5.6.7 Development Standards for Floodplain Corridor Lands

For all land use actions which could result in development of the Floodplain Corridor, the following is required in addition to any requirements of <FEMA Flood Hazard Ordinance> : A. Standards for fill in Floodplain Corridor lands: 1. Fill shall be designed as required by the <building code>, where applicable. Town of Wallsburg Development Code 2. The toe of the fill shall be kept at least ten feet outside of floodway channels, as defined in this chapter. 3. The amount of fill in the Floodplain Corridor shall be kept to a minimum. Fill and other material imported from off the lot that could displace floodwater shall be limited to the following: a. Poured concrete and other materials necessary to build permitted structures on the lot. b. Aggregate base and paving materials. c. Plants and other landscaping material. d. A total of fifty cubic yards of other imported fill material, or three hundred cubic yards per acre, whichever is greater. These amounts are the maximum cumulative fill that can be imported onto the site, regardless of the number of permits issued. e. The above limits on fill shall be measured from <date of adoption>, and shall not exceed the above amounts. 4. If additional fill is necessary beyond the permitted amounts in (3) above, then fill materials must be obtained on the lot from cutting or excavation only to the extent necessary to create an elevated site for permitted development. All additional fill material shall be obtained from the portion of the lot in the Floodplain Corridor. 5. Adequate drainage shall be provided for the stability of the fill. 6. Fill to raise elevations for a building site shall be located as close to the outside edge of the Floodplain Corridor as feasible. B. Culverting or bridging of any waterway or creek identified on the official maps adopted pursuant to SECTION 6 must be designed by an engineer. Stream crossings shall be designed to the standards contained in the <Flood Hazard Ordinance> or where no floodway has been identified, to pass a 100-year flood without any increase in the upstream flood height elevation. The engineer shall consider in the design the probability that the culvert will be blocked by debris in a severe flood, and accommodate expected overflow. Fill for culverting and bridging shall be kept to the minimum necessary, but is exempt from the limitations in section (A) above. Culverting or bridging of streams identified as Riparian Preservation is subject to the requirements of SECTION 8. C. Non-residential structures shall be flood-proofed to the standards in <Flood Hazard Ordinance> to one foot above the elevation contained in the maps adopted by <Flood Hazard Ordinance>, or up to the elevation contained in the official maps adopted by SECTION 6, whichever height is greater. Where no specific elevations exist, buildings shall be elevated to three feet above the stream channel on all drainage ways identified on the official maps. D. No new residential structures are permitted in the Floodplain Corridor, except as permitted in E and F below. All residential structures shall be elevated so that the lowest habitable floor shall be raised to one foot above the elevation contained in the maps adopted in <Flood Hazard Ordinance>, or to the elevation contained in the official maps adopted by SECTION 6, whichever height is greater. Where no specific elevations exist, buildings shall be elevated to three feet above the stream channel on all drainage ways identified on the official maps. E. The elevation of the finished lowest habitable floor shall be certified to the Wallsburg Town Board by an engineer or surveyor prior to issuance of a certificate of occupancy for the structure. F. All lots modified by lot line adjustments or new lots created from lots which contain Floodplain Corridor land must contain a building envelope on all lot(s) which contain(s) buildable area of a sufficient size to accommodate the uses permitted in the underlying zone, unless the action is for open space or conservation purposes. This section shall apply even if the effect is to prohibit further division of lots that are larger than the minimum size permitted in the zoning ordinance. G. Basements. 1. Habitable basements are not permitted for new residential structures or additions located within the Floodplain Corridor. 2. Non-habitable basements, used for storage, parking, and similar uses are permitted for Town of Wallsburg Development Code residential structures but must be flood-proofed to the standards of <FEMA Flood Hazard Ordinance>. 3. Development of habitable basements of existing non-residential structures that are at or below the flood elevations contained in the official maps shall be permitted in the Wallsburg Historic Interest Area, as defined in the Wallsburg Comprehensive Plan. 4. No new habitable basements lower than two feet below the floodplain corridor elevations shall be permitted on any existing or new non-residential structure outside the historic interest area. 5. Habitable basements shall not be used for sleeping quarters. H. Storage of petroleum products, pesticides, or other hazardous or toxic chemicals is not permitted in Floodplain Corridor lands. I. Fences constructed within twenty feet of any Riparian Preservation Creek designated by this ordinance shall be limited to wire or electric fence, or similar fence that would not collect debris or obstruct flood waters, but not including wire mesh or chain link fencing. J. Decks and structures other than buildings, if constructed on Floodplain Corridor Lands and at or below the levels specified in Paragraphs (C) and (D) of the section, shall be floodproofed to the standards contained in <FEMA Flood Hazard Ordinance>. K. Local streets and utility connections to developments in and adjacent to the Floodplain Corridor shall be located outside of the Floodplain Corridor, except for crossing the Corridor in the shortest possible distance.