FEMA flood zone rules in San Mateo County, CA — also called floodplain regulations or special flood hazard area (SFHA) rules — determine flood insurance requirements and elevation standards for new construction.
Unincorporated San Mateo County has significant flood risk in coastal lowlands, creek corridors, and bayfront areas. FEMA flood zones require permits, elevation certificates, and flood insurance for federally-backed loans. Sea level rise is a major threat.
San Mateo County participates in the NFIP. FEMA-designated Special Flood Hazard Areas (SFHAs) exist along the Bay shoreline, major creek corridors (San Francisquito, Pescadero, San Gregorio, Pilarcitos), and low-lying coastal areas on the Pacific Coast. New construction in SFHAs must be elevated to or above Base Flood Elevation and requires a Floodplain Development Permit from the County Planning & Building Department. Sea level rise poses increasing risk to bayfront and coastal unincorporated communities. The county maintains a Local Hazard Mitigation Plan addressing flood risk. Check FEMA's Flood Map Service Center (msc.fema.gov) for property-specific status.
Construction below flood elevation: retroactive compliance required, fines $500 to $5,000. Floodway encroachment: removal order. Failure to maintain flood insurance: lender force-placement at higher cost.
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See how San Mateo County's flood zones rules stack up against other locations.
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