Ames, IA Environmental Rules: Flood Elevation Requirements (2026)

Ames Municipal Code Sec. 9.5(2) sets the city's freeboard standard for the Floodway Fringe Overlay District, the area shown as Zone AE excluding the Floodway Areas in Zone AE on the Official Flood Plain Zoning Map. Until the city designates a regulatory floodway, no development may increase the base flood elevation by more than one foot, and the applicant bears the burden of giving the Iowa Department of Natural Resources enough technical information to make that determination. Sec. 9.5(2)(b) then sets the residential freeboard itself: new or substantially improved residential structures, including basements, must have their lowest floor elevated a minimum of three feet above the base flood elevation, built on compacted fill that stays at least three feet above the base flood elevation at every point and extends at least 18 feet beyond the structure's limits.

The Zoning Board of Adjustment can approve alternate elevation methods, such as piers, through a Conditional Use Permit where topography or street grades make fill impractical, provided the alternate method still withstands flood forces. Sec. 9.5(2)(c) applies a parallel three-foot floodproofing standard to non-residential structures, certified by a professional engineer licensed in Iowa, and Sec. 9.5(2)(d) requires factory-built homes to be anchored and elevated to the same three-foot minimum. The Flood Plain Administrator keeps a permanent record of each structure's certified elevation under Sec. 9.7.