Whatcom County, WA Environmental Rules: Flood Elevation Requirements (2026)

Whatcom County adopted the FEMA Flood Insurance Study for Whatcom County (dated January 18, 2019) and its flood insurance rate maps by reference to fix special flood hazard area (SFHA) boundaries (WCC § 17.10.010). Within an SFHA, base flood elevation (the 100-year flood level) is set from the FIRM data, and the flood protection elevation (FPE) used for construction is that base flood elevation plus a one-foot freeboard (WCC § 17.10.020(A), (D)). Where FEMA has not mapped elevation data, the administrator gathers the best available federal, state or local data, and if none exists the FPE defaults to two feet above the highest adjacent grade (WCC § 17.10.020(F)).

Before any construction or development begins in an SFHA, a floodplain development permit is required from the department of public works or planning and development services (WCC § 17.12.010). New construction and substantial improvement of residential structures must have the lowest floor, including any basement, elevated to or above the FPE (WCC § 17.16.080(A)); fully enclosed space below that line must either be free of obstruction or built with flood vents meeting a one-square-inch-per-square-foot opening ratio (WCC § 17.16.080(B)). Nonresidential buildings may instead be dry floodproofed watertight to the FPE with a licensed engineer's certification (WCC § 17.16.090).

Coastal V and VE zone structures must be elevated on pilings so the lowest horizontal structural member clears the FPE (WCC § 17.16 provisions on coastal high hazard areas). Applicants who cannot meet these standards may seek a variance, but any variance grant comes with written notice that flood insurance costs will rise because of the reduced elevation.