Bothell, WA Environmental Rules: Flood Zones (2026)

Bothell Municipal Code § 14.04.700 defines the regulated area. Special flood hazard areas are the lands identified by the Federal Insurance Administrator in the Flood Insurance Study for King County dated August 19, 2020, and the Flood Insurance Study for Snohomish County dated June 19, 2020, with any revisions. The code names both studies because the City of Bothell sits on both sides of the county line. The area can include streams, lakes, wetlands and their associated floodplains, or flood fringes. The article sets minimum standards that supersede any inconsistent ordinance requiring lower or less restrictive standards, but it does not repeal zoning, stormwater, environmental or building rules.

Permits are governed by BMC 14.04.720. A special flood hazard area permit must be obtained before construction or development begins. It covers all structures, including manufactured homes, and every other development or redevelopment, including tenant improvements and fill. It is separate from and in addition to any critical areas alteration permit. The public works director is the floodplain administrator and grants or denies these permits. Applicants must provide the lowest floor elevation, including any basement, in relation to mean sea level on a current elevation certificate, and a development in a floodway needs an engineering analysis indicating no rise of the base flood elevation.

BMC 14.04.760 adds hard limits. Encroachments in a floodway, including fill, new construction and substantial improvements, are prohibited unless a registered professional engineer certifies no increase in flood levels during the base flood. Critical facilities, sewage treatment facilities and livestock manure storage facilities cannot be built in the 100-year floodplain. New building lots in a subdivision must contain 5,000 square feet or more of buildable land outside the 100-year floodplain.