Winnebago County, IL Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard required
- 1 foot above base flood elevation
- Applies to
- New buildings and additions in floodplain
- Floodproofing
- Must operate without human intervention
- Certification
- Professional engineer required
- Permit
- Surface water management permit
Summary
New and improved buildings in Winnebago County's floodplain must have their lowest usable space at least one foot above the base flood elevation.
Within the boundary of the regulatory floodplain, all usable space in new buildings, or added to existing buildings, shall either be elevated, floodproofed, or otherwise protected such that the lowest entry shall be at least one foot above the nearest base flood elevation to prevent the entry of surface stormwater. Floodproofing devices shall be operational without human intervention.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 64).
Full Breakdown
Winnebago County's floodplain ordinance requires that within the regulatory floodplain, all usable space in new buildings, or space added to existing buildings, be elevated, floodproofed, or otherwise protected so the lowest entry sits at least one foot above the nearest base flood elevation. Floodproofing devices must operate without human intervention, and any electrically dependent flood protection needs a backup power source that activates automatically. A professional engineer must certify floodproofing measures. The county's zoning ordinance backs this with an FP Floodplain Overlay District that restricts land uses within mapped floodways and floodplains.
Violations & Fines
Building without the required elevation or certified floodproofing violates the county's surface water management permit requirements and can result in denial of a certificate of occupancy, a recorded notice of violation against the property's title, and suspension of flood insurance coverage.
Frequently Asked Questions
How high above the base flood elevation must a new building's lowest floor be in Winnebago County?
What happens if a floodproofed building loses power?
Sources & Official References
Other rules in Winnebago County
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