Detroit, MI Environmental Rules: Flood Zones (2026)

Detroit is enrolled in the Federal Emergency Management Agency (FEMA) National Flood Insurance Program (NFIP) and is also a participant in the voluntary Community Rating System, which can reduce flood-insurance premiums for residents. The local floodplain rules are in Detroit City Code Chapter 50 (Zoning), Article XIV (Development Standards), Division 5 - Floodplains and Hazard Areas (Sec. 50-14-521 et seq.). Definitions appear in Sec. 50-14-524 and floodplain-development permits and standards appear in Sec. 50-14-527. Any 'development' as defined by the NFIP — including new construction, substantial improvement, fill, grading, or paving — within a designated Special Flood Hazard Area (Zone A / AE / shaded X on the city's adopted FIRM) requires a floodplain-development permit and pre-permit site-plan review. Substantial improvements to existing buildings (work costing 50 percent or more of pre-improvement value, the FEMA '50 percent rule') must bring the whole structure into compliance with the flood-resistant construction provisions in Appendix G of the Detroit Building Code (2019). The Buildings, Safety Engineering, and Environmental Department's Environmental Affairs Division administers floodplain permits and coordinates with the U.S. Army Corps and EGLE for any work affecting the Detroit River, Rouge River, or city drains. Owners in Special Flood Hazard Areas with federally backed mortgages must carry flood insurance.