FEMA expects more hazard damage per building in Alta Sierra than in 76% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Alta Sierra gets a C− for hazard risk: higher expected damage per building than 76% of U.S. towns, #147 of 847 in California. Most of that expected damage is river and rain flooding (69%), then wildfire (27%). FEMA’s files show no paid flood insurance claims here.
Graded on FEMA’s expected yearly building damage per dollar of building value (NRI v1.20, December 2025), weighted by where residents live; flood claims are shown, not graded. How hazard risk is graded
What Alta Sierra faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
River and rain flooding
Wildfire
Shares are of FEMA’s expected building damage, the measure the grade uses; ranks compare each hazard’s building-damage rate with all 85,154 U.S. census tracts. In FEMA’s terms, river and rain flooding is FEMA’s “Inland Flooding” (rivers and streams overflowing their banks, or rain overwhelming drainage). FEMA defines coastal flooding as high or rising tides and storm surge, so surge damage is counted there. Drought isn’t listed: FEMA counts its losses in crops only.
What’s behind Alta Sierra’s grade
River and rain flooding is 69% of the building damage FEMA expects in Alta Sierra, and Alta Sierra’s rate of river and rain flooding damage is higher than 77% of U.S. census tracts. Wildfire adds 27%, at a rate in the top 2% of U.S. census tracts.
C− #147 of 847 in California; higher expected damage per building than 76% of U.S. towns (21,298).
Alta Sierra’s residents live in 2 census tracts; FEMA’s figures are combined by where they live.
The typical California town has higher expected damage than 92% of U.S. towns; within the state, Alta Sierra has less expected damage per building than 83% of California towns.
In dollars, FEMA expects about $2.4M a year in losses across Alta Sierra: $2.3M to buildings, the rest to people and crops.
Does Alta Sierra flood? No paid flood claims on record
FEMA’s records show no paid flood insurance claims in Alta Sierra. That’s not a promise: most homes don’t carry flood insurance, so small floods go unrecorded.
Alta Sierra isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Nevada County.The storms Alta Sierra remembers
None of the 17 disasters declared for Nevada County shows FEMA aid or repair money reaching Alta Sierra itself in FEMA’s records, so these are its biggest flood-claim years.
Nevada County has had 17 natural disasters declared by the President since 1953, most often severe storms, then floods. Not counted: the 2005 Hurricane Katrina evacuee emergency, which covered counties that took in evacuees.
Also 3 FEMA wildfire suppression grants (Fire Management Assistance, not a disaster declaration) for fires in Nevada County, 2009–2020.
Get ready for what Alta Sierra faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Turn around at flooded roads: a foot of moving water can carry off a car.
- Flood insurance usually takes 30 days to start, so buy it before the forecast.
- Keep papers and medicines up high, in a grab-and-go bag.
- Clear dead leaves and brush within 5 feet of the house.
- Sign up for local alerts and know two ways out.
- Keep N95 masks for smoky days.
- Look up the address on FEMA’s flood map.
- Ask the seller or landlord whether it has ever flooded, and what flood insurance costs there.
- Get a flood insurance quote early: policies usually start 30 days after you buy.
Know where neighbors sign up for alerts? Add it to the Handbook so everyone has it.
Questions about natural hazards in Alta Sierra
Is Alta Sierra at risk for natural disasters?
On FEMA’s National Risk Index, Alta Sierra has higher expected damage per building than 76% of U.S. towns: C− for hazard risk, #147 of 847 in California. Most of the expected damage is river and rain flooding (69%) and wildfire (27%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Is Alta Sierra in a flood zone?
Flood zones are drawn street by street, so the answer depends on the address: look it up on FEMA’s flood map. In Nevada County, 23% of homes in mapped flood zones carry federal flood insurance, and 0.2% of all homes do.
How much is flood insurance in Alta Sierra?
FEMA’s Community Rating System list shows no discount for Alta Sierra’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
Is Alta Sierra at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (69%), and Alta Sierra’s rate for it is higher than 77% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Alta Sierra.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Alta Sierra’s residents lived in the 2020 census; OpenFEMA: NFIP redacted claims, multiple-loss properties, community status book and residential penetration rates, housing assistance (owners and renters), public assistance funded projects, hazard mitigation properties and disaster declarations. Homes: Census ACS 2020–24. Preparedness tips: Ready.gov. FEMA’s model is an average of expected damage, not a forecast. How hazard risk is graded.