Brentwood, CA Environmental Rules: Flood Zones (2026)

Brentwood participates in the National Flood Insurance Program (NFIP) and enforces a floodplain management ordinance consistent with 44 CFR §60.3. FEMA Flood Insurance Rate Maps (FIRMs) identify Zone AE (1% annual chance flood with base flood elevations) along Marsh Creek and its tributaries, along with Zone X (0.2% annual chance / moderate risk) in adjacent areas. Residents can check their specific property via FEMA's Flood Map Service Center (msc.fema.gov). Structures in SFHAs must be built with the lowest floor (including basement) elevated at or above the Base Flood Elevation (BFE), typically with 1 to 2 feet of freeboard added by local ordinance. Substantial improvements (cost exceeding 50% of market value) and substantial damage trigger full floodplain compliance for existing structures. An Elevation Certificate prepared by a licensed surveyor is required for new construction and is useful for flood insurance rating. Fill, grading, and any development that could obstruct flood flows within the regulatory floodway is prohibited or heavily restricted. Lenders require flood insurance for federally-backed mortgages on properties in SFHAs. Homeowners in Zone X can obtain Preferred Risk Policies at lower premiums. Brentwood has participated in FEMA Community Rating System activities to reduce flood insurance costs for residents. Marsh Creek Reservoir upstream provides some flood control, but large storm events (particularly atmospheric rivers) can still produce flooding along the creek corridor.