Laserfiche WebLink
<br />The hydraulic analyses for this study were based on unobstructed <br />flow. The flood elevations shown on the profiles are thus con- <br />sidered valid only if hydraulic structures remain unobstructed, <br />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 this <br />study are shown on the maps. <br /> <br />4.0 <br /> <br />FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />. <br /> <br />The NFIP encourages State and local governments to adopt sound flood- <br />plain management programs. Therefore, each Flood Insurance Study <br />produces maps designed to assist communities in developing floodplain <br />management measures. <br /> <br />4.1 Floodplain Boundaries <br /> <br />To provide a national standard without regional discrimination, <br />the 1 percent annual chance (lOO-year) flood has been adopted by <br />FEMA as the base flood for floodplain 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 by detailed methods, the 100- and SOD-year <br />floodplain boundaries have been delineated using the flood <br />elevations determined at each cross section. Between cross <br />sections, the boundaries were interpolated using topographic maps <br />at a scale of 1:2,400, with a contour interval of 2 feet <br />(Reference 6). <br /> <br />The 100-year floodplain boundaries for the following streams were <br />obtained from a 1979 UDFCD report (Reference 2): <br /> <br />City Park Channel <br />City Park Channel South Tributary <br />Gay Reservoir Channel <br />Gay Reservoir Channel North Tributary <br />Nissen Reservoir Channel <br />West Lake Channel <br />West Lake Channel Tributary <br /> <br />. <br /> <br />Additional 100-year floodplain boundaries on the Gay Reservoir <br />Channel were obtained from individual consultant engineers. <br /> <br />The SOD-year floodplain boundaries for each of these streams were <br />delineated by the study contractor. <br /> <br />The floodplain boundaries for Big Dry Creek were obtained from the <br />Flood Insurance Study for Adams County (Reference 7). The flood- <br />plain boundaries for Rock Creek were taken from a 1976 U.S. Soil <br />Conservation Service report (Reference 8). <br /> <br />13 <br />