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

Winnebago County is an NFIP-participating community. The county's Surface Water Management Ordinance (SWMO), adopted by the County Board on August 24, 2006, governs floodplain development in unincorporated areas through the Highway Department's Surface Water Management division. The ordinance covers stormwater detention, floodplain regulation, and construction-site sediment and erosion control. Within incorporated cities, the local floodplain ordinance governs - Rockford, Loves Park, Machesney Park, Rockton, Roscoe, Cherry Valley, South Beloit, and Winnebago each have their own NFIP community ID numbers and floodplain administrators. Major Special Flood Hazard Areas are mapped along the Rock River (which bisects the county and Rockford), the Pecatonica River (drainage area 2,643 sq mi at confluence), the Kishwaukee River (drainage area 1,247 sq mi), and Sugar River. Effective FEMA Flood Insurance Rate Maps are available through the FEMA Map Service Center at msc.fema.gov; the county is currently engaged in flood-risk study updates including Kishwaukee River Tributaries (Project Initiation Coordination Meeting held 9/4/2024) and Turtle Creek. Illinois state law adds a layer above the federal NFIP minimum: the Rivers, Lakes, and Streams Act (615 ILCS 5, originally enacted 1911) administered by the Illinois Department of Natural Resources Office of Water Resources requires a Construction in Floodways permit for any construction, fill, or excavation in a regulated floodway. The state regulates floodways with a drainage area of one square mile or more in urban areas or ten square miles or more in rural areas. State rules at 17 Ill. Adm. Code 3700-3708 govern floodway construction. Federal NFIP minimums require a 1-foot freeboard above base flood elevation for residential structures (44 CFR Part 60); local ordinances may require more. The 'substantial improvement' rule (improvements/repairs equaling 50% or more of pre-improvement market value) triggers full code compliance.