Blog · October 14, 2026 · California
San Mateo County Flood Zone Map, California
How to check whether a property in San Mateo County sits in a FEMA flood zone, and what the answer means for a buyer near East Palo Alto.
Main page: San Mateo County, CA GIS & Parcel Viewer (official map link, San Mateo County facts and neighboring maps).
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Is that lot in Daly City in a flood zone? The San Mateo County flood zone map answer comes from FEMA, and it is free to look up. Here's how to read FEMA's map for a San Mateo County, CA property and match it to the parcel record.
Next: FEMA's search tool, the zone labels you'll see for San Mateo County, and how the parcel record confirms which tract you're on.
How to check the San Mateo County flood zone map
Start at the FEMA Flood Map Service Center and enter the property address in Foster City or anywhere else in the county. If a piece of ground near Daly City has no street number yet, search the nearest road and pan to it. For an interactive view of the county, the National Flood Hazard Layer viewer is easier to use and reports the zone wherever you click near Foster City. Then open the San Mateo County parcel viewer for San Mateo County to confirm the parcel near Foster City. Match the San Mateo County lines and acreage to the FEMA view, since flood maps do not draw property lines in detail.
Search San Mateo County parcels by owner, address or ID
The county's own public map is the San Mateo County parcel viewer, and it opens without an account for parcels in Belmont and the rest of the county. Click any San Mateo County parcel near Belmont to open its record: owner, parcel ID and assessed acreage are most commonly listed. For a backup route to the map covering Redwood City, our San Mateo County directory entry keeps the link current.
What the flood zone letters mean
For a lot in Foster City, the label matters more than the color: A and V zones are Special Flood Hazard Areas, defined by a 1-percent annual chance of being flooded. Where a San Mateo County tract displays Zone AE, there's a base flood elevation to compare a building against; in Zone A there is not one. If a San Mateo County parcel displays shaded Zone X, it is moderate risk, between the 1-percent and 0.2-percent annual chance lines. Unshaded X (or C) on the San Mateo County panel means minimal risk.
Low ground and small streams around Foster City
Small streams and ditches near Foster City may not be studied in detail, which is why it is worth walking the ground after a heavy rain.
Questions to ask before buying in San Mateo County
Request any past flood claims history for a San Mateo County property before closing; it tells you more than the map alone. An agent working in San Mateo County can quote flood coverage once you know the zone for the lot near Belmont.
Insurance, permits and map changes
The zone displays up again when a loan on a house near Daly City is underwritten. If a barn or house outside Foster City falls inside an A or V zone and secures a loan from a federally regulated or insured lender, flood insurance is mandatory, provided the community near Foster City takes part in the National Flood Insurance Program. For a San Mateo County home in shaded or unshaded X, coverage is optional, although a lender in California can still ask for it. When a San Mateo County homesite is on a rise inside a mapped zone, a Letter of Map Amendment request is the formal route, supported by elevation data from a professional surveyor. New construction in a San Mateo County Special Flood Hazard Area has to meet local floodplain rules, so call the county or the town office in Foster City before work starts.
San Mateo County flood zones questions
What does 100-year flood mean for San Mateo County land?
Not at all; a San Mateo County tract in that zone carries a 1-in-100 chance in any single year, not a once-a-century schedule.
What does Zone AE mean on a San Mateo County flood map?
For a San Mateo County parcel, Zone AE means a Special Flood Hazard Area with a 1-percent annual chance of flooding and a published base flood elevation.
Where can I see flood zones for land near Redwood City?
Look it up at FEMA's Flood Map Service Center, then match the parcel lines in the county parcel viewer; for land near Redwood City, a zone starting with A or V is high risk.
Is flood insurance required for a Zone X lot in Brisbane?
FEMA doesn't require it for a Zone X lot in Brisbane, but coverage is available and some lenders ask for it.
What is a base flood elevation for a San Mateo County property?
On the map covering Brisbane, it is the projected water surface in the base flood; elevation certificates in San Mateo County are measured against it.
Open the official San Mateo County, CA parcel map San Mateo County in the Platbookmapper directory
Not a survey. County GIS and tax parcel maps are assessment and planning layers. They are not a substitute for a recorded plat, deed, or licensed survey, especially for fences, setbacks, or boundary disputes.