Black Hawk County, IA Environmental Rules: Flood Elevation Requirements (2026)

020(C)(2)(c) sets a three-foot freeboard standard above the 100-year (base) flood level. New or substantially improved residential structures must have the lowest floor, including any basement, elevated a minimum of three feet above that level, preferably on piles, posts, piers, columns or a crawl space, with utilities also raised at least three feet above base flood elevation; elevation on fill is discouraged and is barred outright where natural grade sits more than two feet below base flood elevation unless compensatory storage offsets the lost flood capacity.

Nonresidential structures face the same three-foot elevation requirement, but may instead be floodproofed to that level if a professional engineer registered in Iowa certifies the floodproofing can withstand flood depths, pressures, velocities and impact forces, with the certified elevation recorded with the Zoning Administrator. Any enclosed area below the lowest floor that floods must have at least two openings totaling one square inch of net area per square foot of enclosed space, with the lowest opening no higher than one foot above grade, and can be used only for parking, access or low-damage storage.

Structural flood control works such as levees and flood walls must provide at least three feet of design freeboard above the 100-year flood and adequate interior drainage, and must be approved by the Iowa Department of Natural Resources. A narrow exemption exists for detached garages and sheds under 600 square feet that are incidental to a residence, are built of flood-resistant materials below one foot above base flood elevation, and are never used for human habitation; the county warns that using this exemption can raise the structure's flood insurance premiums.