A. The development of rural acreage subdivisions, one acre or larger lots, shall be carried out in such a manner that surface water from each lot will flow to a roadway side ditch, swale, channel, or natural creek. Prior to final plat or building permit approval the developer shall provide the community development department detailed construction plans showing channel and roadway side ditch sizes, grades, and driveway pipe sizes as well as erosion control measures necessary to prevent erosion of the proposed channel construction. These improvements shall include, but not be limited to, sodding, channel lining or ditch checks as required to prevent erosion of the proposed or existing channel. These improvements shall be the responsibility of the developer and shall be installed by the developer and inspected by the city prior to the issuance of building permits.
B. Runoff from a 25-year frequency storm shall be used for the purpose of determining the sizing of roadway side ditches and driveway pipes. Surface water collected in roadway side ditches shall be directed to a secondary drainage channel not located within the street right of way as often as the terrain will allow.
C. Runoff from a 50-year frequency storm shall be used for sizing channels, creeks, and any structures that are needed for street crossings.
D. Site improvements shall provide for the grading of all building pads to an elevation that will not be subject to overflow from a regulatory flood and in a manner that will provide for the rapid runoff of stormwater. Manufactured home placement pads shall be elevated to the level of the regulatory flood. All manufactured homes shall be anchored in accordance with requirements outlined in the federal emergency management agency floodplain management regulations, subpart A, section 60.3(b)(8). Mechanical and utility equipment for residential or nonresidential structures shall be designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding. Substantial improvements to existing structures within the regulatory floodplain will be subject to all regulations and requirements of this chapter. The areas projected for inundation by the 50-year frequency flood shall remain free of all structures and shall be preserved in as natural a condition as possible. The maintenance of channels serving drainage areas of less than five hundred (500) acres shall be the responsibility of the property owner, the adjoining or abutting property owner or owners, or a duly constituted homeowners' association unless such improvements are installed by the developer as described above and accepted for maintenance by the city. Drainage areas containing more than five hundred (500) acres shall be improved as outlined above. (Ord. 2017, 2014: Ord. 1969, 2011)