FEMA expects more hazard damage per building in Alto than in 89% of U.S. towns, mostly from river and rain flooding
On FEMA’s National Risk Index, Alto gets a D for hazard risk: higher expected damage per building than 89% of U.S. towns. Most of that expected damage is river and rain flooding (53%), then earthquakes (36%). 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 Alto 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
Earthquakes
Tsunamis
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 Alto’s grade
River and rain flooding is 53% of the building damage FEMA expects in Alto, and Alto’s rate of river and rain flooding damage is higher than 81% of U.S. census tracts. Earthquakes add 36%, at a rate in the top 10% of U.S. census tracts.
D higher expected damage per building than 89% of U.S. towns (21,298).
All of Alto’s residents live in one census tract; the figures are that tract’s.
In dollars, FEMA expects about $522K a year in losses across Alto: $472K to buildings, the rest to people and crops.
Does Alto flood? No paid flood claims on record
FEMA’s records show no paid flood insurance claims in Alto. That’s not a promise: most homes don’t carry flood insurance, so small floods go unrecorded.
Alto isn’t in FEMA’s Community Rating System, which cuts flood insurance up to 45% in towns that do extra flood-proofing.
Insurance rates: Marin County.The storms Alto remembers
None of the 22 disasters declared for Marin County shows FEMA aid or repair money reaching Alto itself in FEMA’s records, so these are its biggest flood-claim years.
Marin County has had 22 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.
Alto and its neighbors
Alto is 3rd of the 3 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 |
|---|---|---|---|
| Strawberry | Dmore damage than 85% | river and rain flooding | 20 |
| Mill Valley | Dmore damage than 86% | earthquakes | 144 |
| Alto | Dmore damage than 89% | river and rain flooding | 0 |
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 Alto 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.
- Drop, cover and hold on.
- Strap tall furniture and the water heater to the wall.
- Know how to shut off the gas.
- Strong shaking or a sudden drop in the sea means head for high ground now.
- Learn the tsunami route signs near the shore.
- Stay away until officials say it’s safe.
- 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 Alto
Is Alto at risk for natural disasters?
On FEMA’s National Risk Index, Alto has higher expected damage per building than 89% of U.S. towns: D for hazard risk. Most of the expected damage is river and rain flooding (53%) and earthquakes (36%). The figures are for the one census tract the town shares with its neighbors. This is FEMA’s model of an average year for today’s buildings, not a forecast.
Is Alto 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 Marin County, 38% of homes in mapped flood zones carry federal flood insurance, and 5.4% of all homes do.
How much is flood insurance in Alto?
FEMA’s Community Rating System list shows no discount for Alto’s flood program. Premiums depend on the building; policies usually start 30 days after you buy, so get a quote early.
Is Alto at risk from river and rain flooding?
It is the largest share of the building damage FEMA expects here (53%), and Alto’s rate for it is higher than 81% of U.S. census tracts.
Storm stories
Memories, warnings and help from neighbors in Alto.
Sources: FEMA National Risk Index v1.20 (December 2025), census-tract table, combined by where Alto’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.