West Bloomfield, MI Environmental Rules: Flood Elevation Requirements (2026)

Township Code § 24-185 governs stormwater holding facilities required of all new developments to retain runoff and cap peak discharge at existing hydrology rates, with the two-year, twenty-four-hour peak discharge held to the existing rate and volume. Subsection (e) sets the elevation standard directly: every detention basin must carry a one-foot freeboard above the design one-hundred-year high water elevation, and must include an overflow provision that drains to a location able to accept the overflow without property damage or a health or safety hazard. Overflow must discharge to a recognized natural drainage course or drain, and every spillway must have a hard surface of concrete, asphalt or grouted rip-rap unless the township engineer approves another material for the circumstances.

Side slopes on detention basins may be no steeper than one vertical to six horizontal, per subsection (f), and basins must be able to fully dewater by gravity under subsection (c), with pump discharge allowed only where the engineer finds gravity drainage infeasible. Design volumes are computed using the Oakland County Water Resources Office's Variable Release Rate method for a one-hundred-year peak runoff on developed sites under subsection (j), and an operation and maintenance agreement approved by township legal counsel must be executed before a building permit or final plat approval issues under subsection (i).

This freeboard standard applies to the detention and retention infrastructure required of new subdivisions and site plans rather than to individual building foundations, which are instead addressed through the flood hazard area permit requirements of chapter 12.