Santa Rosa, CA Environmental Rules: Flood Elevation Requirements (2026)

080(C), Elevation and Floodproofing, part of the Flood Damage Protection chapter, sets Santa Rosa's construction standard inside mapped special flood hazard areas. Subsection (C)(1) states that new construction and substantial improvement of any structure 'shall have the lowest floor, including basement, elevated to or above one foot above base flood elevation,' with nonresidential structures permitted to instead meet the floodproofing standard in subsection (C)(3). Upon completion, a registered professional engineer or surveyor must certify the elevation, or the Building Inspector must verify it, with that certification submitted to the Floodplain Administrator.

For AH or AO zones without a mapped base flood elevation, subsection (C)(2) instead requires the lowest floor to sit above the highest adjacent grade by at least the depth number shown on the FIRM, or at least two feet if no depth number is specified. Nonresidential buildings that choose floodproofing instead of elevation must, under subsection (C)(3), be watertight below the base flood level with walls substantially impermeable to water, have structural components able to resist hydrostatic and hydrodynamic loads, and carry a registered engineer's or architect's certification.

Fully enclosed areas below the lowest floor that could flood must automatically equalize hydrostatic pressure, generally satisfied by at least two openings totaling one square inch of net area per square foot of enclosed area, with opening bottoms no higher than one foot above grade.