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

1 of the Alameda floodplain regulations sets the city's freeboard standard: new buildings and structures, substantial improvements, and buildings built as part of a new subdivision in a flood hazard area must reach the base flood elevation plus one foot, or comply with the Building Standards Code's flood provisions, whichever protects more. Mechanical, plumbing, and electrical systems, including plumbing fixtures serving the building, must be elevated to that same one-foot freeboard unless installed to resist flooding under ASCE 24 (Sec. 8). Property owners who build or substantially improve a structure with a finish floor more than four feet above the lowest adjacent grade must sign a non-conversion agreement promising the enclosed space below the lowest floor stays limited to parking, storage, or access, is never used for habitation, and keeps its walls, ceilings, and floors below the freeboard elevation unfinished and made of flood-resistant materials (Sec.

2). Detached garages and accessory storage structures can sit below the base flood elevation only if they are one story, no larger than six hundred square feet in a special flood hazard area, anchored against flotation, built with flood openings, and finished below the freeboard line in flood-resistant materials (Sec. 3). Utility and miscellaneous Group U structures, including retaining walls, sheds, and private garages, must be anchored against flotation and, when fully enclosed, elevated to the design flood elevation under the ASCE 24 standard (Sec.

4). The Floodplain Administrator, the Public Works Director, reviews design certifications and elevation documentation as part of building permit review in a flood hazard area (Sec. 4).