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

The county's flood hazard reduction standards in Chapter 18.06.500 apply to every area of special flood hazard shown on the Flood Insurance Rate Maps for Grays Harbor County. In AE and A1-30 zones, or any A-zoned area where a base flood elevation (BFE) has been set, new construction and substantial improvement of a residential structure must have the lowest floor, including any basement, elevated one foot or more above the BFE, and mechanical equipment and utilities must sit at least that high too. Manufactured homes placed or substantially improved in zones A, A1-A30, AH and AE must go on a permanent foundation with the lowest floor one foot or more above the BFE and be securely anchored against flotation, collapse and lateral movement.

In AO zones, where the map shows only a depth number, the lowest floor must clear that depth number by one foot, or clear the highest adjacent grade by three feet if no depth number is printed. Non-residential buildings may instead be dry floodproofed one foot above the BFE if a registered engineer certifies the design under Section 18.06.500(G). A development permit from Planning and Building, 100 West Broadway, Montesano, is required before any construction begins in a special flood hazard area, and the application must state the elevation of the lowest floor and, for floodproofed buildings, the elevation to which the structure is proofed, per Section 18.06.480.

Where a regulatory floodway is mapped, Section 18.06.510 bars new residential construction outright except for narrow repair, replacement and farmhouse-replacement exceptions capped at fifty percent of market value. Variances go to the board of adjustment under the criteria in Section 18.06.530, which the code itself says should be granted rarely, and an owner who receives one must be notified in writing that flood insurance will cost more because the lowest floor sits below the BFE.