Riverside County, CA

Supports FEMA checklist item B1-a Hazard identification

15 of the 18 National Risk Index hazards apply here.

Not applicable to this county per NRI, with no federal declaration and no Storm Events record since 1996: ice storm and tsunami. That is the evidence for leaving them out of the plan.

Highest expected annual loss (NRI, modeled): Inland Flooding, Earthquake and Wildfire.

Not covered by NRI (local data needed): dam failure (incl. upstream dams); levee failure; flash flood as its own subtype; ice jams; debris flows; erosion (riverine and coastal); land subsidence and sinkholes; expansive soils.

The state hazard mitigation plan also lists hazards for this county; FEMA asks the plan to explain any hazard it leaves out.

Supports FEMA checklist item B1-b Hazard location

• Avalanche, Coastal Flooding, Earthquake, Hurricane, Landslide, Tornado, Volcanic Activity and Wildfire vary within the county; the packet lists the highest-rated census tracts for each.
• Cold Wave, Drought, Hail, Heat Wave, Lightning, Strong Wind and Winter Weather: affects the whole county; national data give no location within it.
• Inland Flooding: the FEMA Flood Insurance Rate Map (FIRM) is the required location source for flooding. See the FEMA Flood Map Service Center (https://msc.fema.gov) for this county.

Supports FEMA checklist item B1-c Hazard extent

Storm Events records for 15 of the 20 NOAA event-type groups mapped to the 18 hazards, with the scale, observed range and worst recorded event for each; the others say which local data are needed.

Worst recorded tornado, hail and thunderstorm wind (the three event types on record since the 1950s; the packet has every group):

• Hail: 2.75 in hail, 1960-09-02
• Thunderstorm Wind: 88 kt (101 mph), measurement type not recorded, Thunderstorm Wind, 1973-08-03
• Tornado: F3 tornado, 1973-08-16, 33 yd wide, $25,000 property; crops not recorded (1973 dollars)

Supports FEMA checklist item B1-d Previous occurrences

Federal declarations for this area: 66 declarations covering 59 separate hazard incidents counted in this packet; each with type, dates and county Public Assistance dollars.

New since the last plan (approved 2023-04-18): FM-5636-CA, FM-5538-CA, FM-5515-CA and DR-4750-CA.

10 statewide declarations listed separately.

Hazards with no Storm Events record and no federal declaration are stated as such (3 of 18).

Storm Events history: 1,717 records (notable ones in the PDF, all of them in the Excel file).

Supports FEMA checklist item B1-e Probability of future events

FEMA annualized frequency (modeled) for each hazard, with a descriptor from a scale defined in the packet.

• Highly likely: Inland Flooding, Landslide, Lightning, Wildfire and Winter Weather
• Likely: Cold Wave, Drought, Heat Wave, Strong Wind and Tornado
• Possible: Avalanche, Hail and Hurricane
• Unlikely: Volcanic Activity

Historical frequency by intensity band (tornado, hail, wind): 9 bands from Storm Events.

Supports FEMA checklist item B1-f Hazards that vary across jurisdictions

Range of census tract risk scores within the area for 16 of the 18 hazards (518 tracts; rated tracts only).

26 jurisdictions: plan clock, repeat-flood count, Public Assistance dollars and event records naming the place (starting figures from federal data).

County Public Assistance in B1-d also includes applicants filed under the county that are not jurisdictions in this plan (for example state agencies, special districts and nonprofits), so the jurisdiction rows add up to less.

Supports FEMA checklist items B2-a and B2-b Vulnerability and potential impacts

The packet's table gives county-level starting figures; the plan describes impacts for each jurisdiction and its own assets.

Storm Events damage since 2023-04-18: $293,000 in county-coded records (77 records); $83,808,000 reported for the zone (106 zone records). Data through 2026-06-30; nominal dollars.

Local data needed

To gather:

• Critical facilities and lifelines per hazard
• A problem statement per jurisdiction per hazard
• Changes in development in hazard-prone areas since the last approval, or a statement of none (E1-a)
• Future assets

Supports FEMA checklist item B2-a Vulnerability (county context)

Population 2,416,838; building value $470,055,458,576 and agriculture value $1,200,000,752 (total, not at risk).

National Risk Index rating Very High; social vulnerability Relatively Low; community resilience Very Low.

Supports FEMA checklist item B2-c Repetitive loss properties

Repetitive-loss properties, FMA definition (44 CFR 77.2): 2 repetitive loss, 4 severe repetitive loss. NFIP insurance definition: 67 and 3.

Mitigated 1; insured 20; NFIP data as of 2026-08-02. Counts by occupancy group and for each jurisdiction are in the packet.