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<br />Flood profiles were drawn showing computed water-surface elevations <br />to an accuracy of 0.5 foot for floods of the selected recurrence <br />intervals (Exhibit 1). <br /> <br />For the stream studied by approximate methods, the elevation of the <br />100-year flood was developed from normal depth calculations. <br /> <br />The hydraulic analyses for this study were based on unobstructed <br />flow. The flood elevations shown on the profiles are thus considered <br />valid only if all bridges remain unobstructed, operate properly, and <br />do not fail. <br /> <br />All elevations are referenced to the National Geodetic Vertical Datum <br />of 1929 (NGVD). Elevation reference marks used in the study are <br />shown on the maps. <br /> <br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />A prime purpose of the National Flood Insurance Program is to encourage <br />State and local governments to adopt sound flood plain management pro- <br />grams. Each Flood Insurance Study, therefore, includes a flood boundary <br />map designed to assist communities in developing sound flood plain manage- <br />ment 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 Insurance <br />Administration as the base flood for purposes of flood plain manage- <br />ment measures. The SOO-year flood is employed to indicate additional <br />areas of flood risk in the community. For each stream studied in <br />detail, the boundaries of the 100- and 500-year floods have been <br />delineated using the flood elevations determined at each cross <br />section; between cross sections, the boundaries were interpolated <br />using topographic maps at a scale of 1:2400, with a contour interval <br />of 5 feet (Reference 8). <br /> <br />For the stream studied by approximate methods, the boundary of the <br />100-year flood was delineated using topographic maps at a scale of <br />1:2400 with a contour interval of 5 feet (Reference 8). <br /> <br />In cases where the 100- and 500-year flood boundaries are close <br />together, only the laO-year flood boundary has been shown. <br /> <br />The study contractor has determined that some areas shown on the <br />Federal Insurance Administration's Flood Hazard Boundary Map (Refer- <br />ence 9) are areas of minimal flooding; therefore, they were not <br />delineated on the maps. <br /> <br />Flood boundaries for the 100- and 500-year floods are shown on the <br />Flood Boundary and Floodway Map (Exhibit 2). <br /> <br />7 <br />