Contra Costa County, CA Environmental Rules: Flood Zones (2026)

602. 802 requires a floodplain permit from the Contra Costa County Public Works Department, obtained before a grading or building permit is issued. The application, filed on forms from the floodplain administrator at Public Works, must include triplicate scaled plans showing the nature, location, dimensions and elevation of the site and any existing or proposed structures, fill, storage of materials, or drainage facilities. Applicants must also list the proposed elevation, relative to mean sea level, of the lowest floor of every structure, and for AO or VO zones, the elevation of the highest adjacent grade.

The ordinance exists so the county can keep participating in the National Flood Insurance Program administered by FEMA, which provides flood insurance and federal disaster assistance to property owners; without a compliant local ordinance the county's homeowners would lose access to that coverage. The floodplain administrator reviews every permit for compliance with FEMA's elevation and floodway-carrying-capacity requirements, and can require a hydrology and hydraulics study for developments proposing more than ten new insurable structures. Enforcement runs through the county's general compliance provision rather than a separate floodplain penalty schedule.