Palm Desert, CA Environmental Rules: Flood Elevation Requirements (2026)

The elevation rule sits in § 28.10.010(C)(1) of the Palm Desert Municipal Code and applies in all areas of special flood hazards. New residential construction and substantial improvements must have the lowest floor, including a basement, at a set height that depends on the zone on the FIRM. In an AO zone the lowest floor must be elevated above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the FIRM, or at least two feet above the highest adjacent grade if no depth number is specified. In an A zone and in all other zones, the lowest floor must be elevated to or above the base flood elevation. The code prints the State of California's recommendation of two feet above the base flood elevation in those zones, but the city's own requirement is to or above the base flood elevation. When the structure is complete, a registered professional engineer or surveyor certifies the lowest floor elevation, the community building inspector verifies it, and the certification goes to the floodplain administrator.

Nonresidential buildings can be elevated the same way or flood proofed so the structure is watertight with walls substantially impermeable to the passage of water, with certification by a registered professional engineer or architect (§ 28.10.010(C)(2)). Manufactured homes in Zones A1-30, AH and AE need the lowest floor at or above the base flood elevation, and in some existing parks the chassis can instead sit on piers no less than thirty-six inches in height above grade (§ 28.10.040).

The base flood elevation itself comes from § 28.08.030(B). The administrator uses any base flood elevation and floodway data available from a federal or state agency or other source and submits it to the city council for adoption. If none exists, the elevation is obtained by one of two methods from the FEMA publication dated July 1995: a simplified method using the Quick-2 program, or a detailed method using the HEC-HMS and HEC-RAS programs. Subdivision proposals must identify the special flood hazard area and the elevation of the base flood, and a site filled above the base flood elevation needs certified lowest floor and pad elevations (§ 28.10.030). When physical alterations change the base flood elevation, the administrator submits data to FEMA for a letter of map revision within six months of information becoming available or project completion, whichever comes first (§ 28.08.030(D)).