Macon County, IL Environmental Rules: Flood Elevation Requirements (2026)

Macon County Code § 151.02 defines the flood protection elevation, the standard every regulated floodplain building has to meet, as the base flood elevation plus one foot of freeboard at any given location. That one-foot cushion above FEMA's mapped 100-year flood line is meant to cover the uncertainty in flood calculations, future development in the watershed, and unpredictable effects like ice or debris jams, and it is the number the Planning and Zoning Department checks every floodplain building permit against.

§ 151.07 sets out when that elevation standard kicks in: for any new building or the placement of one, or any alteration or addition to an existing building valued at more than $1,000 or adding more than 70 square feet of floor area, the building protection requirement applies. The same standard reaches substantial improvements, repairs after substantial flood damage, new manufactured-home installations, and long-term travel trailers or recreational vehicles left on a floodplain site. For any covered building, the lowest floor, including the basement, has to sit at or above the flood protection elevation, whether the builder gets there by elevating on fill, on stilts or piles, or, for a non-residential building, through engineer-certified dry floodproofing instead of full elevation.