Springfield, IL Environmental Rules: Flood Elevation Requirements (2026)

02 as "the elevation of the base flood plus one foot of freeboard at any given location in the floodplain," and the base flood is the 100-year, 1%-annual-chance flood. 03 pins down how that base flood elevation is calculated for each Springfield floodplain: for the Sangamon River, Spring Creek, Horse Creek, Sugar Creek, Polecat Creek, the Town Branch, the Jacksonville Branch and its tributary, it's taken from the 100-year flood profiles in the countywide Flood Insurance Study prepared by FEMA and dated August 2, 2007, or any later update; for AH or AO zones it comes from the Flood Insurance Rate Map elevation or depth; and for other A-zone floodplains without other data, the applicant must finance an engineering study.

07 then imposes the actual freeboard mandate: all buildings in the floodplain valued at more than $1,000 or 70 square feet, substantial improvements that grow floor area by more than 20% or value by 50%, and repairs to substantially damaged structures must have their lowest floor, including basement, built at or above the flood protection elevation, whether achieved through fill, elevation on solid walls or piles, or an engineered crawlspace. Non-residential buildings can instead be dry floodproofed to that elevation if a licensed engineer or architect certifies the design. 13.