Located within the areas of special flood hazard (Zones A and V) established in § 153.04, are small streams where no base flood data has been provided or where no floodways have been identified. The following provisions apply within such areas:
(A) In all areas of special flood hazard where base flood elevation data are not available, the applicant shall provide a hydrologic and hydraulic engineering analysis that generates base flood elevations for all subdivision proposals and other proposed developments containing at least 50 lots or five acres, whichever is less.
(B) No encroachments, including fill, new construction, substantial improvements or new development shall be permitted within 100 feet of the stream bank unless certification with supporting technical data by a registered professional engineer is provided demonstrating that such encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge.
(C) If division (A) above is satisfied and base flood elevation data is available from other sources, all new construction and substantial improvements within such areas shall comply with all applicable flood hazard provisions of §§ 153.30 through 153.34 and shall be elevated or floodproofed in accordance with elevations established in accordance with Article § 153.23(K)
(D) Data from preliminary, draft, and final Flood Insurance Studies constitutes best available data. Refer to FEMA Floodplain Management Technical Bulletin 1 -98 Use of Flood Insurance Study (FIS) Data as Available Data. If an appeal is pending on the study in accordance with 44 CFR Ch. 1, Part 67.5 and 67.6, the data does not have to be used.
(E) When base flood elevation (BFE) data is not available from a federal, state, or other source one of the following methods may be used to determine a BFE For further information regarding the methods for determining BFEs listed below, refer to FEMA's manual Managing Floodplain Development in Approximate Zone A Areas:
(1) Contour interpolation.
(a) Superimpose approximate Zone A boundaries onto a topographic map and estimate a BFE.
(b) Add one-half of the contour interval of the topographic map that is used to the BFE.
(c) Data extrapolation. A BFE can be determined if a site within 500 feet upstream of a reach of a stream reach for which a 100-year profile has been computed by detailed methods, and the floodplain and channel bottom slope characteristics are relatively similar to the downstream reaches.
(d) Hydrologic and hydraulic calculations. Perform hydrologic and hydraulic calculations to determine BFEs using FEMA approved methods and software.
(Ord. 17-19, passed 12-14-17)