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

020 defines base flood elevation as the elevation shown on the Flood Insurance Rate Map for Zone A that reflects the water surface produced by a base (100-year) flood. 110 turns that definition into a hard construction standard: the lowest floor, including any basement, of every new or substantially improved residential structure must be elevated to or above the base flood level, with no floodproofing alternative allowed. Non-residential structures get a choice under subsection (H): elevate to or above base flood level, or dry-floodproof the entire structure below that level with substantially impermeable walls and components engineered to resist hydrostatic and hydrodynamic loads and buoyancy, while providing the Floodplain Administrator the exact elevation to which the structure was waterproofed relative to mean sea level.

120: new or substantially improved units in a new or expanding park must sit on a permanent foundation with the lowest floor at or above base flood elevation, anchored to resist flotation and lateral movement; homes in an existing park not covered by that rule may instead sit on reinforced piers at least 36 inches above grade. 100(B) directs the Floodplain Administrator to obtain and use the best available federal or state data instead.