Hayward, CA Environmental Rules: Flood Elevation Requirements (2026)

10(k) defines base flood elevation (BFE) as the water surface elevation shown on the Flood Insurance Rate Map for Zones AE, AG, A1-30, VE and V1-V30 for a flood with a one percent or greater annual chance of being equaled or exceeded, commonly called the 100-year flood. 110(c) then sets the construction standard: in an AO zone, the lowest floor must be elevated to the depth number shown on the FIRM, or at least two feet above the highest adjacent grade if no depth number is given; in an A zone and in all other special flood hazard zones, the lowest floor must be elevated to a level at or above the base flood elevation.

A registered civil engineer or licensed land surveyor must certify the as-built elevation of the lowest floor, including any basement, and the City's community building inspector verifies it before the Flood Plain Administrator, the Director of Public Works, signs off. Non-residential structures may floodproof instead of elevate, making walls below the base flood level substantially impermeable and structurally able to resist hydrostatic and hydrodynamic loads, certified by a registered engineer or architect. Attached garages with a floor below the BFE must be built with flood-resistant materials and designed to let floodwater automatically enter and exit; small detached garages and accessory sheds may have a floor below the BFE only if built with flood-resistant materials below that line, anchored against flotation, and designed for automatic floodwater entry.