FEMA flood zone rules in Johnson County, KS β also called floodplain regulations or special flood hazard area (SFHA) rules β determine flood insurance requirements and elevation standards for new construction.
Johnson County participates in the National Flood Insurance Program (NFIP) and administers floodplain rules through its Zoning Regulations and the Stormwater Management Program (SMP). FEMA adopted the County's digital Flood Insurance Rate Maps (D-FIRMs) on August 3, 2009, based on watershed studies completed by the Stormwater Management Advisory Council (SMAC) between 1998 and 2002. Flood-prone corridors include the Kansas River along the north county line and tributaries such as Indian Creek, Mill Creek, Cedar Creek, Tomahawk Creek, and Blue River headwaters. The County also operates the Stormwatch flood warning system and a repetitive-loss home buyout program.
Authority: K.S.A. 12-734 (state floodplain management) and the Johnson County Zoning Regulations (floodplain provisions for unincorporated areas). FEMA NFIP rules are incorporated by reference. SMAC partners β the County and 20 cities β used watershed studies between 1998 and 2002 to generate updated 1% annual chance (100-year) floodplain maps for both current and ultimate (fully developed) conditions; FEMA adopted the resulting D-FIRMs on August 3, 2009. Building permit applications are checked against the FEMA flood maps. In the regulatory floodway, new construction is prohibited except for limited uses that do not raise base flood elevations. In the floodplain fringe (Special Flood Hazard Area outside the floodway), new residential structures must have the lowest floor elevated to or above the Base Flood Elevation (BFE), and non-residential structures may be elevated or dry-flood-proofed to the BFE. Substantial improvements (per NFIP, repairs/improvements equal to or exceeding 50% of market value) trigger full compliance. The Stormwater Management Program is funded by a dedicated 1/10th-of-one-percent county sales tax that has financed roughly $200 million in projects, plus the Stormwatch flood warning system and home buyouts for repetitive-loss properties. Floodplain administration inside incorporated cities (Overland Park, Olathe, Lenexa, Shawnee, etc.) is handled by each city's floodplain administrator.
Building, filling, or grading in the regulatory floodway without authorization, or constructing in the floodplain fringe below BFE, violates the Johnson County Zoning Regulations and federal NFIP rules. Planning and Public Works can issue notices of violation, stop-work orders, and withhold Certificates of Occupancy; unresolved violations are referred to the County Counselor. Non-compliant structures jeopardize the property owner's NFIP flood insurance eligibility and may force the County to suspend community NFIP participation, raising premiums countywide. Each day a violation continues may be treated as a separate offense.
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