Parcel Risk Report

Flood risk in and around Foster City, San Mateo County

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. Here's how the tracts in and around Foster City rate, and how to check one address.

13 of 15

census tracts in and around Foster City are rated Relatively High or Very High for riverine or coastal flood risk by FEMA's National Risk Index.

Census tracts intersecting Foster City	15
… rated Relatively High or Very High for flood (riverine or coastal)	13

That puts parts of the Foster City area among the higher-rated neighborhoods in FEMA's national flood-risk comparison. The National Risk Index rating is a comparative, composite measure (it reflects expected losses and community vulnerability, not just the mapped floodplain), so it complements the official FEMA flood map rather than contradicting it — check a specific address to see the map's call for one property. These are tract-level ratings (neighborhood scale), not parcel-precise and not a count of homes.

Flood-rating breakdown for Foster City

Riverine flood — Very High	4
Riverine flood — Relatively High	9
Coastal flood — Very High	1

FEMA rates riverine and coastal flood separately, so one tract can appear in two rows — these rows can therefore add up to more than the 13 elevated tracts above (a tract is "elevated" if either rating is Relatively High or Very High). Categorical classes from FEMA's National Risk Index — never a proprietary score.

Check a specific Foster City address

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

Open the free Beyond-FEMA checker → · See all of San Mateo County →

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

Counts come from FEMA's National Risk Index census-tract layer, limited to the tracts that intersect the U.S. Census Bureau 2020 boundary of Foster City (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 comparative categorical classes, never a proprietary score, never a per-parcel prediction.
We say "in and around Foster City" on purpose: census tracts don't line up with city limits, so a tract is included if it touches the boundary — and for a small city, many counted tracts may extend well beyond its limits. Read the figure as the surrounding neighborhood, not the city alone. It is a tract count, not a homes count, and not parcel-precise.
Ratings: FEMA National Risk Index (https://hazards.fema.gov/nri/). City boundary: U.S. Census 2020 incorporated places (census.gov). Both update rarely; data retrieved 2026-06-02.
This is general public-data information — not a Natural Hazard Disclosure Statement, and it does not satisfy California Civil Code §1103.2 (the seller's statutory disclosure in a sale).

Other cities in San Mateo County

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