Rochester Hills, MI Environmental Rules: Flood Elevation Requirements (2026)

Chapter 114's floodplain standards division sets elevation requirements once a structure is allowed in or next to the floodplain. Section 114-194(a)(1) requires the lowest floor of a residential structure to be elevated at least two feet above the base flood level, the two-foot margin functioning as the city's freeboard above FEMA's one-percent-annual-chance flood elevation. A nonresidential structure gets a choice under Section 114-194(a)(2): the same two-foot elevation, or floodproofing to a watertight, substantially impermeable standard certified by a licensed professional engineer or architect as able to resist hydrostatic and hydrodynamic loads.

Fully enclosed areas below the lowest floor that could flood must equalize hydrostatic pressure automatically, meeting either an engineer's certification or the code's own minimum, a minimum of two openings totaling at least one square inch of net area per square foot of enclosed area, with the bottom of every opening no higher than one foot above grade. Before any of this is built, Section 114-157 requires the floodplain use permit application to show existing and proposed ground elevations and contours at one-foot intervals, a contour marking the base flood elevation, and the elevation of the lowest floor of every structure, all measured against the North American Vertical Datum of 1988 (NAVD88).

Once construction finishes, Section 114-160 requires the permit holder to give the engineering department a certified as-built elevation of the lowest floor, again referenced to NAVD88, certified by a licensed professional land surveyor or engineer licensed in Michigan. Manufactured homes are barred from the floodplain entirely under Section 114-193, regardless of elevation.