Kendall County, IL Environmental Rules: Flood Zones (2026)

The floodplain protections sit in Kendall County Code Chapter 16, Article II, Subdivision IV, Protection of Floodplain and Floodway. Sec. 16-138(c) requires a stormwater permit from the Floodplain Administrator before any person, firm, corporation, or government body begins development in the floodplain, and Sec. 2-percent-annual-chance flood elevation. The Administrator may only issue that permit once the project meets the performance standards of Sec. 16-140. Those standards bar development that alone or cumulatively raises flood stage or velocity off site, or creates a damaging or potentially damaging increase in flood heights on site, unless the work qualifies for the floodway exceptions in Sec.

16-142. Any channel modification, fill placement, stream maintenance, or levee project must preserve the floodplain's existing flood conveyance and storage capacity, and a proposal that would change the base flood elevation or the regulatory floodplain boundary requires the developer to obtain a Letter of Map Revision from FEMA with concurrence from the Illinois Department of Natural Resources Office of Water Resources before any building permit issues. Public health standards layered onto the same permit forbid storing chemicals, explosives, or other hazardous materials below the flood protection elevation and prohibit new septic systems in the floodplain absent a variance meeting strict setback and elevation conditions. Subdivisions and planned unit developments over fifty lots or five acres must submit base flood elevation data and floodway delineations with their application.