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Flood profiles were drawn showing computed water-surface elevations to an accuracy of O.S foot for floods of the selected recurrence intervals (Exhibit 1). ~ The depths for the areas of shallow sheet flow were determined using normal depth calculations. The elevation for the shallow ponding area near Lehman Gulch was determined using culvert computations to estimate the inflow from the Blue River. l The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the profiles are, thus, considered valid only if hydraulic structures remain unobstructed, operate properly, and do not fail. All elevations are referenced to the National Geodetic Vertical Datum of 1929 (NGVD). Elevation reference marks used in the study are shown on the maps. 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS A prime purpose of the National Flood Insurance Program is to encourage State and local governments to adopt sound flood plain management pro- grams. Each Flood Insurance StUdy, therefore, includes a flood boundary map designed to assist communities in developing sound flood plain management measures. 4.1 Flood Boundaries In order to provide a national standard without regional discrimina- tion, the 100-year flood has been adopted by the Federal Insurance Administration as the base flood for purposes of flood plain management measures. The SOO-y€ar flood is employed to indicate additional areas of flood risk in the community. For each stream studied in detail, the boundaries of the 100- and SOD-year floods have been delineated using the flood elevations determined at each cross section; between cross sections, the boundaries were inter- polated using topographic maps at a scale of 1:1200, with a contour interval of 2 feet (Reference 8). The boundaries of the shallow flooding areas were also determined using topographic maps (Refer- ence 8). In cases where the 100- and SOa-year flood boundaries are close together, only the 100-year flood boundary has been shown. Flood boundaries for the 100- and SOD-year floods are shown on the Flood Boundary and Floodway Map (Exhibit 2). 9