Lenexa, KS Environmental Rules: Flood Zones (2026)

Lenexa's floodplain rules are in Section 4-1-D-3 of the Unified Development Code. They apply to all lands identified as Special Flood Hazard Areas or Zone X (Future Base Flood) on the Flood Insurance Rate Map panels referenced on the index dated August 3, 2009, plus any Letter of Map Revision - Fill location. The Flood Insurance Study for Johnson County, Kansas and Incorporated Areas dated August 3, 2009 is adopted by reference. No development or land can be located, extended, converted or structurally altered without a floodplain development permit. The Community Development Director administers the rules, and the Engineering and Construction Services Administrator grants or denies permit applications.

An application lists the lowest floor elevation, any floodproofing elevation and engineer certification, watercourse alterations, the assessed value of the structure and fair market value of the improvement, and whether the site is in the flood fringe or floodway.

The standards are specific. Residential lowest floors, including basements, and mechanical equipment must be at least 1 foot above base flood elevation. Nonresidential buildings are either elevated 1 foot or dry floodproofed watertight with engineer or architect certification. Fully enclosed areas below the lowest floor that are subject to flooding are prohibited. Critical facilities such as police stations, fire stations, hospitals and schools must be elevated above the 500-year flood, with access routes above that level and none in a floodway. Hazardous material storage sites must be outside the flood area. Until a floodway is designated, no development including landfill is allowed unless the applicant shows it will not raise the base flood water surface more than 1 foot. Accessory structures up to 600 square feet used for parking and limited storage can be wet-floodproofed with a permit. Improvements within five calendar years whose cumulative value exceeds 50 percent of the structure's market value trigger full compliance. Recreational vehicles must stay fewer than 180 consecutive days, be highway ready, or meet manufactured home standards.

The Board of Zoning Appeals hears variances and appeals, with further appeal to the District Court under K.S.A. 12-759 and 12-760. No variance issues in a designated floodway if flood levels would rise, and applicants are told in writing that building below base flood level can raise flood insurance premiums up to $25.00 per $100.00 of coverage.