Pursuant to the purpose and methods of reducing flood damage stated in these regulations, the following additional standards are adopted to assure that the reduction of the flood carrying capacity of watercourses is minimized:
(a) Development in floodways.
(1) In floodway areas, development shall cause no increase in flood levels during the occurrence of the base flood discharge. Prior to issuance of a floodplain development permit, the applicant must submit a hydrologic and hydraulic analysis, conducted by a registered professional engineer, demonstrating that the proposed development would not result in any increase in the base flood elevation; or
(2) Development in floodway areas causing increases in the base flood elevation may be permitted provided all of the following are completed by the applicant:
A. Meet the requirements to submit technical data in § 1169.21(a);
B. An evaluation of alternatives, which would not result in increased base flood elevations and an explanation why these alternatives are not feasible;
C. Certification that no structures are located in areas that would be impacted by the increased base flood elevation;
D. Documentation of individual legal notices to all impacted property owners within and outside the community, explaining the impact of the proposed action on their property; and
E. Concurrence of the Mayor of City of Mason and the Chief Executive Officer of any other communities impacted by the proposed actions.
(b) Development in riverine areas with base flood elevations but no floodways.
(1) In riverine special flood hazard areas identified by FEMA where base flood elevation data are provided but no floodways have been designated, the cumulative effect of any proposed development, when combined with all other existing and anticipated development, shall not increase the base flood elevation more than 1.0 (one) foot at any point. Prior to issuance of a floodplain development permit, the applicant must submit a hydrologic and hydraulic analysis, conducted by a registered professional engineer, demonstrating that this standard has been met; or
(2) Development in riverine special flood hazard areas identified by FEMA where base flood elevation data are provided but no floodways have been designated causing more than one foot increase in the base flood elevation may be permitted provided all of the following are completed by the applicant:
A. An evaluation of alternatives which would result in an increase of one foot or less of the base flood elevation and an explanation why these alternatives are not feasible;
B. Section 1169.33(a)(2), items A. and C. through E.
(c) Alterations of a watercourse. For the purpose of these regulations, a watercourse is altered when any change occurs within its banks. The extent of the banks shall be established by a field determination of the “bankfull stage.” The field determination of “bankfull stage” shall be based on methods presented in Chapter 7 of the USDA Forest Service General Technical Report RM-245, Stream Channel Reference Sites: An Illustrated Guide to Field Technique or other applicable publication available from a federal, state, or other authoritative source. For all proposed developments that alter a watercourse, the following standards apply:
(1) The bankfull flood carrying capacity of the altered or relocated portion of the watercourse shall not be diminished. Prior to the issuance of a floodplain development permit, the applicant must submit a description of the extent to which any watercourse will be altered or relocated as a result of the proposed development, and certification by a registered professional engineer that the bankfull flood carrying capacity of the watercourse will not be diminished.
(2) Adjacent communities, the U.S. Army Corps of Engineers, and the Ohio Department of Natural Resources, Division of Water, must be notified prior to any alteration or relocation of a watercourse. Evidence of such notification must be submitted to the Federal Emergency Management Agency.
(3) The applicant shall be responsible for providing the necessary maintenance for the altered or relocated portion of said watercourse so that the flood carrying capacity will not be diminished. The Floodplain Administrator may require the permit holder to enter into an agreement with City of Mason specifying the maintenance responsibilities. If an agreement is required, it shall be made a condition of the floodplain development permit.
(4) The applicant shall meet the requirements to submit technical data in § 1169.21(a)(1)(C) when an alteration of a watercourse results in the relocation or elimination of the special flood hazard area, including the placement of culverts.
(Ord. 2010-110, passed 11-1-2010)