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

611 defines FLOOD PROTECTION ELEVATION (FPE) as the elevation of the base flood plus two feet of freeboard at any given location in the floodplain. 612 ties the base flood elevation itself to the countywide 'Flood Insurance Study of Rock Island County, Illinois,' prepared by FEMA and dated April 5, 2010, covering the Rock River, North Channel Rock River, Coal Creek, Mississippi River, Sylvan Slough, and several other named waterways; where no floodway is delineated, the FIRM's AH or AO zone elevation controls instead. 616(A) triggers the building-protection requirement for new construction or additions valued at more than $1,000 or 70 square feet, substantial improvements that add more than 20% of floor area or equal 50% of market value, repairs to substantially damaged structures, new manufactured homes, and recreational vehicles sited more than 180 days a year.

616(B)(1)(a), one compliance path is permanent land fill: the lowest floor, including any basement, must sit at or above the FPE, with fill placed in compacted six-inch layers extending at least ten feet beyond the foundation. 614, and keeps records of as-built elevation certificates.