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<br />3.2 Hydraulic Analyses <br /> <br />Analyses of the <br />ri verine sources <br />the elevations of <br /> <br />hydraulic characteristics of flooding from the <br />studied were carried out to provide estimates of <br />floods of the selected recurrence intervals. <br /> <br />The profiles for the St. Charles River, Fountain Creek, wild Horse- <br />Dry Creek, Dry Creek, and Goodnight Arroyo were computed by stream <br />characteristics, topographic maps and valley cross sections. The <br />cross sections for the St. Charles River and Fountain Creek were <br />surveyed in August 1969 and August 1967, respectively. <br /> <br />For Sal t Creek and <br />topographic maps and <br />stream characteristics <br />situation. <br /> <br />Sixmile Creek, channel <br />aerial photographs were <br />needed to compute and <br /> <br />cross <br />used to <br />define <br /> <br />sections, <br />determine <br />the flood <br /> <br />Locations of selected cross sections used in the hydraulic analyses <br />are shown on the Flood Profiles (Exhibit 1). <br /> <br />Flood profiles were drawn showing the computed water-surface <br />elevations for floods of the selected recurrence intervals. <br /> <br />The hydraulic analyses for this study are based on unobstructed <br />flow. The flood elevations shown on the profiles are thus <br />considered valid only if hydraulic structures remain unobstructed, <br />operate properly, and do not fail. <br /> <br />All elevations are <br />Datum (NGVD) of 1929. <br />are shown on the maps. <br /> <br />referenced to the National Geodetic Vertical <br />Elevation reference marks used in this study <br /> <br />4.0 FLOODPLAIN MANAGEMENT APPLICATIONS <br /> <br />The NFIP encourages State and local governments <br />plain management programs. Therefore, each <br />includes a flood boundary map designed to <br />developing sound floodplain management measures. <br /> <br />to adopt sound flood- <br />Flood Insurance Study <br />assist communities in <br /> <br />4.1 Floodplain Boundaries <br /> <br />To provide a national standard without regional discrimination, the <br />I-percent annual chance (lOO-year) flood has been adopted by FEMA as <br />the base flood for floodplain management purposes. For each stream <br />studied by detai led methods, the boundaries of the IOO-year flood- <br />plain boundaries have been delineated using the flood elevations <br />determined at each cross section. <br /> <br />10 <br />