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

Section 9-235 sets the technical method for pinning down the base flood elevation, the standard against which every floodplain development permit is measured. Subsection (a) makes the State Water Survey's Floodplain Information Repository the default source of the best available data; anyone who disputes that data has to personally finance a detailed engineering study, and that study must go to both the State Department of Transportation's Division of Waterways and the City Engineer for review and approval before it can replace the Repository figure. Subsection (b) locks in a specific data source for the City's named waterways, Boneyard Creek, Upper Boneyard Creek, the Third Street Boneyard Creek tributary, Copper Slough, the John Street Copper Slough tributary, and the Phinney Branch: their base flood elevation is whatever the 100-year flood profiles in the July 16, 1980 Flood Insurance Study for the City of Champaign show, as later amended.

S. Geological Survey's 1976 report 'Depth & Frequency of Floods in Illinois,' or an equivalent formula recommended by the State Water Survey. That calculated elevation is what the Building Safety Supervisor or City Engineer then compares against the site grade under Section 9-233 before a development permit can issue.