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

Evanston's floodplain chapter defines the Flood Protection Elevation (FPE) at § 4-13-2 as the base flood elevation (BFE) plus one foot of freeboard, an added safety margin for calculation uncertainty, future watershed development, and unpredictable ice or debris effects. Section 4-13-4(A) ties the BFE itself to FEMA's Flood Insurance Study for Cook County dated September 10, 2021, and its amendments. Under § 4-13-8(C)(2), new construction and substantial improvement of residential buildings in zones A, AO, AH, and AE must have the lowest floor, including any basement, elevated to the FPE.

If fill is used to reach that elevation, the fill must be placed in layers no more than six inches deep before compaction, extend at least twenty feet beyond the foundation before sloping below the FPE absent a geotechnical report, and be protected against erosion by vegetative cover or riprap. Where the lowest floor sits above an enclosed area below it, that area needs at least two permanent openings on two different walls, no more than one foot above grade and below the BFE, providing one square inch of opening for every square foot of enclosed floor area, so floodwater can enter and exit freely rather than build hydrostatic pressure against the walls.

Nonresidential buildings may dry-floodproof to the FPE instead of elevating, under § 4-13-8(C)(3), with a licensed engineer's certification. Detached accessory structures under 600 square feet may sit below the FPE if wet-floodproofed under § 4-13-8(C)(6). Property owners who cannot meet these standards may apply for a variance under § 4-13-10, but the City Engineer must warn in writing that a variance lowering flood protection can raise flood insurance premiums by as much as $25 per $100 of coverage.