Illinois Floodplain Construction Permit Statewide Standards

Under the Rivers, Lakes, and Streams Act (615 ILCS 5/) and 17 Ill. Adm. Code 3700-3708, IDNR Office of Water Resources requires permits for construction in regulatory floodways statewide. NFIP-participating communities must enforce minimum FEMA standards, including elevating residential structures one foot above base flood elevation in northeastern Illinois counties. The Urban Flood Awareness Act and statewide statute establish floor elevation, anchoring, and floodway encroachment rules that local floodplain ordinances cannot weaken.

Building in a regulatory floodway without an IDNR permit, placing residential structures below required base flood elevation, or filling floodways without compensatory storage.