Troy, MI Environmental Rules: Flood Elevation Requirements (2026)

Chapter 42, Section 6, Specific Base Flood Elevation Standards, sets Troy's freeboard rule on top of FEMA's mapped 100-year flood level. Residential new construction and substantial improvements must have the lowest floor, including any basement, elevated to a minimum of one foot above the base flood level (added by the 10/06/2008 revision, effective 01/16/2009). Nonresidential buildings may meet the same one-foot freeboard, or instead be constructed watertight below the base flood elevation with impermeable walls, structural components able to resist hydrostatic and hydrodynamic loads, and design that resists buoyancy.

Either flood-proofing route requires a registered professional engineer or architect to certify that the standards are satisfied and that the methods employed can withstand the flood depth, pressures, velocities, impact and uplift forces expected at that location; that certification must be submitted to the City Engineer and must state the elevation to which the structure is flood-proofed. Section 6(2) further provides that the most recent base flood elevation data from the Federal Emergency Management Agency takes precedence over data from any other source when the two conflict, meaning a developer cannot rely on an older study or a private engineer's more permissive number once FEMA has issued updated data for the parcel.