Washington County, WI Environmental Rules: Flood Zones (2026)

§ 275-14A defines the reach of Washington County's floodplain zoning: it covers all lands in the unincorporated county that would be covered by the regional flood, as identified on the Flood Insurance Rate Map (FIRM) in Zones A, AO, AH, A1-30 and AE. § 275-14C(2) splits that mapped area into four districts. The Floodway District is the river or stream channel and the portions of the floodplain next to it needed to carry and discharge regional floodwaters. The Floodfringe District is the part of a riverine flood hazard area outside the floodway. The General Floodplain District covers riverine areas that may flood during a regional flood but where no floodway boundary has been drawn on the FIRM, plus shallow-flooding AH and AO zones. The Flood Storage District is floodplain land where floodwater storage is calculated to reduce the regional flood discharge.

Development inside any of these districts needs a County permit, and § 275-14D(2) directs the zoning administrator to deny a permit outright if the proposed project would obstruct floodwater flow or raise the regional flood height, based on the officially adopted FIRM, unless a floodplain map amendment under § 275-22D is obtained first. The County also reviews subdivision proposals in flood-prone areas to confirm adequate drainage and that utilities are located to minimize flood damage. Cities and villages inside the county, West Bend, Hartford, Germantown, Jackson, Slinger, Kewaskum, Richfield and Newburg, administer their own floodplain rules within their own limits.