Channel design standards for constructed drainage channels and other flood control structures shall be established by the chief engineer. The requirements as specified in this title are minimum standards and address general floodplain management requirements. Specific projects may warrant additional requirements that may be imposed by the chief engineer. In unusual conditions and on a case-by-case basis, permitting and construction of perimeter channels, flood walls, levees or unlined constructed channels may be allowed with approval of the engineering and construction specifications by the chief engineer.
A. Drainage channels shall be designed to provide containment of the regulatory flood and to minimize erosion, but shall not be fully lined so that the improved channel bottoms shall remain natural.
B. Perimeter channels that route flow around the outer edge of the development are prohibited in all areas where there is an established natural channel. Where used, perimeter channels shall be adequately armored against erosion from flow intercepted by the channel, as well as from flow within the channel.
C. Flood walls or levees for flood proofing shall only be allowed under special circumstances with approval of the chief engineer, and shall be designed to meet FEMA's levee design requirements when located within a regulatory floodplain. Where approved for use, the levee or flood wall shall be constructed with a minimum of three feet of freeboard above the base flood elevation. Adjacent finished floor elevations shall be one-foot above the base flood elevation until the levee construction has been approved by the district, and a LOMR has been issued by FEMA, if necessary.
D. For regulatory flows greater than five hundred cfs, the construction of earthen, unlined channels shall require written approval by the chief engineer as well as an engineering analysis prepared and sealed by an Arizona registered civil engineer.
(Ord. 2010-FC5 § 1 (part), 2010; Ord. 2005 FC-2 § 2 (part), 2005; Ord. 1999 FC-1 § 1 (part), 1999; Ord. 1998 FC-1 Section 5, 1998)