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(a) No permit for floodplain development shall be granted for new construction, substantial improvements, and other improvements, including the placement of manufactured or mobile homes, within any numbered or unnumbered A, AE, AO, and AH zones, unless the conditions of this section are satisfied.

(b) All areas identified as unnumbered A zones on the FIRM are subject to inundation of the one percent annual chance or 100-year flood; however, the base flood elevation is not provided. Development within unnumbered A zones is subject to all provisions of this chapter. If flood insurance study data is not available, the Floodplain Administrator shall obtain, review, and reasonably utilize any base flood elevation or floodway data currently available from Federal, State, or other sources.

(c) Until a floodway is designated, no new construction, substantial improvements, or other development that exceeds 5,000 square feet of impervious surface or is part of a larger common plan of development that exceeds 5,000 square feet of impervious surface, including fill, shall be permitted within any unnumbered or numbered A zones or AE zones on the FIRM, unless it is demonstrated that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot at any point within the community, will not exceed the lowest adjacent grade of the lowest impacted habitable structure, and will not exceed the current water surface elevation at the location of a habitable structure currently impacted by the floodplain.

(d) No new construction, substantial improvements or other development, including fill, shall be permitted within a designated zone AH floodplain or levee ponding area designated by the City of Topeka unless it is demonstrated that all fill in the zone AH/ponding area is offset by compensating cut to negate volume losses, with the compensatory storage being frequency/stage based for the two-year, 10-year, 25-year, 50-year, and 100-year events.

(e) No new construction, substantial improvements or other development that exceeds 5,000 square feet of impervious surface or is part of a larger common plan of development that exceeds 5,000 square feet of impervious surface, including fill, shall be permitted within a zone AE floodplain fringe zone on the FIRM, unless it is demonstrated that the water surface elevation will not exceed the lowest adjacent grade of the lowest impacted habitable structure, and will not exceed the current water surface elevation at the location of a habitable structure currently impacted by the floodplain.

(f) No new construction, substantial improvements or other development, including fill, resulting in alternations to a stream that has a drainage area greater than 640 acres (one square mile) shall be permitted without KDA-DWR approval for the stream change, unless the change is specifically exempt from the KDA-DWR regulations.

(g) All new construction, subdivision proposals, substantial improvements, prefabricated structures, placement of manufactured or mobile homes, and other developments shall require:

(1) Design or adequate anchorage to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy;

(2) Construction with materials resistant to flood damage;

(3) Utilization of methods and practices that minimize flood damages;

(4) All electrical, heating, ventilation, plumbing, air-conditioning equipment, and other service facilities be designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding;

(5) New or replacement water supply systems and/or sanitary sewage systems be designed to minimize or eliminate infiltration of flood waters into the systems and discharges from the systems into flood waters, and on-site waste disposal systems be located so as to avoid impairment or contamination; and

(6) Subdivision proposals and other proposed new development, including manufactured home parks or subdivisions, located within special flood hazard areas are required to assure that:

(i) All such proposals are consistent with the need to minimize flood damage;

(ii) All public utilities and facilities, such as sewer, gas, electrical, and water systems, are located and constructed to minimize or eliminate flood damage;

(iii) Adequate drainage is provided so as to reduce exposure to flood hazards; and

(iv) All proposals for development, including proposals for manufactured home parks and subdivisions, of greater than five acres or 50 lots, whichever is lesser, include within such proposals base flood elevation data.

(h) Storage of material or equipment may be allowed if not subject to major damage by floods, if firmly anchored to prevent flotation, or if readily removable from the area within the time available after a flood warning.

(i) Accessory Structures. Structures used solely for parking and limited storage purposes, not attached to any other structure on the site, of limited investment value, and not larger than 400 square feet, may be constructed at-grade and wet-floodproofed provided there is no human habitation or occupancy of the structure; the structure is of single-wall design; the accessory structure meets the following floodplain management requirements; and a floodplain development permit has been issued. Wet-floodproofing is only allowed for small low cost structures.

Any permit granted for an accessory structure shall be decided individually based on a case-by-case analysis of the building’s unique circumstances. Permits shall meet the following conditions:

In order to minimize flood damages during the one percent annual chance flood event, also referred to as the 100-year flood, and the threat to public health and safety, the following conditions shall be required for any permit issued for accessory structures that are constructed at-grade and wet-floodproofed:

(1) Use of the accessory structures must be solely for parking and limited storage purposes in any special flood hazard area as identified on the community’s flood insurance rate map (FIRM).

(2) For any new or substantially damaged accessory structures, the exterior and interior building components and elements (i.e., foundation, wall framing, exterior and interior finishes, flooring, etc.) below the base flood elevation must be built with flood-resistant materials in accordance with subsection (g)(2) of this section.

(3) The accessory structures must be adequately anchored to prevent flotation, collapse, or lateral movement of the structure in accordance with subsection (g)(1) of this section. All of the building’s structural components must be capable of resisting specific flood-related forces including hydrostatic, buoyancy, and hydrodynamic and debris impact forces.

(4) Any mechanical, electrical, or other utility equipment must be located above the base flood elevation or floodproofed so that they are contained within a watertight, floodproofed enclosure that is capable of resisting damage during flood conditions in accordance with subsection (g)(4) of this section.

(5) The accessory structures must meet all NFIP opening requirements. The NFIP requires that enclosure or foundation walls, subject to the one percent annual chance flood event, also referred to as the 100-year flood, contain openings that will permit the automatic entry and exit of flood waters in accordance with TMC 17.30.190(a)(3).

(6) The accessory structures must comply with the floodplain management floodway encroachment provisions of TMC 17.30.220(b). No permits may be issued for accessory structures within any designated floodway, if any increase in flood levels would result during the 100-year flood.

(7) Equipment, machinery, or other contents must be protected from any flood damage.

(8) No disaster relief assistance under any program administered by any Federal agency shall be paid for any repair or restoration costs of the accessory structures.

(9) Wet-floodproofing construction techniques must be reviewed and approved by the Floodplain Administrator or designee. The Floodplain Administrator or designee may request approval by a registered professional engineer or architect prior to the issuance of any floodplain development permit for construction. Cost for any required professional certification shall be paid by the developer.

(j) Hazardous Materials. All hazardous material storage and handling sites shall be located out of the special flood hazard area.

(k) Cumulative Improvement. A structure may be improved (remodeled or enlarged) without conforming to current requirements for elevation so long as the cumulative value of all work done does not exceed 50 percent of the structure’s current market value. If the cumulative value of the improvement exceeds 50 percent of the structure’s current market value, the structure must be brought into compliance with TMC 17.30.190 which requires elevation of residential structures to one foot above the base flood elevation or the elevation/floodproofing of nonresidential structures to one foot above the base flood elevation. (Ord. 20425 § 9, 6-20-23.)