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<br />4,1 Flood Boundaries <br /> <br />To provide a national standard without regional discrimination, <br />the 1 percent annual chance (lOa-year) flood has been adopted by <br />FEMA as the base flood for flood plain management purposes. The <br />0.2 percent annual chance (SOO-year) flood is employed to indicate <br />additional areas of flood risk in the community. For each stream <br />studied in detail, the 100- and SO a-year flood plain boundaries <br />have been delineated using the flood elevations determined at each <br />cross section. Between cross sections, the boundaries were inter- <br />polated using topographic maps at a scale of 1:2,400, with a contour <br />interval of 2 feet (Reference 11). <br /> <br />The 100- and SOO-year flood plain boundaries are shown on the Flood <br />Insurance Rate Map (Exhibit 2). On this map, the lOa-year flood <br />plain boundary corresponds to the boundary of the areas of special <br />flood hazards (Zones A and AE); and the SOO-year flood plain boundary <br />corresponds to the boundary of areas of moderate flood hazards. <br />In cases where the 100- and SOO-year flood plain boundaries are <br />close together, only the lOa-year flood plain boundary has been <br />shown. Small areas within the flood plain boundaries may lie above <br />the flood elevations but cannot be shown due to limitations of the <br />map scale and/or lack of detailed topographic data. <br /> <br />Approximate lOa-year flood plain boundaries in some portions of <br />the study area were taken directly from the Flood Hazard Boundary <br />Map (Reference 12). <br /> <br />4.2 Floodways <br /> <br />The floodway is the channel of a stream, plus any adjacent flood <br />plain areas, that must be kept free of encroachment so that the <br />lOa-year flood can be carried without substantial increases in <br />flood heights. <br /> <br />No floodways have been computed for Frenchman, North Frenchman, or <br />South Frenchman Creeks. <br /> <br />S.O INSURANCE APPLICATION <br /> <br />For flood insurance rating purposes, flood insurance zone designations <br />are assigned to a community based on the results of the engineering analyses. <br />These zones are as follows: <br /> <br />Zone A <br /> <br />Zone A is the flood insurance rate zone that corresponds to the <br />lOa-year flood plains that are determined in the Flood Insurance <br />Study by approximate methods. Because detailed hydraulic analyses <br />are not performed for such areas, no base flood elevations or depths <br />are shown in this zone. <br /> <br />9 <br />