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<br />Starting water-surface elevations were calculated using the slope- <br />area method. <br /> <br />The approximate flood elevations for Buzzard Creek were determined <br />using normal-depth calculations and computing the backwater elevation <br />from the bridge upstream of its confluence with Plateau Creek. <br /> <br />The hydraulic analyses for this study were based on unobstructed <br />flow. The flood elevations shown on the flood profiles are, thus, <br />considered valid only if the hydraulic structures considered remain <br />unobstructed, operate properly, and do not fail. <br /> <br />All elevations are referenced to the National Geodetic Vertical <br />Datum of 1929 (NGVD). Elevation reference marks used in the study <br />are shown on the maps. <br /> <br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />The National Flood Insurance Program encourages State and local governments <br />to adopt sound flood plain management programs. Therefore, each Flood <br />Insurance Study includes a flood boundary map designed to assist communi- <br />ties in developing sound flood plain management measures. <br /> <br />4.1 Flood Boundaries <br /> <br />In order to provide a national standard without regional discrimina- <br />tion, the 100-year flood has been adopted by the Federal Emergency <br />Management Agency as the base flood for purposes of flood plain <br />management measures. The SOO-year flood is employed to indicate <br />additional areas of flood risk in the community. For each stream <br />studied in detail, the boundaries of the 100- and SOO-year floods <br />have been delineated using the flood elevations determined at <br />each cross section; between cross sections, the boundaries were <br />interpolated using topographic maps at a scale of 1:2400, with <br />a contour interval of 4 feet (Reference 10). <br /> <br />Flood boundaries for the areas studied by approximate methods <br />were delineated using the previously determined elevations and <br />topographic maps at a scale of 1:2400, with a contour interval <br />of 4 feet (Reference 10). <br /> <br />Flood boundaries for the 100- and SOO-year floods are shown on <br />the Flood Boundary and Floodway Map (Exhibit 2). In cases where <br />the 100- and SOD-year flood boundaries are close together, only <br />the 100-year flood boundary has been shown. Small areas within <br />the flood boundaries may lie above the flood elevations and, there- <br />fore, not be subject to flooding, owing to limitations of the <br />map scale and/or lack of detailed topographic data, such areas <br />are not shown. <br /> <br />9 <br />