Lenexa, KS Environmental Rules: Flood Elevation Requirements (2026)

Section 4-1-D-3 of the Lenexa City Code covers every parcel the City treats as a Special Flood Hazard Area or Zone X (Future Base Flood) on the Flood Insurance Rate Map panels tied to the FIRM Index dated August 3, 2009, plus any site with a Letter of Map Revision, Fill. The City adopted the Flood Insurance Study for Johnson County, Kansas and Incorporated Areas, dated August 3, 2009, by reference. No person can begin development or a substantial improvement in those areas without first obtaining a separate floodplain development permit.

The freeboard rule is in subsection D-2. A new or substantially improved residential structure needs its lowest floor, basement included, at least one foot above base flood elevation, and the mechanical, heating, ventilation, machinery, equipment and utility items must sit at that same height. A licensed land surveyor or professional engineer certifies the lowest-floor elevation. A commercial, industrial or other nonresidential building follows the same one-foot elevation, or is dry floodproofed so the structure is watertight one foot above the base flood level, with a registered professional engineer or architect certifying the design. Manufactured homes go on a permanent foundation with the lowest floor at least one foot above base flood elevation. Fully enclosed areas below the lowest floor that are subject to flooding, such as parking structures, unimproved storage and building access, are prohibited.

Critical facilities such as fire stations, police stations, hospitals and schools must be elevated above the 500-year flood level, with access routes above that elevation and no siting in a designated floodway. A remodel or enlargement escapes the elevation rule only while the cumulative value of work in the last five calendar years stays at or under fifty percent of the structure's current market value.

The permit application must show the elevation of the lowest floor in relation to mean sea level, the existing base flood elevation and the elevation of the proposed development. The Community Development Director administers the provisions, and the Engineering and Construction Services Administrator issues the permits and records the actual elevation of each new or substantially improved building. Where a Zone A map shows no base flood elevation, the City uses any data available from federal, state or other sources.