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

12's flood hazard development standards, sets the freeboard requirement for new construction or substantial improvement of residential structures within the unincorporated area. In AE and A1-30 zones, or other A-zoned areas where base flood elevation (BFE) has been determined or can reasonably be obtained, the lowest floor, including any basement, must be elevated one foot or more above the BFE, and mechanical equipment and utilities must be waterproofed or elevated to that same one-foot standard. Where a structure sits in an unnumbered A zone and a BFE cannot reasonably be obtained, the lowest floor must instead be at least two feet above the highest adjacent grade.

052 as the elevation to which floodwater is anticipated to rise during the base flood, the flood with a one percent annual chance of occurring, also called the 100-year flood. 090(E) additionally requires any fully enclosed area below the lowest floor that is subject to flooding to either be prohibited or engineered to automatically equalize hydrostatic pressure, using at least two openings totaling one square inch of net area per square foot of enclosed space, with opening bottoms no higher than one foot above grade; an attached garage with a floor slab below the BFE must be designed the same way.

070 warns that failing to elevate at least two feet above the highest adjacent grade may result in higher flood insurance premiums. This chapter binds only the unincorporated county; Bremerton, Port Orchard, Poulsbo and Bainbridge Island administer their own flood ordinances.