Agenda packet — Portola City Council, June 10, 2026 (part 4 of 14)

Plumas County 4-320
Local Hazard Mitigation Plan Update
January 2026
Assets at Risk
Assets at risk from 1% and 0.2% annual chance floods 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.

Methodology (Parcel and Structures)
The Planning Area has mapped FEMA DFIRMs with flood hazard areas. GIS was used to determine the possible impacts of flooding within the Planning Area and how the risk varies across the Plumas County Planning Area. The following methodology was utilized in determining assets at risk to the 1% annual chance flood event and 0.2% annual chance flood event.
2024 Plumas County Parcel/Assessor Data was used as the basis for the Plumas County inventory of parcels, values, and acres. Plumas County has a FEMA effective DFIRM dated 3/27/2024, which was obtained from FEMA’s National Flood Hazard Layer to perform the flood analysis. In some cases, there are parcels in multiple flood zones, such as Zone A, Zone X, or Shaded X. GIS was used to analyze the data. Since it is possible for any given parcel to intersect with multiple categories for purposes of this analysis, the most conservative (or highest risk) DFIRM flood zone that intersected each parcel was used to determine which flood zone to assign to each parcel. Once completed, the flood zone parcel layer was joined to the assessor data to determine the number of parcels and values falling within each DFIRM flood zone. Based on this approach, the flood zones for the Planning Area and unincorporated Plumas County were determined and further broken out by property use and included information on both land and improved values, personal property values, and estimated contents values. Improved parcels include those with improved structure values identified in the Plumas County Assessor’s database. The property use categories for the Plumas County Planning Area (derived from general plan property use descriptions) were used to develop estimated content replacement values (CRV) that are potentially at loss from hazards, using FEMA Hazus methodologies as previously described in Section 4.2. The CRVs were added to the land, improved parcel, and personal property values.

The parcels and associated values were segregated and analyzed in this fashion to determine parcels, structures, and values at risk to the flood hazard for the Plumas County Planning Area. This flood analysis can be misleading since multiple classes may fall within one polygon, and there are many large polygons throughout the County.

Methodology (Loss Estimate)
The loss estimate for flood is based on the total of improved and contents value. Only improved parcels and the value of their structure improvements were included in the flood loss analysis. The value of land is not included in the loss estimates as generally the land is not at loss to floods, just the value of

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Local Hazard Mitigation Plan Update
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improvements and structure contents. The land value is represented in the detailed flood tables but is primarily present to show the value of the land associated with parcels and leach flood zone.

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

Potential losses from flooding are related to a variety of factors including flood depth, flood velocity, building type, and construction. The percentage of damage is primarily related to the flood depth. FEMA’s flood benefit/cost module uses a simplified approach to model flood damage based on building type and flood depth. The values at risk in the flood analysis tables were refined by applying an average damage estimation of 20% of the total building value. The 20% damage estimate utilized FEMA’s Flood Building Loss Table based on an assumed average flood depth of 2 feet. The end result of this more refined flood hazard loss estimate analysis is an inventory of the numbers, types, and values of parcels subject to the flood hazard.

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

Plumas County Planning Area residents that live in the 1% and 0.2% annual chance floodplains are often the most vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to the Planning Area’s residential population residing within these hazard areas, the DFIRM flood zones were overlayed on the parcel layer and linked to the Assessor Data. Those residential parcel polygons that intersect the flood zones were counted and multiplied by the 2023 Census Bureau American Community Survey average household factors for each jurisdiction. This is shown in Table 4-85.

Table 4-85 Plumas County Planning Area – Improved Residential Parcels and Populations in FEMA DFIRM Flood Zones by Jurisdiction
Jurisdiction
1% Annual Chance 0.2% Annual Chance
Improved
Residential
Parcels
Population at
Risk
Improved
Residential
Parcels
Population at
Risk
City of Portola 36 82 0 0
Unincorporated County 1,497 3,578 680 1,625
Source: FEMA DFIRM 03/02/05, Plumas County 2024 Parcel/Assessor’s Data, 2023 US Census American Community Survey Average Household Size – City of Portola (2.29); Unincorporated Plumas County (2.39).

Structures
Results are presented here first for the Plumas County Planning Area and secondly for unincorporated County.

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Plumas County Planning Area
Certain structures in the Plumas County Planning Area are at risk of DFIRM flooding and primarily include those structures located within the 1% and 0.2% annual chance floodplains. GIS was used to determine the possible impacts of flooding on parcels and structures within the Planning Area. Table 4-86 shows parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), personal property values, content replacement values, and total values in the Planning Area. This is shown for the 1% and

0.2% annual chance flood zones, as well as for those properties that fall outside of the mapped FEMA DFIRM flood zones.

Table 4-86 Plumas County Planning Area – Count and Value of Parcels and Structures in FEMA DFIRM 1% and 0.2% Annual Chance Flood Zones by Jurisdiction Jurisdiction /
Flood Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola
1% Annual
Chance Flood
Hazard
136 50 $5,846,857 $23,227,628 $1,322,526 $20,717,340 $51,114,351

0.2% Annual
Chance Flood
Hazard
2 1 $137,332 $374,544 $0 $374,544 $886,420
Other Areas 1,505 970 $31,966,182 $127,648,862 $592,546 $73,550,325 $233,757,915 City of Portola
Total
1,643 1,021 $37,950,371 $151,251,034 $1,915,072 $94,642,209 $285,758,686 Unincorporated Plumas County
1% Annual
Chance Flood
Hazard
3,035 1,714 $436,754,330 $533,266,332 $68,252,298 $300,503,098 $1,338,776,058

0.2% Annual
Chance Flood
Hazard
943 787 $42,128,297 $144,725,179 $34,596,689 $91,002,831 $312,452,996 Other Areas 20,256 10,926 $1,186,112,101 $2,524,953,767 $38,678,576 $1,342,652,693 $5,092,397,137 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 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: FEMA 03/02/2005 DFIRM, Plumas County 2024 Parcel/Assessor Data *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone **This parcel count only includes those parcels in the 0.2% annual chance flood zone, exclusive of the 1% annual chance flood zone.

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

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Table 4-87 shows Planning Area loss estimates and improved values at risk by FEMA 1% and 0.2% annual chance flood zones. More detailed tables and discussions can be found in each jurisdiction’s respective annex to this Base Plan.

Table 4-87 Plumas County Planning Area – FEMA DFIRM Flood Loss Estimates Flood
Zone
Total
Parcel
Count
Imp.

Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value Loss
Estimate
Loss
Ratio
1% Annual
Chance
Flood
Hazard
3,171 1,764 $442,601,187 $556,493,960 69,574,824 $321,220,438 $947,289,222 $189,457,845 3.75%

0.2%
Annual
Chance
Flood
Hazard
945 788 $42,265,629 $145,099,723 $34,596,689 $91,377,375 $271,073,787 $54,214,758 1.07% Grand
Total
4,116 2,552 $484,866,816 $701,593,683 $104,171,513 $412,597,813 $1,218,363,009 $243,672,603 4.82% Source: FEMA 03/02/2005 DFIRM, Plumas County 2024 Parcel/Assessor Data *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone **This parcel count only includes those parcels in the 0.2% annual chance flood zone, exclusive of the 1% annual chance flood zone.

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

According to the information in Table 4-86 and Table 4-87, the Plumas County Planning Area has 1,764 improved parcels and roughly $947.3 million of structure and contents value in the 1% annual chance floodplain. There are an additional 788 improved parcels and roughly $271.1 million of structure and contents value in the 0.2% annual chance flood event. A loss ratio of 3.75% and 1.07% indicates that while the Plumas County Planning Area does have structural assets at risk to flood, the County should be able to effectively recover from a major flood event.

Unincorporated Plumas County
Numerous structures in unincorporated Plumas County are at risk of DFIRM flooding and primarily include those structures located within the 1% and 0.2% annual chance floodplains. GIS was used to determine the possible impacts of flooding on parcels and structures within the unincorporated County. Table 4-88 shows parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), personal property values, estimated content replacement values, and total values in the unincorporated County. This is shown for the detailed flood zones by 1% and 0.2% annual chance flood zones by property use, as well as for those properties that fall outside of the mapped FEMA DFIRM flood zones.

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Table 4-88 Unincorporated Plumas County – Count and Value of Parcels and Structures in Detailed FEMA DFIRM 1% and 0.2% Annual Chance Flood Zones by Property Use
Flood Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
1% Annual Chance Flood Hazard
Zone A
Agricultural 297 79 $38,287,431 $14,953,243 $1,997,675 $14,953,243 $70,191,592 Commercial 66 35 $9,813,026 $14,638,475 $1,748,420 $14,638,475 $40,838,396 Federal Lands 42 0 $0 $0 $0 $0 $0
Government 79 0 $0 $0 $0 $0 $0
Industrial 27 14 $2,357,231 $2,918,804 $0 $4,378,206 $9,654,241 Institutional 6 0 $0 $0 $0 $0 $0
Miscellaneous 2 0 $0 $0 $0 $0 $0
Recreational 39 28 $7,020,109 $9,854,924 $699,406 $9,854,924 $27,429,363 Residential 1,772 1,279 $346,035,966 $413,794,910 $5,541,684 $206,897,455 $972,270,015 ROW/Utilities 168 0 $0 $0 $0 $0 $0
Zone A Total 2,498 1,435 $403,513,763 $456,160,356 $9,987,185 $250,722,303 $1,120,383,607 Zone AE
Agricultural 16 4 $1,449,736 $601,029 $50,970 $601,029 $2,702,764 Commercial 38 28 $5,744,975 $13,653,796 $241,593 $13,653,796 $33,294,160 Government 14 0 $0 $0 $0 $0 $0
Industrial 12 9 $1,017,704 $2,587,779 $0 $3,881,669 $7,487,152 Residential 212 170 $14,823,192 $46,546,047 $57,234,227 $23,273,024 $141,876,490 ROW/Utilities 35 0 $0 $0 $0 $0 $0
Zone AE Total 327 211 $23,035,607 $63,388,651 $57,526,790 $41,409,517 $185,360,565 Zone AE: Regulatory Floodway
Agricultural 16 6 $1,308,547 $988,581 $74,000 $988,581 $3,359,709 Commercial 14 4 $1,403,253 $1,913,256 $658,482 $1,913,256 $5,888,247 Federal Lands 3 0 $0 $0 $0 $0 $0
Government 3 0 $0 $0 $0 $0 $0
Industrial 4 2 $406,737 $61,697 $0 $92,546 $560,980
Institutional 1 0 $27,886 $0 $0 $0 $27,886
Miscellaneous 1 0 $0 $0 $0 $0 $0
Residential 133 48 $6,412,558 $8,964,199 $5,841 $4,482,100 $19,864,698 ROW/Utilities 21 0 $0 $0 $0 $0 $0

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Flood Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Zone AE:

Regulatory
Floodway Total
196 60 $9,558,981 $11,927,733 $738,323 $7,476,482 $29,701,519 Zone AH
Government 1 0 $0 $0 $0 $0 $0
Residential 11 8 $645,979 $1,789,592 $0 $894,796 $3,330,367 ROW/Utilities 2 0 $0 $0 $0 $0 $0
Zone AH Total 14 8 $645,979 $1,789,592 $0 $894,796 $3,330,367 1% Annual
Chance Flood
Hazard Total
3,035 1,714 $436,754,330 $533,266,332 $68,252,298 $300,503,098 $1,338,776,058

0.2% Annual Chance Flood Hazard
Zone X (shaded)
Agricultural 2 1 $25,857 $574,148 $0 $574,148 $1,174,153 Commercial 103 90 $11,112,003 $27,549,347 $603,156 $27,549,347 $66,813,853 Government 9 0 $0 $0 $0 $0 $0
Industrial 21 12 $1,796,224 $2,900,367 $33,531,160 $4,350,551 $42,578,302 Institutional 9 4 $272,853 $3,356,253 $3,050 $3,356,253 $6,988,409 Residential 758 680 $28,921,360 $110,345,064 $459,323 $55,172,532 $194,898,279 ROW/Utilities 41 0 $0 $0 $0 $0 $0
Zone X
(shaded) Total
943 787 $42,128,297 $144,725,179 $34,596,689 $91,002,831 $312,452,996

0.2% Annual
Chance Flood
Hazard Total
943 787 $42,128,297 $144,725,179 $34,596,689 $91,002,831 $312,452,996 Other Areas
Zone X (unshaded)
Agricultural 570 21 $16,443,313 $6,917,572 $643,882 $6,917,572 $30,922,339 Commercial 585 371 $47,503,071 $101,167,535 $28,731,777 $101,167,535 $278,569,918 Federal Lands 85 0 $0 $0 $0 $0 $0
Government 299 0 $95,301 $0 $0 $0 $95,301
Industrial 74 47 $5,101,553 $9,957,202 $19,048 $14,935,803 $30,013,606 Institutional 64 35 $1,844,377 $10,579,916 $193,330 $10,579,916 $23,197,539 Miscellaneous 10 0 $0 $0 $0 $0 $0
Recreational 172 54 $9,503,364 $10,937,803 $1,114,080 $10,937,803 $32,493,050 Residential 13,414 8,787 $939,342,063 $2,161,874,103 $6,744,374 $1,080,937,052 $4,188,897,592 ROW/Utilities 660 0 $0 $0 $0 $0 $0

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Flood Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Zone X
(unshaded)
Total
15,933 9,315 $1,019,833,042 $2,301,434,131 $37,446,491 $1,225,475,681 $4,584,189,345 Zone D (unmapped)
Agricultural 409 7 $12,767,933 $945,072 $0 $945,072 $14,658,077 Commercial 47 28 $3,023,552 $5,422,003 $292,457 $5,422,003 $14,160,015 Federal Lands 87 0 $0 $0 $0 $0 $0
Government 194 0 $29,655 $0 $0 $0 $29,655
Industrial 2 1 $54,172 $23,684 $0 $35,526 $113,382
Miscellaneous 13 0 $9,591 $0 $0 $0 $9,591
Recreational 308 9 $1,666,675 $4,419,946 $638 $4,419,946 $10,507,205 Residential 3,124 1,566 $148,727,481 $212,708,931 $938,990 $106,354,466 $468,729,868 ROW/Utilities 139 0 $0 $0 $0 $0 $0
Zone D
(unmapped)
Total
4,323 1,611 $166,279,059 $223,519,636 $1,232,085 $117,177,013 $508,207,793 Other Areas
Total
20,256 10,926 $1,186,112,101 $2,524,953,767 $38,678,576 $1,342,652,693 $5,092,397,137 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: FEMA 03/02/2005 DFIRM, Plumas County 2024 Parcel/Assessor Data *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone **This parcel count only includes those parcels in the 0.2% annual chance flood zone, exclusive of the 1% annual chance flood zone.

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

Table 4-89 shows unincorporated Plumas County loss estimates and improved values at risk by FEMA 1% and 0.2% annual chance flood zones.

Table 4-89 Unincorporated Plumas County – FEMA DFIRM Flood Loss Estimates Flood
Zone
Total
Parcel
Count
Imp.

Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value Loss
Estimate
Loss
Ratio
1%
Annual
Chance
Flood
Hazard
3,035 1,714 $436,754,330 $533,266,332 $68,252,298 $300,503,098 $902,021,728 $180,404,346 3.6%

0.2%
Annual
Chance
943 787 $42,128,297 $144,725,179 $34,596,689 $91,002,831 $270,324,699 $54,064,940 1.1%

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Flood
Zone
Total
Parcel
Count
Imp.

Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value Loss
Estimate
Loss
Ratio
Flood
Hazard
Total 3,978 2,501 $478,882,627 $677,991,511 $102,848,987 $391,505,929 $1,172,346,427 $234,469,286 4.7% Source: FEMA 03/02/2005 DFIRM, Plumas County 2024 Parcel/Assessor Data *With respect to improve parcels within the floodplain, the actual structures on the parcels may not be located within the actual floodplain, may be elevated and or otherwise outside of the identified flood zone **This parcel count only includes those parcels in the 0.2% annual chance flood zone, exclusive of the 1% annual chance flood zone.

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

According to the information in Table 4-88 and Table 4-89, the unincorporated Plumas County has 1,714 improved parcels and roughly $902.0 million of structure and contents value in the 1% annual chance floodplain. There are an additional 787 improved parcels and roughly $270.3 million of structure and contents value in the 0.2% annual chance flood event. A loss ratio of 3.6% and 1.1% indicates that while the County does have structural assets at risk to flood, the County should be able to effectively recover from a major flood event.

Insurance Coverage, Claims Paid, and Repetitive Losses
Standard property insurance does not include flood coverage because of the relatively high risk. The NFIP provides flood insurance to residents in those communities that participate in the NFIP. Federal financial assistance requires the purchase of flood for structures located within a 1% annual chance floodplain – a requirement that affects nearly all mortgages financed through commercial lending institutions. Flood insurance is also recommended for all structures protected by levees, even if not mapped within a floodplain. Flood insurance promotion and outreach will be important moving forward to ensure these vulnerable structures are adequately insured and protected.

Unincorporated Plumas County joined the NFIP on September 24, 1984. The County does not participate in the Community Rating System (CRS). NFIP insurance data provided by CA DWR indicates that as of December 2, 2024, there were 93 policies in force in the unincorporated County, resulting in $61,661,100 of insurance in force. There have been 59 closed paid losses totaling $1,099,373.04. Of these losses, 46 were parcels in A zones and 12 parcels were in B, C, or X zone, with 1 claim unknown. Of the 59 claims, 52 claims were associated with pre-FIRM structures and 6 with post-FIRM structures, with 1 claim unknown. There have been 4 repetitive loss (RL) structures, and 0 severe repetitive loss (SRL) structures in the County. There have been 9 substantial damage claims since 1978. There has been 1 Increased Cost of Compliance (ICC) loss totaling $0.

Based on this analysis of insurance coverage, unincorporated Plumas County has significant values at risk to the 1% annual chance and greater floods. Of the 1,505 improved parcels within the 1% annual chance flood zone, only 93 (or 6.2 percent) of those parcels maintain flood insurance. This can be seen on Table 4-90, along with insurance information from City of Portola.

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Table 4-90 Plumas County Planning Area – Percentage of Policy Holders to Improved Parcels in the 1% Annual Chance Floodplain
Jurisdiction Improved Parcels in
SFHA (1% Annual
Chance) Floodplain*
Insurance Policies
in the SFHA (1%
Annual Chance)
Floodplain
Percentage of 1%
Annual Chance
Floodplain Parcels
Currently Insured
City of Portola 36 1 2.8%
Unincorporated Plumas County 1,505 93 6.2%
Source: FEMA 03/02/2005 DFIRM, FEMA CIS 2024, Plumas County 2024 Parcel/Assessor’s Data FEMA also supplied data from their PIVOT database, which provides property use information specific to the RL and SRL properties. However, according to FEMA, there is a discrepancy between CIS and the PIVOT database on numbers of RL and SRL properties based on how information is transferred between systems. According to the PIVOT database, there are 3 RL properties and 1 SRL properties in the unincorporated County. This can be seen for all communities on Table 4-91. FEMA’s CIS data does not include searchable information on property use for RL and SRL properties.

Table 4-91 Plumas County Planning Area – RL and SRL Properties and their Status Jurisdiction RL Properties SRL Properties
City of Portola 0 0
Unincorporated Plumas County
Single-family dwelling 3 1
Source: FEMA, PIVOT, 3/24/2025
Critical Facilities and Infrastructure
Flooding presents a threat to critical facilities and infrastructure, and community lifelines. Critical facilities and infrastructure play an immensely important role in our communities. As previously noted, communities rely on roads, rail corridors, and related biking and pedestrian routes for transportation, and on critical infrastructure for drinking water, wastewater service, and draining streets of rainwater. Other utilities play an important role in providing critical services to area residents. Fire, police and other emergency response facilities and functions are also critical to the wellbeing of the community and the ability to respond and recover from hazard events, such as floods. Damage to any one of these systems can threaten public safety, wreak havoc on daily life, impact properties far from flood zones, and result in economic impacts that cascade throughout California. The following GIS analysis identifies critical facilities and infrastructure at risk to 1% and 0.2% annual chance flooding.

A separate analysis was performed on the critical facility inventory in the Plumas County Planning Area to determine critical facilities in the 1% and 0.2 annual chance flood zones. Using GIS, the DFIRM flood zones were overlayed on the critical facility GIS layer. Figure 4-142 shows critical facilities and the detailed DFIRM flood zones (with the inset maps shown). These inset maps are shown in Figure 4-143 through Figure 4-145. Table 4-92 details critical facilities in detailed DFIRM flood zones by facility type and count for the Plumas County Planning Area broken out by jurisdiction. Details of critical facilities by type, name, and address by flood zone are listed in Appendix G.

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As shown on these tables, 3 critical facilities in the City of Portola fall in the 1% annual chance flood zone; 111 and 27 critical facilities in the unincorporated County fall in the 1% and 0.2% annual chance flood zone, respectively; and 2 and 1 of the critical facilities in the surrounding counties fall in the 1% and 0.2% annual chance flood zone, respectively.

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Figure 4-142 Plumas County Planning Area – Critical Facilities in DFIRM Flood Zones (Overview Maps with Insets)

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Figure 4-143 Plumas County Planning Area – Critical Facilities in DFIRM Flood Zones (Map Inset 1)

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Figure 4-144 Plumas County Planning Area – Critical Facilities in DFIRM Flood Zones (Map Inset 2)

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Figure 4-145 Plumas County Planning Area – Critical Facilities in DFIRM Flood Zones (Map Inset 3)

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Table 4-92 Plumas County Planning Area – Critical Facilities in Detailed DFIRM Flood Zones by Jurisdiction and Critical Facility Category
Jurisdiction / Flood Zone Critical Facility Category Facility Count Portola
1% Annual Chance Flood Hazard
Essential Services Facilities 2
At Risk Populations Facilities 1
Hazardous Materials Facilities 0
1% Annual Chance Total 3
Other Areas
Essential Services Facilities 14
At Risk Populations Facilities 7
Hazardous Materials Facilities 0
Other Areas Total 21
Portola Total 24
Unincorporated Plumas County
1% Annual Chance Flood Hazard
Essential Services Facilities 111
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
1% Annual Chance Flood Hazard Total 111

0.2% Annual Chance Flood Hazard
Essential Services Facilities 26
At Risk Populations Facilities 0
Hazardous Materials Facilities 1

0.2% Annual Chance Flood Hazard Total 27
Other Areas
Essential Services Facilities 692
At Risk Populations Facilities 33
Hazardous Materials Facilities 3
Other Areas Total 728
Unincorporated Plumas County Total 866
Unincorporated Butte County
Other Areas
Essential Services Facilities 4
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Other Areas Total 4
Unincorporated Butte County Total 4
Unincorporated Lassen County
1% Annual Chance Flood Hazard
Essential Services Facilities 2
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
1% Annual Chance Flood Hazard Total 2

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Jurisdiction / Flood Zone Critical Facility Category Facility Count

0.2% Annual Chance Flood Hazard
Essential Services Facilities 1
At Risk Populations Facilities 0
Hazardous Materials Facilities 0

0.2% Annual Chance Flood Hazard Total 1
Other Areas
Essential Services Facilities 31
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Other Areas Total 31
Unincorporated Lassen County Total 34
Unincorporated Sierra County
Other Areas
Essential Services Facilities 4
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Other Areas Total 4
Unincorporated Sierra County Total 4
Unincorporated Tehama County
Other Areas
Essential Services Facilities 2
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Other Areas Total 2
Unincorporated Tehama County Total 2
Grand Total 934
Source: FEMA 3/2/2005 DFIRM, Plumas County GIS
Natural, Historic, and Cultural Resources
Large flood events can affect natural, historic, and cultural resources. There are a number of ways floodwaters can impact natural resources and the environment: Wildlife habitats can be destroyed by floodwaters. Contaminated floodwater can pollute rivers and habitats. Silt and sediment can destroy natural areas. Riverbanks and natural levées can be eliminated as rivers reach bankfull capacity. Rivers can be widened, and deposition can increase downstream. Trees can be uprooted by high-velocity water flow.

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

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FEMA NRI Hazard Vulnerability Assessment
The HMPC looked at the FEMA NRI for additional specific data on Plumas County’s vulnerability to Flood: 1%/0.2% annual chance and Flood: Localized Flooding. The NRI contains data and analysis for 18 separate natural hazards. The NRI hazard related to Plumas County’s Flood: 1%/0.2% annual chance and Flood: Localized Flooding is riverine flooding. As shown in Table 4-93, riverine flooding could cause a total of $1,910,839 in expected annual losses, with a historic loss rating of relatively moderate. Riverine flooding has a relatively low rating for social vulnerability and relatively high community resilience, with a risk index score of 85.9 out of 100. According to the NRI, there have been 11 riverine flooding events between the years 1996-2019 with an average of 0.5 events per year.

Table 4-93 Plumas County Planning Area – Riverine Flooding Vulnerability Ratings from

FEMA NRI
NRI Hazard Hazard Risk Index
Rating
Expected Annual
Loss Values
(total)**
Exposure Value
(total)***
Historic Loss Ratio
Rating
Riverine Flooding 85.9 $1,910,839 $8,960,873,982 Relatively moderate 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 Flood: 1% and 0.2% Annual Chance Flood
Floods are among the costliest natural disasters in terms of human hardship and economic loss nationwide.

Large flood events, including those associated with 1% and 0.2% annual chance floods, can cause substantial damage to structures, landscapes, and utilities as well as life safety issues. People may be swept away in floodwaters, causing injuries or deaths. Floods can be extremely dangerous, and even six inches of moving water can knock over a person given a strong current. During a flood, people can also suffer heart attacks or electrocution due to electrical equipment short outs. Direct impacts, such as drowning, can be limited with adequate warning and public education about what to do during floods. Floodwaters can transport large objects downstream which can damage or remove stationary structures. Structures can be damaged directly from floodwaters and can also be damaged from trees falling as a result of water-saturated soils. Ground saturation can result in instability, collapse, or other damage. Objects can also be buried or destroyed through sediment deposition. Floodwaters can also break utility lines and interrupt services causing power outages. The interruption of power causes major problems and can result in the closure of governmental offices and community businesses. Public schools may also be required to close or be placed on a delayed start schedule. Roads can be damaged and closed, causing safety and evacuation issues.

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

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Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure, utilities, and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Significant economic impact (jobs, sales, tax revenue) to the community; and ➢ Negative impact on commercial and residential property values Health Hazards from Flooding
Certain health hazards are also common to flood events. While such problems are often not reported, three general types of health hazards accompany floods. The first comes from the water itself. Floodwaters carry anything that was on the ground that the upstream runoff picked up, including dirt, oil, animal waste, and lawn, farm and industrial chemicals. Pastures and areas where cattle, hogs, and other livestock are kept or their wastes are stored can contribute polluted waters to the receiving streams.

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

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

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

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

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.

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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 flood conditions and associated impacts and vulnerability of the County to 1% and 0.2% annual chance flooding.
➢ Population in Plumas County is expected to decrease. Additional growth within the flood-risk areas of the County would place additional populations at risk to flooding. Additional population growth would likely bring continued diversity to the County. Vulnerable population groups could face disproportionate effects from a flood and should be planned for. 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. Locating new development, structures and critical facilities and infrastructure within or near areas of flood risk may put additional development at risk. However, County building codes and the County’s floodplain ordinance are in effect to reduce this risk and should be updated as necessary to continue to address future flood conditions. Depending on the location of new development and adherence to protective building codes and the floodplain ordinance, changes in land use and development may or may not increase the impacts and associated vulnerabilities of the County to this hazard.

This section discusses considerations in evaluating future flooding conditions and also provides an analysis of the flood hazard and proposed future development within the County based on FEMA floodplains.

Future Development: General Considerations
Communities that participate in the NFIP adopt regulations and codes that govern development in special flood hazard areas (SFHAs) and enforce those requirements through their local floodplain management ordinances through the issuance of permits. Plumas County’s floodplain management ordinance provides standards for development, subdivision of land, construction of buildings, and improvements and repairs to buildings that generally meet the minimum requirements of the NFIP.

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The International Residential Code (IRC) and International Building Code (IBC), by reference to ASCE 24, include requirements that govern the design and construction of buildings and structures in flood hazard areas. FEMA has determined that the flood provisions of the I-Codes are consistent with the requirements of the NFIP (the I-Code requirements shown either meet or exceed NFIP requirements). ASCE 24, a design standard developed by the American Society of Civil Engineers, expands on the minimum NFIP requirements with more specificity, additional requirements, and some limitations.

With the adoption of the International Codes, communities will be moving towards a more stringent approach to regulatory floodplain management, beyond the minimum requirements of the NFIP. The adoption and enforcement of disaster-resistant building codes is a core community action to promote effective mitigation. When communities ensure that new buildings and infrastructure are designed and constructed in accordance with national building codes and construction standards, they significantly increase local resilience now and in the future. With continued advancements in building codes, local ordinances should be reviewed and updated to meet and exceed standards as practicable to protect new development from future flood events and to further promote disaster resiliency.

One of the most effective ways to reduce vulnerability to potential flood damage is through careful land use planning that fully considers applicable flood management information and practices. Master planning will also be necessary to assure that open channel flood flow conveyances serving the smaller internal streams and drainage areas are adequately prepared to accommodate the flows. Preservation and maintenance of natural and riparian areas should also be an ongoing priority to realize the flood control benefits of the natural and beneficial functions of these areas.

Future development in the County may be built in the floodplain, in conformance to the standards of the floodplain ordinance. The County enforces the floodplain ordinance on new development in unincorporated Plumas County.

Future development areas and their vulnerability to DFIRM flooding is discussed further in the below GIS analysis.

Future Development: GIS Analysis
Plumas County provided 13 future development areas which were used as the basis for the inventory of future development for the unincorporated County. These were mapped in GIS. Where multiple parcels are listed, the parcels are merged to form one polygon, and the hazards are assigned to the highest annual chance flood zone category. Figure 4-146 shows the locations of the future development areas and FEMA DFIRM flood zones as well as the National Levee Database areas. As shown, some of these areas fall inside of the 1% and 0.2% annual chance flood zones, as shown on Table 4-94.

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Figure 4-146 Unincorporated Plumas County – Future Development in FEMA DFIRM Flood Zones

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Table 4-94 Unincorporated Plumas County – Future Development in FEMA DFIRM Flood Zones with Parcel Counts and Acreages
Flood Zones /
Site / Map ID
and Future
Development
Name
Total Parcel
Count
Improved
Parcel Count
Unimproved
Parcel Count
Total Acres Total
Improved
Acres
Total
Unimproved
Acres
1% Annual Chance Flood Hazard
Approved
K - North Star
Navigation
Center - Phase 2
1 1 0 1.00 1.00 0.00
Approved Total 1 1 0 1.00 1.00 0.00
Proposed
L - Plumas
County
Courthouse
1 1 0 2.86 2.86 0.00
Proposed Total 1 1 0 2.86 2.86 0.00
1% Annual
Chance Flood
Hazard Total
2 2 0 3.86 3.86 0.00

0.2% Annual Chance Flood Hazard
Approved
A - CHP Station 1 0 1 5.00 0.00 5.00
F - Plumas
District Hospital
Skilled Nursing
Facility
1 0 1 4.12 0.00 4.12
Approved Total 2 0 2 9.12 0.00 9.12

0.2% Annual
Chance Flood
Hazard Total
2 0 2 9.12 0.00 9.12
Other Areas
Approved
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

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Flood Zones /
Site / Map ID
and Future
Development
Name
Total Parcel
Count
Improved
Parcel Count
Unimproved
Parcel Count
Total Acres Total
Improved
Acres
Total
Unimproved
Acres
E - Plumas
County Search
and Rescue
1 1 0 4.50 4.50 0.00
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
J - Meadow
Edge Mobile
Home Park
1 1 0 42.74 42.74 0.00
Approved Total 8 2 6 66.90 47.24 19.66
Conceptual
M - Housing
Element RHNA
Site
1 1 0 3.64 3.64 0.00
Conceptual
Total 1 1 0 3.64 3.64 0.00
Other Areas
Total 9 3 6 70.54 50.88 19.66
Grand Total 13 5 8 83.52 54.74 28.78
Source: FEMA 03/02/2005 DFIRM, Plumas County GIS

4.3.12. Flood: Localized Flooding
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
Flooding occurs in areas other than the FEMA mapped floodplains. Flooding may be from drainages not studied by FEMA, lack of or inadequate drainage infrastructure, or inadequate maintenance. Localized, stormwater flooding occurs throughout the Plumas County Planning Area during the rainy season from November through April. Prolonged heavy rainfall contributes to a large volume of runoff resulting in high peak flows of moderate duration. Flooding is more severe when previous rainfall has created saturated

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ground conditions. Urban storm drainpipes and pump stations have a finite capacity. When rainfall exceeds this capacity, or the system is clogged, water accumulates in the street until it reaches a level of overland release. This type of flooding may occur when intense storms occur over areas of development.

Location and Extent
There is no established scientific scale or measurement system for localized flooding. Localized flooding is generally measured by depth of flooding and the area affected. Localized flooding often happens quickly and has a short speed of onset. In the County this happens more often during the winter months, as was shown on Figure 4-50 above. Localized flooding often has a short duration. Specific locations in the County can be seen in the Local Concerns section below.

Past Occurrences
Disaster Declarations
There are no identified state or federal disaster declarations for localized flooding, as shown in Table 4-4.

However, localized flooding was likely an issue during previous declarations for severe storms, heavy rains and floods.

NCDC Events
The past occurrences of localized flooding are included in the 1% and 0.2% annual chance flood hazard profile in Section 4.3.11.

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

Events since 2019/2020 LHMP
The HMPC noted the following events:
➢ 2023 – Spring flooding caused localized flooding to occur in many areas of the County. Roads and culverts were damaged. Juniper Lake Road saw roadway impacted by excessive storm surge and debris dislodging/plugging two culverts and subsequently washing out the roadway. Warner Valley Road saw excessive storm surge resulted in a landslide uphill from the roadway which plugged and/or buried three culvert sites servicing Warner Valley Road. The landslide also diverted streams uphill from the roadway resulting in branches of the stream no longer leading towards the current culvert locations and presently flowing over the roadway. Three culverts along Butterfly Valley Road and Twain Road were plugged and/or washed out by storm debris as well as a section of roadway underneath the railroad washed out by excessive storm surge.

Events before 2019
The HMPC noted the following events:

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➢ Each year there are flood issues throughout the County due to stormwater. There is significant stormwater runoff that occurs throughout the County, and the County has very little stormwater infrastructure
➢ During large storms, such as those in 1986 and 1997, the entire Sierra Valley will fill with several feet of water.
➢ In February of 2017, heavy rains combined with previous heavy snow to cause localized flooding issues throughout the County. The heavy snow blocked the rain from getting into drainage ditches.

Creeks also rose above their banks (discussed in Section 4.3.11). The Greenhorn Creek Community was particularly hard hit. Greenhorn Ranch Road Greenhorn Creek CSD well-house #1 sustained water damage from Estray Creek rising above its banks and flooding the well-house. Greenhorn Ranch Rd. was closed until waters receded and the road could be repaired. Approximately 1 day. Flood damage to Greenhorn Creek CSD properties/buildings was covered by insurance. More information on some of the damages from this flood can be found in the Past Occurrences in Section 4.3.11.

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Figure 4-147 2017 Localized Flooding at High Street in Quincy Source: Plumas County Ag Commissioner
➢ The HMPC noted that there are yearly bottlenecks in Spanish Creek, for example at Oakland Camp, that create backups into American Valley to varying degrees.

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

It is likely that climate change will increase the chance of future occurrence as well as future impacts. More information on climate change and localized flood 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 Localized Flood
Even if average annual rainfall may decrease slightly, the intensity of individual rainfall events is likely to increase during the 21st century, increasing the likelihood of overwhelming stormwater systems built to historical rainfall averages. This makes localized flooding more likely.

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

Many areas of the Planning Area are at some measure of vulnerability to localized flooding. 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 vulnerabilities to this hazard.

According to Plumas County, numerous parcels and roads throughout the County not included in the FEMA 1% and 0.2% annual chance floodplains are subject to flooding in heavy rains. In addition to flooding, damage to these areas during heavy storms includes pavement deterioration, washouts, mudslides, debris

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areas, and downed trees. The frequency and type of damage or flooding that occurs varies from year to year, depending on the quantity of runoff.

It was noted that the County has 6 maintenance yards with backhoes to assist with managing areas of localized flooding. In Quincy, the County has all the supplies to be dispatched to areas as needed.

Localized flood areas within Plumas County can be organized by elevation within the Upper Feather River watershed, thus examining the impact of water as it travels downhill on its journey to the Central Valley.

The primary areas at risk of loss from flooding are: Sierra Valley, Chester, Indian Valley, American Valley, and the North Fork Feather River Canyon.

Sierra Valley
The Sierra Valley is a large intermountain valley on the eastern edge of Plumas County. It has an area of 120,000 acres and is primarily located in Plumas County but also extends southward into Sierra County.

The valley has an average elevation of 4,850 feet and serves as the headwaters for the Middle Fork Feather River. The Sierra Valley has minimal topographic relief, and flooding is generally shallow and low velocity. Table 4-95 provides a summary of the primary localized flooding problems in the Sierra Valley.

See Figure 4-148 through Figure 4-151 for photos of localized flooding in the Sierra Valley.

Table 4-95 Sierra Valley Localized Flooding Issues
Sierra Valley
Areas
Issues Road
Impacts
Home and
Business
Impacts
Evacuation
Route
Marble Hot
Springs Road
Annual flooding in various locations from rain and irrigation

0.7 mile stretch east of the historic bridge experiences repeated flooding
Closed in winter due to snow
Primary evacuation route
X X
Rocky Point
Road (Old
Highway 70)
Experiences shoulder and bank erosion and repeated
flooding
Will flood nearly up to road centerline during major events One or two homes have been damaged
X X
Harriet Lane Experiences sheet flow across road
Often inundates nearby agricultural/ranch facilities,
specifically around Island Ranch
Road has sub-layer integrity issues and contains clay road base requiring constant repair
Major corridor for Hay transportation
X
Dyson Lane Experiences sheet flow and shallow flooding
Flooded with entire valley in 1992

0.1 mile low spot across the valley drainage area
Serves local population and as a bypass
X X
Sloat Road Flooding in Sloat is limited to little Long Valley Creek flooding SR70 during high flow events and high flows in the Middle Fork Feather River, which has flooded houses near Sloat Bridge crossing.

X X
Source: Plumas County 2014 LHMP, HMPC

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Figure 4-148 High Water Mark from 1992 Flood Event on Rocky Point Road Source: Plumas County 2014 LHMP
Figure 4-149 Sierra Valley Marble Hot Springs Road – Localized Flood Area Source: Plumas County 2014 LHMP

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Figure 4-150 Rocky Point Road – Shoulder Erosion from Localized Flooding Source: Plumas County 2014 LHMP
Figure 4-151 Harriet Lane – Pavement Deterioration from Localized Flooding Source: Plumas County 2014 LHMP

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Chester/Lake Almanor
Lake Almanor is a higher elevation alpine reservoir located in the northwestern portion of Plumas County.

Chester is the largest community of several that surround the lake and is located at the inlet of the North Fork Feather River. The outflow of the North Fork Feather River is controlled by Canyon Dam at the southern edge of the lake. The dam and outflow rates are managed and maintained by PG&E. The Canyon dam spillway elevation is 4,505 FT and PG&E property ownership around the lake resides at 4,500 FT.

Currently, PG&E's FERC license allows lake levels to be operated at 4,494 FT. Flooding issues in this region are minimal due to the construction of the Chester Flood Control Channel, or ACE bypass, a large diversion channel from the North Fork Feather River upstream of Chester/Lake Almanor. The diversion channel allows river water to enter once it reaches a certain height and directs it around Chester into Lake Almanor. The bypass also has a secondary set-back levee system outside of the channel for extreme flooding events. The hydrography in the Lake Almanor area is important to understand as all water that flows through this region travels down into the Feather River Canyon that contains major road and rail transportation routes and a number of communities.

Indian Valley
Indian Valley is located in the north-central portion of Plumas County at an average elevation of 3,500 feet.

It contains several developed communities and is also utilized for farming. Indian Valley is the meeting place of four creeks: Wolf Creek, Cooks Creek, Lights Creek, and Indian Creek. Indian Creek is the dominant stream reach as the other three creeks confluence with it and then exits the valley past Arlington Bridge.

Indian Valley exhibits a number of flooding issues due to its flat topography and hydrography. Much of the water that flows through the Upper Feather River watershed makes its way through Indian Valley on its journey into the Feather River Canyon. Table 4-96 provides a summary of the primary localized flooding issues in Indian Valley: Figure 4-152 through Figure 4-156 provide photos and descriptions of localized Indian Valley flooding issues.

Table 4-96 Summary of Indian Valley Localized Flooding Issues Indian Valley
Areas
Issues Road
Impacts
Home and
Business
Impacts
Evacuation
Route
Williams
Creek @
North Valley
Road
Road over culverts that drain water from upstream private land into the valley
Road has been overtopped resulting from debris blockage in culverts
Road Department uses logging equipment/poles to
remove debris during high flows preventing flooding,
which is a dangerous activity
Major flooding in 1986 and 1997
Roadway serves large populations in Taylorsville and
Diamond Valley and is heavily trafficked during winter due to its tendency to receive less snow and ice than alternative routes
X X
Cassidy’s Turn Shows high water mark from 1997 flood

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Indian Valley
Areas
Issues Road
Impacts
Home and
Business
Impacts
Evacuation
Route
Stampfli Lane Cross-valley road traveling E-W sits at low point in drainage area
Annual flooding of 0.5-1.0 feet of water on roadway often renders road impassible
Repeated flooding of residential structures
Poor drainage and flooding are caused by saturation of
adjacent agricultural fields
X X X
Mt. Hough
Estates
Low-lying subdivision, portion of which has repeated
flooding
Houses appear to be slab-on-grade
Typically, during valley-flooding events
Residents aware of impending flooding by the presence of water in neighboring fields
X
Old Wagon
Road,
Crescent Mills
Residential structure flooded repeatedly (5-6 times)
High water mark 6 feet high in some locations
House built at drain point for basin
X
Arlington
Bridge (State#
09C-007)
Bridge overtopped by 3 feet during 1997 flood
Flows often approach height of bridge deck
Major drainage point for entire valley
Sedimentation issues on downstream side
Adding culverts may improve drainage
X X
Genesee Road
@ Little
Grizzly Creek
Flooding can close road cutting off access for 15-20 homes X X Source: Plumas County 2014 LHMP

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Figure 4-152 Indian Valley Localized Flooding – North Valley Road crossing Williams Creek where Culverts often Clog with Debris
Source: Plumas County 2014 LHMP
Figure 4-153 Indian Valley Localized Flooding – Ponding area of Stampfli Lane has Poor Drainage and Floods Annually
Source: Plumas County 2014 LHMP

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Figure 4-154 Indian Valley Localized Flooding – Low-lying area of Mt. Hough Estates Subdivision Subject to Flooding from Indian Valley Creeks.

Source: Plumas County 2014 LHMP
Figure 4-155 Indian Valley Localized Flooding – Residential Structure in Crescent Mills built at Drain Point of Basin Experiences Repeated Flooding
Source: Plumas County 2014 LHMP

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Figure 4-156 Indian Valley Localized Flooding – Location along Genesee Road Where Flood Waters Can Cover Road and Cut Off Access
Source: Plumas County 2014 LHMP
American Valley
American Valley is located in the geographic center of Plumas County and sits at an average elevation of 3,500 feet. In American Valley, Greenhorn Creek confluences with Spanish Creek upstream near the Town of Quincy. A majority of the flooding issues are caused by localized drainage as opposed to valley-flooding events. The water in Spanish Creek that passes through American Valley confluences with Indian Creek flowing out of Indian Valley into the Feather River Canyon. Table 4-97 provides a summary of the primary localized flooding issues in American Valley. Figure 4-157 through Figure 4-166 provides photos and descriptions of American Valley localized flooding issues.

Table 4-97 American Valley Localized Flooding Issue Summary American
Valley Areas
Issues Road
Impacts
Home and
Business
Impacts
Evacuation
Route
Les Schwab Storm grate behind facility becomes clogged with debris causing water to overtop and flow into building
Typically, only floods with major events, not large storms; recalled events were in 1986, 1993, and 1997
Overtopping waters also flow into a nearby home and
businesses further downhill
X

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American
Valley Areas
Issues Road
Impacts
Home and
Business
Impacts
Evacuation
Route
Lindan
Avenue
The drainage ditch that runs behind the Lindan Avenue
properties (west side of street) provides drainage for a large area of Quincy including the shopping center and housing developments to the south. The ditch doesn’t have enough capacity to contain larger flood events, since it pre‐dates all the construction of the shopping center and housing on the
southeast side of Quincy. Potential build of 30 units south Lindan.

X
Paradise Grill Water can overtop edges of earthen ditch Water flooding from behind Les Schwab will flow down street and into businesses in strip mall
Historic flooding up to 2 feet of water in strip mall businesses X X
Hentschel Storm drain on small creek gets clogged with debris and backs up, causing water to flow onto roadway and into the school and neighboring building across the street
Grate is not easily accessible
X X
Old Sewer
Plant (at bike
path)
Drainage path takes 90-degree turn into culverts underneath bike path
Water drains poorly and overtops path
X
West’s Ranch
Road (at CA70)
Road needs to be elevated and larger pipes installed X
East Quincy
Drains
Drainage problems at high water
Pipes/drainage too small and becomes clogged with debris Vieira’s Field Better/safer access and larger pipe. Runs behind and alongside private property
Small drain on private property can clog with debris
During heavy rains and large-scale events water will bypass drain and flow down gravel road toward CA-70
X
Chandler
Road (West)
Beddell Ranch and Green Bridge areas often flood
Easy fix is to elevate road and install culverts where needed X
Oakland
Camp Road
Floods from intersection with Chandler Road to Oakland
Camp gate
Easy fix is to elevate road and install culverts where needed X
Gansner
Creek
Storm grate on south side of West Main Street becomes
clogged with debris causing water to overtop and flow across road
Flood water flows down into hospital flooding the ambulance entrance, ER entrance, and X-ray doors
Hospital flooded in 1986, 1993, and 1997
X X X
Mill Creek Runs behind and alongside private property
Small drain on private property can clog with debris
During heavy rains and large-scale events water will bypass drain and flow down gravel road toward CA-70
X X

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American
Valley Areas
Issues Road
Impacts
Home and
Business
Impacts
Evacuation
Route
Clear Creek Located in Meadow Valley outside of American Valley Grate clogs with debris causing water to back up
Water can back up high enough to swirl around the base of Meadow Valley Road potentially causing erosion and damage to roadway
System is stressed several times annually
X
Oakland
Camp at
Spanish
Creek
Oakland Camp Road floods regularly during high flow events when Spanish Creek flows over the low water crossing
adjacent to the Oakland Camp Bridge. The concrete low
water crossing is designed for high water to flow over
X
Source: Plumas County 2014 LHMP
Figure 4-157 American Valley Localized Flooding – Storm Grate behind Les Schwab Becomes Clogged with Debris Causing Flooding
Source: Plumas County 2014 LHMP

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Figure 4-158 American Valley Localized Flooding – Strip Mall Containing Paradise Grill and other Businesses. Water can Overtop Earthen Ditch on Right, or Flow Down Street on Left when Storm Drain Floods behind Les Schwab Source: Plumas County 2014 LHMP
Figure 4-159 American River Localized Flooding – Lindan Avenue in 2012 Source: Member of HMPC (Marty Walters)

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Figure 4-160 American Valley Localized Flooding – Hentschel’s Storm Grate, Small Grate for Localized Drainage Clogs with Debris and Causing Flooding over Roadway.

Source: Plumas County 2014 LHMP
Figure 4-161 American Valley Localized Flooding – Flood Water from Hentschel’s Flows Across Street and into School.

Source: Plumas County 2014 LHMP

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Figure 4-162 American Valley Localized Flooding – Water Overtops Drainage at Culverts Where Forced to take 90-degree Right Turn.

Source: Plumas County 2014 LHMP
Figure 4-163 American Valley Localized Flooding – View of Plumas District Hospital from Storm Grate along Gansner Creek. Apparent that Hospital is Down Slope from Culvert and Subject to Flooding from Overtopping Water.

Source: Plumas County 2014 LHMP

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Figure 4-164 American Valley Localized Flooding – Plumas District Hospital downhill from West Main Street, Susceptible to Flooding from Waters Overtopping Storm Grate on Gansner Creek
Source: Plumas County 2014 LHMP
Figure 4-165 American Valley Localized Flooding – Small drain for Mill Creek can be Bypassed During Larger Storms Causing Water to Flow Down Adjacent Gravel Road.

Source: Plumas County 2014 LHMP

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Figure 4-166 American Valley Localized Flooding – Culvert on Clear Creek in Meadow Valley Becomes Clogged with Debris. Rising and Swirling Water poses Erosion Issue that Could Jeopardize Roadway.

Source: Plumas County 2014 LHMP
Feather River Canyon
The Feather River Canyon is a narrow river valley occupied by the North Fork Feather River and East Branch North Fork Feather River. At its upstream end is the confluence of Indian Creek, flowing from Indian Valley, and Spanish Creek, flowing from American Valley; here is the beginning of the East Branch North Fork Feather River. The East Branch meets the North Fork Feather River, flowing from Lake Almanor, about two miles upstream from Belden.

The Feather River Canyon is occupied by CA-70 and the Union Pacific Railroad, which comprise the two major E-W transportation routes through Plumas County. The canyon is home to a number of small towns adjacent to the riverbanks, highway, and train tracks.

Flooding issues in the Canyon are primarily related to larger events involving the North Fork Feather River, such as the 1986 and 1997 floods. Typical damage is washouts to roadways or train tracks. Much of the precipitation that falls in Plumas County flows through the Canyon.

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 localized flood 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.

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

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

Structures in low lying areas, or those with basements can be at greater risk. Buildings with older foundations that are prone to water intrusion are also at greater risk. Once water finds its way into a structure, it tends to continue to do so until the path that brings water into a structure is mitigated. Ground saturation can result in instability, collapse, or other damage to structures. Trees can also be compromised and uprooted falling on structures causing damage.

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

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

Natural, Historic, and Cultural Resources
Natural resource assets may have some vulnerabilities to localized flood during major storm events, but can benefit from floodwaters, often by design. Many parks and green spaces are designed to take overflow water and release it into the underlying soils and natural areas. Wetlands areas in the Planning Area actually help reduce the risk of flooding, as they can absorb excess rainfall that would have to be drained away from impervious surfaces. Flooding can provide many benefits to the natural environment, including recharging wetlands and groundwater, increasing fish production, creating wildlife habitat, and rejuvenating soil fertility. These smaller localized flooding events often provide more benefits to the environment in comparison to negative impacts associated with large flood events. Historic and cultural resources may be at some measure of vulnerability if they are located in areas subject to repeated localized flooding.

FEMA NRI Hazard Vulnerability Assessment
Localized flooding is not an NRI hazard; therefore, no data is presented.

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

Life safety issues from localized flooding would be more limited. The amount and type of damage or flooding that occurs varies from year to year and from storm to storm, depending on the quantity of precipitation and runoff.

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.

Vulnerable population groups such as low-income individuals and households living in floodprone areas could face disproportionate effects from localized flood and should be planned for. 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. Locating new development, structures and critical facilities and infrastructure within or near areas of localized flooding risk may put additional development at risk. County building codes are in effect to reduce this risk and should be updated as necessary to continue to address future localized flood conditions. Depending on the location of new development and adherence to protective building codes, changes in land use and development may or may not increase the impacts and associated vulnerabilities of the County to this hazard.

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Future Development
The potential for flooding may increase as stormwater is channeled due to land development. Such changes can create localized flooding problems inside and outside of natural floodplains by altering or confining natural drainage channels. Mitigating the root causes of the localized stormwater flooding or choosing not to develop in areas that often are subject to localized flooding will reduce future risks of losses due to stormwater/localized flooding. Floodplain modeling and master planning should be based on build out property conditions to ensure that all new development remains safe from future flooding.

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 to make for a more resilient community.

4.3.13. Hazardous Materials Transportation
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 the Environmental Protection Agency (EPA), a hazardous material is any item or agent (biological, chemical, physical) which has the potential to cause harm to humans, animals, or the environment, either by itself or through interaction with other factors. Hazardous materials can be present in any form; gas, solid, or liquid. Environmental or atmospheric conditions can influence hazardous materials if they are uncontained.

The U.S. Occupational Safety and Health Administration’s (OSHA) definition of hazardous material includes any substance or chemical which is a “health hazard” or “physical hazard,” including: chemicals which are carcinogens, toxic agents, irritants, corrosives, sensitizers; agents which act on the hematopoietic system; agents which damage the lungs, skin, eyes, or mucous membranes; chemicals which are combustible, explosive, flammable, oxidizers, pyrophorics, unstable-reactive or water-reactive; and chemicals which in the course of normal handling, use, or storage may produce or release dusts, gases, fumes, vapors, mists or smoke which may have any of the previously mentioned characteristics.

The EPA incorporates the OSHA definition and adds any item or chemical which can cause harm to people, plants, or animals when released by spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping or disposing into the environment. The EPA maintains a list of 366 chemicals that are considered extremely hazardous substances (EHS). This list was developed under the Superfund Amendments and Reauthorization Act. The presence of EHSs in amounts in excess of a threshold planning quantity requires that certain emergency planning activities be conducted.

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A release or spill of bulk hazardous materials could result in fire, explosion, toxic cloud or direct contamination of water, people, and property. The effects may involve a local area or many square miles.

Health problems may be immediate, such as corrosive effects on skin and lungs, or be gradual, such as the development of cancer from a carcinogen. Damage to property could range from immediate destruction by explosion to permanent contamination by a persistent hazardous material.

Location and Extent
In Plumas County there are multiple hazardous materials transportation routes. State Roads 36, 49, 70, 89, and 147 are all hazardous materials routes. The Union Pacific (UP), Burlington Northern Santa Fe (BNSF), Quincy Railroad, and Almanor Railroad are railroad hazardous materials routes. Figure 4-167 shows the hazardous materials transportation corridors (for roadways and rail) in the County as well as the one-mile buffer zone (on each side of the corridor for a two-mile total buffer) used for this analysis as detailed further in the methodology below. This map shows three insets for communities within the County. Maps zoomed to these areas are shown in Figure 4-168, Figure 4-169, and Figure 4-170.

Geographic hazardous materials buffer zones for the unincorporated County are detailed by highway in Table 4-98 and by railroad in Table 4-99.

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Figure 4-167 Plumas County Planning Area – Hazardous Materials Transportation Routes and Buffer Zones (Overview Map with Insets)

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Figure 4-168 Plumas County Planning Area – Hazardous Materials Transportation Routes and Buffer Zones (Inset 1)

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Figure 4-169 Plumas County Planning Area – Hazardous Materials Transportation Routes and Buffer Zones (Inset 2)

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Figure 4-170 Plumas County Planning Area – Hazardous Materials Transportation Routes and Buffer Zones (Inset 3)

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Table 4-98 Plumas County Planning Area – Geographical Extent of Hazardous Materials Transportation Buffer Zones for Highways
Hazardous
Materials
Routes
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
City of Portola
Highway 70 1,357 38.9% 303 13.6% 1,053 84.0%
Unincorporated Plumas County
Highway 147 13,535 1% 599 1% 12,936 1%
Highway 36 25,562 2% 1,527 2% 24,035 2%
Highway 49 10,503 1% 6,459 7% 4,044 0.3%
Highway 70 122,574 7% 23,388 26% 99,187 6%
Highway 89 99,818 6% 13,463 15% 86,355 5%
Source: National Hazardous Materials Routes Registry (2025) Table 4-99 Plumas County Planning Area – Geographical Extent of Hazardous Materials Transportation Buffer Zones for Railroads
Hazardous
Materials
Routes
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
City of Portola
UP / BNSF 1,403 40% 279 12% 1,124 90%
Unincorporated Plumas County
BNSF 45,223 2.7% 3,745 4.1% 41,478 2.6%
Quincy
Railroad
5,479 0.3% 1,961 2.2% 3,518 0.2%
UP / BNSF 130,941 7.8% 20,940 23.1% 110,000 7.0%
Source: National Hazardous Materials Routes Registry (2025) In addition, while most routes are known, Plumas County has not quantified the amount of hazardous materials that are transported through it en route to local deliveries or to adjoining counties. Accidents involving the transportation of hazardous materials could be just as catastrophic as accidents involving stored chemicals, possibly more so, since the location of a transportation accident is not predictable. The U.S. Department of Transportation (USDOT) divides hazardous materials into nine major hazard classes.

A hazard class is a group of materials that share a common major hazardous property, i.e., radioactivity, flammability, etc. These hazard classes include:
➢ Class 1—Explosives
➢ Class 2—Compressed Gases
➢ Class 3—Flammable Liquids
➢ Class 4—Flammable Solids; Spontaneously Combustible Materials; Dangers When Wet Materials/Water-Reactive Substances
➢ Class 5—Oxidizing Substances and Organic Peroxides

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➢ Class 6—Toxic Substances and Infectious Substances
➢ Class 7—Radioactive Materials
➢ Class 8—Corrosives
➢ Class 9—Miscellaneous Hazardous Materials/Products, Substances, or Organisms The speed of onset of a hazardous materials spill is generally short. The duration is typically short as well, though certain chemicals can pollute earth and groundwater for long periods of time. The actual extent of any given incident will depend on the type of release, location, and nature and extent of any release.

Past Occurrences
Disaster Declaration History
There have been no federal or state disaster declarations for hazardous materials in the County, as shown on Table 4-4.

NCDC Events
The NCDC does not track hazardous materials events.

Pipeline and Hazardous Materials Safety Administration Events The USDOT Pipeline and Hazardous Materials Safety Administration’s (PHMSA) Office of Hazardous Materials Safety performs a range of functions to support the safe transport of hazardous materials. One of these functions is the tracking of hazardous materials incidents in the United States. The database was searched for hazardous materials incidents in the County. A summary of rail and highway incidents since 1970 in the Plumas County Planning Area are shown in Table 4-100. 11 separate events were contained in the database.

Table 4-100 Plumas County Planning Area – Hazardous Materials Transportation Incidents Since 1970
Date of
Incident Incident Route
Mode of
Transportation Commodity Short Name
Quantity
Released
Amount of
Damages
11/21/1995 State Route 70 Highway Fuel Oil 2,200
gallons
$37,000
7/14/1992 Highway 70 Highway Methanol 1 gallon $1,100
11/19/2012 348 Questa Way Highway Liquefied Petroleum Gas 40 gallons $0 9/14/2018 Hwy 70 & Spanish
Creek
Highway Gasoline Includes Gasoline Mixed
With Ethyl Alcohol, With Not More
Than 10% Alcohol
1,762
gallons
$377,246
4/19/2006 Main Track,
Milepost 202.8,
BNSF
Railroad Methanol 3.5 gallons $61,005
6/30/2007 Milepost 252.50 Highway Alcohols, N.O.S. 29,357 gallons
$2,035,200

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Date of
Incident Incident Route
Mode of
Transportation Commodity Short Name
Quantity
Released
Amount of
Damages
2/5/2004 State Route 166 Highway Petroleum Gases, Liquefied Or Liquefied Petroleum Gas
0 $10,000
12/20/2007 Not reported Highway Petroleum Distillates, N.O.S. Or Petroleum Products, N.O.S.
1,641
gallons
$20,865
8/31/1999 560 Cresent Street Highway Fuel, Aviation, Turbine Engine 100 gallons $0 12/1/2014 1690 E. Main Highway Liquefied Petroleum Gas 6.684 $0 12/30/2002 State Highway 70 Highway Petroleum Gases, Liquefied Or Liquefied Petroleum Gas
0 $75,000
Source: PHMSA Database – Search dates 01/01/1970 – 04/01/2025 Hazard Mitigation Planning Committee Events
These sections separate events since the 2019/2020 LHMPs and those before 2019.

Events since 2019/2020 LHMP
In addition to what was reported to the PHMSA, the HMPC reported the following transportation event.

February 11, 2024 – there was a main line derailment in Plumas County near Blairsden, CA. UPRR mainline structure was eroded due to heavy rain elements and rock/mudslide event. 15 Bituminous Coal hopper cars derailed and released. Out of the 15 cars, 3 had entered the Middle Fork River and resulted in a mass recovery operation in the Feather River. The HMPC were of the opinion that there is a moderate to high future event probability to occur again as topography and terrain continuously migrate during inclement weather.

Summer 2025 – The HMPC recalled a hazardous materials spill from a truck release. 1,200 gallons of fuel spilled at Highway 89 near Arlington. Clean up occurred but the load was lost.

Events before 2019
The HMPC noted that events occurred but could recall no events with specific dates or damages.

Likelihood of Future Occurrence
Occasional – Given that 11 minor hazardous materials incidents have happened in transport through the County in the past 53 years, a hazardous materials incident will occur in the County occasionally. It should be noted, however, that small hazardous materials spills happen often and are cleaned up locally and go unreported to national databases. According to Caltrans, most incidences are related to releases during loading and unloading of cargo, and the release of fluids/materials from the transporting vehicles themselves and not the cargo.

Climate Change and Hazardous Materials
Climate change is unlikely to affect hazardous materials transportation incidents.

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Vulnerability Assessment
Vulnerability—Medium
It is often quite difficult to quantify the potential losses from human-caused hazards. While the facilities themselves have a tangible dollar value, loss from a human-caused hazard often inflicts an even greater toll on a community, both economically and emotionally. The impact to identified values will vary from event to event and depend on the type, location, and nature of a specific hazardous material incident. The most significant impact from hazardous materials transport is life safety and public health. Given the difficulty in quantifying the losses associated with technological hazards, this section focuses on analyzing key Planning Area values relative to the hazardous materials transportation corridors identified above.

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.

The 2023 Plumas County HazMat Response Plan noted that the highest potential for a highway transportation incident exists along the County’s main east-west thoroughfare, State Highway 70. This route follows the Feather River in a steep, rocky canyon and has long been recognized for its history and potential for a significant hazardous materials incident. An additional potential exists on the other State Highways which traverse the county, namely State Highways 36 and 89. The materials transported on these highways are typically destined for a facility within the county. However, when the major trans-Sierra route (Interstate 80) is closed during inclement weather, local highways and especially Highway 70 may see an increase in both the volume and variety of hazardous materials shipments.

As identified during the 2009 commodity flow study, ninety percent of the hazardous materials identified on state highways were bulk petroleum products, which included heating fuels, gasoline, diesel, and propane. Other hazardous materials identified included industrial/medical cylinders and general industrial products. Approximately 10 (ten) percent of all truck traffic on Plumas County roadways were found to be transporting a hazardous commodity.

Rail transport through the county also poses a significant hazmat release potential. This is confirmed by both historical releases and the 2009 commodity flow study. Both UP and Burlington Northern Santa Fe BNSF currently maintain track in Plumas County, and, through the commodity flow study, BNSF was found to be the primary rail shipper of hazardous materials through the county.

BNSF’s primary rail line, known as the High Line route, runs north and south starting near the Feather River Canyon town of Keddie and passing through the northern section of Plumas County east of Lake

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Almanor. BNSF also has an agreement with UP to lease track time for all UP rail lines in Plumas County.

Their highest traffic section of leased line that they use is the Feather River Canyon Route, allowing them to ship between the Bay Area and the Pacific Northwest.

Union Pacific’s rail line passes east-west through Plumas County, connecting the Sacramento Valley to Northern Nevada and includes the Portola rail yard. The majority of UP’s traffic through Plumas County consists of mixed cargo containers, single and doubled stacked. While UP never reported shipping unit trains of light crude on this route, they did report shipping smaller quantities as part of mixed load trains.

Again, while most rail transport includes mixed loads of hazardous materials, the potential for encountering light crude rail shipments in significant volumes in Plumas County should not be overlooked.

The geography of the County can influence the development of incidents and the way in which they are handled. A steep river canyon can restrict or even prevent access to an incident. The Middle Fork of the Feather River below the LaPorte Road Bridge, for example, is not accessible by vehicle. If a spill is not contained by this point, it may not be possible to reach it again until the spill reaches Lake Oroville. As another example, in the Feather River canyon the highway is often on one side of the river and the rail line is on the other. Consequently, a rail incident may not be directly accessible from the highway. Depending on river flows, one of various bridge crossings may be needed, and personnel and equipment may need to be taken to the scene by railroad personnel via a high rail. Another consideration in the Feather River Canyon is that a highway incident may block the highway. With local first responders coming primarily from the Quincy or the Indian Valley/Lake Almanor basin areas, local responders may not be able to access the westerly downriver side of an incident. In such cases early calls for mutual aid from Butte County resources would be important.

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 from Hazardous Materials Transportation
Assets at risk from hazardous materials transportation release include: people and populations; structures; critical facilities; and natural, historic, and cultural resources. These are discussed in the following sections.

The methodology used to analyze hazardous materials transportation for the population, structures, and critical facilities is discussed in the section below.

Methodology: Transportation Release and Buffer Zone
An analysis of the potential vulnerability of the Planning Area to a transportation-related hazardous materials release was conducted using GIS within identified transportation corridors. To evaluate the areas most vulnerable, a one-mile buffer was applied to both sides of Highways 36, 49, 70, 89, and 147, as well as the UP, BNSF, Quincy Railroad, and Almanor Railroad lines. The result is a two-mile buffer zone around each transportation corridor that is included in this analysis. The buffer distance was based on

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guidelines in the USDOT’s Emergency Response Guidebook that suggest distances useful to protect people from vapors resulting from spills involving dangerous goods considered toxic if inhaled. The recommended buffer distance referred to in the guide as the “protective action distance” is the area surrounding the incident in which people are at risk of harmful exposure. Actual buffer distances will vary depending on the nature and quantity of the release, whether the release occurred during the night or daytime, and prevailing weather conditions.

This hazardous materials buffer zone analysis can be misleading since there are many large polygons throughout the County.

People and Populations
All populations are at some vulnerability to a hazardous materials transportation release. Certain vulnerable populations are at the greatest risk to the effects of hazardous materials. Vulnerable populations include:
➢ The unsheltered
➢ Those with breathing difficulties or other underlying health conditions ➢ Infants and children under age five and their caregivers ➢ Elderly (65 and older)
➢ Individuals with disabilities
➢ Individuals dependent on medical equipment
➢ Individuals who work, exercise, or physically train outdoors ➢ Individuals with impaired mobility
To determine the overall populations at risk from a transportation-related hazardous materials release within identified transportation corridors, an analysis was performed using GIS to determine the residential population that resides within the two-mile buffer zone of the highway and railroad corridors. Using GIS, the buffered corridor was overlaid on the improved residential parcel and structure data and results tabulated for the Planning Area, as found in Table 4-101. Those residential parcel polygons that intersect the buffered corridor were counted and multiplied by the 2023 Census Bureau average household factors for Portola and the unincorporated County. According to the analysis, there are 2,075 residents in the City and 19,674 residents in the overall County in the hazardous materials buffer zones associated with the hazardous materials transportation routes and potentially at risk.

Table 4-101 Plumas County Planning Area–Improved Residential Parcels and Populations at Risk in Hazardous Materials Buffer Zones
Jurisdiction
Improved Residential
Parcels
Population at Risk
City of Portola
Highways
Highway 70 906 2,075
Railroads
UP/BNSF 899 2,059

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Jurisdiction
Improved Residential
Parcels
Population at Risk
Unincorporated Plumas County
Highways
Highway 147 618 1,479
Highway 36 1,110 2,653
Highway 36 and 147 0 0
Highway 36 and Highway 89 0 0
Highway 49 1 3
Highway 49 and Highway 70 19 45
Highway 70 1,126 2,692
Highway 70 and Highway 89 2,817 6,733
Highway 89 2,015 4,816
Highway 89 and Highway 147 4 13
Railroads
BNSF 1,010 2,414
BNSF and UP / BNSF 30 72
Quincy Railroad 822 1,965
Quincy Railroad and UP / BNSF 223 533
UP / BNSF 2,819 6,737
Source: National Hazardous Materials Routes Registry (2025), Plumas County 2024 Parcel/Assessor’s Data, 2023 US Census American Community Survey Average Household Size – City of Portola (2.29); Unincorporated Plumas County (2.39).

Structures
Structures in the County have some measure of risk to hazardous materials which can affect the built environment of the County. During a hazardous materials transportation spill, it is generally the people that are at risk to the effects of the spill. During a spill, buildings, property, and their values are at a lessor risk; however, given the location and breadth of hazardous materials routes in the County, an analysis is performed here. This analysis is shown in Table 4-102 for highways and in Table 4-103 for railroads.

These tables summarize by total parcel counts, improved parcel (structure) counts, and their improved and land values, personal property values, and the estimated contents replacement values based on the CRV factors detailed in Table 4-9.

Table 4-102 Plumas County Planning Area – Count and Value of Parcels and Structures in Highway Hazardous Materials Transportation Buffer Zone by Jurisdiction and Route
Jurisdiction/
Hazardous
Materials Routes
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola
Highway 70 1,389 906 $29,280,690 $113,448,396 $283,632 $56,724,198 $199,736,916

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Jurisdiction/
Hazardous
Materials Routes
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Unincorporated Plumas County
Highway 147 804 618 $100,061,736 $159,628,234 $380,288 $79,814,117 $339,884,375 Highway 36 1,437 1,110 $67,198,419 $199,727,901 $792,726 $99,863,951 $367,582,997 Highway 36 and
Highway 89
1 1 $36,214 $18,106 $0 $9,053 $63,373
Highway 49 3 1 $496,763 $7,374 $0 $3,687 $507,824
Highway 49 and
Highway 70
26 19 $974,931 $1,534,625 $54,018 $767,313 $3,330,887
Highway 70 1,840 1,126 $83,808,531 $180,178,813 $1,500,463 $90,089,407 $355,577,214 Highway 70 and
Highway 89
3,424 2,817 $203,563,790 $571,022,756 $58,484,315 $285,511,378 $1,118,582,239 Highway 89 3,358 2,015 $320,453,952 $600,807,297 $622,601 $300,403,649 $1,222,287,499 Highway 89 and
Highway 147
18 4 $951,740 $167,078 $1,221 $83,539 $1,203,578
Source: National Hazardous Materials Routes Registry (2025), Plumas County 2024 Parcel/Assessor’s Data To avoid duplication of parcel count, the parcels located in areas where multiple haz-mat route buffers overlap were assigned the route grouping listed above.

Table 4-103 Plumas County Planning Area – Count and Value of Parcels and Structures in Railroad Hazardous Materials Transportation Buffer Zone by Jurisdiction and Railway
Jurisdiction/
Hazardous
Materials
Routes
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola
UP / BNSF 1,379 899 $28,873,512 $112,305,977 $283,632 $56,152,989 $197,616,110 Unincorporated Plumas County
BNSF 1,849 1,010 $134,325,701 $195,217,680 $523,760 $97,608,840 $427,675,981 BNSF and UP /
BNSF
64 30 $3,768,034 $4,392,811 $0 $2,196,406 $10,357,251
Quincy Railroad 926 822 $39,751,756 $142,273,400 $57,695,029 $71,136,700 $310,856,885 Quincy Railroad
and UP / BNSF
272 223 $18,882,230 $56,093,035 $0 $28,046,518 $103,021,783 UP / BNSF 4,250 2,819 $259,724,454 $605,239,651 $3,508,993 $302,619,826 $1,171,092,924 Source: National Hazardous Materials Routes Registry (2025), Plumas County 2024 Parcel/Assessor’s Data To avoid duplication of parcel count, the parcels located in areas where multiple haz-mat route buffers overlap were assigned the route grouping listed above.

Table 4-104 and Table 4-110 show additional analysis for the unincorporated County. Table 4-104 shows the specific hazardous materials routes for highways and then separates by property use the total parcel counts, improved parcel and structure counts, improved and land values, personal property values, and the

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Plumas County 4-378
Local Hazard Mitigation Plan Update
January 2026
estimated contents replacement values. Table 4-110 shows the specific hazardous materials routes for railways and then separates by property use the total parcel counts, improved parcel and structure counts, improved and land values, personal property values, and the estimated contents replacement values.

Table 4-104 Unincorporated Plumas County – Count and Value of Parcels and Structures in Highway Hazardous Materials Transportation Buffer Zone by Route and Property Use
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Highway 147
Agricultural 17 0 $872,664 $0 $0 $0 $872,664
Commercial 27 17 $2,784,129 $3,026,622 $16,313 $3,026,622 $8,853,686 Federal Lands 0 0 $0 $0 $0 $0 $0
Government 4 0 $0 $0 $0 $0 $0
Industrial 0 0 $0 $0 $0 $0 $0
Institutional 1 0 $0 $0 $0 $0 $0
Miscellaneous 3 0 $0 $0 $0 $0 $0
Recreational 10 9 $2,687,977 $384,191 $2,024 $384,191 $3,458,383 Residential 804 618 $100,061,736 $159,628,234 $380,288 $79,814,117 $339,884,375 ROW/Utilities 68 0 $0 $0 $0 $0 $0
Highway 147
Total
934 644 $106,406,506 $163,039,047 $398,625 $83,224,930 $353,069,108 Highway 36
Agricultural 81 0 $1,581,818 $0 $0 $0 $1,581,818
Commercial 164 120 $15,241,185 $35,154,836 $24,613,536 $35,154,836 $110,164,393 Federal Lands 1 0 $0 $0 $0 $0 $0
Government 25 0 $0 $0 $0 $0 $0
Industrial 19 13 $1,454,167 $2,954,682 $671 $4,432,023 $8,841,543 Institutional 16 9 $307,206 $1,412,790 $11,680 $1,412,790 $3,144,466 Miscellaneous 1 0 $0 $0 $0 $0 $0
Recreational 8 7 $674,402 $1,155,503 $0 $1,155,503 $2,985,408 Residential 1,437 1,110 $67,198,419 $199,727,901 $792,726 $99,863,951 $367,582,997 ROW/Utilities 74 0 $0 $0 $0 $0 $0
Highway 36
Total
1,826 1,259 $86,457,197 $240,405,712 $25,418,613 $142,019,103 $494,300,625 Highway 36 and Highway 147
Agricultural 4 1 $221,688 $45,572 $0 $45,572 $312,832
Commercial 1 0 $139,896 $0 $0 $0 $139,896

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Plumas County 4-379
Local Hazard Mitigation Plan Update
January 2026
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Federal Lands 0 0 $0 $0 $0 $0 $0
Government 0 0 $0 $0 $0 $0 $0
Industrial 0 0 $0 $0 $0 $0 $0
Institutional 0 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 0 0 $0 $0 $0 $0 $0
ROW/Utilities 0 0 $0 $0 $0 $0 $0
Highway 36
and Highway
147 Total
5 1 $361,584 $45,572 $0 $45,572 $452,728
Highway 36 and Highway 89
Agricultural 21 0 $576,678 $0 $0 $0 $576,678
Commercial 10 2 $4,038,947 $256,995 $10,220 $256,995 $4,563,157 Federal Lands 2 0 $0 $0 $0 $0 $0
Government 20 0 $0 $0 $0 $0 $0
Industrial 1 0 $114,530 $0 $0 $0 $114,530
Institutional 0 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 1 1 $36,214 $18,106 $0 $9,053 $63,373
ROW/Utilities 12 0 $0 $0 $0 $0 $0
Highway 36
and Highway
89 Total
67 3 $4,766,369 $275,101 $10,220 $266,048 $5,317,738
Highway 49
Agricultural 15 5 $2,406,411 $1,261,116 $103,680 $1,261,116 $5,032,323 Commercial 1 0 $0 $0 $0 $0 $0
Federal Lands 0 0 $0 $0 $0 $0 $0
Government 3 0 $0 $0 $0 $0 $0
Industrial 0 0 $0 $0 $0 $0 $0
Institutional 0 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 3 1 $496,763 $7,374 $0 $3,687 $507,824
ROW/Utilities 2 0 $0 $0 $0 $0 $0

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Plumas County 4-380
Local Hazard Mitigation Plan Update
January 2026
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Highway 49
Total
24 6 $2,903,174 $1,268,490 $103,680 $1,264,803 $5,540,147 Highway 49 and Highway 70
Agricultural 15 9 $6,887,098 $1,519,906 $260,631 $1,519,906 $10,187,541 Commercial 5 5 $210,304 $623,600 $550 $623,600 $1,458,054 Federal Lands 0 0 $0 $0 $0 $0 $0
Government 2 0 $0 $0 $0 $0 $0
Industrial 2 1 $191,990 $258,916 $0 $388,374 $839,280
Institutional 1 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 26 19 $974,931 $1,534,625 $54,018 $767,313 $3,330,887 ROW/Utilities 8 0 $0 $0 $0 $0 $0
Highway 49
and Highway
70 Total
59 34 $8,264,323 $3,937,047 $315,199 $3,299,193 $15,815,762 Highway 70
Agricultural 66 14 $5,732,257 $3,487,673 $1,555,244 $3,487,673 $14,262,847 Commercial 95 76 $8,176,275 $22,612,548 $2,566,331 $22,612,548 $55,967,702 Federal Lands 13 0 $0 $0 $0 $0 $0
Government 62 0 $0 $0 $0 $0 $0
Industrial 38 23 $3,163,313 $5,871,624 $190 $8,807,436 $17,842,563 Institutional 8 3 $179,834 $1,706,933 $6,650 $1,706,933 $3,600,350 Miscellaneous 2 0 $0 $0 $0 $0 $0
Recreational 4 4 $573,844 $4,183,042 $638 $4,183,042 $8,940,566 Residential 1,840 1,126 $83,808,531 $180,178,813 $1,500,463 $90,089,407 $355,577,214 ROW/Utilities 93 0 $0 $0 $0 $0 $0
Highway 70
Total
2,221 1,246 $101,634,054 $218,040,633 $5,629,516 $130,887,039 $456,191,242 Highway 70 and Highway 89
Agricultural 90 8 $3,469,408 $2,848,019 $108,566 $2,848,019 $9,274,012 Commercial 281 220 $27,539,816 $66,969,308 $3,020,467 $66,969,308 $164,498,899 Federal Lands 29 0 $0 $0 $0 $0 $0
Government 80 0 $70,569 $0 $0 $0 $70,569
Industrial 57 40 $4,542,641 $8,414,087 $33,549,347 $12,621,131 $59,127,206 Institutional 26 15 $627,402 $5,094,875 $171,670 $5,094,875 $10,988,822

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Plumas County 4-381
Local Hazard Mitigation Plan Update
January 2026
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 70 43 $5,187,298 $9,442,318 $36,430 $9,442,318 $24,108,364 Residential 3,424 2,817 $203,563,790 $571,022,756 $58,484,315 $285,511,378 $1,118,582,239 ROW/Utilities 218 0 $0 $0 $0 $0 $0
Highway 70
and Highway
89 Total
4,275 3,143 $245,000,924 $663,791,363 $95,370,795 $382,487,029 $1,386,650,111 Highway 89
Agricultural 93 5 $4,719,327 $776,986 $12,150 $776,986 $6,285,449 Commercial 99 31 $6,123,411 $9,834,193 $755,529 $9,834,193 $26,547,326 Federal Lands 12 0 $0 $0 $0 $0 $0
Government 75 0 $18,612 $0 $0 $0 $18,612
Industrial 19 6 $1,064,529 $847,891 $0 $1,271,837 $3,184,257 Institutional 16 8 $366,013 $1,533,086 $0 $1,533,086 $3,432,185 Miscellaneous 4 0 $0 $0 $0 $0 $0
Recreational 95 5 $2,031,858 $1,142,034 $1,132,489 $1,142,034 $5,448,415 Residential 3,358 2,015 $320,453,952 $600,807,297 $622,601 $300,403,649 $1,222,287,499 ROW/Utilities 205 0 $0 $0 $0 $0 $0
Highway 89
Total
3,976 2,070 $334,777,702 $614,941,487 $2,522,769 $314,961,784 $1,267,203,742 Highway 89 and Highway 147
Agricultural 7 0 $74,224 $0 $0 $0 $74,224
Commercial 8 2 $404,047 $12,100 $5,500 $12,100 $433,747 Federal Lands 2 0 $0 $0 $0 $0 $0
Government 0 0 $0 $0 $0 $0 $0
Industrial 1 0 $79,590 $0 $0 $0 $79,590
Institutional 0 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 18 4 $951,740 $167,078 $1,221 $83,539 $1,203,578 ROW/Utilities 5 0 $0 $0 $0 $0 $0
Highway 89
and Highway
147 Total
41 6 $1,509,601 $179,178 $6,721 $95,639 $1,791,139

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Plumas County 4-382
Local Hazard Mitigation Plan Update
January 2026
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Unincorporated
Plumas County
Total
13,428 8,412 $892,081,434 $1,905,923,630 $129,776,138 $1,058,551,138 $3,986,332,340 Source: National Hazardous Materials Routes Registry (2025), Plumas County 2024 Parcel/Assessor’s Data Table 4-105 Unincorporated Plumas County – Count and Value of Parcels and Structures in Railroad and Highway Hazardous Materials Transportation Buffer Zone by Property Use
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
BNSF
Agricultural 98 5 $6,570,808 $881,719 $20,260 $881,719 $8,354,506 Commercial 122 44 $7,367,205 $10,387,360 $777,342 $10,387,360 $28,919,267 Federal Lands 10 0 $0 $0 $0 $0 $0
Government 48 0 $16,728 $0 $0 $0 $16,728
Industrial 19 6 $1,144,119 $847,891 $0 $1,271,837 $3,263,847 Institutional 17 9 $379,500 $1,587,499 $0 $1,587,499 $3,554,498 Miscellaneous 7 0 $0 $0 $0 $0 $0
Recreational 16 11 $2,873,781 $661,752 $42,163 $661,752 $4,239,448 Residential 1,849 1,010 $134,325,701 $195,217,680 $523,760 $97,608,840 $427,675,981 ROW/Utilities 162 0 $0 $0 $0 $0 $0
BNSF Total 2,348 1,085 $152,677,842 $209,583,901 $1,363,525 $112,399,007 $476,024,275 BNSF and UP / BNSF
Agricultural 5 0 $0 $0 $0 $0 $0
Commercial 2 0 $130,254 $0 $0 $0 $130,254
Federal Lands 5 0 $0 $0 $0 $0 $0
Government 1 0 $0 $0 $0 $0 $0
Industrial 0 0 $0 $0 $0 $0 $0
Institutional 0 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 1 1 $272,070 $297,381 $0 $297,381 $866,832 Residential 64 30 $3,768,034 $4,392,811 $0 $2,196,406 $10,357,251 ROW/Utilities 12 0 $0 $0 $0 $0 $0

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Plumas County 4-383
Local Hazard Mitigation Plan Update
January 2026
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
BNSF and UP
/ BNSF Total
90 31 $4,170,358 $4,690,192 $0 $2,493,787 $11,354,337
Quincy Railroad
Agricultural 8 2 $350,868 $450,809 $1,420 $450,809 $1,253,906 Commercial 94 76 $9,875,331 $25,223,745 $437,135 $25,223,745 $60,759,956 Federal Lands 2 0 $0 $0 $0 $0 $0
Government 10 0 $0 $0 $0 $0 $0
Industrial 39 23 $3,301,515 $5,283,807 $33,549,347 $7,925,711 $50,060,380 Institutional 13 7 $426,060 $2,515,174 $13,960 $2,515,174 $5,470,368 Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 926 822 $39,751,756 $142,273,400 $57,695,029 $71,136,700 $310,856,885 ROW/Utilities 56 0 $0 $0 $0 $0 $0
Quincy
Railroad Total
1,148 930 $53,705,530 $175,746,935 $91,696,891 $107,252,139 $428,401,495 Quincy Railroad and UP / BNSF
Agricultural 21 8 $2,050,131 $1,582,542 $74,000 $1,582,542 $5,289,215 Commercial 0 0 $0 $0 $0 $0 $0
Federal Lands 3 0 $0 $0 $0 $0 $0
Government 0 0 $0 $0 $0 $0 $0
Industrial 0 0 $0 $0 $0 $0 $0
Institutional 2 0 $0 $0 $0 $0 $0
Miscellaneous 0 0 $0 $0 $0 $0 $0
Recreational 0 0 $0 $0 $0 $0 $0
Residential 272 223 $18,882,230 $56,093,035 $0 $28,046,518 $103,021,783 ROW/Utilities 24 0 $0 $0 $0 $0 $0
Quincy
Railroad and

UP / BNSF
Total
322 231 $20,932,361 $57,675,577 $74,000 $29,629,060 $108,310,998

UP / BNSF
Agricultural 138 20 $13,590,936 $4,507,019 $1,244,367 $4,507,019 $23,849,341 Commercial 182 120 $13,329,365 $44,648,465 $3,991,541 $44,648,465 $106,617,836 Federal Lands 38 0 $0 $0 $0 $0 $0
Government 106 0 $0 $0 $0 $0 $0
Industrial 47 31 $3,750,554 $6,461,503 $190 $9,692,255 $19,904,502

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Plumas County 4-384
Local Hazard Mitigation Plan Update
January 2026
Hazardous
Materials
Routes/
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Institutional 12 3 $184,744 $1,706,933 $6,650 $1,706,933 $3,605,260 Miscellaneous 2 0 $0 $0 $0 $0 $0
Recreational 75 47 $5,535,663 $15,377,033 $497,081 $15,377,033 $36,786,810 Residential 4,250 2,819 $259,724,454 $605,239,651 $3,508,993 $302,619,826 $1,171,092,924 ROW/Utilities 237 0 $0 $0 $0 $0 $0

UP / BNSF
Total
5,087 3,040 $296,115,716 $677,940,604 $9,248,822 $378,551,530 $1,361,856,672 Unincorporated
Plumas County
Total
8,995 5,317 $527,601,807 $1,125,637,209 $102,383,238 $630,325,521 $2,385,947,775 Source: National Hazardous Materials Routes Registry (2025), Plumas County 2024 Parcel/Assessor’s Data Critical Facilities and Infrastructure
A separate analysis was performed on the critical facility inventory in the Plumas County Planning Area to determine critical facilities in the hazardous materials buffer zones. Using GIS, the hazardous material buffer zones were overlayed on the critical facility GIS layer. Figure 4-171 shows critical facilities and the highway and railroad hazardous material buffer zones (with the inset maps shown). These inset maps are shown in Figure 4-172 through Figure 4-174. Table 4-106 and Table 4-107 detail critical facilities in highway and railroad (respectively) hazardous material buffer zone zones by facility type and count for the Plumas County Planning Area broken out by jurisdiction. Details of critical facilities by type, name, and address by flood zone are listed in Appendix G.

As shown on these tables, 24 critical facilities in the City of Portola fall in both the highway and railroad hazardous material buffer zone. In Plumas County, 464 critical facilities fall in the highway hazardous materials buffer zone, while 286 fall in the railroad hazardous materials buffer zone. Additionally, 8 of the critical facilities in the surrounding counties fall in the highway hazardous materials buffer zone, while 9 fall in the railroad hazardous materials buffer zone.

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Plumas County 4-385
Local Hazard Mitigation Plan Update
January 2026
Figure 4-171 Plumas County Planning Area – Critical Facilities in Highway and Railroad Hazardous Materials Buffer Zones (Overview Map with Insets)

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Plumas County 4-386
Local Hazard Mitigation Plan Update
January 2026
Figure 4-172 Plumas County Planning Area – Critical Facilities in Highway and Railroad Hazardous Materials Buffer Zones (Map Inset 1)

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Plumas County 4-387
Local Hazard Mitigation Plan Update
January 2026
Figure 4-173 Plumas County Planning Area – Critical Facilities in Highway and Railroad Hazardous Materials Buffer Zones (Map Inset 2)

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Plumas County 4-388
Local Hazard Mitigation Plan Update
January 2026
Figure 4-174 Plumas County Planning Area – Critical Facilities in Highway and Railroad Hazardous Materials Buffer Zones (Map Inset 3)

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Plumas County 4-389
Local Hazard Mitigation Plan Update
January 2026
Table 4-106 Plumas County Planning Area – Critical Facilities in Critical Facilities in Highway Hazardous Materials Buffer Zones by Jurisdiction and Critical Facility Category
Jurisdiction / Hazardous Materials
Routes
Critical Facility Category Facility Count
Portola
Highway 70
Essential Services Facilities 16
At Risk Populations Facilities 8
Total 24
Portola Total 24
Unincorporated Plumas County
Highway 147
Essential Services Facilities 13
Total 13
Highway 147 and Highway 89
Essential Services Facilities 8
Total 8
Highway 36
Essential Services Facilities 45
At Risk Populations Facilities 10
Hazardous Materials Facilities 1
Total 56
Highway 36 and Highway 89
Essential Services Facilities 8
Total 8
Highway 49 and Highway 70
Essential Services Facilities 3
Total 3
Highway 70
Essential Services Facilities 98
At Risk Populations Facilities 2
Total 100
Highway 70 and Highway 89
Essential Services Facilities 202
At Risk Populations Facilities 14
Hazardous Materials Facilities 2
Total 218
Highway 89
Essential Services Facilities 55
At Risk Populations Facilities 3
Total 58
Unincorporated Plumas County Total 464
Unincorporated Butte County
Highway 70
Essential Services Facilities 1
Total 1
Unincorporated Butte County Total 1

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Plumas County 4-390
Local Hazard Mitigation Plan Update
January 2026
Jurisdiction / Hazardous Materials
Routes
Critical Facility Category Facility Count
Unincorporated Lassen County
Highway 36
Essential Services Facilities 4
Total 4
Unincorporated Lassen County Total 4
Unincorporated Sierra County
Highway 49
Essential Services Facilities 2
Total 2
Unincorporated Sierra County Total 2
Unincorporated Tehama County
Highway 36
Essential Services Facilities 1
Total 1
Unincorporated Tehama County Total 1
Grand Total 496
Source: National Hazardous Route Registry, Plumas County GIS Table 4-107 Plumas County Planning Area – Critical Facilities in Critical Facilities in Railroad Hazardous Materials Buffer Zones by Jurisdiction and Critical Facility Category
Jurisdiction / Hazardous Materials
Routes
Critical Facility Category Facility Count
Portola

UP / BNSF
Essential Services Facilities 16
At Risk Populations Facilities 8
Total 24
Portola Total 24
Unincorporated Plumas County
BNSF
Essential Services Facilities 55
At Risk Populations Facilities 3
Total 58
BNSF and UP / BNSF
Essential Services Facilities 15
Total 15
Quincy Railroad
Essential Services Facilities 44
At Risk Populations Facilities 2
Hazardous Materials Facilities 1
Total 47
Quincy Railroad and UP / BNSF Essential Services Facilities 5

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Plumas County 4-391
Local Hazard Mitigation Plan Update
January 2026
Jurisdiction / Hazardous Materials
Routes
Critical Facility Category Facility Count
Total 5

UP / BNSF
Essential Services Facilities 158
At Risk Populations Facilities 2
Hazardous Materials Facilities 1
Total 161
Unincorporated Plumas County Total 286
Unincorporated Butte County

UP / BNSF
Essential Services Facilities 3
Total 3
Unincorporated Butte County Total 3
Unincorporated Lassen County
BNSF
Essential Services Facilities 3
Total 3

UP / BNSF
Essential Services Facilities 3
Total 3
Unincorporated Lassen County Total 6
Grand Total 319
Source: National Hazardous Route Registry, Plumas County GIS Natural, Historic, and Cultural Resources
Any natural, historic, or cultural resource that falls in the buffer zone shown on Figure 4-167 has some measure of vulnerability. If a release caused a fire, it could affect historic and cultural resources in the County. Natural resources can be more greatly affected by a hazardous materials spill. Clean up of a spill into a natural resource (such as a creek, stream, or river) may be difficult to complete. Hazardous releases can significantly harm wildlife and habitat areas. The contamination also can make its way up the food chain, affecting the food supply. Open water and wetland environments experience significant exposure to hazardous materials events, which may result in further loss of ecosystem functions.

FEMA NRI Hazard Vulnerability Assessment
Hazardous material transport is not an NRI hazard; therefore, no data is presented.

Impacts from Hazardous Materials Transportation
Impacts from hazardous materials transportation incidents vary by location and severity of any given event and will likely only affect certain areas of the County during specific times. Based on the risk assessment, it a hazardous materials transportation release could have potential adverse impacts to affected areas of the County as described below. However, the majority of releases in the County are minor, localized events

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Plumas County 4-392
Local Hazard Mitigation Plan Update
January 2026
that are more of a nuisance than a disaster. Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Contaminated water supplies
➢ Contaminated buildings
➢ Soil contamination that results in mass die-off of vegetation ➢ Fire and explosions
➢ Public health impacts
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Business closures and significant economic impact (jobs, sales, tax revenue) to the community; ➢ Negative impact on commercial and residential property values; and ➢ Impact on the overall mental health of the community.

Future Conditions/Future Development
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 unlikely to exacerbate future hazardous material transportation events and associated impacts and vulnerability of the County.
➢ Population in Plumas County is expected to decrease. Vulnerable population groups could face disproportionate effects from a hazardous materials release and should be planned for. 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. However, it is difficult to locate development outside of the hazardous materials buffer zones, due to the location of rail lines and highways in the County. Building codes do not account for hazardous materials spills or incidents.

More development within the hazardous materials buffer zones is likely to increase the vulnerability of the County to this hazard.

Development will continue to happen within hazardous materials transportation corridors due to the large area within the County located within these corridors. Those who choose to develop in these areas should be made aware of the risks associated with living within close proximity to a hazardous materials transportation route. Future development areas and their vulnerability to hazardous materials transport are discussed further in the below GIS analysis.

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GIS Analysis
Plumas County provided 13 future development areas which were used as the basis for the inventory of future development for the unincorporated County. These were mapped in GIS. Many facilities fall in either the highway or railroad hazardous materials buffer zone. Figure 4-179 show the locations of the future development areas and both the highway and railroad hazardous materials buffer zone. Table 4-108 shows the details of the future development areas that are located in the highway hazardous materials buffer zone. Table 4-109 shows the details of the future development areas that are located in the railroad hazardous materials buffer zone.

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Figure 4-175 Unincorporated Plumas County – Future Development in Highway and Railroad Hazardous Materials Buffer Zones

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Table 4-108 Unincorporated Plumas County – Future Development in Highway Hazardous Materials Buffer Zones with Parcel Counts and Acreages
Hazardous
Materials
Routes /Site /
Map ID and
Future
Development
Name
Total Parcel
Count
Improved
Parcel Count
Unimproved
Parcel Count
Total Acres Total
Improved
Acres
Total
Unimproved
Acres
Highway 36
Approved
G - Seneca
Hospital 1 0 1 11.80 0.00 11.80
Approved Total 1 0 1 11.80 0.00 11.80
Highway 49 and Highway 70
Approved
J - Meadow
Edge Mobile
Home Park
1 1 0 42.74 42.74 0.00
Approved Total 1 1 0 42.74 42.74 0.00
Highway 70 and Highway 89
Approved
A - CHP Station 1 0 1 5.00 0.00 5.00
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
K - North Star
Navigation
Center - Phase 2
1 1 0 1.00 1.00 0.00
Approved Total 5 2 3 15.51 5.50 10.01
Proposed
L - Plumas
County
Courthouse
1 1 0 2.86 2.86 0.00
Proposed Total 1 1 0 2.86 2.86 0.00
Conceptual
M - Housing
Element RHNA
Site
1 1 0 3.64 3.64 0.00

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Hazardous
Materials
Routes /Site /
Map ID and
Future
Development
Name
Total Parcel
Count
Improved
Parcel Count
Unimproved
Parcel Count
Total Acres Total
Improved
Acres
Total
Unimproved
Acres
Conceptual
Total 1 1 0 3.64 3.64 0.00
Highway 89
Approved
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
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
Approved Total 4 0 4 6.97 0.00 6.97
Source: National Hazardous Materials Route Registry, Plumas County GIS Table 4-109 Unincorporated Plumas County – Future Development in Railroad Hazardous Materials Buffer Zones with Parcel Counts and Acreages
Hazardous
Materials
Routes /Site /
Map ID and
Future
Development
Name
Total Parcel
Count
Improved
Parcel Count
Unimproved
Parcel Count
Total Acres Total
Improved
Acres
Total
Unimproved
Acres
BNSF
Approved
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
H - Way Station 1 0 1 0.28 0.00 0.28

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Hazardous
Materials
Routes /Site /
Map ID and
Future
Development
Name
Total Parcel
Count
Improved
Parcel Count
Unimproved
Parcel Count
Total Acres Total
Improved
Acres
Total
Unimproved
Acres
I - Indian Valley
Public Safety
Center
1 0 1 5.00 0.00 5.00
Approved Total 4 0 4 6.97 0.00 6.97
Quincy Railroad
Approved
A - CHP Station 1 0 1 5.00 0.00 5.00
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
Approved Total 3 1 2 10.39 4.50 5.89

UP / BNSF
Approved
J - Meadow
Edge Mobile
Home Park
1 1 0 42.74 42.74 0.00
Approved Total 1 1 0 42.74 42.74 0.00
Source: National Hazardous Materials Route Registry, Plumas County GIS

4.3.14. Landslides, Mudslides, and Debris Flows
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
Like its earthquake‐generating faults, California’s mountainous terrain is a consequence of dynamic geologic processes in operation as the North American Plate grinds past the Pacific Plate. According to the CGS, a landslide is a general term for a variety of mass-movement processes that generate a down-slope movement of mud, soil, rock, and/or vegetation. Landslides are classified into many different types based on form and type of movement. They range from slow‐moving rotational slumps and earth flows, which can slowly distress structures but are less threatening to personal safety, to fast‐moving rock avalanches and debris flows that are a serious threat to structures and have been responsible for most fatalities during

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landslide events. For the purposes of this LHMP Update, the term landslide includes mudslides, debris flows, and rockfalls that tend to occur suddenly; as well as hillside erosion, which is a similar process that tends to occur on smaller scales and more gradually but can exacerbate landslide events.

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

Soil erosion is another common form of soil instability. Erosion is a function of soil type, slope, rainfall intensity, and groundcover. It accounts for a loss in many dollars of valuable soil, is aesthetically displeasing, and often induces even greater rates of erosion and sedimentation. Sedimentation is simply the accumulation of soil as a result of erosion. Construction activities often contribute greatly to erosion and sedimentation. Besides being a pollutant in its own right, sediment acts as a transport medium for other pollutants, especially nutrients, pesticides, and heavy metals, which adhere to the eroded soil particles. As the sediment drains into watercourses, the combination of these pollutants adversely affects water quality and can eventually impact stream flows and contribute to flooding potential. Conditions that contribute to landslide, mudslides, debris flows, hillside and streambank erosion, include the following:
➢ Degree of slope
➢ Water (heavy rain, river flows, or wave action)
➢ Unconsolidated soil or soft rock and sediments
➢ Lack of vegetation (no stabilizing root structure)
➢ Previous wildfires and other forest disturbances (discussed in Section 4.3.15) ➢ Road building, excavation, and grading
➢ Earthquake
The 2023 State of California Hazard Mitigation Plan noted that more than one third of California is mountainous terrain that generally trends parallel to the coast, forming a barrier that captures moisture from offshore storms originating in the Gulf of Alaska and Mexico. Steep topography, weak rocks, heavy winter rains, and occasional earthquakes all lead to slope failures more frequently than would otherwise occur under gravity alone. This is true in the mountainous, sloped areas within the Planning Area where the topography is characterized by more substantial elevation changes.

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

Figure 4-176 shows the CGS areas susceptible to deep seated landslides. The legend on Figure 4-176 shows the susceptibility scale (from 0-X with 0 being the least and X being the most susceptible) that the CGS uses to show the susceptibility of landslides. It is a primarily a combination of slope class and rock strength.

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Geographic extents of these classes for the unincorporated Plumas County are shown on Table 4-110.

Details on each participating jurisdiction’s CGS deep-seated landslide extents can be found in their respective annexes to this LHMP Update. According to the 2023 State Hazard Mitigation Plan, the susceptibility classes were further categorized into Very High (susceptibility class X) and High (susceptibility classes VII, VIII, & IX) for exposure analysis. The rest of the classes were not categorized.

CGS mapping indicates that much of the County and surrounding area have areas at high to very high susceptibility areas for landslides. This can be seen in the darker orange and red colors.

The speed of onset of landslide is often short, especially in post-wildfire burn scar areas, but it can also take years for a slope to fail. Landslide duration is usually short, though digging out and repairing landslide areas can take some time. In Plumas County, landslides generally occur where there is very little population or infrastructure.

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Figure 4-176 Plumas County Planning Area – Susceptibility to Deep Seated Landslides

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Table 4-110 Plumas County Planning Area – Geographical Extent of Deep-Seated Landslide Classes
Deep Seated
Landslide Class
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
City of Portola
0 2,001 57% 1,372 61% 629 50%
III 402 12% 402 18% 0.5 0.04%
V 116 3% 5 0.2% 111 9%
VI 248 7% 248 11% -
VII 598 17% 204 9% 394 31%
VIII 60 2% 1 0.03% 59 5%
IX 59 2% 4 0.2% 55 4%
X 6 0.2% 1 0.1% 5 0.4%
Grand Total 3,491 100% 2,237 100% 1,254 100%
Unincorporated Plumas County
0 269,918 21% 17,483 36% 252,435 20%
III 111,182 8% 2,240 5% 108,941 9%
V 171,220 13% 5,456 11% 165,764 13%
VI 110,673 8% 1,821 4% 108,851 9%
VII 224,116 17% 12,774 26% 211,342 17%
VIII 223,848 17% 2,774 6% 221,074 17%
IX 180,031 14% 4,154 9% 175,876 14%
X 21,713 2% 1,782 4% 19,931 2%
Grand Total 1,312,701 100% 48,485 100% 1,264,216 100%
Source: Susceptibility to Deep-Seated Landslides map – CSG Map Sheet 58 (05/2011) Past Occurrences
Disaster Declaration History
There have been no disaster declarations associated solely with landslides in Plumas County; however, as shown in Table 4-111, there have been 7 state and 5 federal disaster declarations for flood which included landslides as a component.

Table 4-111 Plumas County – Federal and State Disaster Declarations Summary 1950-2025 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Flood (those events that
included landslide)
7 1992*, 1995 (twice*), 2017
(twice*), 2023 (twice*)
5 2006*, 2017 (twice*), 2023
(twice*)
Source: Cal OES, FEMA. Retrieved March 2025.

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NCDC Events
The NCDC contains 21 records for landslides or debris flows in Plumas County since 1993, which can be seen in Table 4-111.

Table 4-112 NCDC Landslide and Debris Flow Events for Plumas County 1993-7/31/2024* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Debris Flows 21 0 0 0 0 $2,000 $0
Source: NCDC
*Note: Losses reflect totals for all impacted areas, some of which fell outside of Plumas County Hazard Mitigation Planning Committee Events
There are certain areas within the County that are susceptible to slope failure resulting in localized landslides, mudslides, and debris flows. These areas are detailed in the Local Concern section below.

These sections separate events since the 2019/2020 LHMPs and those before 2019.

Events since 2019/2020 LHMP
The County noted no damaging landslides that have occurred since 2019. Minor landsliding has likely occurred, but no damages could be recalled.

Events before 2019
The HMPC reported the following events of landslide in the County:
➢ 2006 – A rockslide occurred on State Route 70 1.5 miles west of Pulga. No injuries or deaths occurred.

Damages were unknown from this event.
➢ 2009 – A rockslide occurred on State Route 70 near Rich bar. Some injuries were reported, but details could not be recalled. Damages were unknown from this event. ➢ 2010 – A landslide occurred on the USFS Road (Scales Road). No injuries or deaths occurred.

Damages were unknown from this event.
➢ 2010 – A rockslide occurred on State Route 70 between Greenville Way and Elephant Butte Tunnel.

No injuries or deaths occurred. Damages were unknown from this event. ➢ 2013 – A rockslide occurred. There was damage to County Road 411 5 miles west of State Route 70 at Quincy in the Bucks Lake area. No injuries or deaths occurred. Damages were unknown from this event.
➢ 2013 – Major slope failure has occurred on Johnsville Road / County Highway A14 approximately 4.6 miles west of the intersection of the intersection of SR89 at Blairsdale / Graeagle. The slope failure condition has been prevalent for more than 5 years, and is a result of weak soils, slop and water related erosion. This particular roadway is the only paved road that connects Graeagle to Johnsville. The only other transportation route connecting Johnsville is a dirt road which is essentially impassable in the winter. As a safety precaution, the roadway shoulder has been narrowed several times in order to avoid the on-site erosion issues. Slope saturation by water is a primary cause of landslide issue at this location.

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Figure 4-177 Slope Failure near Johnsonville on County Highway A14 Source: Plumas County
➢ 2017 – A flood occurred in a canyon above Greenville in February. This caused multiple mudslides that blocked Highway 89. This road is an ingress and egress route for Indian Valley.

Likelihood of Future Occurrence
Likely—Based on data provided by the HMPC, landslides are naturally occurring events that will inevitably happen as long as gravity itself is a controlling factor upon the landscape. Since Plumas County’s mountainous terrain in much of the County challenges gravity as it rapidly rises to upper elevations, much of the high-relief topography in the County can be identified as land with the potential for landslides. Much of that land though is in remote and undeveloped locales, which reduces the risk and vulnerability of this natural hazard. Given the nature of localized problems identified within the County, landslides will likely continue to impact the area when heavy precipitation occurs, as they have in the past.

It is likely that climate change will increase the chance of future occurrence as well as future impacts. More information on climate change and landslide and debris flow 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 Landslide and Debris Flows
According to the 2021 CAS (as well as the 2024 Draft CAS), climate change may result in precipitation extremes (i.e., wetter wet periods and drier dry periods). More information on precipitation increases can be found in Section 4.3.3. While total average annual rainfall may decrease only slightly, rainfall is

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predicted to occur in fewer, more intense precipitation events. The combination of a generally drier climate in the future, which will increase the chance of drought and wildfires, and the occasional extreme downpour is likely to cause more mudslides, landslides, and debris flows.

Vulnerability Assessment
Vulnerability—Medium
According to historical hazard data and landslide hazard mapping, landslides can occur in the Plumas County Planning Area. 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.

The 2035 Plumas County General Plan Public Health & Safety Element noted that areas with steep slopes in the County could be prone to landslides, mud slides and avalanches. Landslides, or ground failure, are dependent on slope, geology, rainfall, excavation or seismic activity. Mud slides are often caused by heavy rainfall. Areas that have recently been subject to wildfire are susceptible to mud slides. In Plumas County, landslides generally occur where there is very little population or infrastructure. However, there are certain areas throughout the Plumas County Planning Area prone to landslides and where damages have occurred.

Though not shown on the USGS map, the 2035 General Plan Public Health and Safety Element noted that the volcanic soils in the eastern portion of the Plumas National Forest are prone to landslides. It was also noted that areas concentrated along the North and Middle Forks of the Feather River are also susceptible to landslides, as well as post-wildfire fire areas.

Plumas County Public Works also noted areas of reoccurring slope failure on County Roads:
➢ Hwy 89 on the way to Greenville
➢ Hwy 70 continuous
➢ Chester/Warner Valley drainage has changed
➢ Butterfly/Twain Road
➢ Beckwourth/Genesse Road
➢ Arlington Road
➢ Gold Lake Forest Highway
➢ Quincy-LaPorte Road
➢ Bucks Lake Road
➢ Big Creek Road
➢ North Valley Road

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➢ Mill Creek at SR70
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 landslide 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.

Methodology (Parcels and Structures)
The 2011 California Geologic Survey Deep Seated Landslide Susceptibility data was obtained for the Plumas County Planning Area. The 2024 Plumas County Parcel/Assessor Data was used as the basis for the inventory of all parcels within the Plumas County Planning Area. GIS was used to overlay the landslide hazard layer onto the parcel layer. Since it is possible for any given parcel to intersect with multiple categories for purposes of this analysis, the most conservative (or highest risk) deep-seated landslide class that intersected each parcel was used to determine which class to assign to each parcel. Once completed, the deep-seated landslide class parcel layer was joined to the assessor data to determine the number of parcels and values falling within each class. Based on this approach, the deep-seated landslide classes for the Planning Area and unincorporated Plumas County were determined and further broken out by property use and included information on both land and improved values and estimated contents values.

Note: similar to other hazard analyses, all analyses were performed on the parcel polygon. For the landslide (and other) hazard, the highest hazard category applied to the parcel polygon. This landslide analysis can be misleading since multiple classes may fall within one polygon, and there are many large polygons throughout the County.

People and Populations
All populations located within areas of landslide susceptibility, especially in the High to Very High hazard areas (i.e., Classes VII to X) are at some vulnerability to landslide. This includes those people residing in these landslide potential areas as well as those that might reside or work within the landslide run out areas.

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

Plumas County Planning Area residents that live in the High and Very High landslide susceptibility areas are often the most vulnerable, but those who live in in the landslide run out areas (which are not mapped)

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are also vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to Planning Area’s residential population residing within these hazard areas, an analysis was conducted of those who physically reside in the mapped landslide susceptibility areas. The CGS Susceptibility to Deep Seated Landslide maps were overlayed on the parcel layer and linked to the assessor data. Those residential parcel polygons that intersect the High or Very High risk areas (Class VII or higher) were counted and multiplied by the 2023 Census Bureau American Community Survey average household factors each jurisdiction in the Planning Area. Analysis results are shown in Table 4-113.

Table 4-113 Plumas County Planning Area – Residential Populations in High or Very High Deep Seated Landslide Classes
Deep Seated Landslide
Class/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
Class VII
City of Portola 513 1,175
Unincorporated County 2,710 6,477
Class VIII
City of Portola 0 0
Unincorporated County 933 2,230
Class IX
City of Portola 44 101
Unincorporated County 1,444 3,451
Class X
City of Portola 9 21
Unincorporated County 830 1,984
Source: CGS, Plumas County 2024 Parcel/Assessor’s Data, 2023 US Census American Community Survey Average Household Size – City of Portola (2.29); Unincorporated Plumas County (2.39).

Structures
Landslides can affect the built environment of the Plumas County Planning Area and those structures located within the high to very high hazard areas (i.e., Classes VII to X) are especially vulnerable, as are the structures located within the landslide run out areas. The CGS Deep Seated Landslide Susceptibility layer was overlaid with the County parcel (structure) layer in GIS and linked to the assessor data. The mapped landslide areas are shown on Figure 4-176. Table 4-114 summarizes parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), personal property values, estimated content replacement values, and total values in the Planning Area for deep seated landslide classes. Table 4-115 summarizes parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), personal property values, estimated content replacement values, and total values by property use for the unincorporated County for deep seated landslide classes. As shown, many improved parcels fall in Classes VII to X in the Portola as well as in the unincorporated County.

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Table 4-114 Plumas County Planning Area – Count and Value of Parcels and Structures in Deep Seated Landslide Class by Jurisdiction
Jurisdiction /
Susceptibility
to Deep-Seated
Landslide Class
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola
0 540 395 $12,942,889 $49,148,720 $53,696 $29,001,715 $91,147,020 III 2 0 $56,463 $0 $0 $0 $56,463
V 22 10 $560,793 $2,627,044 $0 $2,241,074 $5,428,911
VI 1 1 $21,106 $2,429 $0 $1,215 $24,750
VII 940 557 $19,519,134 $86,443,389 $1,678,026 $55,910,625 $163,551,174 VIII 2 1 $529,643 $1,400,712 $0 $1,400,712 $3,331,067
IX 105 48 $2,773,597 $6,470,686 $35,120 $3,507,842 $12,787,245 X 31 9 $1,546,746 $5,158,054 $148,230 $2,579,027 $9,432,057 Not in a
Landslide Class
0 0 $0 $0 $0 $0 $0
City of Portola
Total
1,643 1,021 $37,950,371 $151,251,034 $1,915,072 $94,642,209 $285,758,686 Unincorporated Plumas County
0 7,133 4,848 $377,748,466 $941,215,911 $98,515,649 $546,539,951 $1,964,019,977 III 426 188 $18,511,321 $33,844,115 $203,800 $17,392,879 $69,952,115 V 3,478 1,991 $313,658,890 $620,338,134 $1,853,913 $316,361,786 $1,252,212,723 VI 447 184 $18,609,277 $30,571,867 $183,993 $15,715,842 $65,080,979 VII 4,899 2,847 $282,021,385 $605,509,339 $6,302,556 $319,914,993 $1,213,748,273 VIII 2,196 970 $191,923,312 $284,500,071 $1,141,051 $150,585,108 $628,149,542 IX 3,466 1,486 $293,745,442 $446,129,929 $2,611,482 $230,868,937 $973,355,790 X 2,188 912 $167,960,204 $239,869,245 $30,715,119 $136,295,794 $574,840,362 Not in a
Landslide Class
1 1 $816,431 $966,667 $0 $483,334 $2,266,432
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 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: Susceptibility to Deep-Seated Landslides map – CSG Map Sheet 58 (05/2011), Plumas County 2024 Parcel/Assessor Data

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Table 4-115 Unincorporated Plumas County – Count and Value of Parcels and Structures in Deep Seated Landslide Class by Property Use
Susceptibility to
Deep-Seated
Landslide Class
/ Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
0 Agricultural 117 25 $10,455,490 $3,300,763 $95,569 $3,300,763 $17,152,585 Commercial 544 375 $48,461,504 $105,470,321 $4,369,631 $105,470,321 $263,771,777 Federal Lands 3 0 $0 $0 $0 $0 $0
Government 128 0 $46,383 $0 $0 $0 $46,383
Industrial 112 73 $8,641,335 $16,776,154 $33,550,208 $25,164,231 $84,131,928 Institutional 52 25 $1,072,469 $6,582,289 $183,350 $6,582,289 $14,420,397 Miscellaneous 1 0 $0 $0 $0 $0 $0
Recreational 100 43 $2,932,129 $2,958,310 $42,163 $2,958,310 $8,890,912 Residential 5,859 4,307 $306,139,156 $806,128,074 $60,274,728 $403,064,037 $1,575,605,995 ROW/Utilities 217 0 $0 $0 $0 $0 $0
0 Total 7,133 4,848 $377,748,466 $941,215,911 $98,515,649 $546,539,951 $1,964,019,977 III
Agricultural 4 0 $59,483 $0 $0 $0 $59,483
Commercial 3 2 $159,876 $938,111 $69,620 $938,111 $2,105,718 Federal Lands 4 0 $0 $0 $0 $0 $0
Government 1 0 $0 $0 $0 $0 $0
Miscellaneous 1 0 $0 $0 $0 $0 $0
Recreational 45 1 $318,263 $3,531 $0 $3,531 $325,325
Residential 341 185 $17,973,699 $32,902,473 $134,180 $16,451,237 $67,461,589 ROW/Utilities 27 0 $0 $0 $0 $0 $0
III Total 426 188 $18,511,321 $33,844,115 $203,800 $17,392,879 $69,952,115 V
Agricultural 25 0 $185,335 $0 $0 $0 $185,335
Commercial 48 24 $3,923,156 $6,030,434 $603,043 $6,030,434 $16,587,067 Federal Lands 1 0 $0 $0 $0 $0 $0
Government 25 0 $1,884 $0 $0 $0 $1,884
Industrial 3 2 $410,326 $283,628 $0 $425,442 $1,119,396 Institutional 3 2 $644,990 $4,127,648 $6,380 $4,127,648 $8,906,666 Miscellaneous 1 0 $0 $0 $0 $0 $0
Recreational 143 14 $1,058,206 $1,660,099 $4,080 $1,660,099 $4,382,484 Residential 3,099 1,949 $307,434,993 $608,236,325 $1,240,410 $304,118,163 $1,221,029,891 ROW/Utilities 130 0 $0 $0 $0 $0 $0

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Plumas County 4-409
Local Hazard Mitigation Plan Update
January 2026
Susceptibility to
Deep-Seated
Landslide Class
/ Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
V Total 3,478 1,991 $313,658,890 $620,338,134 $1,853,913 $316,361,786 $1,252,212,723 VI
Agricultural 9 0 $65,468 $0 $0 $0 $65,468
Commercial 7 4 $317,418 $619,186 $2,140 $619,186 $1,557,930 Federal Lands 2 0 $0 $0 $0 $0 $0
Government 12 0 $0 $0 $0 $0 $0
Institutional 1 0 $0 $0 $0 $0 $0
Recreational 48 1 $889,560 $240,630 $0 $240,630 $1,370,820 Residential 340 179 $17,336,831 $29,712,051 $181,853 $14,856,026 $62,086,761 ROW/Utilities 28 0 $0 $0 $0 $0 $0
VI Total 447 184 $18,609,277 $30,571,867 $183,993 $15,715,842 $65,080,979 VII
Agricultural 145 31 $11,886,009 $6,169,855 $1,744,048 $6,169,855 $25,969,767 Commercial 123 84 $10,104,580 $23,790,387 $2,577,642 $23,790,387 $60,262,996 Federal Lands 8 0 $0 $0 $0 $0 $0
Government 87 0 $0 $0 $0 $0 $0
Industrial 17 7 $1,369,781 $1,121,799 $0 $1,682,699 $4,174,279 Institutional 14 9 $230,101 $1,448,564 $0 $1,448,564 $3,127,229 Miscellaneous 4 0 $718 $0 $0 $0 $718
Recreational 102 6 $1,712,467 $668,243 $638 $668,243 $3,049,591 Residential 4,124 2,710 $256,717,729 $572,310,491 $1,980,228 $286,155,246 $1,117,163,694 ROW/Utilities 275 0 $0 $0 $0 $0 $0
VII Total 4,899 2,847 $282,021,385 $605,509,339 $6,302,556 $319,914,993 $1,213,748,273 VIII
Agricultural 293 4 $6,834,080 $3,147,203 $14,808 $3,147,203 $13,143,294 Commercial 44 26 $7,903,254 $8,373,995 $455,031 $8,373,995 $25,106,275 Federal Lands 43 0 $0 $0 $0 $0 $0
Government 77 0 $70,569 $0 $0 $0 $70,569
Industrial 1 1 $29,916 $239,168 $0 $358,752 $627,836
Institutional 2 0 $0 $0 $0 $0 $0
Miscellaneous 9 0 $4,158 $0 $0 $0 $4,158
Recreational 35 6 $5,098,413 $4,670,611 $643,730 $4,670,611 $15,083,365 Residential 1,586 933 $171,982,922 $268,069,094 $27,482 $134,034,547 $574,114,045 ROW/Utilities 106 0 $0 $0 $0 $0 $0
VIII Total 2,196 970 $191,923,312 $284,500,071 $1,141,051 $150,585,108 $628,149,542

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January 2026
Susceptibility to
Deep-Seated
Landslide Class
/ Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
IX
Agricultural 470 14 $23,445,085 $3,827,148 $50,490 $3,827,148 $31,149,871 Commercial 49 20 $3,040,750 $7,712,649 $190,618 $7,712,649 $18,656,666 Federal Lands 61 0 $0 $0 $0 $0 $0
Government 133 0 $6,120 $0 $0 $0 $6,120
Industrial 6 2 $191,926 $28,784 $0 $43,176 $263,886
Institutional 4 0 $0 $0 $0 $0 $0
Miscellaneous 6 0 $4,715 $0 $0 $0 $4,715
Recreational 24 6 $1,833,144 $4,010,580 $627,070 $4,010,580 $10,481,374 Residential 2,547 1,444 $265,223,702 $430,550,768 $1,743,304 $215,275,384 $912,793,158 ROW/Utilities 166 0 $0 $0 $0 $0 $0
IX Total 3,466 1,486 $293,745,442 $446,129,929 $2,611,482 $230,868,937 $973,355,790 X
Agricultural 247 44 $17,351,867 $8,534,676 $861,612 $8,534,676 $35,282,831 Commercial 35 21 $4,689,342 $11,409,329 $24,008,160 $11,409,329 $51,516,160 Federal Lands 95 0 $0 $0 $0 $0 $0
Government 136 0 $0 $0 $0 $0 $0
Industrial 1 0 $90,337 $0 $0 $0 $90,337
Institutional 4 3 $197,556 $1,777,668 $6,650 $1,777,668 $3,759,542 Miscellaneous 4 0 $0 $0 $0 $0 $0
Recreational 22 14 $4,347,966 $11,000,669 $496,443 $11,000,669 $26,845,747 Residential 1,527 830 $141,283,136 $207,146,903 $5,342,254 $103,573,452 $457,345,745 ROW/Utilities 117 0 $0 $0 $0 $0 $0
X Total 2,188 912 $167,960,204 $239,869,245 $30,715,119 $136,295,794 $574,840,362 Not in a Landslide Class
Residential 1 1 $816,431 $966,667 $0 $483,334 $2,266,432 Not in a
Landslide Class
Total
1 1 $816,431 $966,667 $0 $483,334 $2,266,432
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: Susceptibility to Deep-Seated Landslides map – CSG Map Sheet 58 (05/2011), Plumas County 2024 Parcel/Assessor Data

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Critical Facilities and Infrastructure
Landslides present a threat to critical facilities and infrastructure. The following analysis discusses critical facilities and infrastructure. A separate analysis was performed on the critical facility inventory in the Plumas County Planning Area to determine critical facilities by deep-seated landslide class. Using GIS, the landslide classes were overlayed on the critical facility GIS layer. Figure 4-178 shows critical facilities, as well as the deep-seated landslide classes. Table 4-116 details critical facilities by deep seated landslide class by facility category and count for the Planning Area. Details of critical facility category, type, name and address by deep-seated landslide classes are listed in Appendix G. As shown, 276 critical facilities fall in classes VII to X, 5 of which are in Portola, 265 in the unincorporated County, and the 6 in the surrounding counties.

Figure 4-178 Plumas County Planning Area – Critical Facilities in Deep-Seated Landslide Class

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January 2026
Table 4-116 Plumas County Planning Area – Critical Facilities in Deep-Seated Landslide Class by Jurisdiction and Critical Facility Category
Jurisdiction / Susceptibility to DeepSeated Landslide ClassCritical Facility Category Facility Count Portola
0 Essential Services Facilities 14
At Risk Populations Facilities 5
Hazardous Materials Facilities 0
0 Total 19
VII
Essential Services Facilities 1
At Risk Populations Facilities 3
Hazardous Materials Facilities 0
VII Total 4
IX
Essential Services Facilities 1
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
IX Total 1
Portola Total 24
Unincorporated Plumas County
0 Essential Services Facilities 407
At Risk Populations Facilities 25
Hazardous Materials Facilities 3
0 Total 435
III
Essential Services Facilities 52
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
III Total 52
V
Essential Services Facilities 70
At Risk Populations Facilities 2
Hazardous Materials Facilities
V Total 72
VI
Essential Services Facilities 41
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
VI Total 41
VII
Essential Services Facilities 154
At Risk Populations Facilities 6
Hazardous Materials Facilities 0

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January 2026
Jurisdiction / Susceptibility to DeepSeated Landslide ClassCritical Facility Category Facility Count VII Total 160
IX
Essential Services Facilities 94
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
IX Total 94
X
Essential Services Facilities 11
At Risk Populations Facilities 0
Hazardous Materials Facilities 1
X Total 12
Unincorporated Plumas County Total 866
Unincorporated Butte County
0 Essential Services Facilities 3
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
0 Total 3
VII
Essential Services Facilities 1
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
VII Total 1
Unincorporated Butte County Total 4
Unincorporated Lassen County
0 Essential Services Facilities 27
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
0 Total 27
V
Essential Services Facilities 4
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
V Total 4
VII
Essential Services Facilities 2
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
VII Total 2
IX
Essential Services Facilities 1
At Risk Populations Facilities 0
Hazardous Materials Facilities 0

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January 2026
Jurisdiction / Susceptibility to DeepSeated Landslide ClassCritical Facility Category Facility Count IX Total 1
Unincorporated Lassen County Total 34
Unincorporated Sierra County
0 Essential Services Facilities 4
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
0 Total 4
Unincorporated Sierra County Total 4
Unincorporated Tehama County
V
Essential Services Facilities 1
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
V Total 1
VIII
Essential Services Facilities 1
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
VIII Total 1
Unincorporated Tehama County Total 2
Grand Total 934
Source: Susceptibility to Deep-Seated Landslides map – CSG Map Sheet 58 (05/2011), Plumas County GIS Natural, Historic, and Cultural Resources
Landslides can affect natural, historic, and cultural resources that lie in the landslide area, or the landslide run out area. Landslides can destroy large tracts of forest and open space areas, destroy wildlife habitat, and remove productive soils and vegetation from slopes. It can also fill in waterways, impact water quality, and potentially affect flooding potential. Natural resources that fall in the High or Very High susceptibility classes shown on Figure 4-176 would be most vulnerable, as well as those in the run out areas. As shown on the map, this would include a relatively small area of the developed area, since most of the higher risk areas occur in the undeveloped areas of the Planning Area.

FEMA NRI Hazard Vulnerability Assessment
The HMPC looked at the FEMA NRI for additional specific data on Plumas County’s vulnerability to Landslides, Mudslides, and Debris Flow. The NRI contains data and analysis for 18 separate natural hazards. The NRI hazard related to Plumas County’s Landslides, Mudslides, and Debris Flow is only landslide. As shown in Table 4-117, landslides could cause a total of $233,919 in expected annual losses, with a historic loss rating of very low. Landslide has a relatively low rating for social vulnerability and a

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January 2026
relatively high community resilience, with a risk index score of 94.9 out of 100. According to the NRI, there have been 6 landslide events between the years 2010-2021 with an average of 0.1 events per year.

Table 4-117 Plumas County Planning Area – Landslide Vulnerability Ratings from FEMA NRI
NRI Hazard Hazard Risk Index
Rating
Expected Annual
Loss Values
(total)**
Exposure Value
(total)***
Historic Loss Ratio
Rating
Landslide 94.9 $233,919 $132,005,510,075 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 Landslide
Any type of landslide may result in damages or complete destruction of buildings in their path, as well as deaths and injuries. Landslides can cause road blockages by depositing debris on road surfaces or road damage if the road surface itself slides downhill. Utility lines and pipes are also prone to breakage in slide areas.

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

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

Landslides, debris flows, and mud flows impacts vary by location and severity of any given event and will likely only affect certain areas of the Planning Area susceptible to landslide. Based on the risk assessment, there is a potential for significant landslides to occur in the Planning Area. However, most, but not all, of the historic landslides in the Plumas County Planning Area have been minor, localized events that are more of a nuisance than a disaster. Impacts that are not quantified, but can be anticipated in large future events, include:
➢ Injury and loss of life;
➢ Commercial and residential structural and property damage; ➢ Disruption of and damage to public infrastructure, utilities, and services; ➢ Damage to roads/bridges resulting in loss of mobility; ➢ Significant economic impact (jobs, sales, tax revenue) to the community; and

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➢ Negative impact on commercial and residential property values 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.

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. Locating new development, structures and critical facilities and infrastructure within or near areas of landslide risk may put additional development at risk. However, County building codes are in effect to reduce this risk and should be updated as necessary to continue to address future landslide conditions. It should be noted that most of the growth in the County is occurring in areas outside the landslide risk areas. Thus, depending on the location of new development and adherence to protective building codes, changes in land use and development may or may not 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 are followed, and varying needs for different demographic groups with intersecting identities that reside within the County are considered can help to make for a more resilient community. Although new growth and development corridors would fall in the area affected by moderate risk of landslide, given the small chance of a major landslide and the building codes and erosion ordinance in effect, development in the landslide areas will continue to occur.

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GIS Analysis
Plumas County provided 13 future development areas which were used as the basis for the inventory of future development for the unincorporated County. These were mapped in GIS. Figure 4-179 show the locations of the future development areas and deep-seated landslide classes. Table 4-118 shows the details of the future development areas that are located in each deep-seated landslide class.

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January 2026
Figure 4-179 Unincorporated Plumas County – Future Development in Deep-Seated Landslide Classes

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Table 4-118 Unincorporated Plumas County – Future Development in Deep-Seated Landslide Classes with Parcel Counts and Acreages
Susceptibility
to Deep-Seated
Landslide
Class / 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
0 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
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 8 1 7 29.16 4.50 24.66
Residential
K - North Star
Navigation
Center - Phase
2 1 1 0 1.00 1.00 0.00
Residential
Total 1 1 0 1.00 1.00 0.00
Approved Total 9 2 7 30.16 5.50 24.66
Proposed
Commercial
L - Plumas
County
Courthouse
1 1 0 2.86 2.86 0.00

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Susceptibility
to Deep-Seated
Landslide
Class / 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
Commercial
Total 1 1 0 2.86 2.86 0.00
Proposed Total 1 1 0 2.86 2.86 0.00
0 Total 10 3 7 33.02 8.36 24.66
VI
Approved
Commercial
F - Plumas
District
Hospital
Skilled Nursing
Facility
1 0 1 4.12 0.00 4.12
Commercial
Total 1 0 1 4.12 0.00 4.12
Approved
Total 1 0 1 4.12 0.00 4.12
VI Total 1 0 1 4.12 0.00 4.12
X
Approved
Residential
J - Meadow
Edge Mobile
Home Park
1 1 0 42.74 42.74 0.00
Residential
Total 1 1 0 42.74 42.74 0.00
Approved Total 1 1 0 42.74 42.74 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
X Total 2 2 0 46.38 46.38 0.00
Grand Total 13 5 8 83.52 54.74 28.78
Source: CGS, Plumas County GIS

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4.3.15. Volcano
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
The 2023 California State Hazard Mitigation Plan identifies volcanoes as one of the hazards that can adversely impact the State. However, there have been few losses in California from volcanic eruptions.

Along with this, the State Plan does not list volcano as one of Plumas County's high impact hazards.

As shown in Figure 4-180, active volcanoes pose a variety of natural hazards. Explosive eruptions blast lava fragments and gas into the air with tremendous force. The finest particles (ash) billow upward, forming an eruption column that can attain stratospheric heights in minutes. Simultaneously, searing volcanic gas laden with ash and coarse chunks of lava may sweep down the flanks of the volcano as a pyroclastic flow.

Ash in the eruption cloud, carried by the prevailing winds, is an aviation hazard and may remain suspended for hundreds of miles before settling to the ground as ash fall. During less energetic effusive eruptions, hot, fluid lava may issue from the volcano as lava flows that can cover many miles in a single day. Alternatively, a sluggish plug of cooler, partially solidified lava may push up at the vent during an effusive eruption, creating a lava dome. A growing lava dome may become so steep that it collapses, violently releasing pyroclastic flows potentially as hazardous as those produced during explosive eruptions.

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Figure 4-180 Volcanoes and Associated Hazards
Source: USGS Publication 2014-3120
During and after an explosive or effusive eruption, loose volcanic debris on the flanks of the volcano can be mobilized by heavy rainfall or melting snow and ice, forming powerful floods of mud and rock (lahars) resembling rivers of wet concrete. These can rush down valleys and stream channels as one of the most destructive types of volcano hazards.

The USGS notes specific characteristics of volcanic ash. Volcanic ash is composed of small jagged pieces of rocks, minerals, and volcanic glass the size of sand and silt, as shown in Figure 4-181. Very small ash particles can be less than 0.001 millimeters across. Volcanic ash is not the product of combustion, like the soft fluffy material created by burning wood, leaves, or paper. Volcanic ash is hard, does not dissolve in water, is extremely abrasive and mildly corrosive, and conducts electricity when wet.

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Figure 4-181 Ash Particle from 1980 Mt. St Helens Eruption Magnified 200 Times Source: US Geological Survey: Volcanic Ash: Effect & Mitigation Strategies.

Volcanic ash is formed during explosive volcanic eruptions. Explosive eruptions occur when gases dissolved in molten rock (magma) expand and escape violently into the air, and also when water is heated by magma and abruptly flashes into steam. The force of the escaping gas violently shatters solid rocks.

Expanding gas also shreds magma and blasts it into the air, where it solidifies into fragments of volcanic rock and glass. Once in the air, wind can blow the tiny ash particles tens to thousands of miles away from the volcano.

The average grain-size of rock fragments and volcanic ash erupted from an exploding volcanic vent varies greatly among different eruptions and during a single explosive eruption that lasts hours to days. Heavier, large-sized rock fragments typically fall back to the ground on or close to the volcano and progressively smaller and lighter fragments are blown farther from the volcano by wind. Volcanic ash, the smallest particles (2 mm in diameter or smaller), can travel hundreds to thousands of kilometers downwind from a volcano depending on wind speed, volume of ash erupted, and height of the eruption column.

The size of ash particles that fall to the ground generally decreases exponentially with increasing distance from a volcano. Also, the range in grain size of volcanic ash typically diminishes downwind from a volcano (becoming progressively smaller). At specific locations, however, the distribution of ash particle sizes can vary widely.

The USGS has ranked the volcanic threat at all U.S. volcanoes using volcano age, types of potential hazards, and estimates of the societal exposure to those hazards. Sixteen volcanoes are on California’s watch list to monitor. Research suggests that partially molten rock (magma) lies beneath seven of these volcanoes— Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, the Long Valley Volcanic Region, Coso Volcanic Field, and Salton Buttes. At these volcanoes, earthquakes

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(seismicity), hot springs, volcanic gas emissions, and (or) ground movement (deformation) attest to their restless nature. Information on the Lassen Volcanic Center threat, the volcano with the greatest potential to affect Plumas County, is shown in Table 4-119.

Table 4-119 Volcano Threat near Plumas County
Volcano Lassen Volcanic Center
Threat Very High Threat
Information Lassen Volcanic National Park, located about 50 miles east of Redding, showcases the dynamic history of this area and draws more than 350,000 visitors each year. Lassen Peak erupted violently in the early twentieth century.

Source: USGS Fact Sheet 2014-3120
Though the table above shows the threat as very high, given the likelihood of future occurrences, the HMPC still ranks the risk to this hazard as low for this LHMP.

Location and Extent
Of the approximately 20 volcanoes in the State, only a few are active and pose a threat. Of these, Lassen Peak is the closet potential threat to Plumas County. Figure 4-182 shows volcanoes in or near California and their location relative to the Plumas County.

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Figure 4-182 Active Volcanoes in California and in the Plumas County Area Source: 2018 State of California Hazard Mitigation Plan According to the USGS, Lassen Volcanic Center lies in Lassen Volcanic National Park 55 mi east of Redding. The park draws over 350,000 visitors each year with its spectacular volcanic landscapes. Lassen Volcanic Center is located at the southern edge of the Cascade Range, which is bounded on the west by the Sacramento Valley and the Klamath Mountains, on the south by the Sierra Nevada, and on the east by the

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Basin and Range geologic provinces. Volcanism in the Lassen segment is a result of subduction of the Juan de Fuca oceanic plate eastward beneath the North American continental plate.

Volcano extent is traditionally measured in magma production and ashfall. Maps showing ashfall or magma affected areas have been created for the Lassen Volcanics Area:
➢ These potential ashfall zones can be seen in Figure 4-183. The USGS noted that basaltic eruptions may build cinder cones as high as a few hundred meters (around 1,000 ft) and blanket many square kilometers with ash a few centimeters to meters thick. However, these eruptions would not typically impact human life if they occurred at Lassen volcanic center, because they are relatively nonviolent.

More devastating ash eruptions occur when dacite magma charged with volcanic gases reaches the surface. In this case, an explosive vertical column of gas and ash may rise several kilometers into the atmosphere. Fallout from the eruption column can blanket areas within a few kilometers of the vent with a thick layer of tephra and high-altitude winds may carry finer ash tens to hundreds of kilometers from the volcano and pose a hazard to aircraft.
➢ Potential lava flow (among other volcanic issues) were mapped in the 2023 State of California Hazard Mitigation Plan. These areas touch the northeast portion of the County, as shown on Figure 4-184.

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Figure 4-183 Potential Ashfall Areas for California Volcanoes Source: USGS Bulletin 1847

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Figure 4-184 Potential Volcano Eruption Hazards
Source: 2023 California State Hazard Mitigation Plan

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Past Occurrences
Disaster Declaration History
There have been no FEMA or Cal OES disasters related to volcano, as shown in Table 4-4. There have been no USDA disaster declarations for volcano.

NCDC Events
The NCDC does not track volcanic activity.

USGS Events
Within the last 825,000 years, hundreds of explosive eruptions came from vents scattered over approximately 200 mi2. Surrounding Lassen Volcanic Center, over fifty effusive (non-explosive) eruptions have occurred in the last 100,000 years. The area has been relatively quiet for the last 25,000 years with three notable exceptions—the Chaos Crags eruption (1,100 years ago), the eruption of Cinder Cone (1666 A.D.), and the Lassen Peak eruption (A.D. 1914 to 1917). The Lassen Peak eruption consisted mostly of sporadic steam blasts. In May of 1915, however, partially molten rock oozing from the vent began building a precarious lava dome. The dome collapsed on May 19, sending an avalanche of hot rock down the north flank of the volcano. Three days later, a vertical column of ash exploded from the vent reaching altitudes of 30,000 feet. The ash column spawned a high-speed ground flow of hot gas and fragmented lava. Ash from the top of the column drifted downwind 200 miles to the east, as far as Winnemucca, NV. On both days, melting snow fueled mudflows, flooding drainages 20-30 miles away. Before and after pictures are shown on Figure 4-185, while Figure 4-186 shows the extent of damages due to the eruption.

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Figure 4-185 1915 Lassen Volcano Eruption
Source: USGS

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Figure 4-186 Deposits from Lassen Peak May 1915 Eruptions Source: USGS – A Sight “Fearfully Grans” – Eruptions of Lassen Peak California, 1914 to 1917

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The older Chaos Crags eruption was similar in style, but considerably larger in magnitude. Lassen Volcanic Center hosts a vigorous geothermal system, numerous hot springs, steam vents, and boiling mud pots.

Volcanic earthquakes are common, although most are too small to be felt. Non-volcanic earthquakes along regional faults also occur—earthquake swarms in 1936, 1945-1947, and 1950 included several events above magnitude 4.0, with the two largest registering 5.0 and 5.5. Ground surveys show localized subsidence of the volcano, probably due to motion on regional faults.

Hazard Mitigation Planning Committee Events
The HMPC noted no volcanic events.

Likelihood of Future Occurrence
Unlikely—According to the USGS, volcanoes in the Lassen area tend to erupt infrequently, and may be inactive for periods lasting centuries or even millennia. The most recent eruptions in the Lassen area were the relatively small events that occurred at Lassen Peak between 1914 and 1917. The most recent large eruption produced Chaos Crags about 1,100 years ago. Such large eruptions in the Lassen area have an average recurrence interval of about 10,000 years. However, the geological history of the Lassen area indicates that volcanism there is episodic, having periods of relatively frequent eruptions separated by long quiet intervals. For example, the last large event before Chaos Crags eruption was the one that built Lassen Peak 27,000 years.

Climate Change and Volcano
Climate change is unlikely to influence volcanic eruptions.

Vulnerability Assessment
Vulnerability—Low
The population of Plumas County, California, faces low vulnerability to volcanic impacts due to the absence of active or high-threat volcanoes within or near the County. Lassen, located in Shasta County, last erupted in 1914-1917, and while it poses risks such as pyroclastic flows, ashfall, and lahars, these hazards diminish with distance. While lava flow wouldn’t be a concern to the County, volcanic ash and gases could pose respiratory risks, particularly for vulnerable populations (e.g., the elderly, who make up a significant portion of Plumas County’s residents).

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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 vulnerabilities to this hazard.

Low-level volcanic unrest can persist for decades or even hundreds of years without an eruption. Although steady, low-level unrest is normal for many young volcanoes, rapidly accelerating unrest is cause for concern. At California’s most threatening volcanoes, monitoring sensors are in place to continuously track levels of unrest. Such monitoring is necessary to determine the baseline, or background level, of activity at a volcano to help volcanologists know what is normal. An uptick in unrest may be a sign of increased volcanic threat.

Local concerns for each of the jurisdictions can be found under the Local Concerns heading in each respective jurisdictional annex to this LHMP Update.

Assets at Risk
Assets at risk from volcano 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.

People and Populations
Populations living near volcanoes are most vulnerable to volcanic eruptions and lava flows, although volcanic ash can travel and affect populations many miles away and cause problems for aviation.

Vulnerable populations with respiratory issues would be at greatest vulnerability to the volcano hazard.

The USGS, in Bulletin 1847, described the nature and probable distribution of potentially hazardous volcanic phenomena and their threat to people and property. It included hazard zonation maps that depicted areas relatively likely to be affected by future eruptions in California. Affected areas fall in Plumas County.

This is shown on Figure 4-183.

Structures
Volcanic magma is expected to see limited impact to structures in Plumas County. Structures may be damaged by accumulation of falling lava fragments or burnt by their high heat. Ashfall can affect solar panels and other appurtenances. Ash may affect air conditioning and other HVAC systems. There is a risk of wildfires that may be ignited due to coarse ash that could impact structures within the County depending on where the wind would be blowing.

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Critical Facilities and Infrastructure
Depending on their type and function, critical facilities and infrastructure can also be affected by a volcanic eruption. Ash can cause ventilation issues and large deposits can even clog pipes. Schools may have to close or operate on a reduced schedule due to health concerns of breathing in the ash. Hospitals may be temporarily overrun with patients with breathing issues.

Natural, Historic, and Cultural Resources
Park areas and natural resource assets in the Plumas County Planning Area may be vulnerable to a volcano.

These include turfed areas; landscapes, trees, wildlife and habitat areas, and wetlands and marsh lands.

Environmentally, ash contains toxic elements that can contaminate water, degrade soils, and disrupt local ecosystems. Historic and cultural resources that are protected by structures are not expected to be affected by this hazard.

FEMA NRI Hazard Vulnerability Assessment
Volcano is not an NRI hazard; therefore, no data is presented.

Impacts from Volcano
With respect to Plumas County, it is unlikely that lava flows would impact the Planning Area given the distance from Mt. Lassen; it is the potential for ash and gases associated with an eruption that could extend into the County causing issues. The impact of coarse ash fall is limited to the immediate area of the volcanic vent. Structures may be damaged by accumulation of falling lava fragments or burnt by their high heat.

Wildfires may be ignited by coarse ash. Although generally non‐lethal, fine ash fall is the most widespread and disruptive volcanic hazard. People exposed to fine ash commonly experience various eye, nose, and throat symptoms. Short‐term exposures are not known to pose a significant health hazard. Long‐term health effects have not been demonstrated conclusively. Ash deposited downwind of the volcano covers everything like a snowfall, but also infiltrates cracks and openings in machinery, buildings, and electronics.

Falling ash can obscure sunlight, reducing visibility to zero. When wet, it can make paved surfaces slippery and impassable. Fine ash is abrasive, damaging surfaces and moving parts of machinery, vehicles, and aircraft. Life‐threatening and costly damage can occur to aircraft that fly through fine ash clouds. Newly fallen volcanic ash may result in short‐term physical and chemical changes in water quality. Close to the volcano, heavy ash fall may cause roofs to collapse, wastewater systems to clog, and power systems to shut down. In agricultural areas, fine ash can damage crops, and sicken livestock. Resuspension of ash by human activity and wind cause continuing disruption to daily life.

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Future Conditions/Future Development
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 unlikely to affect volcanic eruptions 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. Changes in population and population patterns may or may not increase the impacts and vulnerability of the County to this hazard. ➢ Land use planning will have limited to no effects on volcanic eruption. There are no building codes in effect that take volcano into account. Additionally, there are no land use restrictions in volcano prone areas. Changes in land use are unlikely to increase or decrease the vulnerability of the County to a volcanic eruption.

Future development in the County may be at risk to volcanic activity; however, future development is at no greater risk to volcanic activity than current development. Further, given the uncertainties with regard to volcanic activity, it is unlikely that future development activities would be constrained in any manner.

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

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

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

In addition, catastrophic wildfire can create favorable conditions for other hazards such as flooding, landslides and mudflows, and erosion during the rainy season. Additional losses could occur if PG&E or

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PSREC initiates a power shutdown during extreme fire weather conditions. This is discussed in greater detail at the beginning of Section 4.3.

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

Wildfire smoke can have negative effects to those who live in or near a fire burn area. Smoke and air pollution from wildfires can be a severe health hazard. Significant wildfires occurring in nearby northern California communities since the 2019/2020 LHMPs have created significant air pollution affecting area residents. County residents have been affected by wildfire smoke and poor air quality, from fires both within the Planning Area and from those much further away. The County has seen air quality impacts from smoke from wildfires since the 2019/2020 LHMPs. During these times, air sensors in the County showed periods of very poor air quality in Plumas County. This was especially a concern during Covid. A document titled Smoke Impacts CA: 2020 Lessons – 2021 Actions that was published by the US Forest Service noted that wildfire smoke exposure could result in greater susceptibility to COVID-19 and other viruses/bacteria (decrease in local and systemic immune function).

According to FirstStreet.org, a climate risk data organization, elderly individuals are at an adversely high risk of experiencing negative health impacts from poor air quality, like worsening of heart disease and the potential for stroke, reduced lung capacity, and increase in lung disease.

The paper “Wildland fire management and air quality in the southern Sierra Nevada: Using the Lion Fire as a case study with a multi-year perspective on PM2.5 impacts and fire policy” by D. Schweizer and R.

Cisneros explores the impacts of smoke from high-intensity, stand replacing fires versus lower intensity fires in the Sierra Nevada and explains that while smoke and fire mitigation is important with any fire, we the extreme effects of smoke from large wildfires can be prevented by managing forests and allowing low intensity fires to burn.

Location and Extent
Fires can have a quick speed of onset, especially during periods of drought. Fires can burn for a short period of time or may have durations lasting for a week or more. Wildfire can affect any area of the Planning Area; however, CAL FIRE has mapped areas in California that are at risk to wildfire. Maps showing the various Fire Hazard Severity Zones, which range from Non-Wildland/Non-Urban to Very High, can be found below. CAL FIRE Fire Hazard Severity Zones have been developed specific to Fire Responsibility Areas located in the County which details the responsible fire agency for each area of the County; specifically, federal, state, and local areas also shown in the below maps.

This section is broken down into three parts: a discussion on the wildland urban interface in Plumas, the Plumas County wildfire setting, and the (CAL FIRE) Fire Responsibility Area (FRA) and Fire Hazard Severity Zone (FHSZ) Mapping.

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Wildland Urban Interface
Throughout California, communities are increasingly concerned about wildfire safety as increased development in the foothills and mountain areas and subsequent fire control practices have affected the natural cycle of the ecosystem. While wildfire risk is predominantly associated with wildland urban interface (WUI) areas, significant wildfires can also occur in heavily populated areas. The wildland urban interface is a general term that applies to development adjacent to landscapes that support wildland fire.

The WUI defines the community development into the foothills and mountainous areas of California. The WUI describes those communities that are mixed in with grass, brush and timbered covered lands (wildland). These are areas where wildland fire once burned only vegetation but now burns homes as well.

The WUI for Plumas County consists of communities at risk (shown in Section 4.3.15) as well as the area around the communities that pose a fire threat.

There are two types of WUI environments. The first is the true urban interface where development abruptly meets wildland. The second WUI environment is referred to as the wildland urban intermix. Wildland urban intermix communities are rural, low-density communities where homes are intermixed in wildland areas. Wildland urban intermix communities are difficult to defend because they are sprawling communities over a large geographical area with wild fuels throughout. This profile makes access, structure protection, and fire control difficult as fire can freely run through the community.

WUI fires are often the most damaging. WUI fires occur where the natural forested landscape and urban built environment meet or intersect. Even relatively small acreage fires may result in disastrous damages.

The damages are primarily reported as damage to infrastructure, built environment, loss of socio‐economic values and injuries to people.

The WUI for Plumas County adopted by the County is shown on Figure 4-187.

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Figure 4-187 WUI Boundaries in Plumas County
Source: Plumas County Fire Safe Council

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The HMPC did note that there is no standard definition of how to delineate the boundaries of any particular WUI area. The Fire Safe Council map that is embedded in the document was approved by the Plumas County Board of Supervisors. From the Community Wildfire Protection Plan (CWPP) regarding Plumas County's WUI:

In 2004-2005 when the first Plumas County WUI map was developed the concept was to have two WUI boundaries, an "Adjacent WUI" and an Extended WUI", (0-.75 and.75 to 1.5 mile respectively). Consequently, the GIS program generated WUI's with circles around the CAR’s, using the above criteria.

In 2010, the WUI boundaries were expanded to better link communities and the WUI. While implementing the CWPP since 2005, it became apparent to PC FSC during collaborative project outreach & development that the earlier computer generated WUI boundaries should be more contiguous with respect to connecting communities and logical in terms of watersheds, ridges, valleys or roads. Earlier WUI circle maps weren’t well suited to watershed scale and larger community project planning. On November 2, 2010, the Plumas County Board of Supervisors approved the updated “Wildland Urban Interface” Map.

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

Also to be considered as a fuel source, are man-made structures and other associated combustibles. The type of prevalent fuel directly influences the behavior of wildfire. Light fuels such as grasses burn quickly and serve as a catalyst for fire spread. The volume of available fuel is described in terms of Fuel Loading. Certain areas in and surrounding Plumas County are extremely vulnerable to fires as a result of overgrown fuels combined with a growing number of structures being built near and within rural lands. Fuel is the only factor that is under human control. ➢ Topography – An area’s terrain and land slopes affect its susceptibility to wildfire spread. Fire intensities and rates of spread increase as slope increases due to the tendency of heat from a fire to rise via convection. The natural arrangement of vegetation throughout a hillside can also contribute to increased fire activity on slopes. According to the Plumas County 2019 CWPP, Plumas County sits mostly in the Sierra Nevada Range and lies between the Central Valley and Great Basin. There are about 30 mountain peaks over 7,000 feet in elevation. Most of the population centers are over 3,400 feet. Wide ranges of elevation (1,600- 8,000+ feet) are responsible in part for the variety of climates

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and vegetation found in the County. Another significant factor is the continuous interaction of maritime air masses with those of continental origin. The combination of these influences results in pronounced climatic changes within short distances.
➢ Weather – Weather components such as temperature, relative humidity, wind, and lightning also affect the potential for wildfire. High temperatures and low relative humidity dry out the fuels that feed wildfire creating a situation where fuel will more readily ignite and burn more intensely. Wind is the most treacherous weather factor. The greater the wind, the faster a fire will spread, and the more intense it will be. Winds can be significant at times in Plumas County. Wind from the Central Valley is especially conducive to hot, dry conditions, in the Sierra Foothills, which can lead to extreme fire danger. Wind shifts, in addition to wind speed, can occur suddenly due to temperature changes or the interaction of wind with topographical features such as slopes or steep hillsides. Most wind shifts in Plumas County occur in the Feather River Canyon. According to the 2019 CWPP, since 1970, most of the acres burned have been under southwest and north wind conditions. Critical fire weather patterns vary within the County, but mostly a southwest flow, which occurs across Plumas County due to the general wind flow associated with air moving from sea to land and California lying in the “Belt of the Westerlies” global circulation pattern. In addition to the general southwesterly flow, topography and local up canyon flow from diurnal heating of the Sacramento Valley complement this air movement, usually increasing speeds. The strongest southwest winds are associated with frontal system or lowpressure trough. These winds tend to cause most of the large fires in the county to burn from the southwest to the northeast. On the western slopes of the County, before the crest of the Sierras, most large fires are driven from east to west by north and east winds, when a high-pressure form over the Great Basin and reversing normal air flows from land to sea. These conditions are magnified at night and in the early morning hours when down canyon winds are accelerated by the local diurnal process, the general flow and channeled topographically. These north and east wind events usually occur in the spring and fall and have the largest impacts in the Feather River Canyons. In these events, relative humidity is also lower as the air mass originates on land versus sea, and as the air moves downslope it compresses, creating additional lowering. This is similar to what occurs in Southern California during Santa Ana conditions. Meteorologists with the USFS conducted a study of these wind events. They found that while these patterns only occurred about 25% of the time in fire season, that 90% of large fires, on the western slopes, burned during those events. As part of a weather system, lightning also ignites wildfires, often in difficult to reach terrain for firefighters. Related to weather is the issue of recent drought conditions contributing to concerns about wildfire vulnerability. During periods of drought, the threat of wildfire increases.
➢ Human Actions – Most wildfires are ignited by human action, the result of direct acts of arson, carelessness, or accidents. Many fires originate in populated areas along roads and around homes and are often the result of arson or careless acts such as the disposal of cigarettes, use of equipment or debris burning. Recreation areas that are located in high fire hazard areas also result in increased human activity that can increase the potential for wildfires to occur.

California Department of Forestry and Fire Protection (CAL FIRE) Fire Responsibility Area and Fire Hazard Severity Zone Mapping
CAL FIRE mapping of Fire Responsibility Areas and Fire Hazard Severity Zone Mapping is shown below for the Plumas County Planning Area.

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CAL FIRE Fire Responsibility Areas
There are various wildland fire protection agencies that have responsibility within the California communities. There are also numerous fire departments and fire protection districts that serve local areas, many of whom have mutual aid agreements with each other as well as federal and state agencies for fire suppression and protection. Fire Responsibility areas are generally categorized by Federal Responsibility Area (FRA), State Responsibility Area (SRA) and Local Responsibility Area (LRA).

The CAL FIRE data, detailing Fire Responsibility Areas within the City Planning Area, was utilized to determine the locations of the County falling within each Fire Responsibility Area. CAL FIRE has a legal responsibility to provide fire protection on all SRA lands, which are defined based on land ownership, population density and land use. CAL FIRE’s LRA lands show where the local jurisdictions have primary responsibility for fire protection. CAL FIRE’s FRA areas detail where the federal government has responsibility. Using the 2023 FRA mapping layer, Fire Responsibility Areas are shown below.

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Figure 4-188 Plumas County Planning Area – SRA/FRA/LRA Areas

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CAL FIRE Fire Hazard Severity Zone Mapping
As part of the Fire and Resource Assessment Program (FRAP), the State Fire Marshall was mandated to map areas of significant fire hazards based on fuels, terrain, weather, and other relevant factors, including areas where winds have been identified as a major cause of wildfire spread. These zones, referred to as FHSZs, include non-wildland/non-urban, moderate, high, and very high FHSZs. The FHSZ map evaluates hazard, not risk. Hazard is based on the physical conditions that create a likelihood and expected fire behavior over a 30-50 year period without considering mitigation measures such as home hardening, recent wildfire, or fuel reduction efforts. Risk is the potential damage a fire can do to an area under existing conditions, accounting for any modification such as fuel reduction projects, defensible space, and ignition resistant building construction.

CAL FIRE’s FHSZ mapping for California, including Plumas County, has recently been updated as detailed below. The new FHSZ mapping will create more accurate zone designations that can direct the implementation of mitigation strategies in areas where hazards warrant these investments.

Effective April 1, 2024, CAL FIRE updated its FHSZ maps for the SRA to provide updated map zones based on new science in local climate data and improved fire assessment modeling. The FHSZ model for wildland fire has two key elements: probability of an area burning and expected fire behavior under extreme fuel and weather conditions. The factors considered in determining fire hazard within wildland areas are fire history, flame length, terrain, local weather, and the potential fuel over a 50-year period. Outside of wildlands, the model considers factors that might lead to buildings being threatened, including terrain, weather, urban vegetation cover, blowing embers, proximity to wildland, fire history and fire hazard in nearby wildlands. FHSZs are not a structure loss model, as key information regarding structure ignition (such as roof type, etc.) is not included.

The FHSZ data for the Federal Responsibility Area has not been updated since 2007.

Effective February 10, 2025, CAL FIRE also updated its FHSZ maps for the LRA to provide updated map zones based on new science in local climate data and improved fire assessment modeling.

New FHSZ mapping for Plumas County is utilized for this LHMP using two separate analyses: The SRA/FRA FHSZ mapping has been combined into one map and analysis and the LRA FHSZ mapping is included in a separate analysis and described below:
➢ Figure 4-189 shows the FHSZ map for the SRA/FRA in the Plumas County Planning Area. Geographic extents of wildfire FHSZs in the FRA and SRA for the Plumas County Planning Area is detailed in Table 4-120.
➢ Figure 4-190 shows the FHSZ map for the LRA in the Plumas County Planning Area. This map has three inset areas. These inset maps are shown on Figure 4-191, Figure 4-192, and Figure 4-193.

Geographic extents of wildfire FHSZs in the LRA for the Plumas County Planning Area is detailed in Table 4-121.

Details on each jurisdiction’s Fire Hazard Severity Zone extents (for both SRA/FRA and LRA) can be found in their respective annexes to this LHMP Update.

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Figure 4-189 Plumas County Planning Area – CAL FIRE SRA/FRA Fire Hazard Severity Zones

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Table 4-120 Plumas County Planning Area – Geographical Extent of CAL FIRE SRA/FRA Fire Hazard Severity Zones
SRA/FRA Fire
Hazard Severity
Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
City of Portola
Very High 5 0.2% 3 0.1% 2 0.2%
High 5 0.1% 0.0001 0.000004% 5 0.4%
Moderate 0 0.0% 0 0.0% 0 0.0%
Non-Wildland/NonUrban0 0.0% 0 0.0% 0 0.0%
Outside of Federal /
State Responsibility
Area
3,481 99.7% 2,234 99.9% 1,246 99.4%
Grand Total 3,491 100.0% 2,237 100.0% 1,254 100.0%
Unincorporated Plumas County
Very High 1,454,532 87.2% 40,739 44.9% 1,413,793 89.6%
High 116,705 7.0% 19,400 21.4% 97,305 6.2%
Moderate 39,004 2.3% 6,405 7.1% 32,599 2.1%
Non-Wildland/NonUrban13,602 0.8% 0.01 0.00001% 13,602 0.9% Outside of Federal /
State Responsibility
Area
44,775 2.7% 24,214 26.7% 20,560 1.3%
Grand Total 1,668,618 100.0% 90,759 100.0% 1,577,859 100.0% Source: CAL FIRE (FHSZ SRA 2024, FHSZ FRA 2007)

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Figure 4-190 Plumas County Planning Area – CAL FIRE LRA Fire Hazard Severity Zones (Overview and Map Insets)

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Figure 4-191 Plumas County Planning Area –CAL FIRE LRA Fire Hazard Severity Zones (Map Inset 1)

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Figure 4-192 Plumas County Planning Area –CAL FIRE LRA Fire Hazard Severity Zones (Map Inset 2)

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Figure 4-193 Plumas County Planning Area –CAL FIRE LRA Fire Hazard Severity Zones (Map Inset 3)

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Table 4-121 Plumas County Planning Area – Geographical Extent of CAL FIRE LRA Fire Hazard Severity Zones
LRA Fire Hazard
Severity Zone
Total Acres % of Total
Acres
Improved
Acres
% of Total
Improved
Acres
Unimproved
Acres
% of Total
Unimproved
Acres
City of Portola
Very High 3,235 92.7% 2,016 90.1% 1,219 97.2%
High 250 7.2% 221 9.9% 28 2.26%
Moderate 0 0.0% 0 0.0% 0 0.0%
Non-Wildland 0 0.0% 0 0.0% 0 0.0%
Outside of Local
Responsibility Area
6 0.2% 0 0.0% 6 0.5%
Grand Total 3,491 100.0% 2,237 100.0% 1,254 100.0%
Unincorporated Plumas County
Very High 1,400 0.1% 742 0.8% 658 0.04%
High 1,279 0.1% 588 0.6% 690 0.04%
Moderate 488 0.03% 258 0.3% 230 0.01%
Non-Wildland 41,625 2.5% 22,641 24.9% 18,984 1.2%
Outside of Local
Responsibility Area
1,623,211 97.3% 66,542 73.3% 1,556,670 98.7%
Grand Total 1,668,003 100.0% 90,771 100.0% 1,577,231 100.0% Source: CAL FIRE (LRA 2025)
CAL FIRE Fire Hazard Severity Zone Comparison
Given the new CAL FIRE Fire Hazard Severity Zone mapping for the SRA (2024) and the LRA (2025), a comparison of the previous CAL FIRE FHSZ mapping from 2007 was conducted. Figure 4-194 and Table 4-122 shows the 2007 FHSZ data compared to the 2024 FHSZ data for the SRA within the Plumas County Planning Area and Figure 4-195 and Table 4-123 shows the FHSZ data comparison for the LRA datasets.

Based on this comparative analysis, while many of the FHSZs have changed within the two (SRA and LRA) analyses, much of the change can be contributed to mapped areas being reallocated to new State and Local Fire Responsibility Areas. As such, the risk and vulnerability of the County Planning Area to wildfire remains significant. Further given the topography and fuels located throughout the Planning Areas, and the history of devastating wildfires in and around Plumas County, wildfire continues to be one of the County’s most significant hazard of concern.

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Figure 4-194 Plumas County Planning Area – SRA FHSZ Comparison

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Table 4-122 Plumas County Planning Area – SRA/FRA FHSZ Comparisons by Jurisdiction Jurisdictions /
Fire Hazard
Severity Zones
Overall Acre Change % Acre Change
Total Acres
Plumas 2007
Total Acres
Plumas 2024
Overall
Change in
Total Acres
% of Total
Acres Plumas
2007
% of Total
Acres Plumas
2024
Overall
Change in %
Total Acres
City of Portola
Very High 1,265 0.02 -1,265 0.3% 0.000004% -0.3%
High 777 0.0001 -777 0.2% 0.00000002% -0.2%
Moderate 0.001 0 -0.001 0.0000002% 0% -0.0000002%
City of Portola
Total
2,043 0.0201 -2,043 0.5% 0.000004% -0.5%
Unincorporated Plumas County
Very High 342,434 354,154 11,720 77% 81% 3.5%
High 35,436 52,768 17,332 8% 12% 4.1%
Moderate 62,329 30,500 -31,829 14% 7% -7.1%
Unincorporated
Plumas County
Total
440,199 437,422 -2,778 99.5% 100.0% 0.5%
Source: CAL FIRE

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Figure 4-195 Plumas County Planning Area – LRA FHSZ Comparison

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Table 4-123 Plumas County Planning Area – LRA FHSZ Comparisons by Jurisdiction Jurisdictions /
Fire Hazard
Severity Zones
Overall Acre Change % Acre Change
Total Acres
Plumas 2007
Total Acres
Plumas 2025
Overall
Change in
Total Acres
% of Total
Acres Plumas
2007
% of Total
Acres Plumas
2025
Overall
Change in %
Total Acres
City of Portola
Very High 812 3,235 2,423 2% 6.7% 5.0%
High 468 250 -218 1% 0.5% -0.5%
Moderate 205 0 -205 0.4% 0% -0.4%
NonWildland/NonUrban0 0 0 0% 0% 0%
Urban Unzoned 0 0 0 0% 0% 0%
City of Portola
Total
1,485 3,485 2,000 3% 7% 4%
Unincorporated Plumas County
Very High 772 1,400 628 2% 3% 1%
High 8,098 1,279 -6,819 17% 3% -15%
Moderate 361 488 127 1% 1% 0.2%
NonWildland/NonUrban35,815 41,625 5,810 77% 86% 9%
Urban Unzoned 106 0 -106 0.2% 0% -0.2%
Unincorporated
Plumas County
Total
45,152 44,792 -360 97% 93% -4%
Source: CAL FIRE
Post-Wildfire Landslides and Debris Flows
Post-wildfire landslides and debris flows are a concern in Plumas County. Fires that burn in sloped areas remove vegetation that holds hillsides together during rainstorms. Once that vegetation is removed, the hillside may be compromised, resulting in landslides and debris flows. USGS has been developing maps of these areas post fire.

Post-fire debris flow hazard assessments for each fire below were performed by the USGS. These assessments are prepared at the request of land and emergency management agencies responsible for managing wildfires impacts. The assessments are presented as a series of maps and geospatial data showing the probability of debris flows and their expected volume for burned drainage basins. Other landslide hazard assessments produced by the USGS are performed at the request of government agencies or sometimes as demonstration products from research to improve methods of hazard and risk assessment.

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2017 Minerva 5 Wildfire
Figure 4-196 estimates of the likelihood of debris flow (in %), potential volume of debris flow (in m3), and combined relative debris flow hazard from the Minerva 5 Fire. These predictions are made at the scale of the drainage basin, and at the scale of the individual stream segment. Estimates of probability, volume, and combined hazard are based upon a design storm with a peak 15-minute rainfall intensity of 24 millimeters per hour (mm/h).

Figure 4-196 Minerva 5 Fire Landslide and Debris Flow Probabilities Source: USGS (https://landslides.usgs.gov/hazards/postfire_debrisflow/detail.php?objectid=105). Retrieved 5/5/2025. 2019 Walker Fire Landslide and Debris Flow Mapping
Figure 4-197 estimates of the likelihood of debris flow (in %), potential volume of debris flow (in m3), and combined relative debris flow hazard from the Walker Fire. These predictions are made at the scale of the drainage basin, and at the scale of the individual stream segment. Estimates of probability, volume, and combined hazard are based upon a design storm with a peak 15-minute rainfall intensity of 24 millimeters per hour (mm/h).

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Figure 4-197 Walker Fire Landslide and Debris Flow Probabilities Source: USGS (https://landslides.usgs.gov/hazards/postfire_debrisflow/detail.php?objectid=261). Retrieved 5/5/2025. 2020 North Complex Fire
Figure 4-198 estimates of the likelihood of debris flow (in %), potential volume of debris flow (in m3), and combined relative debris flow hazard from the Walker Fire. These predictions are made at the scale of the drainage basin, and at the scale of the individual stream segment. Estimates of probability, volume, and combined hazard are based upon a design storm with a peak 15-minute rainfall intensity of 24 millimeters per hour (mm/h).

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Figure 4-198 North Complex Fire Landslide and Debris Flow Probabilities Source: USGS (https://usgs.maps.arcgis.com/apps/dashboards/c09fa874362e48a9afe79432f2efe6fe#fire_id=nrt2020). Retrieved 5/5/2025.
2021 Dixie Fire Landslide and Debris Flow Mapping
Figure 4-199 estimates of the likelihood of debris flow (in %), potential volume of debris flow (in m3), and combined relative debris flow hazard from the Walker Fire. These predictions are made at the scale of the drainage basin, and at the scale of the individual stream segment. Estimates of probability, volume, and combined hazard are based upon a design storm with a peak 15-minute rainfall intensity of 24 millimeters per hour (mm/h).

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Figure 4-199 Dixie Fire Landslide and Debris Flow Probabilities Source: USGS (https://usgs.maps.arcgis.com/apps/dashboards/c09fa874362e48a9afe79432f2efe6fe#fire_id=dix2021). Retrieved 5/5/2025.

Past Occurrences
Disaster Declaration History
A search of FEMA and Cal OES disaster declarations shows eight state and six federal disaster declarations.

These are shown in Table 4-124.

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Table 4-124 Plumas County – Federal and State Disaster Declaration from Wildfire 1950-2025 Disaster Type State Declarations Federal Declarations
Count Years Count Years
Fire 8 1960 (unnamed), 1987 (Clarks
Fire), 1999 (Bucks Fire), 2020
(twice – Bear Fire, North
Complex Fire), 2021 (three –
Dixie Fire, Monument Fire,
Lava Fire/Beckwourth
Complex)
6 1999 (Bucks Fire), 2008 (BTU
Lightning Complex), 2020
(twice – Bear Fire, North
Complex Fire), 2021 (twice –
Dixie Fire, Lava
Fire/Beckwourth Complex)
Source: Cal OES, FEMA
NCDC Events
The NCDC has tracked wildfire events in the County dating back to 1993. The 15 events in Plumas County in the database are shown in Table 4-125. Many more fires have occurred but were not reported to the NCDC database.

Table 4-125 NCDC Wildfire Events in Plumas County 1993 to 7/31/2024* Event Type Number
of Events
Deaths Deaths
(indirect)
Injuries Injuries
(indirect)
Property
Damage
Crop
Damage
Dense Smoke 1 0 0 0 0 $0 $0
Wildfire 14 1 0 3 0 $22,775,000 $0
Total 15 1 0 3 0 $22,775,000 $ 0
Source: NCDC
*Deaths, injuries, and damages are for the entire event, and may not be exclusive to the County.

CAL FIRE Events
CAL FIRE, USDA Forest Service Region 5, Bureau of Land Management (BLM), the National Park Service (NPS), Contract Counties and other agencies jointly maintain a comprehensive fire perimeter GIS layer for public and private lands throughout the state. The data covers fires back to 1878 (though the first recorded incident for the County was in 1917). For the NPS, BLM, and USFS, fires of 10 acres and greater are reported. For CAL FIRE, timber fires greater than 10 acres, brush fires greater than 50 acres, grass fires greater than 300 acres, and fires that destroy three or more residential dwellings or commercial structures are reported. CAL FIRE recognizes the various federal, state, and local agencies that have contributed to this dataset, including USDA Forest Service Region 5, BLM, NPS, and numerous local agencies.

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

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The data provides a reasonable view of the spatial distribution of past large fires in California. Using GIS, fire perimeters that intersect Plumas County were extracted and are listed in Table 4-126, sorted by the highest wildfire acres affecting each jurisdiction to the lowest acreage. There are 276 total fires recorded in this database for Plumas County. Of these, 186 burn areas in each jurisdiction exceeded 50 acres in size which are included in both the map and table below. Many more small fires likely have occurred but were not included in the CAL FIRE dataset.

Figure 4-200 shows fire history for the Plumas County Planning Area, colored by the size of the acreage burned and includes those fires exceeding 50 acres. This map contains fires from 1950 to 2024, while the detailed tables of wildfire shown in Table 4-126 contain fires from 1910 to 2024 and also includes those fires exceeding 50 acres.

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Figure 4-200 Plumas County Wildfire History – CAL FIRE 1910 to 2024

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Table 4-126 Plumas County – CAL FIRE Wildfire History Summary 1910-2024s by Jurisdiction Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
City of Portola
(Unnamed) 1988 8/29/1988 Lightning 528 224
(Unnamed) 1949 (blank) Unknown /
Unidentified
312 77
Unincorporated Plumas County
Dixie 2021 7/14/2021 Powerline 963,405 699,689
North Complex 2020 8/17/2020 Lightning 318,797 166,617
Chips 2012 7/28/2012 Campfire 76,350 76,346
Beckwourth Complex (Sugar) 2021 7/2/2021 Unknown /
Unidentified
105,004 67,828
Moonlight 2007 9/3/2007 Equipment Use 64,960 64,512
Storrie 2000 8/17/2000 Railroad 56,076 55,729
Walker 2019 9/4/2019 Miscellaneous 54,615 54,613
Bucks 1999 8/23/1999 Lightning 34,236 27,888
(Unnamed) 1931 (blank) Unknown /
Unidentified
32,336 27,215
(Unnamed) 1936 (blank) Unknown /
Unidentified
34,113 23,573
Wheeler 2007 7/5/2007 Lightning 22,332 22,330
Plumas NF #531 (Clark) 1987 8/30/1987 Miscellaneous 39,921 19,391 (Unnamed) Unknown /
Unidentified
17,156 17,127
(Unnamed) 1929 (blank) Unknown /
Unidentified
13,346 16,980
BTU Lightning Complex 2008 7/2/2008 Lightning 53,699 16,476 Milk Ranch 1951 9/11/1951 Miscellaneous 21,979 14,505
(Unnamed) 1927 (blank) Unknown /
Unidentified
36,663 12,250
(Unnamed) 1934 (blank) Unknown /
Unidentified
12,180 12,181
(Unnamed) Unknown /
Unidentified
12,385 10,810
(Unnamed) 1959 (blank) Miscellaneous 10,362 10,362
Scotch 2008 6/21/2008 Lightning 13,008 9,799
(Unnamed) 1926 (blank) Unknown /
Unidentified
9,476 9,476
Sheep 2020 8/17/2020 Lightning 29,541 7,700

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Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
(Unnamed) Unknown /
Unidentified
7,593 7,593
Elephant 1981 9/17/1981 Lightning 6,852 6,852
Ingalls (Assist #12) 1981 9/17/1981 Unknown /
Unidentified
6,697 6,697
Beckwourth Complex
(Loyalton)
2020 8/14/2020 Lightning 46,721 6,415
Rich 2008 7/29/2008 Railroad 6,111 6,111
Cold 2008 6/21/2008 Lightning 5,599 5,600
(Unnamed) 1960 (blank) Lightning 5,064 5,064
Babcock 1977 8/2/1977 Lightning 5,057 5,056
Horton 2 1999 8/24/1999 Equipment Use 4,941 4,942
(Unnamed) Miscellaneous 7,949 4,889
Pidgeon 1999 8/23/1999 Lightning 4,713 4,714
Layman 1989 9/6/1989 Miscellaneous 4,449 4,450
Minerva 5 2017 7/29/2017 Arson 4,339 4,340
Maddalena 1996 7/25/1996 Equipment Use 3,975 3,976
(Unnamed) Miscellaneous 3,918 3,918
(Unnamed) Unknown /
Unidentified
3,745 3,745
Stream 2001 7/25/2001 Lightning 3,526 3,526
(Unnamed) 1921 (blank) Unknown /
Unidentified
3,355 3,355
Ferris 1974 6/25/1974 Miscellaneous 3,289 3,289
Boulder 2006 6/25/2006 Lightning 2,919 2,919
(Unnamed) Unknown /
Unidentified
2,697 2,697
(Unnamed) 1966 (blank) Lightning 2,681 2,681
Lookout 1999 8/23/1999 Lightning 2,615 2,615
(Unnamed) 1978 10/30/1978 Railroad 2,596 2,596
(Unnamed) 1945 (blank) Miscellaneous 6,358 2,527
(Unnamed) 1946 (blank) Lightning 2,448 2,448
(Unnamed) Miscellaneous 73 2,416
Will 1979 9/18/1979 Miscellaneous 3,128 2,396
(Unnamed) 1937 (blank) Unknown /
Unidentified
2,361 2,361
(Unnamed) Miscellaneous 2,844 2,213

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Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
Ramelli 1950 8/31/1950 Unknown /
Unidentified
2,178 2,178
(Unnamed) 1942 (blank) Unknown /
Unidentified
7,916 2,162
(Unnamed) 1947 (blank) Miscellaneous 2,036 2,036
(Unnamed) Miscellaneous 3,864 1,837
Carman #2 1972 8/9/1972 Lightning 1,790 1,790
Chilcoot 2003 7/20/2003 Lightning 5,642 1,770
(Unnamed) Unknown /
Unidentified
1,737 1,737
(Unnamed) Miscellaneous 2,692 1,693
(Unnamed) 7/5/1972 Miscellaneous 1,676 1,676
(Unnamed) 1930 (blank) Unknown /
Unidentified
1,828 1,658
Cashman 1977 7/30/1977 Smoking 1,556 1,556
Walker 1990 8/6/1990 Lightning 1,496 1,496
Devils Gap 1999 8/22/1999 Lightning 1,480 1,480
(Unnamed) 1943 (blank) Unknown /
Unidentified
1,425 1,425
Plumas N.F. #2 1959 8/4/1959 Miscellaneous 1,409 1,409
Rack 1989 7/8/1989 Miscellaneous 1,399 1,399
Little 2008 6/22/2008 Lightning 1,399 1,291
(Unnamed) 1928 (blank) Miscellaneous 1,242 1,242
(Unnamed) Miscellaneous 1,198 1,198
COOKS 1996 8/9/1996 Equipment Use 1,138 1,138
(Unnamed) 1951 (blank) Miscellaneous 1,106 1,106
BELL 1970 8/25/1970 Miscellaneous 1,082 1,082
(Unnamed) Miscellaneous 2,035 1,063
Assist P.N.F. 1987 8/31/1987 Unknown /
Unidentified
1,047 1,047
Bar 2010 7/31/2010 Arson 1,039 1,039
Chilcoot 2017 8/6/2017 Lightning 1,020 1,020
Garnier 1950 8/8/1950 Miscellaneous 4,097 1,009
Sloat 1981 7/21/1981 Miscellaneous 907 907
(Unnamed) 1922 (blank) Miscellaneous 865 865
(Unnamed) 1933 (blank) Unknown /
Unidentified
914 857

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Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
(Unnamed) Unknown /
Unidentified
619 855
Hot Springs 1980 8/14/1980 Arson 838 838
(Unnamed) 8/2/1973 Equipment Use 775 775
(Unnamed) 1938 (blank) Unknown /
Unidentified
721 721
Peak 2012 7/28/2012 Debris 712 712
Junction 1974 9/26/1974 Miscellaneous 1,136 678
(Unnamed) 1939 (blank) Lightning 668 668
(Unnamed) 1917 (blank) Lightning 614 614
Reno 1969 9/1/1969 Unknown /
Unidentified
641 610
(Unnamed) 1924 (blank) Unknown /
Unidentified
596 596
Cottonwood 2004 5/4/2004 Debris 567 567
(Unnamed) 1941 (blank) Unknown /
Unidentified
564 564
Dotta 2021 6/30/2021 Unknown /
Unidentified
532 532
(Unnamed) 1918 (blank) Lightning 531 530
Hungry 2006 6/25/2006 Lightning 512 512
Cooks 1964 7/24/1964 Miscellaneous 501 501
Greenhorn 1990 6/29/1990 Playing With Fire 497 497
Ross 1977 8/8/1977 Arson 475 475
(Unnamed) Unknown /
Unidentified
1,386 475
(Unnamed) 1999 (blank) Unknown /
Unidentified
3,625 469
Stag 1999 8/23/1999 Lightning 467 467
Cabin W.P.R.R. #2 1976 6/28/1976 Unknown /
Unidentified
632 452
Eureka 2017 9/5/2017 Lightning 446 446
Chambers Creek 1957 9/6/1957 Miscellaneous 432 432
(Unnamed) 1900 (blank) Unknown /
Unidentified
419 419
(Unnamed) 8/18/1987 Equipment Use 409 409
(Unnamed) 1955 (blank) Miscellaneous 408 408
Babcock Peak 2007 7/5/2007 Lightning 407 407
Hay 1952 9/3/1952 Miscellaneous 401 401

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Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
(Unnamed) 1932 (blank) Miscellaneous 395 395
(Unnamed) Unknown /
Unidentified
387 387
GREASE 2006 7/16/2006 Arson 366 366
(Unnamed) Unknown /
Unidentified
348 348
Beckwith (Tahoe NF) 1984 7/30/1984 Unknown /
Unidentified
344 344
(Unnamed) 10/24/1972 Miscellaneous 344 344
(Unnamed) 1935 (blank) Unknown /
Unidentified
340 340
Ridge/Heights 2013 8/18/2013 Lightning 336 336
Hartman 2008 6/21/2008 Lightning 331 331
Martineck 1996 8/12/1996 Lightning 661 331
(Unnamed) 1923 (blank) Unknown /
Unidentified
323 323
Coyote 1973 9/9/1973 Miscellaneous 319 319
Silver 2009 9/19/2009 Miscellaneous 311 311
Camp 2018 11/8/2018 Powerline 153,336 306
(Unnamed) 8/29/1988 Lightning - 304
Millford 1950 9/2/1950 Miscellaneous 9,185 301
(Unnamed) 6/13/1979 Miscellaneous 297 297
Lone Rock Valley 1950 8/7/1950 Lightning 293 293
Milford Grade 2009 4/22/2009 Lightning 284 284
Point 1980 8/14/1980 Unknown /
Unidentified
284 284
Elephant 2009 8/16/2009 Miscellaneous 274 270
Tobin 2016 9/26/2016 Miscellaneous 248 248
(Unnamed) 1919 (blank) Lightning 247 247
(Unnamed) 1920 (blank) Lightning 219 219
(Unnamed) Miscellaneous 217 217
(Unnamed) 1911 (blank) Unknown /
Unidentified
201 201
Cub 2008 6/21/2008 Lightning 14,729 190
Wilson 2018 9/28/2018 Miscellaneous 261 187
(Unnamed) 1949 (blank) Lightning 185 185
Eagle 1989 7/7/1989 Lightning 4,665 179
Claremont 1999 8/23/1999 Lightning 178 178

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Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
South-Frey 2008 6/21/2008 Lightning 12,402 171
(Unnamed) 1964 (blank) Lightning 170 170
Carman #1 1972 8/8/1972 Lightning 158 158
(Unnamed) 1971 11/6/1971 Debris 140 140
Chrome 1999 8/23/1999 Miscellaneous 135 135
Martin 2004 11/2/2004 Debris 131 131
(Unnamed) 1984 5/29/1984 Arson 130 130
Ward 2015 6/2/2015 Unknown /
Unidentified
129 129
(Unnamed) 1916 (blank) Lightning 127 127
5-6 Cascade Creek 2020 8/17/2020 Lightning 260 119
(Unnamed) 1983 7/5/1983 Arson 119 119
(Unnamed) 1986 8/14/1986 Smoking 118 118
Murphy 2018 8/7/2018 Miscellaneous 117 117
Squirrel 2017 9/27/2017 Arson 113 113
Gulch 2010 7/25/2010 Lightning 103 103
(Unnamed) 1972 8/11/1972 Miscellaneous 102 102
Cateyes 1996 5/2/1996 Debris 96 96
Johnson 2013 8/18/2013 Lightning 91 91
Stony 2004 4/27/2004 Debris 91 91
Crocker 2018 7/24/2018 Lightning 87 87
Ranch 2017 9/6/2017 Lightning 84 84
West 2019 9/17/2019 Lightning 89 84
(Unnamed) 1981 9/17/1981 Lightning 79 79
Keddie 2008 6/21/2008 Illegal Alien
Campfire
78 78
Lone Rock 2021 8/6/2021 Unknown /
Unidentified
78 78
Clifton 2007 5/10/2007 Debris 77 77
Mills 2017 9/3/2017 Miscellaneous 75 75
Big 2008 6/21/2008 Lightning 74 74
Creek 2019 11/21/2019 Lightning 74 74
(Unnamed) 1987 8/30/1987 Lightning 73 73
(Unnamed) 5/6/1974 Railroad 72 72
(Unnamed) 8/26/1984 Lightning 71 71
(Unnamed) 8/19/1984 Miscellaneous 68 68
(Unnamed) 8/9/1988 Lightning 63 63

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Jurisdiction / Wildfire Name Year Date Cause
Description
Total Wildfire
Acres
Wildfire Acres
Within
Jurisdiction
Rock 2010 8/13/2010 Arson 62 62
(Unnamed) 9/1/1981 Equipment Use 62 62
Toll 2017 8/20/2017 Arson 58 58
Copper 2020 8/18/2020 Lightning 55 55
Hartman 2021 6/29/2021 Unknown /
Unidentified
54 54
Crescent 2017 6/30/2017 Arson 53 53
Correco 2003 7/27/2003 Lightning 52 52
Source: CAL FIRE (May 2024)
Hazard Mitigation Planning Committee Events
These sections separate events since the 2019/2020 LHMPs and those before 2019.

Events since 2019/2020 LHMP
The HMPC noted the following fires to affect the County:
2019 Walker Fire – The Walker Fire was a wildfire that was burning in Genesee Valley in the Plumas National Forest approximately 11 miles east of the community of Taylorsville in Plumas County, California. The blaze was reported on Wednesday, September 4, 2019, and immediately expanded in size over its several days of burning. The fire actively threatened homes from Genesee Valley to Antelope Road.

Communities along Highway 395 from Thunder Mountain Road (Wales Canyon) to the Laufman Grade (Old Highway 59), including the communities of Murdock Crossing, Stoney, Milford and Brockman Canyon, were under mandatory evacuation. On September 10, the Walker Fire had grown to 47,340 acres and was 12 percent contained. The Lassen County Fairground evacuation center was closed that morning.

The majority of residential evacuation orders were lifted, except the Murdock Crossing and Stoney areas.

The next evening, the fire continued to grow, but was 28 percent contained. Crews extended dozer lines and handlines to expand the containment. Structural defense was put in place for buildings at Murdock Crossing and mop up continued at Antelope Lake, Round Mountain and the eastern side of the fire.

However, by the morning of September 14, the fire had expanded to 54,612 acres and was 97 percent contained. By the time the fire was extinguished, 9 structures had been destroyed. 55,000 acres of grazing land were burned, with livestock water troughs and fencing burned. Damages to livestock grazing were in excess of $1.2 million. The Agriculture Commissioner noted that the loss of grazing lands affected both current year and potential future loss for up to 3 years based on government regulations and weather.

It is important to note that in addition to the Plumas County fire history detailed above, there are numerous smaller fires that occur in the area year after year. These smaller fires have the ability to quickly get out of hand and become significant fires. Also, depending on the area, small fires in acreage can result in large losses. The HMPC provided the following details on fire history in Plumas County.

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July 2020 Hog Fire – The 2020 Hog Fire affected nearby Lassen County. Though it did not burn areas in Plumas County, there were impacts to Plumas County. The Hog Fire, in Lassen County near Susanville, destroyed the one cable bringing Internet into the Lake Almanor Basin, Greenville and beyond. Sheriff Todd Johns said that Frontier Communications replaced the damaged lines, only to have them destroyed again. Officials say an essential fiber optic cable was damaged by the fire on the morning of the 21st and impacted communications and connectivity for Susanville and neighboring Plumas County.

August and September 2020 North Complex Fire – The North Complex Fire was a massive wildfire currently burning in Northern California in the counties of Plumas and Butte. The fires were started by lightning on August 17, 2020; by September 5, all the individual fires had been put out with the exception of the Claremont and Bear Fires, which merged on that date. Starting on September 8, strong winds caused the Bear Fire to explode in size to the southwest. Frequent ashfall occurred in Quincy through 9/17. The North Complex fire had burned an estimated 291,200 acres. Smoke from the fire has created extremely unhealthy air conditions in Quincy and nearby communities for several weeks. Major destruction was reported in the Greenville, Canyon Dam, and surrounding area. There is a worry that the post-wildfire burn scar will pose landslide, debris flow, and flooding issues.

Figure 4-201 North Complex Fire Burn Area
Source: Cal Fire Inciweb. Retrieved 9/28/2020
2021 Beckwourth Complex Fire - Beckwourth Fire Comprised of two separate fires. Dotta Fire started on 03/30/2021 and Sugar Fire started on 07/02/2021. They combined on 07/03/2021 Cause was dry lightning combined with red flag warnings. Total acres burned were 105,670. 106 residences and 42 outbuildings were destroyed in Plumas County. The fire was on USFS property and burned through 4 campgrounds owned by the federal government. All 4 campgrounds had to be evacuated as well as all the homes in the

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Frenchman Lake Area. All USFS roads and two highways were closed and all USFS trails were closed (see detailed list). There are approximately 250 homes within the Beckwourth Fire footprint, but because most of the homes in the footprint of the were second homes or recreation, no sheltering of people was needed.

The full-time homes below the fire in Chilcoot, CA were also under mandatory and warning status evacuations, but still, no one needed sheltering.
2021 Dixie Fire – The Dixie Fire began Tuesday, July 13, 2021, and burned nearly 1 million acres of land across five counties: Plumas, Butte, Lassen, Shasta, and Tehama, before it was considered contained October 25, 2021, 103 days later. It is the second largest wildfire in California history after the August Complex Fire. In total there were 95 structures damaged, and 1,329 structures destroyed by the fire and one fatality. During the Dixie Fire, the Seneca Health staff at the Chester facility were evacuated and the facility was temporarily shuttered. The facility was shuttered from August 4th to the 21st.

Evacuation centers for livestock opened on the 18th of July. In October, the evacuation center for livestock closed on the 2nd and the fire was 100% contained on the 24th. In addition, the fire tore through the town of Greenville and decimated most of what was in its path. The Greenville Rancheria lost their medical and dental facilities, the tribal office, the environmental office, as well as two fire trucks and other vehicles in the fire. The Dixie Fire impacted every person in Plumas County – whether directly or indirectly, including the social safety net providers. While the lack of housing was a strong concern pre-fire, the Dixie Fire significantly worsened an already tight housing market in Plumas County. Air quality in the County suffered from wildfire smoke during this event.

Figure 4-202 Dixie Fire billowing smoke as seen from nearby Deer Creek Source: Plumas County
The magnitude of the Dixie Fire would have overburdened any region’s social safety net and has been especially detrimental to the less vibrant system of care in rural Plumas County.

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July 24, 2024, Wildfire Smoke – Seneca Healthcare noted that the Park Fire in nearby Butte County caused air quality issues in the County. Seneca prepares Skilled Nursing Unit for Evacuation due to possible Air Quality and/or Wildfire Threat. Highway 32 and 36 impacted making transfer difficult. This continued until August 12, 2024.
2024 Gold Complex Fire – On July 22, 2024, a thunderstorm in eastern Plumas County resulted in four dry lightning strikes that became wildfires on the Plumas National Forest Beckwourth Ranger District. The first fire was reported around 2:45 p.m. The Mill, Mill 2 and Mill 3 fires burned near the community of Clio and Whitehawk Ranch. The Smith Fire burned north of California State Highway 70 between Smith Peak and Maybe, California. All four fires grew rapidly due to winds, slope, and dry fuels. Structures were threatened by all four fires, including the communities of Whitehawk Ranch, Clio, Gold Mountain, Delleker, Maybe, Lake Davis Area, and the south and west sides of Portola. These four fires were combined into the Gold Complex.

Events before 2019
The HMPC noted the following fires to affect the County:

An unnamed fire occurred in 1960 which caused a state declaration (along with other California wildfires that summer).
1979 – A member of the HMPC from Viera Ranch noted there was a forest fire in Indian Valley. 1984 - A member of the HMPC from Viera Ranch noted there were multiple fires caused by dry lightning in the area. These wildfires caused air quality issues in Quincy. 1987 – The Plumas National Forest Fire #531 (known as the Clarks Fire) cause a state declaration in 1987 (along with other California wildfires that summer).
1999 – The Bucks Fire caused a federal and state disaster declaration in 1999. Dry lightning caused 25 fires in the forest in the County. The Quincy area was very smokey, with ash falling like now. Winds increased and Meadow Valley was placed on standby for evacuation. Tobin was surrounded by fire. 2000 Storrie Fire – The Forest Service had about 2,600 federal, state and local firefighters, air tankers and helicopter crews to battle the fire that burned 52,000 acres over three weeks. The federal government estimates the cost of the fire at $22 million. The fire caused extensive damage to trees and destroyed 21,000 acres of wildlife habitat. The remaining $80 million of the settlement is earmarked for damages to natural resources, with the money used for the remediation of Lassen and Plumas national forests. Union Pacific Railroad Co. has agreed to a $102 million settlement for damages from the Storrie forest fire in Lassen and Plumas national forests in 2000, the largest-ever federal settlement for a forest fire. Federal authorities allege Union Pacific employees failed to clear the area when they were using grinders and rail saws during repair work, sparking the fire on Aug. 17, 2000.

The 2007 Moonlight Fire was one of the most destructive fires in Plumas County history with a burn perimeter of 64,997 acres. Seven structures were destroyed, 2 residences and 5 outbuildings, and 1 outbuilding was damaged. An additional 25 residences and 10 outbuildings were threatened due to their

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location within the interior of the fire containment lines. 34 injuries and zero deaths were reported. The total cost of fighting the fire was $31.5 million, utilizing 42 engines, one helicopter, 11 dozers, 34 water tenders, 11 fire crews, and 707 total fire personnel. The blaze was caused by employees of Sierra Pacific Industries and a contractor who struck a rock with a dozer, causing sparks to ignite the dry ground in the area. The federal government was able to successfully sue the logging company for $122.5 million in damages resulting from the fire that killed 15 million trees.

The 2008 BTU Lightning Complex Fire caused the federal disaster in 2008 (along with other California wildfires that summer).
2012 Chips Fire – The Chips Fire burned in the Plumas National Forest. The fire started on July 28, causing damage estimated by the US Forest Service of $53.3 million. The Plumas County Sheriff’s Office issued a mandatory evacuation for Butt Reservoir, Ohio Valley, Humbug, Humboldt Area, and Yellow Creek. An evacuation advisory was issued to all Canyon Dam, Big Meadows, Rocky Point Campground, Prattville, Almanor, and West Almanor residents and visitors. The distribution lines powering Quincy and the Eastern Feather River were damaged by fire. PG&E crews were working to restore damaged distribution lines. A mandatory evacuation was ordered for Seneca and Ohio Valley, with voluntary evacuations for Rush Creek, Canyon Dam, Big Meadow, and Rocky Point. A Sheriff’s advisory was in effect for West Almanor, Almanor, and Prattville.
2017 Minerva Fire – The Minerva Fire burned in July and August of 2017. The Minerva Fire almost burned into Quincy. On July 29th, the Plumas County Sherriff and OES stated “Residents of Quincy are strongly encouraged to start making emergency plans for the possibility of evacuation. Residents are encouraged to shut all windows, collect all personal documents, photos, avoid use of air conditioning, and locate your pets and keep them nearby.” Air quality was poor in the County, especially near Quincy. The Oakland Camp area needed to be evacuated. The HMPC noted that they had school buses pick up evacuees from a fire near Oakland Camp and drop at fairgrounds/Red Cross. More than 1,800 firefighters were brought in to fight the blaze. The fire burned more than 4,300 acres. Authorities in Plumas County arrested a 36-year-old Quincy resident on suspicion of starting several fires in the surrounding forest, including the Minerva Fire. The burn area from the fire is shown on Figure 4-203.

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Figure 4-203 Minerva Fire Burn Area
Source: https://yubanet.com/containedlocal16/minerva/
2018 Camp Fire – During the 2018 Camp Fire, there was a small area of Plumas County that was burned.

High amounts of smoke caused air quality issues throughout the County. The EOC was mobilized for 4 to 5 days. Evacuees from Butte County were housed for a period of approximately 5 days. Mobilization costs were borne by the County and reimbursed by FEMA.

Likelihood of Future Occurrence
Highly Likely—Plumas County faces a serious wildland fire threat every year. While often limited to the sparsely populated, forested areas in the western portion of the County, fires will continue to occur on an annual basis throughout the Plumas County Planning Area. The threat of wildfire and potential losses are constantly increasing as human development and population increase, and the wildland urban interface areas expand. Due to its high fuel load and long, dry summers, portions of Plumas County continue to be at risk from wildfire.

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It is likely that climate change will increase the chance of future occurrence as well as future impacts. More information on climate change and wildfire 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 Wildfire
Climate change and its effects on wildfire come from two sources:
➢ Cal-Adapt
➢ 2019 Plumas County CWPP
Cal-Adapt
Warmer temperatures can exacerbate drought conditions. Drought often kills plants and trees, which serve as fuel for wildfires. Warmer temperatures could increase the number of wildfires and pest outbreaks, such as the western pine beetle. Cal-Adapt’s wildfire tool predicts the potential increase in the amount of burned areas for the year 2 090-2099, as compared to recent (2010) conditions. This is shown in Figure 4-204.

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

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Figure 4-204 Plumas County Planning Area – Projected Increase in Wildfire Burn Areas Source: Cal-Adapt. Retrieved 2/6/2025.

Wildfire scenario projections were done by Cal-Adapt, based on statistical modeling from historical data of climate, vegetation, population density, and fire history. The fire modeling ran simulations on five variables on a monthly time step - Large fire presence/absence, Number of fires given presence, Area burned in a grid cell given a fire, High severity burned area given a fire and emissions. These are shown on Figure 4-205. The upper chart shows modeled annual averages of area burned for the Planning Area under the RCP 4.5 scenario, while the lower chart shows modeled annual averages of area burned for the Planning Area under the RCP 8.5 scenario.

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Figure 4-205 Plumas County Planning area – Future Annual Averages of Acres Burned under RCP 4.5 and 8.5 Scenarios
Source: Cal-Adapt. Retrieved 2/6/2025.

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2019 Plumas County CWPP
The 2019 Plumas County CWPP noted that the majority of scientific research concerning climate trends indicates that climate has been changing since the mid-twentieth century. Trends suggest that the northern Sierra Nevada may become generally warmer and wetter, with longer periods of prolonged summer drought. While warmer and wetter weather patterns may increase forest growth and carbon sequestration, warmer temperatures – in combination with longer periods of prolonged summer drought – will likely increase forest insect and disease outbreaks and the occurrence of high severity fire – disturbances which may result in increased carbon losses. Such high severity disturbances could result in type-conversion to shrublands in forested ecosystems that are not adapted to such disturbance patterns – which could drastically alter carbon cycles in the short and long term. High-intensity wildfires, drought, and declining forest health are some effects of climate change that are worsening the threats to forests and reducing forest productivity.

Hotter and drier weather alter forest hydrology and water balance available to forest communities.

Increased temperatures alter the timing of snowmelt, affecting the seasonal availability of water with earlier dry conditions which then provides fuel to earlier and hotter fires from stressed trees and shrubs. Drought also reduces trees' ability to produce sap, which protects them from destructive insects and diseases.

Research has found that large trees may be most susceptible to climate driven mortality – which the authors suggested can also be compounded by high stand densities of small trees due to fire suppression. Others suggest that “regional warming and consequent increases in water deficits are likely contributors to the increase in mortality rates,” and suggest that exogenous warming trends may be more of a driver of mortality, particularly in large diameter trees, than increasing stand density. Nonetheless, research indicates that warming climate is driving changes in forest structure.

Vulnerability Assessment
Vulnerability—Extremely High
Risk and vulnerability to the County from wildfire is of significant concern. Wildfires that occur in the County occur from a variety of both natural and manmade causes. The County can be affected both by fires that start on or near County lands as well as those that start elsewhere and move into the County. In addition to burning large areas of land, air quality can be affected in the County by fires occurring inside the County as well as those from many miles away. As growth continues and populations increase in the County, the potential for catastrophic wildfires will also increase.

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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 vulnerability to this hazard.

According to the County and HMPC, the areas with the highest risk of wildfire are spread throughout the County and are generally located in areas with greater fuel loads resulting from denser forestation. The area that has seen the highest number of fires is the Feather River Canyon along the CA-70 corridor due to the high volume of auto and rail traffic. The Canyon’s accessibility to the population areas, also increases its risk for human-triggered fires. Areas of lower fire hazard, which include the larger valleys such as Indian, American, and Sierra areas of the County, and also the high elevation peaks that receive the most precipitation.

Wildland fires that burn in natural settings with little or no development are part of a natural ecological cycle and may actually be beneficial to the landscape. Century old policies of fire exclusion and aggressive suppression have given way to better understanding of the importance fire plays in the natural cycle of certain forest types.

In Plumas County, past wildfires have caused damages to the County. The County has suffered loss of structures, loss of tax revenue, high costs to battle fires, and loss of lives. The County has noted that both developed and undeveloped areas are at risk. Loss of industrial timberlands, grazing lands, agricultural crops may occur as a result of wildfire. Localized road and school closures have been reported during wildfires. Roads, bridges, utility infrastructure, telecommunications and high voltage transmission lines are also at risk to wildfire. Past wildfires have resulted in loss of timber and recreational lands, which have caused economic issues. This was the case after the Gold Complex Fire.

The County noted that increasingly frequent and severe wildfires throughout California pose a major threat.

Limited road networks and dispersed rural communities mean that the vulnerable populations mentioned below may struggle to evacuate quickly and safely.

Additionally, a concern from a fuels mitigation and post fire cleanup perspective, the County is limited with only one mill taking lumber. There is a finite mill capacity. A temporary mill is needed to process waste.

The County is looking for more of a biomass project instead of a new mill. However, the County did indicate that there are several constraints to a biomass project; haul routes and distances are two primary issues related to a viable biomass project.

After wildfires, it was noted that there is a sensitive time period to reforest before next fire occurs. There is also a need to help private landowners with reforestation efforts after a fire and before the next fire.

The County and HMPC further noted that in the WUI areas, there has been increased difficulty in obtaining home insurance and the cost of insurance premiums. Some residents have experienced cancellations of their policies due to catastrophic and recent wildfires occurring throughout California which has reduced the risk tolerance of many insurance companies. This increases costs to those who live in the WUI, and in some circumstances limits where people choose to live.

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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 wildfire 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.

Methodology (Parcels and Structures)
Utilizing the current FHSZ mapping for the Plumas County Planning Area, two separate analyses were performed: one for the combined SRA/FRA datasets and one for the LRA dataset. Specifically, the following datasets were utilized for the analysis and contained all FHSZ hazard classes from Very High to Non-Wildland: CAL FIRE State Responsibility Area (FHSZSRA_23_3) April 2024 and CAL FIRE Federal Responsibility Area: (Adopted FRA FHSZ 11/2007 - fhszs06_3_6). The following LRA dataset was used for the LRA FHSZ analysis: CAL FIRE LRA (FHSZLRA25_Phase3_v1) released in March 2025. Since it is possible for any given parcel to intersect with multiple categories for purposes of this analysis, the most conservative (or highest risk) FHSZ that intersected each parcel was used to determine which FHSZ to assign to each parcel. Once completed, the FHSZ parcel layer was joined to the assessor data to determine the number of parcels and values falling within each FHSZ. Based on this approach, the FHSZs for the Planning Area and unincorporated Plumas County were determined and further broken out by property use and included information on land and improved values, personal property values and estimated contents values.

This methodology is used below for the FHSZ analysis of people and populations, structures, and critical facilities at risk as well as with respect to future development areas. This FHSZ analysis can be misleading since multiple classes may fall within one polygon, and there are many large polygons throughout the County.

People and Populations
All populations are at some vulnerability to wildfire. Certain vulnerable populations are at greater risk to the effects of wildfire as well as smoke and air quality issues that wildfires bring. Vulnerable populations include:
➢ Unhoused
➢ Infants and children under age five and their caregivers ➢ Elderly (65 and older)
➢ Individuals with disabilities
➢ Individuals’ dependent on medical equipment

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➢ Individuals who exercise or recreate outdoors
➢ Individuals who work outdoors
➢ Individuals with impaired mobility
Plumas County Planning Area residents that live in CAL FIRE FHSZs are often the most vulnerable. Not only are the residents at risk, but their homes and contents are all at risk, compounding the impacts associated with significant hazard events. To further evaluate the impact to the residential population within the Planning Area, CAL FIRE’s wildfire hazard layers were overlayed on the parcel layer and linked to the Assessor data. Those residential parcel polygons that intersect the mapped FRA and SRA layers were counted and multiplied by the 2023 Census Bureau American Community Survey average household factors for each jurisdiction. These are shown by jurisdiction in Table 4-127. Those residential parcel polygons that intersect the mapped LRA layers were counted and multiplied by the 2023 Census Bureau American Community Survey average household factors for each jurisdiction. These are shown by jurisdiction in Table 4-128.

Table 4-127 Plumas County Planning Area – Residential Populations in Moderate or Higher CAL FIRE SRA/FRA Fire Hazard Severity Zones
SRA/FRA Fire Hazard Severity
Zone/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
Moderate
City of Portola 0 0
Unincorporated County 98 234
High
City of Portola 0 0
Unincorporated County 1,415 3,382
Very High
City of Portola 29 66
Unincorporated County 9,275 22,167
Source: CAL FIRE, Plumas County 2024 Parcel/Assessor’s Data, 2023 US Census American Community Survey Average Household Size – City of Portola (2.29); Unincorporated Plumas County (2.39).

Table 4-128 Plumas County Planning Area – Residential Populations in Moderate or Higher CAL FIRE LRA Fire Hazard Severity Zones
LRA Fire Hazard Severity
Zone/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
Moderate
City of Portola 0 0
Unincorporated County 184 440
High
City of Portola 125 286

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LRA Fire Hazard Severity
Zone/Jurisdiction
Improved
Residential
Parcels
Population at
Risk
Unincorporated County 282 674
Very High
City of Portola 781 1,788
Unincorporated County 1,494 3,571
Source: CAL FIRE, Plumas County 2024 Parcel/Assessor’s Data, 2023 US Census American Community Survey Average Household Size – City of Portola (2.29); Unincorporated Plumas County (2.39).

Structures
This section is presented in two sections: SRA/FRA Fire Hazard Severity Zone Analysis and LRA Fire Hazard Severity Zone Analysis.

For the following analysis, the SRA/FRA and LRA FHSZ layer was overlaid with the parcel data as described above and further broken out by property use and included information on both land and improved values.

It should be noted that fire does not just affect structural values, fire can also affect land values. As such the Assessor’s land values and all parcels were accounted for in this analysis to represent total County values at risk. However, it is highly unlikely the whole County will ever be on fire at once.

SRA/FRA Fire Hazard Severity Zone Analysis
All structures in the Plumas County Planning Area have some risk to wildfire. The Plumas County Planning Area parcel inventory and associated values by FRA and SRA are provided in Table 4-129. This is broken down further for the unincorporated County in Table 4-129. Table 4-129 shows FRA and SRA parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), personal property values, estimated content replacement values, and total values in the unincorporated County. Note: while most SRA/FRA mapped areas fall within the unincorporated County areas, due to differing boundaries in mapped datasets, a few SRA/FRA mapped areas are found in the incorporated communities as shown below. Details on each jurisdiction’s SRA/FRA Fire Hazard Severity Zones can be found in their respective annexes to this LHMP Update.

Table 4-129 Plumas County Planning Area – Count and Value of Parcels and Structures in CAL FIRE SRA/FRA FHSZ by Jurisdiction
Jurisdiction /
SRA/FRA Fire
Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola
Very High 92 31 $4,749,530 $10,547,742 $12,605 $6,035,035 $21,344,912 High 2 0 $76,842 $0 $0 $0 $76,842
Moderate 0 0 $0 $0 $0 $0

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Jurisdiction /
SRA/FRA Fire
Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
NonWildland/NonUrban0 0 $0 $0 $0 $0 $0
Outside of
State/ Federal
Responsibility
Area
1,549 990 $33,123,999 $140,703,292 $1,902,467 $88,607,174 $264,336,932 City of Portola
Total
1,643 1,021 $37,950,371 $151,251,034 $1,915,072 $94,642,209 $285,758,686 Unincorporated Plumas County
Very High 19,315 9,693 $1,383,692,274 $2,467,545,493 $41,465,180 $1,302,647,402 $5,195,350,349 High 2,252 1,542 $143,214,394 $357,339,463 $5,071,453 $194,104,091 $699,729,401 Moderate 159 108 $11,808,219 $16,685,606 $318,296 $9,002,272 $37,814,393 NonWildland/NonUrban1 0 $91,800 $0 $0 $0 $91,800
Outside of
State/ Federal
Responsibility
Area
2,507 2,084 $126,188,041 $361,374,716 $94,672,634 $228,404,857 $810,640,248 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 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: CAL FIRE, Plumas County 2024 Parcel/Assessor’s Data Table 4-130 Unincorporated Plumas County – Count and Value of Parcels and Structures in CAL FIRE SRA/FRA FHSZ by Property Use
SRA/FRA Fire
Hazard
Severity Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Very High
Agricultural 1,149 65 $46,154,317 $15,340,446 $986,996 $15,340,446 $77,822,205 Commercial 458 242 $42,543,301 $75,736,553 $26,524,529 $75,736,553 $220,540,936 Federal Lands 212 0 $0 $0 $0 $0 $0
Government 509 0 $124,956 $0 $0 $0 $124,956
Industrial 72 40 $5,519,454 $7,103,600 $10,600 $10,655,400 $23,289,054 Institutional 43 19 $1,512,925 $10,149,108 $26,990 $10,149,108 $21,838,131 Miscellaneous 25 0 $9,591 $0 $0 $0 $9,591

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SRA/FRA Fire
Hazard
Severity Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Recreational 471 52 $16,440,859 $22,316,004 $1,773,985 $22,316,004 $62,846,852 Residential 15,474 9,275 $1,271,386,871 $2,336,899,782 $12,142,080 $1,168,449,891 $4,788,878,624 ROW/Utilities 902 0 $0 $0 $0 $0 $0
Very High
Total
19,315 9,693 $1,383,692,274 $2,467,545,493 $41,465,180 $1,302,647,402 $5,195,350,349 High
Agricultural 79 26 $10,317,552 $5,546,971 $225,254 $5,546,971 $21,636,748 Commercial 65 47 $4,611,970 $14,771,694 $3,919,965 $14,771,694 $38,075,323 Federal Lands 5 0 $0 $0 $0 $0 $0
Government 53 0 $0 $0 $0 $0 $0
Industrial 26 15 $1,341,184 $3,809,343 $0 $5,714,015 $10,864,542 Institutional 8 1 $49,910 $300,000 $0 $300,000 $649,910 Recreational 47 38 $1,696,229 $2,631,367 $40,139 $2,631,367 $6,999,102 Residential 1,875 1,415 $125,197,549 $330,280,088 $886,095 $165,140,044 $621,503,776 ROW/Utilities 94 0 $0 $0 $0 $0 $0
High Total 2,252 1,542 $143,214,394 $357,339,463 $5,071,453 $194,104,091 $699,729,401 Moderate
Agricultural 16 5 $2,458,399 $695,338 $131,260 $695,338 $3,980,335 Commercial 5 5 $210,304 $623,600 $550 $623,600 $1,458,054 Institutional 1 0 $0 $0 $0 $0 $0
Miscellaneous 1 0 $0 $0 $0 $0 $0
Residential 131 98 $9,139,516 $15,366,668 $186,486 $7,683,334 $32,376,004 ROW/Utilities 5 0 $0 $0 $0 $0 $0
Moderate Total 159 108 $11,808,219 $16,685,606 $318,296 $9,002,272 $37,814,393 Non-Wildland/Non-Urban
Residential 1 0 $91,800 $0 $0 $0 $91,800
NonWildland/NonUrban Total1 0 $91,800 $0 $0 $0 $91,800 Outside of State/Federal Responsibility Area
Agricultural 66 22 $11,352,549 $3,396,890 $1,423,017 $3,396,890 $19,569,346 Commercial 325 262 $31,234,305 $73,212,565 $1,830,841 $73,212,565 $179,490,276 Government 37 0 $0 $0 $0 $0 $0
Industrial 42 30 $3,872,983 $7,536,590 $33,539,608 $11,304,885 $56,254,066 Institutional 28 19 $582,281 $3,487,061 $169,390 $3,487,061 $7,725,793 Recreational 1 1 $53,060 $265,302 $0 $265,302 $583,664

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SRA/FRA Fire
Hazard
Severity Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Residential 1,943 1,750 $79,092,863 $273,476,308 $57,709,778 $136,738,154 $547,017,103 ROW/Utilities 65 0 $0 $0 $0 $0 $0
Outside of
State/ Federal
Responsibility
Area Total
2,507 2,084 $126,188,041 $361,374,716 $94,672,634 $228,404,857 $810,640,248 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: CAL FIRE, Plumas County 2024 Parcel/Assessor’s Data LRA Fire Hazard Severity Zone Analysis
All structures in the Plumas County Planning Area have some risk to wildfire. The Plumas County Planning Area parcel inventory and associated values by LRA are provided in Table 4-131. This is broken down further for the unincorporated County in Table 4-137. Table 4-137 shows LRA parcel counts, land and improved values (i.e., those with a structure improvement on the parcel), personal property values, estimated content replacement values, and total values in the unincorporated County. Details on each jurisdiction’s SRA/FRA Fire Hazard Severity Zones and property use types can be found in their respective annexes to this LHMP Update.

Table 4-131 Plumas County Planning Area – Count and Value of Parcels in CAL FIRE LRA FHSZ by Jurisdiction
Jurisdiction /
LRA Fire
Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
City of Portola
Very High 1,488 891 $35,371,649 $139,031,606 $1,912,223 $88,048,386 $264,363,864 High 155 130 $2,578,722 $12,219,428 $2,849 $6,593,823 $21,394,822 Moderate 0 0 $0 $0 $0 $0 $0
NonWildland/NonUrban0 0 $0 $0 $0 $0 $0
Outside of Local
Responsibility
Area
0 0 $0 $0 $0 $0 $0
City of Portola
Total
1,643 1,021 $37,950,371 $151,251,034 $1,915,072 $94,642,209 $285,758,686

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Jurisdiction /
LRA Fire
Hazard
Severity Zone
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Unincorporated Plumas County
Very High 2,212 1,775 $110,540,627 $345,315,982 $93,775,633 $219,780,962 $769,413,204 High 480 343 $29,466,872 $52,827,286 $2,723,330 $33,896,596 $118,914,084 Moderate 235 196 $7,886,778 $22,845,115 $137,783 $12,529,989 $43,399,665 NonWildland/NonUrban188 119 $15,785,356 $13,424,512 $1,611,613 $9,153,000 $39,974,481 Outside of Local
Responsibility
Area
21,119 10,994 $1,501,315,095 $2,768,532,383 $43,279,204 $1,458,798,076 $5,771,924,758 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 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: CAL FIRE, Plumas County 2024 Parcel/Assessor’s Data Figure 4-206 Unincorporated Plumas County – Count and Value of Parcels in CAL FIRE LRA FHSZ by Property Use
LRA Fire
Hazard
Severity Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Very High
Agricultural 13 2 $1,018,633 $759,651 $0 $759,651 $2,537,935 Commercial 298 238 $30,845,467 $73,154,517 $1,765,945 $73,154,517 $178,920,446 Federal Lands 3 0 $0 $0 $0 $0 $0
Government 46 0 $0 $0 $0 $0 $0
Industrial 38 25 $3,326,859 $7,767,049 $33,540,558 $11,650,574 $56,285,040 Institutional 27 16 $542,169 $4,797,675 $160,890 $4,797,675 $10,298,409 Residential 1,668 1,494 $74,807,499 $258,837,090 $58,308,240 $129,418,545 $521,371,374 ROW/Utilities 119 0 $0 $0 $0 $0 $0
Very High
Total
2,212 1,775 $110,540,627 $345,315,982 $93,775,633 $219,780,962 $769,413,204 High
Agricultural 18 7 $6,275,715 $1,674,393 $103,680 $1,674,393 $9,728,181 Commercial 56 41 $4,555,339 $9,216,431 $2,565,851 $9,216,431 $25,554,052 Government 6 0 $0 $0 $0 $0 $0

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Plumas County 4-486
Local Hazard Mitigation Plan Update
January 2026
LRA Fire
Hazard
Severity Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
Industrial 8 7 $920,532 $1,414,350 $0 $2,121,525 $4,456,407 Institutional 8 5 $249,084 $981,080 $11,550 $981,080 $2,222,794 Recreational 1 1 $53,060 $265,302 $0 $265,302 $583,664
Residential 362 282 $17,413,142 $39,275,730 $42,249 $19,637,865 $76,368,986 ROW/Utilities 21 0 $0 $0 $0 $0 $0
High Total 480 343 $29,466,872 $52,827,286 $2,723,330 $33,896,596 $118,914,084 Moderate
Commercial 13 12 $690,326 $2,214,862 $97,460 $2,214,862 $5,217,510 Government 2 0 $0 $0 $0 $0 $0
Residential 214 184 $7,196,452 $20,630,253 $40,323 $10,315,127 $38,182,155 ROW/Utilities 6 0 $0 $0 $0 $0 $0
Moderate Total 235 196 $7,886,778 $22,845,115 $137,783 $12,529,989 $43,399,665 Non-Wildland
Agricultural 67 24 $9,247,840 $3,715,159 $1,554,277 $3,715,159 $18,232,435 Commercial 1 1 $35,700 $117,300 $0 $117,300 $270,300
Industrial 8 4 $704,368 $524,514 $0 $786,771 $2,015,653 Residential 105 90 $5,797,448 $9,067,539 $57,336 $4,533,770 $19,456,093 ROW/Utilities 7 0 $0 $0 $0 $0 $0
Non-Wildland
Total
188 119 $15,785,356 $13,424,512 $1,611,613 $9,153,000 $39,974,481 Outside of Local Responsibility Area
Agricultural 1,212 85 $53,740,629 $18,830,442 $1,108,570 $18,830,442 $92,510,083 Commercial 485 264 $42,473,048 $79,641,302 $27,846,629 $79,641,302 $229,602,281 Federal Lands 214 0 $0 $0 $0 $0 $0
Government 545 0 $124,956 $0 $0 $0 $124,956
Industrial 86 49 $5,781,862 $8,743,620 $9,650 $13,115,430 $27,650,562 Institutional 45 18 $1,353,863 $8,157,414 $23,940 $8,157,414 $17,692,631 Miscellaneous 26 0 $9,591 $0 $0 $0 $9,591
Recreational 518 90 $18,137,088 $24,947,371 $1,814,124 $24,947,371 $69,845,954 Residential 17,075 10,488 $1,379,694,058 $2,628,212,234 $12,476,291 $1,314,106,117 $5,334,488,700 ROW/Utilities 913 0 $0 $0 $0 $0 $0
Outside of
Local
Responsibility
Area Total
21,119 10,994 $1,501,315,095 $2,768,532,383 $43,279,204 $1,458,798,076 $5,771,924,758

Page 633 ends

Plumas County 4-487
Local Hazard Mitigation Plan Update
January 2026
LRA Fire
Hazard
Severity Zone /
Property Use
Total
Parcel
Count
Improved
Parcel
Count
Total Land
Value
Improved
Structure
Value
Personal
Property
Value
Estimated
Contents
Value
Total Value
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: CAL FIRE, Plumas County 2024 Parcel/Assessor’s Data Critical Facilities and Infrastructure
Wildfire presents a threat to critical facilities and infrastructure. The following analysis discusses critical facilities and infrastructure. A separate analysis was performed on the critical facility inventory in the Plumas County Planning Area to determine critical facilities in fire hazard severity zones. This was done for both SRA/FRA and LRA fire hazard severity zones.

Using GIS, the SRA/FRA and LRA fire hazard severity zones were overlayed on the critical facility GIS layer. Figure 4-207 shows critical facilities, as well as the SRA/FRA fire hazard severity zones. Table 4-132 details critical facilities by SRA/FRA fire hazard severity zone by facility category and count for the Planning Area.

Figure 4-207 is an overview map (with insets) that shows critical facilities, as well as the LRA fire hazard severity zones. Figure 4-208 through Figure 4-211 show the zoomed inset maps from Figure 4-207. Table 4-133 details critical facilities by LRA fire hazard severity zone by facility category and count for the Planning Area.

Details of critical facility category, type, name and address by SRA/FRA and LRA fire hazard severity zones are listed in Appendix G.

Page 634 ends

Plumas County 4-488
Local Hazard Mitigation Plan Update
January 2026
Figure 4-207 Plumas County Planning Area – Critical Facilities in SRA/FRA Fire Hazard Severity Zones

Page 635 ends

Plumas County 4-489
Local Hazard Mitigation Plan Update
January 2026
Table 4-132 Plumas County Planning Area – Critical Facilities in SRA/FRA Fire Hazard Severity Zones by Jurisdiction and Critical Facility Category Jurisdiction / Fire Hazard Severity Zones Critical Facility Category Facility Count Portola
Outside of Federal / State Responsibility Area
Essential Services Facilities 16
At Risk Populations Facilities 8
Hazardous Materials Facilities 0
Outside of Federal / State Responsibility
Area Total
24 Portola Total 24
Unincorporated Plumas County
Very High
Essential Services Facilities 619
At Risk Populations Facilities 9
Hazardous Materials Facilities 2
Very High Total 630
High
Essential Services Facilities 70
At Risk Populations Facilities 3
Hazardous Materials Facilities 1
High Total 74
Moderate
Essential Services Facilities 4
At Risk Populations Facilities 1
Hazardous Materials Facilities 0
Moderate Total 5
Non-Wildland/Non-Urban
Essential Services Facilities 6
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Non-Wildland/Non-Urban Total 6
Outside of Federal / State Responsibility Area
Essential Services Facilities 130
At Risk Populations Facilities 20
Hazardous Materials Facilities 1
Outside of Federal / State Responsibility
Area Total
151
Unincorporated Plumas County Total 866
Unincorporated Butte County
Very High
Essential Services Facilities 3
At Risk Populations Facilities 0
Hazardous Materials Facilities 0
Very High Total 3
No Data Available Essential Services Facilities 1

Page 636 ends

Portola City CouncilJune 10, 2026

Portola City Council
June 10, 2026