Rancho Cucamonga, CA Environmental Rules: Flood Elevation Requirements (2026)

050(A)(3)(a) governs elevation and floodproofing for residential construction. In an AO zone, the lowest floor must be elevated above the highest adjacent grade to a height exceeding the depth number shown on the FIRM by at least two feet, or at least four feet above the highest adjacent grade if no depth number is listed. 040(C)(2) when FEMA has not already published a base flood elevation. Nonresidential structures have an alternative path under subsection (A)(3)(b): they may either meet the same elevation standard or be floodproofed below that elevation so the structure is watertight, with structural components able to resist hydrostatic and hydrodynamic loads, certified by a registered engineer or architect.

Once a residential structure is finished, the elevation of the lowest floor must be certified by a registered professional engineer or surveyor and verified by the community building inspector, with that certification delivered to the floodplain administrator, the city engineer. Enclosed areas below the lowest floor used only for parking, access, or storage must also have flood vents equal to at least one square inch of net opening per square foot of enclosed area, with the lowest opening no higher than one foot above grade, unless a licensed engineer certifies an equivalent design.