(A) Permitted uses in the floodplain. The following uses of land are permitted uses in the floodplain district:
(1) Any use of land which does not involve a structure, fence, an addition to the outside dimensions to an existing structure (including a fence), or an obstruction to flood flows such as fill, excavation, or storage of materials or equipment;
(2) Any use of land involving the construction of new structures, a fence, the placement or replacement of manufactured homes, the addition to the outside dimensions of an existing structure (including a fence), or obstructions such as fill or storage of materials or equipment, provided these activities are located in the flood fringe portion of the floodplain. These uses shall be subject to the development standards in division (B) below, and the floodplain evaluation criteria in division (C) below for determining floodway and flood fringe boundaries; and
(3) Recreational vehicles are regulated by § 152.29.
(B) Standards for floodplain permitted uses.
(1) Fill shall be properly compacted, and the slopes shall be properly protected, by the use of riprap, vegetative cover, or other acceptable method. The Federal Emergency Management Agency (FEMA) has established criteria for removing the special flood hazard area designation for certain structures properly elevated on fill above the 100-year flood elevation. FEMA’s requirements incorporate specific fill compaction and side slope protection standards for multi-structure or multi-lot developments. These standards should be investigated prior to the initiation of site preparation if a change of the special flood hazard area designation will be requested.
(2) The storage of materials and equipment standards are:
(a) The storage or processing of materials that are, in the time of flooding, flammable, explosive, or potentially injurious to human, animal, or plant life is prohibited; and
(b) Storage of other materials or equipment may be allowed if readily removable from the area within the time available after a flood warning, or if placed on fill to the regulatory flood protection elevation.
(3) No use shall be permitted which will adversely affect the capacity of the channels or floodways of any tributary to the main stream or of any drainage ditch, or any other drainage facility or system.
(4) All structures, including accessory structures, additions to existing structures, and manufactured homes, shall be constructed on fill so that the lowest floor, including the basement floor, is at, or two feet above, the regulatory flood protection elevation. The finished fill elevation must be no lower than one foot below the regulatory flood protection elevation, and shall extend at that elevation at least 15 feet beyond the limits of the structure constructed thereon.
(5) Uses that do not have vehicular access at, or above, an elevation not more than two feet below the regulatory flood protection elevation to lands outside of the floodplain shall not be permitted unless granted a variance by the Board of Adjustment. In granting a variance, the Board of Adjustment shall specify limitations on the period of use or occupancy of the use, and only after determining that adequate flood warning time, and local emergency response and recovery procedures, exist.
(6) Accessory land uses, such as yards, railroad tracks, and parking lots, may be at elevations lower than the regulatory flood protection elevation. However, a permit for the facilities to be used by the employees or the general public shall not be granted in the absence of a flood warning system that provides adequate time for evacuation if the area would be inundated to a depth and velocity that when multiplying the depth (in feet) times velocity (in feet per second), the product number exceeds four upon occurrence of the regional flood.
(7) Where public utilities are not provided:
(a) On-site water supply systems must be designed to minimize or eliminate infiltration of floodwaters into the systems; and
(b) New or replacement on-site sewage treatment systems must be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters, and shall not be subject to impairment or contamination during times of flooding. Any sewage treatment system designed in accordance with the state’s current statewide standards for on-site sewage treatment systems shall be determined to be in compliance with this section.
(8) All manufactured homes must be securely anchored to an adequately anchored foundation system that resists flotation, collapse, and lateral movement. Methods of anchoring may include, but are not to be limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state or local anchoring requirements for resisting wind forces.
(C) Floodplain elevation.
(1) Upon receipt of an application for a permit for a use, or other approval, within the floodplain district, the applicant shall be required to furnish the following information as is deemed necessary by the Zoning Administrator for the determination of the regulatory flood protection elevation and whether the proposed use is within the floodway or flood fringe.
(a) A certificate of survey.
(b) Plan (surface view) showing elevations or contours of the ground, pertinent structure, fill, or storage elevations, the size, location, and spatial arrangement of all proposed and existing structures on the site, and the location and elevations of streets.
(c) Photographs showing existing land uses, vegetation upstream and downstream, and soil types.
(d) Profile showing the slope of the bottom of the channel, or flow line of the stream, for at least 500 feet in either direction from the proposed development.
(2) The applicant shall be responsible to submit one copy of the above information in division (C)(1) above to a designated engineer, or other expert person or agency, for technical assistance in determining whether the proposed use is in the floodway or flood fringe, and to determine the regulatory flood protection elevation. Procedures consistent with Minn. Rules parts 6120.5000 through 6120.6200, and 44 C.F.R. part 65, shall be followed in this expert evaluation. The designated engineer or expert is strongly encouraged to discuss the proposed technical evaluation methodology with the respective Department of Natural Resources’ Area Hydrologist prior to commencing the analysis. The designated engineer or expert shall:
(a) Estimate the peak discharge of the regional flood;
(b) Calculate the water surface profile of the regional flood based upon a hydraulic analysis of the stream channel and overbank areas; and
(c) Compute the floodway necessary to convey or store the regional flood without increasing flood stages more than one-half foot. A lesser stage increase than one-half foot shall be required if, as a result of the additional stage increase, increased flood damages would result. An equal degree of encroachment on both sides of the stream within the reach shall be assumed in computing floodway boundaries.
(3) The Zoning Administrator shall present the technical evaluation and findings of the designated engineer or expert to the City Council. The City Council must formally accept the technical evaluation and the recommended floodway and/or flood fringe district boundary, or deny the permit application. The City Council, prior to official action, may submit the application and all supporting data and analyses to the Federal Emergency Management Agency, the Department of Natural Resources, or the Planning Commission for review and comment. Once the floodway and flood fringe district boundaries have been determined, the City Council shall refer the matter back to the Zoning Administrator who shall process the permit application consistent with the applicable provisions of this chapter.
(Ord. 262, passed 10-12-2009)