Photo: Lights and freedom · CC BY-SA 4.0FEMA puts Castro Valley’s expected hazard damage per building above that of 92% of U.S. towns, mostly from earthquakes
On FEMA’s National Risk Index, Castro Valley gets a D for hazard risk: higher expected damage per building than 92% of U.S. towns, #423 of 847 in California. Most of that expected damage is earthquakes (58%), then river and rain flooding (37%). Flood insurance has paid 17 claims here since 1978.
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 Castro Valley faces
Each hazard’s share of the building damage FEMA expects here, and how its rate compares with the rest of the country.
Earthquakes
River and rain flooding
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 Castro Valley’s grade
Earthquakes are 58% of the building damage FEMA expects in Castro Valley, and Castro Valley’s rate of earthquakes damage is in the top 4% of U.S. census tracts. Wildfire adds 4%, at a rate in the top 6% of U.S. census tracts.
D #423 of 847 in California; higher expected damage per building than 92% of U.S. towns (21,298).
Castro Valley’s residents live in 16 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, Castro Valley has less expected damage per building than 50% of California towns.
In dollars, FEMA expects about $51.6M a year in losses across Castro Valley: $40.4M to buildings, the rest to people and crops.
Does Castro Valley flood? Sometimes: 17 flood claims since 1978
Every paid claim on a federal flood insurance policy in Castro Valley, from FEMA’s records: 0.7 per 1,000 homes, fewer than 84% of the 13,809 U.S. towns with a flood insurance record.
- The California Atmospheric River7 claims · $247K
- The Pineapple Express - Southern6 claims · $280K
- The Winter storm1 claim · $709
Castro Valley isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Alameda County.1 federal disaster brought FEMA money to Castro Valley
Disasters that paid out in Castro Valley itself (aid to households or repair grants to Castro Valley), newest first, with that year’s flood claims.
- 2022Severe Winter Storms, Flooding, Landslides, and Mudslides175 households applied for aid$845K aid approved6 flood claims paid that year
Alameda County has had 20 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.
Old photos of Castro Valley after a storm or flood belong in the town’s history. Add one, or share what you remember below.
Add to the Castro Valley archive →Castro Valley and its neighbors
Castro Valley is 2nd of the 6 graded towns here, from least expected damage per building to most. Tap a town to see its hazards.
| Town | Hazard risk | Mostly (buildings) | Flood claims |
|---|---|---|---|
| Fairview | Dmore damage than 92% | earthquakes | — |
| Castro Valley | Dmore damage than 92% | earthquakes | 17 |
| Ashland | Dmore damage than 93% | earthquakes | 1 |
| Hayward | Dmore damage than 95% | earthquakes | 16 |
| Oakland | D−more damage than 97% | earthquakes | 103 |
| San Leandro | D−more damage than 97% | earthquakes | 5 |
Hazard risk = FEMA’s expected yearly building damage per dollar of building value, vs. the 21,298 U.S. towns we grade; the map is shaded by fifths of the same scale. Flood claims = paid federal flood insurance claims on record.
Get ready for what Castro Valley faces
A short kit for the hazards that drive the building damage here, what to check before you buy, and where neighbors get alerts.
- Drop, cover and hold on.
- Strap tall furniture and the water heater to the wall.
- Know how to shut off the gas.
- 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.
- 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 Castro Valley
Is Castro Valley at risk for natural disasters?
On FEMA’s National Risk Index, Castro Valley has higher expected damage per building than 92% of U.S. towns: D for hazard risk, #423 of 847 in California. Most of the expected damage is earthquakes (58%) and river and rain flooding (37%). This is FEMA’s model of an average year for today’s buildings, not a forecast.
Does Castro Valley flood?
Flood insurance has paid 17 claims in Castro Valley since 1978, $538K in all, or 0.7 per 1,000 homes, fewer than 84% of U.S. towns with a flood insurance record. The most claims came from California Atmospheric River (7).
Is Castro Valley 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 Alameda County, 36% of homes in mapped flood zones carry federal flood insurance, and 0.8% of all homes do.
How much is flood insurance in Castro Valley?
FEMA’s Community Rating System list shows no discount for Castro Valley’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
What was the biggest storm in Castro Valley?
By FEMA money that reached Castro Valley, Severe Winter Storms, Flooding, Landslides, and Mudslides (2022): 175 households applied for aid, $845K approved. By flood claims, California Atmospheric River: 7 paid, $247K.
Is Castro Valley at risk from earthquakes?
It is the largest share of the building damage FEMA expects here (58%), and Castro Valley’s rate for it is in the top 4% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Castro Valley.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Castro Valley’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.