San Diego County, CA Environmental Rules: Flood Elevation Requirements (2026)

All new construction, substantial improvements and placement of a residential structure within a special flood hazard area located outside an alluvial fan shall have the lowest floor, including basement, mechanical and utility equipment, and ductwork, but excluding garages used solely for parking or storing vehicles, access to or from the residence or storage in a manner that prevents stored objects from being carried away in a flood, elevated 1 foot above the base flood elevation. The elevation shall be certified on a FEMA elevation certificate by a registered civil engineer or licensed land surveyor, an architect may certify structural elevations only when the certification relies on survey data prepared by a licensed land surveyor or registered civil engineer; and the design and method of construction of any portion of a garage allowable below base flood elevation certified by a registered civil engineer, or architect as meeting these standards and standards imposed by the National Flood Insurance Program, and verified by the County building inspector. Such certification and verification shall be provided to the Floodplain Administrator.

(2)   Construction in alluvial fans. New construction, substantial improvement and placement of any structure in Zone AO or within the alluvial fan boundaries shown on the Borrego Valley alluvial fans map or FIRM, shall have the lowest floor, including basement, mechanical and utility equipment,