lightning events can occur in any location of the County and are often associated with thunderstorms. All portions of the County are at risk to lightning. Lightning tends to be infrequent in the County, as discussed in the extent section below.

Lightning in the County can occur during thunderstorms. The speed of onset of thunderstorms that can cause lightning can be short, but accurate weather prediction mechanisms often let the public know of upcoming events. Duration of thunderstorms in California is often short, ranging from minutes to hours.

Thunderstorms and lightning are rare in the County. Lightning can also occur in the County outside of a thunderstorm event. Vaisala maintains the National Lightning Detection Network. It tracks cloud to ground lightning incidences in the United States. Figure 4-55 shows lightning incidences in the County and the rest of the United States from 2008 to 2017 (the most recent long term tracking map available). Figure 4-56 shows a more recent lightning density by county map.

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Figure 4-55 Plumas County – Lightning Incidence Map 2008 to 2017 Source: Vaisala National Lightning Detection Network. Retrieved 4/23/2025.

Figure 4-56 Plumas County – Average US Total Lightning Density per County 2015-2019 Source: Vaisala National Lightning Detection Network. Retrieved 4/23/2025.

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Past Occurrences
Disaster Declaration History
A search of FEMA and Cal OES disaster declarations turned up multiple events. Heavy rains and storms have caused flooding in the County. Events where flooding and heavy rains and storms resulted in a state or federal disaster declaration are shown in Table 4-42. More information on USDA disaster declarations from heavy rain and storms (once in 2016 and once in 2017) can be found in Table 4-51 in the Past Occurrences in Section 4.3.6.

Table 4-42 Plumas County – Disaster Declarations from Heavy Rain and Storms 1950-2025 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Flood (including heavy
rains and storms)
22 1950, 1955, 1958 (twice), 1964,
1963, 1964, 1969, 1970 1980,
1986, 1993, 1992*, 1995
(twice*), 1996, 1997, 2006, 2017
(twice*), 2023 (twice*)
19 1950, 1955, 1958 (twice), 1963,
1964, 1969, 1970, 1986, 1992
(twice), 1995 (twice), 1997,
2006*, 2017 (twice*), 2023
(twice*)
Source: FEMA, Cal OES
*indicates heavy rains and storms may have also caused landslide issues NCDC Events
The NCDC data recorded 132 hail and heavy rain weather incidents for Plumas County since 1950. Winter weather events tend to be more rain in the lower elevations of the County, while snow can fall in the upper elevations. No incidents of lightning were found in the NCDC database for the County. A summary of these events is shown in Table 4-43.

Table 4-43 NCDC Severe Weather Events in Plumas County 1950-7/31/2024* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Hail 10 0 0 0 0 $100 $5,000
Heavy Rain 60 0 0 0 0 $1,000 $0
Lightning 1 0 0 0 0 $0 $0
Winter Weather 61 0 0 0 0 $0 $0
Total 132 0 0 0 0 $1,100 $5,000
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of Plumas County Hazard Mitigation Planning Committee Events
These section separates events since the 2019/2020 LHMPs and those before 2019.

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Events since 2019/2020 LHMP
HMPC also noted the following events:
➢ 2019 – 2.65 inches of rain fell in the Quincy area on January 7th. Between the 15th and 17th of January, another 8.05 inches of rain fell. February 13th and 14th saw another 5.47 inches of rain fall. February 25th to 27th, 9.5 more inches or fain fell. March 26th saw 3.52 inches of rain. ➢ On September 5, 2019, quarter size hail was reported near Vinton. No injuries or deaths were reported.

Property damage occurred, but damage estimates were unavailable. ➢ 2020 – In the month of May on the 16th and 17th, 1.40” of rain was recorded for both days, totaling at

2.80”. On July 26. 1/2” hail was reported. On Aug 16 a lightning storm was reported. In the month of November on the 17-18, 2.25” first day and 2.62” the next. Dec 26. 1.30” of rain fell. ➢ 2021 – Dec 13. 4.03” of rain fell.
➢ 2022 – In April, inches worth of rain fell on the 16th, 19th, and 21st. Over an inch fell each day, resulting in a total of 4.59”. In December, two larger rain periods occurred. In the beginning of the month, a total of 5.03” fell. At the end of the month, an atmospheric river caused another 3.81” to fall. ➢ 2023 – In January, 15.92” fell between the 1st and the 15th. During the event period starting February 21st, 2023, through July 10th, 2023, the State of California experienced a series of atmospheric river events that brought heavy rains and high winds. The heavy rains saturated the ground, caused severe flooding throughout the State of California. An atmospheric river caused 2.5” of rain to fall on the County; only a few days after 86” of snow had fallen in the region. Plugged culverts caused damage to road surface, base and subbase. On November 18, 1.85” of rain fell. On December 19, 2.32” of rain fell.
➢ 2024 – In February, 1.90” of rain fell on the 5th. More rain fell on the 19th-20th, dropping a total of

4.57”. In March, an atmospheric river along with high winds impacted the County on the first two days. This rain event dropped a total of 4.53”. In May, alongside snowfall, 2.86” of rain fell on the County. In December, an atmospheric river during the 21st-23rd dropped a total of 13.92” of rain. ➢ 2025 – In August, lightning caused multiple fires to occur in Plumas National Forest. 29 fires were started by lightning. Fortunately, heavy rains followed the lightning event which kept the fires to a small burn area (the largest being 2.75 acres).

Events before 2019
In 1977 and 1981 there were lightning events that caused damages in the County.

A member of the HMPC from Viera Ranch searched through records kept by the ranch, and found the following heavy rain and storm events:
➢ November 6, 1994 – 4.2 inches of rain fell in the Quincy area. ➢ December 2, 1994 – 3.5 inches of rain fell in the Quincy area. ➢ From January 7th to 15th of 1995, 27.85 inches of rain fell in the Quincy area. This came after 3 inches of snow had fallen the previous two days.
➢ April 26, 1995, saw 4.1 inches of rain fall in the Quincy area. ➢ January 16th to 23rd 1999 – 7.85 inches of rain fell in the Quincy area. From February 6th to the 9th, another 10.3 inches of rain fell in the Quincy area.
➢ In early 2000, large amounts of rain fell. Between January 10th and 24th, 14.9 inches of rain fell in the Quincy area. From February 11th to 27th, another 13.7 inches fell.

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➢ July 10, 2001 – Portola had 2 inches of rain in 30 minutes. 4" of 1" diameter hail fell. Flash flooding occurred.
➢ December 2002 - 49.3 inches of rain and 21.5 inches of snow fell in the Quincy area. ➢ 2003 – 5.7 inches rain fell in Quincy on March 14th and 15th. Marble size hail was seen on June 23rd.

1.25 inches of rain fell in 3 hours on August 22nd. 3.25 inches and 3.4 inches fell on the 6th and 10th of December, respectively.
➢ June 8, 2004 – A thunderstorm with pea sized hail occurred in the Quincy area. ➢ 2006 - 5.8 inches rain fell on the 27th and 28th of February, and 5.33 inches fell on the 3rd and 4th of April.
➢ 2007 – between February 8th and 12th, 7.4 inches of rain fell. ➢ 2015 – 3.4 inches of rain fell in the Quincy area between February 5th and 7th. Trees were blown down, and power outages were reported.
➢ 2016 – Heavy rains fell in the Quincy area in both January and March. January saw 18.44 inches of rain, while March saw 18.24 inches of rain.
➢ 2017 – From January 7th to 22nd, 13.03 inches of rain fell in the Quincy area. Between February 1st and 11th, another 18.71 inches fell. April 7th says 3.72 inches of rain fall. 0.5-inch hail was reported on May 29th.
➢ 2018 – Between the 8th and 9th of January, 3.75 inches of rain fell.

The HMPC also noted some events of heavy rain and storm that caused agricultural impacts. Those are discussed in the Past Occurrences in Section 4.3.6. The HMPC also noted that Plumas County experience localized heavy rains yearly. Additionally, the County noted many of these past events are discussed in the Section 4.3.11 Flood: 1%/0.2% Annual Chance and Section 4.3.12 Flood: Localized Stormwater Flooding.

Likelihood of Future Occurrence
Highly Likely – Based on NCDC data and HMPC input, 131 heavy rain and storm incidents over a 75- year period (1950-2024) equates to a severe storm event every year. Severe weather is a well-documented seasonal occurrence that will continue to occur often in the Plumas County Planning Area.

It is likely that climate change will increase the chance of future occurrence as well as future impacts. More information on climate change and heavy rains and storms can be found in the next section. More information on future impacts can be found in the Future Conditions/Future Development section of the Vulnerability Assessment below.

Climate Change and Heavy Rains and Storms
According to the 2021 CAS (and 2024 Draft CAS), while average annual rainfall may increase or decrease slightly, the intensity of individual rainfall events is likely to increase during the 21st century. It is unlikely that hail will become more common in the County. The amount of lightning is not projected to change.

Cal-Adapt noted that, on average, the projections show little change in total annual precipitation in California. Furthermore, among several models, precipitation projections do not show a consistent trend during the next century. The Mediterranean seasonal precipitation pattern is expected to continue, with most precipitation falling during winter from North Pacific storms. One of the four climate models projects slightly wetter winters, and another projects slightly drier winters with a 10 to 20 percent decrease in total

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annual precipitation. However, even modest changes would have a significant impact because California ecosystems are conditioned to historical precipitation levels and water resources are nearly fully utilized.

Future precipitation estimates for the County are shown in Figure 4-57. ➢ The upper chart shows annual averages of observed and projected Precipitation values for the selected area on map under the RCP 4.5 scenario. The gray line (1950 – 2005) is observed data. The colored lines (2006 – 2100) are projections from 10 LOCA downscaled climate models selected for California.

The light gray band in the background shows the least and highest annual average values from all 32 LOCA downscaled climate models.
➢ The lower chart shows annual averages of observed and projected Precipitation values for the selected area on map under the RCP 8.5 scenario. The gray line (1950 – 2005) is observed data. The colored lines (2006 – 2100) are projections from 10 LOCA downscaled climate models selected for California.

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

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Figure 4-57 Plumas County– Future Precipitation Estimates: High and Low Emission Scenarios
Source: Cal-Adapt – Precipitation: Decadal Averages Map. Retrieved 2/10/2025.

Vulnerability Assessment
Vulnerability—Medium
According to historical hazard data, heavy rains and storms, including hail and lightning, are an annual occurrence in the Plumas County Planning Area. Heavy rains can cause both localized flooding and

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flooding in the floodplains. Atmospheric river storms, which have been more frequent in recent years, are of great concern as they can dump large amounts of water in single storms, or in back-to-back storms.

The whole of the Planning Area has some measure of vulnerability to heavy rains and storms, including hail and lightning. An assessment of a community’s vulnerability to this hazard begins with an understanding of local exposure to unincorporated Plumas County. This is included in the Local Concerns section below. After that, vulnerability is discussed in multiple sections that detail how this hazard can affect both the entire Plumas County Planning Area as well as the unincorporated portions of Plumas County. How the hazard affects the other participating jurisdictions can be found in their respective annexes to this LHMP Update. These sections below include assets at risk, impacts, and how future development can be affected by this hazard.

Local Concerns (unincorporated Plumas County)
The unincorporated County has specific concerns regarding this hazard. These concerns form a portion of the basis for the mitigation strategy and mitigation actions that seek to reduce risk and vulnerabilities to this hazard.

One of the primary concerns of the County to heavy rains and storms is the resulting flooding that occurs during extreme storm events. These include large flood events as detailed in the Flood: 1%/0.2% annual chance flood hazard section and the localized flooding that occurs following these storms. Localized flood problem areas in the unincorporated County are shown in Section 4.3.12. Downed trees, power outages, and agricultural impacts are also concerns.

With the increased growth of the area, the lack of adequate drainage systems has become an increasingly important issue.

Lightning in the County is also a concern due to the number of fires that are started by lightning strikes.

Wildfire is discussed in more detail in Section 4.3.15.

Local concerns for Portola and the Special Districts can be found under the Local Concerns heading in each respective jurisdictional annex to this LHMP Update.

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

Additionally, for each hazard in the FEMA NRI in Plumas County, the relevant portions of the hazard analysis done by FEMA is presented below. This includes the Hazard Risk Index Rating, Expected Annual Loss Values, Exposure Values, and the Historic Loss Ratio Rating. These are presented for the Plumas County Planning Area as a whole.

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People and Populations
All populations in the Plumas County Planning Area have some measure of risk to heavy rains and storms.

Those populations that work or recreate outside and unhoused individuals are more vulnerable to impacts from heavy storm events. Heavy rains and storms occur every year and do not generally cause significant adverse impacts to individuals; it is the secondary hazard, flooding, which poses the biggest impact to people. Populations at risk to flooding resulting from heavy rains and storm events include those who live in floodplains (discussed in further detail in the Flood: 1%/0.2% Annual Chance in Section 4.3.11) and those who live in and near localized flooding areas floodplains (discussed in further detail in the Flood:

Localized Stormwater Flooding in Section 4.3.12).

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

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

Many critical facilities are built to modern design standards that take heavy rains and storms into account when siting and building these structures, and others may need to be retrofitted to better withstand these events.

Natural, Historic, and Cultural Resources
Large storm events and associated flooding can affect natural, historic, and cultural resources. Silt and sediment can damage natural areas. Trees can be uprooted and downed by high winds. Extended periods of rainfall can erode natural banks along waterways and degrade soil stability for terrestrial species. While some natural systems can be adversely impacted during these large storms, heavy rain events can also provide benefits. Groundwater and wetland areas can be recharged, and water supplies replenished.

Historic and cultural resources may also be affected. Generally, the impacts are associated with damage to structures affected by large storm events, but other cultural resources such as those associated with Native Americans and old tribal areas can also be disturbed, damaged, and lost during extreme storm and flood events.

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FEMA NRI Hazard Vulnerability Assessment
FEMA’s NRI provides additional data on Plumas County’s vulnerability to Heavy Rains and Storms. The NRI contains data and analysis for 18 separate natural hazards. The NRI hazard related to Plumas County’s Heavy Rains and Storms are: hail and lightning. As shown in Table 4-44, hail could cause a total of $4,198 in expected annual losses, with a historic loss rating of relatively low. Lightning could cause a total of $77,248 in expected annual losses with a historic loss ratio rating of very high. Hail and lighting have a relatively low rating for social vulnerability and a relatively high community resilience, with a risk index score of 6.1 out of 100 for hail and 45.8 out of 100 for lightning. According to the NRI, there have been 5 hail events between the years 1986-2021 with an average of 0.1 events per year and 73 lightning events on record between the years 1991-2012, with an average of 3.3 events per year.

Table 4-44 Plumas County Planning Area – Hail and Lightning Vulnerability Ratings from

FEMA NRI
NRI Hazard Hazard Risk Index
Rating
Expected Annual
Loss Values
(total)**
Exposure Value
(total)***
Historic Loss Ratio
Rating
Hail 6.1 $4,198 $237,469,962,102 Relatively low
Lightning 45.8 $77,248 $237,458,956,144 Very high
Source: FEMA NRI Report
*Hazard Risk Index is calculated using data for only a single hazard type, and reflects a communities expected annual loss value, community risk factors, and the adjustment factor used to calculate the risk value. **Expected annual loss represents the average economic loss in dollars resulting from natural hazards each year. ***Exposure is a natural hazard consequence factor that is the representative value of buildings, populations, or agriculture potentially exposed to a natural hazard occurrence.

Additional information on the FEMA NRI can be found in Section 4.2 and Appendix H.

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

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

Actual damage associated with the primary effects of severe storms and heavy rains has been somewhat limited. It is the secondary hazards caused by these severe weather events, such as floods, landslides, and erosion that have had the greatest impact on the Planning Area. The risk and vulnerability associated with these secondary hazards are discussed in other sections of this Plan (Section 4.3.11 Flood: 100/500-year, Section 4.3.12 Flood: Localized Stormwater – specifically in the localized flood areas shown on the tables in the Local Concerns section, Section 4.3.8 Dam Failure, and Section 4.3.13 Landslide.

Impacts to identified assets at risk to this hazard and the overall vulnerability of the County may be affected in the future by climate change (which was discussed in the hazard profile section above), changes in

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population patterns, and changes in land use and development. The influencing effects of these factors on this hazard are discussed further in the Future Conditions/Future Development discussion below.

Future Conditions/Future Development
This section provides a discussion of how future conditions will influence or affect the hazard over time and also discusses future development relative to each hazard.

Future Conditions
Future conditions may be affected by climate change, changes in population patterns (migration, density, or the makeup of socially vulnerable populations), and changes in land use and development. Findings on this for Plumas County include the following:
➢ Climate change is likely to exacerbate future heavy rain and storm conditions and associated impacts and vulnerability of the County to flooding.
➢ Future population growth should be considered as having more or less people in a community affects the overall hazard vulnerability to the County. Population is expected to decrease slowly for Plumas County; however, the vulnerability may change depending on changes to the makeup of more vulnerable populations. Certain vulnerable populations, such as the unhoused, outdoor workers, and others could experience disproportional effects from this hazard. and should be addressed as the County continues to grow. Thus, changes in population and population patterns may or may not increase the impacts and vulnerability of the County to this hazard depending on the location and nature of growth and continued planning for future hazard conditions.
➢ Land use planning should be proactive to address future hazard conditions. Changes in land use may also amplify the impacts of heavy rains and storms, as additional impervious surfaces can cause additional runoff and localized flooding throughout the County. Building codes in the County ensure that new development is built to current building standards, which should reduce the risk to future development in the County from heavy rains and storms. New critical facilities such as communications towers and others should be built to withstand hail damage, lightning, and thunderstorm winds. With adherence to development standards, changes in land use and development will not likely increase the impacts and associated vulnerabilities of the County to this hazard.

Future Development
Future development considerations should be ongoing and proactive. Ensuring that comprehensive land use planning is conducted, regulatory requirements, such as building codes, are followed, and varying needs for different demographic groups with intersecting identities that reside within the County are considered can help make for a more resilient community.

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

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past occurrences of this hazard; likelihood of future occurrence; and how climate change can affect or influence this hazard.

Hazard/Problem Description
High Winds
High winds, often accompanying severe storms and thunderstorms, can cause significant property and crop damage, threaten public safety, and have adverse economic impacts from business closures and power loss.

High winds, as defined by the NWS glossary, are sustained wind speeds of 40 mph or greater lasting for 1 hour or longer, or winds of 58 mph or greater for any duration. These winds may occur as part of a seasonal climate pattern or in relation to other severe weather events such as thunderstorms.

Straight-line winds may also exacerbate existing weather conditions by increasing the effect on temperature and decreasing visibility due to the movement of particulate matters through the air, as in dust and snowstorms. The winds may also exacerbate fire conditions by drying out the ground cover, propelling fuel around the region, and increasing the ferocity of exiting fires. These winds may damage crops, push automobiles off roads, damage roofs and structures, and cause secondary damage due to flying debris.

A special type of wind event can occur in the County. Microbursts have occurred in the County. According to the NWS, a microburst is a downdraft (sinking air) in a thunderstorm that is less than 2.5 miles in scale.

Some microbursts can pose a threat to life and property, but all microbursts pose a significant threat to aviation. Although microbursts are not as widely recognized as tornadoes, they can cause comparable, and in some cases, worse damage than some tornadoes produce. In fact, wind speeds as high as 150 mph are possible in extreme microburst cases.

Another type of wind in the County is a foehn wind. A foehn wind is a type of dry down-slope wind that occurs in the lee (downwind side) of a mountain range. Winds of this type are called "snow-eaters" for their ability to make snow melt or sublimate rapidly. This snow-removing ability is caused not only by warmer temperatures, but also the low relative humidity of the air mass coming over the mountain(s). They are also associated with the rapid spread of wildfires, making some regions which experience these winds particularly fire prone. Burn patterns of almost all historic large wildfires in the County indicate they occurred during foehn winds. This is discussed in greater detail in the wildfire profile in Section 4.3.15.

Location and Extent
The entire Planning Area is subject to significant, non-tornadic (straight-line), winds. Each area of the County is at risk to high winds. Magnitude of winds is measured often in speed and damages. These events are often part of a heavy rain and storm event but can occur outside of storms. The speed of onset of winds can be short, but accurate weather prediction mechanisms often let the public know of upcoming events.

Duration of winds in California is often short, ranging from minutes to hours. The Beaufort scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. Figure 4-58 shows the Beaufort wind scale.

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Figure 4-58 Beaufort Wind Scale
Source: National Weather Service
Figure 4-59 depicts wind zones for the United States. The map denotes that Plumas County falls into Zone I, which is characterized by high winds of up to 130 mph. Portions of the County are also located in a special wind hazard region, which is a result of foehn winds (as discussed above).

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Figure 4-59 Wind Zones in the United States
Source: FEMA
Tornadoes
Tornadoes and funnel clouds can also occur during these types of severe storms. Tornadoes are another severe weather hazard that, though rare, can affect lower elevations within the Plumas County Planning Area, but most often in the lower elevation, and primarily occur during the storm season in the late fall and early spring. Tornadoes form when cool, dry air sits on top of warm, moist air. Tornadoes are rotating columns of air marked by a funnel-shaped downward extension of a cumulonimbus cloud whirling at destructive speeds of up to 300 mph, usually accompanying a thunderstorm. Tornadoes are the most powerful storms that exist. They can have the same pressure differential across a path only 300 yards wide or less as 300-mile-wide hurricanes. Figure 4-60 illustrates the potential impact and damage from a tornado.

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Figure 4-60 Potential Impact and Damage from a Tornado
Source: FEMA: Building Performance Assessment: Oklahoma and Kansas Tornadoes Location and Extent
Tornadoes, while rare, can occur lower elevation locations in the County, but most often occur in the lower elevations.

Prior to February 1, 2007, tornado intensity was measured by the Fujita (F) scale. This scale was revised and is now the Enhanced Fujita scale. Both scales are sets of wind estimates (not measurements) based on damage. The new scale provides more damage indicators (28) and associated degrees of damage, allowing for more detailed analysis and better correlation between damage and wind speed. It is also more precise because it considers the materials affected and the construction of structures damaged by a tornado. Table 4-45 shows the wind speeds associated with the original Fujita scale ratings and the damage that could result at different levels of intensity. Table 4-46 shows the wind speeds associated with the Enhanced Fujita Scale ratings.

Table 4-45 Original Fujita Scale
Fujita (F)
Scale
Fujita Scale Wind
Estimate (mph)
Typical Damage
F0 < 73 Light damage. Some damage to chimneys; branches broken off trees; shallowrooted trees pushed over; sign boards damaged.

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

F2 113-157 Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

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Fujita (F)
Scale
Fujita Scale Wind
Estimate (mph)
Typical Damage
F3 158-206 Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.

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

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

Source: National Oceanic and Atmospheric Administration Storm Prediction Center, www.spc.noaa.gov/faq/tornado/f-scale.html Table 4-46 Enhanced Fujita Scale
Enhanced Fujita (EF) Scale Enhanced Fujita Scale Wind Estimate (mph) EF0 65-85
EF1 86-110
EF2 111-135
EF3 136-165
EF4 166-200
EF5 Over 200
Source: National Oceanic and Atmospheric Administration Storm Prediction Center, www.spc.noaa.gov/faq/tornado/ef-scale.html It is difficult to predict a tornado or the conditions that preclude a tornado far in advance. Tornadoes can strike quickly with very little warning. In California it is rare for tornadoes to exceed EF3 magnitude. Most tornadoes that touch down are not long lived and cause limited damages.

Past Occurrences
Disaster Declaration History
There have been no past federal or state disaster declarations due to high winds or tornadoes, according to Table 4-4. There was one USDA Secretarial Disaster Declaration for high winds from 2016, which can be found in Table 4-51 in Section 4.3.6 below.

NCDC Events
The NCDC data recorded 94 high wind and no tornado incidents for Plumas County since 1950. A summary of these events is shown in Table 4-47.

Table 4-47 NCDC High Wind and Tornado Events in Plumas County 1950-7/31/2024 Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
High Wind 88 0 0 1 0 $2,245,500 $0
Strong Wind 4 0 0 0 0 $63,300 $0

Plumas County 4-143
Local Hazard Mitigation Plan Update
January 2026
Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Thunderstorm Wind 2 0 0 0 0 $675,000 $0
Total 94 0 0 1 0 $2,983,800 $ 0
Source: NCDC
Hazard Mitigation Planning Committee Events
These section separates events since the 2019/2020 LHMPs and those before 2019.

Events since 2019/2020 LHMP
The County noted that high winds are an annual occurrence, with varying levels of damages. An event occurred in the winter of 2022/2023. That event caused damages in the County. It occurred during a winter weather event. More information on that event can be found in the Past Occurrences in Section 4.3.2.

Events before 2019
HMPC also noted the following events:

In 2002, a microburst occurred in Plumas County. This caused large amounts of damage throughout the County. In all, 122 buildings were damaged. 32 had minor damage, 40 had moderate damage, and 50 had severe damage. Damages to a motel from this event can be seen in Figure 4-61. Total initial damage estimates in the County exceeded $3 million.

Plumas County 4-144
Local Hazard Mitigation Plan Update
January 2026
Figure 4-61 Damage to Motel from Tree Felled during Microburst in 2002 Source: Plumas County
December 10, 1995 – A member of the HMPC from Viera Ranch noted gale force winds. The Ranch lost parts of the well house roof. Other damages were reported in Quincy.

July 11, 2002 – After a day with 109°F highs, a microburst occurred in Quincy. Damage estimates were unavailable. No injuries or deaths were reported.

February 5th to 7th, 2015 – Heavy rains were accompanied by high winds. Gusts over 45 mph were recorded. Many trees were blown down, and power lines were downed.

July 3, 2015 – The Lake Almanor area was hit with high winds. Wind which toppled trees seemed to cause the biggest losses (in terms of cost). Figure 4-62 shows a house suffering the most damage located on the Lake Almanor peninsula. Based only on observations, this looks to be significant damage and could total $250,000 by itself. Two other houses were damaged on the west shore, but these were much less significant perhaps totaling $75,000. Three vehicles were damaged including a Sheriff Deputy patrol car. Total replacement cost could be another $100,000. Many residents suffered mud and debris problems in yards and driveways, but these were not always reported and not easy to tally for damage estimates. A few of the larger incidents may total $100,000, bringing the total for the event just over $500,000.

Plumas County 4-145
Local Hazard Mitigation Plan Update
January 2026
Figure 4-62 Plumas County – 2015 Wind Event Damage

Plumas County 4-146
Local Hazard Mitigation Plan Update
January 2026
January 7th and 8th, 2017 – Heavy rains and winds caused issues in the County. 6.12 inches of rain fell and were accompanied by high winds. This knocked out power in areas of the County.

Likelihood of Future Occurrence
Highly Likely/Unlikely– Based on NCDC data and HMPC input, 94 wind and tornado incidents over a 74-year period (1950-2024) equates to a severe wind event every year. High winds are a well-documented seasonal occurrence that will continue to occur annually in the Plumas County Planning Area. Tornadoes tend to be rare in the County and warrant a likelihood of future occurrence rating of unlikely.

Climate change may increase the chance of future occurrence as well as future impacts. More information on climate change and high winds and tornadoes can be found in the next section. More information on future impacts can be found in the Future Conditions/Future Development section of the Vulnerability Assessment below.

Climate Change and High Winds
According to the 2021 CAS (as well as the 2024 Draft CAS), while average annual rainfall may increase or decrease slightly, the intensity of individual thunderstorm wind events is likely to increase during the 21st century. This may bring stronger thunderstorm winds. The CAS does not discuss non-thunderstorm winds.

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

The whole of the Planning Area has some measure of vulnerability to high winds and tornadoes. An assessment of a community’s vulnerability to this hazard begins with an understanding of local exposure to unincorporated Plumas County. This is included in the Local Concerns section below. After that, vulnerability is discussed in multiple sections that detail how this hazard can affect both the entire Plumas County Planning Area as well as the unincorporated portions of Plumas County. How the hazard affects the other participating jurisdictions can be found in their respective annexes to this LHMP Update. The sections below include assets at risk, impacts, and how future development can be affected by this hazard.

Local Concerns (unincorporated Plumas County)
The unincorporated County has specific concerns regarding this hazard. These concerns form a portion of the basis for the mitigation strategy and mitigation actions that seek to reduce risk and vulnerability to this hazard.