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

UDC section 16-6-4-7's performance standards apply once a parcel falls in the Floodway Fringe (Overlay) District. Residential structures must have the lowest floor, including any basement, elevated a minimum of one foot above the base flood elevation, built on compacted fill extending at least eighteen feet beyond the structure or on certified piers or extended foundations. Non-residential structures must meet the same one-foot elevation or be floodproofed to that level, with a professional engineer registered in Iowa certifying the floodproofing and the Administrator keeping the certification on file.

Fully enclosed areas below the lowest floor need at least two openings on two different walls totaling one square inch of net vent area per square foot of enclosed space, with opening bottoms no higher than one foot above grade, used only for parking or low-damage storage. Flood control structural works such as levees and flood walls must provide a minimum of three feet of design freeboard and adequate interior drainage, subject to Iowa DNR approval. Until a regulatory floodway is designated, no development may raise the base flood elevation more than one foot.

Detached garages and sheds under six hundred square feet accessory to a residential use are exempt from the elevation rule if built of flood-resistant materials below the one-foot mark. Maximum damage potential development must clear the 500-year flood elevation by one foot or be engineer-certified floodproofed to that level. Any floodplain development, including placement of factory-built homes, first needs a Floodplain Development Permit from the city's floodplain Administrator under section 16-6-4-3. The current standards trace to Ordinance 24-21, adopted June 21, 2021.