All primary drainage channels which are located within, or immediately adjacent to, an improvement, construction area, development or subdivision shall be protected and improved by the developer as follows:
A. All land having an elevation below the 50-year maximum flood elevation for the final improved channel shall be dedicated for the purpose of providing drainage, for public park, or drainage and utility easement use.
B. The existing channel lying within or immediately adjacent to the subdivision or parcel of land proposed for development or redevelopment shall be cleaned to provide for the free flow of water, and the channel shall be straightened, widened, and improved to the extent required to prevent overflow, resulting from a 50-year frequency rainfall, beyond the limits of the dedicated drainage easement provided for in subsection A of this section.
C. Site improvement shall provide for the grading of all building pads to an elevation where all building pads will not be subject to overflow from a regulatory flood and in a manner that will provide for a 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). Substantial improvements to existing structures within the 100-year floodplain will be subject to all regulations and requirements of this chapter:
1. New construction or substantial improvements of residential structures (including manufactured homes) and accessory buildings shall have the lowest floor (including basements) elevated to one foot (1') above the level of the 100-year frequency flood.
2. New construction or substantial improvements of nonresidential structures and accessory buildings within the 100-year floodplain must have the lowest floor (including basement) elevated to one foot (1') above the 100-year flood level or floodproofed, including utility and sanitary facilities, up to one foot (1') above the level of the regulatory flood.
3. 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.
4. If a nonresidential structure is intended to be floodproofed, a registered professional engineer or architect shall develop and/or review structural design, specifications and plans for the construction, and shall certify that the design and methods of construction are in accordance with the accepted standards of practice for meeting the elevation requirements of this chapter. A record of such certificates which includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed shall be submitted to and maintained by the office of community development.
D. Whenever channel improvements are carried out, sodding, backsloping, cribbing, and other bank protection shall be designed and constructed to control erosion for the anticipated conditions and flow resulting from a 50-year frequency rainfall.
E. A drainage channel shall not be located in a street easement unless it is placed in an enclosed storm sewer except under the following conditions:
1. Where a paved street surface at least two (2) lanes wide is provided on both sides of a paved channel so as to provide access to abutting properties.
2. Where lots are platted to back up to the street right of way where the drainage channel is located between the rear lot line and the paved street, provided, that there is no access to the rear of the lot from the street, and further provided that at no time in the future shall access be allowed or constructed over the open drainage channel to the rear of a lot so platted. For the purpose of these regulations, a lot which sides to a public street is not considered to back up to the street right of way.
3. When a condition outlined in either subsection E1 or E2 of this section is present, adequate space adjacent to the channel shall be dedicated as right of way to provide for maintenance of the paved drainage channel and its unpaved bank.
F. Culverts, bridges, and other drainage structures shall be constructed in accordance with the specifications and design criteria of the city whenever the city may have present or future maintenance responsibility. (Ord. 1969, 2011)