Parcel Risk Report

How do San Mateo County neighborhoods rate for flood risk on FEMA's National Risk Index?

FEMA's official flood map draws the 1%-annual-chance floodplain. FEMA's National Risk Index adds a comparative flood-risk rating for every census tract — a broader, neighborhood-scale measure (it reflects expected losses and vulnerability, not just the floodplain) that complements the map rather than contradicting it.

58 of 173

census tracts in San Mateo County are rated Relatively High or higher for riverine or coastal flood risk by FEMA's National Risk Index.

Census tracts in San Mateo County	173
… rated Relatively High or Very High for flood (riverine or coastal)	58

These are tract-level ratings (neighborhood scale), not parcel-precise, and not a count of individual homes — see the note below. Every figure is from FEMA's National Risk Index: https://hazards.fema.gov/nri/.

Check a specific San Mateo County address

County figures are a starting point. To see what the official FEMA flood map will say for one property — side by side with these cited federal & state sources — run the free per-address check:

Open the free Beyond-FEMA checker →

How this figure is derived (and what it is not)

Counts come straight from FEMA's National Risk Index census-tract layer, filtered to San Mateo County (state-county FIPS 06081).
A tract is counted when its riverine or coastal flood rating is "Relatively High" or "Very High" — FEMA's own categorical ratings, never a proprietary score.
This is a tract (neighborhood) count, not a homes count. A precise "homes outside the FEMA flood zone" figure can't be derived from the free National Risk Index data, so we don't claim one.
This is general public-data information — not a Natural Hazard Disclosure Statement, and it does not satisfy California Civil Code §1103.2.

Flood risk by city in San Mateo County

Tract-level flood-gap figures for each incorporated city, from the same FEMA National Risk Index data:

Atherton · Belmont · Brisbane · Burlingame · Colma · Daly City · East Palo Alto · Foster City · Half Moon Bay · Hillsborough · Menlo Park · Millbrae · Pacifica · Portola Valley · Redwood City · San Bruno · San Carlos · San Mateo · South San Francisco · Woodside