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<br />All elevations are referenced to the National Geodetic Vertical <br />Datum of 1929 (NGVD). Elevation reference marks used in this <br />study are shown on the maps. <br /> <br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />The NFIP encourages State and local governments to adopt sound flood <br />plain management programs. Therefore, each Flood Insurance Study produces <br />maps designed to assist communities in developing flood plain management <br />measures. <br /> <br />4.1 Flood Boundaries <br /> <br />To provide a national standard without regional discrimination, <br />the I percent annual chance (lOO-year) flood has been adopted <br />by FEMA as the base flood for flood plain management purposes. <br />The 0.2 percent annual chance (SOD-year) flood is employed to <br />indicate additional areas of flood risk in the community. For <br />each stream studied in detail, the lOO-year flood plain boundary <br />has 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 1:1,200, with a contour <br />interval of S feet (Reference 12). <br /> <br />The scope of work for this study did not include SOD-year boundary <br />delineations for the studied streams; therefore, only the 100- <br />year flood plain boundaries are shown on the Flood Boundary and <br />Floodway Map (Exhibit 2). Small areas within the flood plain <br />boundaries may lie above the flood elevations but cannot be shown <br />due to limitations of the map scale and/or lack of detailed topo- <br />graphic data. <br /> <br />Boundaries for streams studied by approximate methods were delineated <br />using topographic maps at a scale of 1:1,200, with a contour interval <br />of 5 feet (Reference 13). <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 />IOO-year flood can be carried without substantial increases in <br />flood heights. <br /> <br />The scope of work for this study did not include floodway determina- <br />tions for the studied streams; therefore, no floodways have been <br />completed. <br /> <br />Computed IOO-year regulatory elevations at selected cross sections <br />for each stream studied in detail are shown in Table 3. <br /> <br />14 <br />