Washtenaw County, MI Environmental Rules: Flood Zones (2026)

Michigan operates a dual federal-state floodplain regime. At the federal level, FEMA-effective Flood Insurance Rate Maps (FIRMs) define Special Flood Hazard Areas (SFHAs — Zones A, AE, AH, AO) and trigger NFIP local floodplain ordinance enforcement; each Washtenaw County community must regulate development in its SFHA per 44 CFR 60.3 to remain in the program. Washtenaw County and its municipalities are listed on FEMA's Community Status Book with active CIDs (countywide 26161C; Ann Arbor City 260213; Ann Arbor Charter Township 260535; Ypsilanti City 260216; Ypsilanti Charter Township 260542; Pittsfield Charter Township 260623; Saline City 260215; Saline Township 261792; Chelsea City 260599; Dexter Village 260600; Dexter Township 260536). Floodplain administrators issue floodplain development permits, require Lowest Floor Elevation at or above the Base Flood Elevation, prohibit floodway development without a no-rise certification by a Michigan-licensed professional engineer, and require flood-resistant construction below the BFE. The Huron River — running through Ann Arbor, Ypsilanti, and Dexter — is the dominant flood source, with floodplains and floodways mapped along its banks; Mill Creek and the Saline River add additional SFHA acreage. Washtenaw County records 132 NFIP claims since 1978 totaling about $1.6M, with roughly 687 active policies. At the state level, Part 31 of NREPA (MCL 324.3101 — 1994 PA 451) and EGLE's Floodplain Regulatory Authority require a state floodplain permit before any alteration or occupation of the 100-year floodplain of a river, stream, or drain with a drainage area of 2 square miles or more. EGLE's permit is independent of and in addition to the local floodplain development permit. Federally-backed mortgages on SFHA properties require flood insurance under 42 U.S.C. §4012a.