Richland, WA Environmental Rules: Flood Zones (2026)

RMC § 22.16.030(A) applies the flood chapter to every special flood hazard area within Richland's city limits, mapped on the 1979 Flood Insurance Study for the city and the 1994 Benton County study, plus any later flood insurance rate maps. RMC § 22.16.040(A)(1) requires a development permit, issued by the development services director acting as floodplain administrator, before any structure, manufactured home or other development, including fill, begins in those areas. Applicants must submit elevation data tied to NAVD-88 for the lowest floor before and after construction, flood-proofing certification for nonresidential buildings, and, for any proposed alteration of a watercourse, an engineering description of the change; the city must then notify adjacent communities and the state Department of Ecology.

Development in a mapped floodway additionally needs an engineering analysis showing no rise in the base flood elevation, per RMC § 22.16.040(C)(1)(e). Subdivisions and other developments of 50 lots or five acres or more, whichever is less, must generate their own base flood elevation data if none exists and must be designed to minimize flood damage under RMC § 22.16.050(A)(5). RMC § 22.16.030(D) makes building or altering land in a special flood hazard area without full compliance a civil violation punishable under Chapter 1.30 RMC, and states that all city remedies for a violation are cumulative. Boundary disputes over where a flood hazard area sits can be appealed under NFIP procedures referenced in RMC § 22.16.040(C)(5).