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

32, Flood Damage Prevention, sets the construction standard for the city's special flood hazard areas mapped on the Flood Insurance Rate Maps. 050(A)(3)(a) requires that residential construction, whether new or a substantial improvement, have its lowest floor, including any basement, elevated at least 2 feet above the base flood elevation as determined for the community. Once the structure is built, a California registered professional engineer or land surveyor must certify the elevation, and the city's chief building official verifies the certification before it goes to the floodplain administrator.

Nonresidential buildings can meet the same 2-foot standard or instead be floodproofed watertight below that elevation with structural components able to resist hydrostatic and hydrodynamic loads, again certified by a California-registered engineer or architect under subsection (A)(3)(b). Manufactured homes get the identical 2-foot lowest-floor standard under subsection (D), and enclosed areas below the lowest floor that are subject to flooding, such as crawl spaces used for parking or storage, must have at least two openings totaling 1 square inch of net area per square foot of enclosed space, with opening bottoms no higher than 1 foot above grade, so floodwaters can enter and exit automatically rather than pressurize the walls.

Floodways carry an even tighter rule: encroachments including fill and new construction are prohibited unless a registered engineer certifies no increase in flood levels, and where no floodway has been identified a 20-foot setback from the watercourse bank applies. 030(C). 060.