Kennewick, WA Environmental Rules: Flood Zones (2026)

The City of Kennewick has adopted a Flood Damage Prevention chapter at KMC Chapter 18.66 (Title 18 Zoning) to maintain its standing in the National Flood Insurance Program (NFIP) under 44 CFR 59 and 60. Within Kennewick, the floodplain administrator (housed in the Community Planning Department) reviews every proposed structure, fill, grading operation, or substantial improvement located in a Special Flood Hazard Area (SFHA) mapped on the effective Benton County FIRM panels. The mapped SFHAs principally follow the Columbia River shoreline along the city's northern and western boundary, the Yakima River confluence, Amon Creek, and Zintel Canyon, plus several smaller tributaries and irrigation conveyances. Within SFHAs, new residential structures must have the lowest floor (including basement) elevated to or above the Base Flood Elevation (BFE) - Washington communities commonly add one or more feet of freeboard above the BFE for Class 5 or better Community Rating System credit. Non-residential structures may instead be dry-floodproofed to the same elevation. Substantial improvement or substantial damage (50% or more of market value) to an existing structure triggers full compliance for the entire building. Floodways within mapped reaches are subject to a no-rise encroachment standard under 44 CFR 60.3(d). A Floodplain Development Permit under KMC 18.66 is required before any work in an SFHA, separate from the standard building permit, and a shoreline substantial development permit under the city's Shoreline Master Program (KMC 18.68) may also apply along the Columbia.