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estimation of topwidth, and direct use of drainage area versus discharge and drainage area versus depth in channel curves from USGS Technical Manual No. 1 (Reference 13). The hydraulic analyses for this study were based on unobstructed flow. The flood elevations shown on the profiles are thus con- sidered 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 this study are shown on the maps; the description of the marks are presented in Elevation Reference Marks (EKhibit 3). 4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS The NFIP encourages State and local governments to adopt sound flood plain management programs. Therefore, each FIS provides lOa-year flood elevations and delineations of the 100- and SOO-year flood plain boundaries and lOa-year floodway to assist communities in developing flood plain management measures. 4.1 Flood Plain Boundaries TO provide a national standard without regional discrimination, the 1 percent annual chance (lOa-year) flood has been adopted by FEMA as the base flood for flood plain management purposes. The 0.2 percent annual chance (SOD-year) flood is employed to indicate additional areas of flood risk in the community. For each stream studied by detailed methods. the 100- and SOa-year flood plain boundaries have been delineated using the flood elevations deter- mined at each cross section. Between cross sections, the bound- aries were interpolated using topographic maps at a scale of 1:24,000, with contour intervals of 10. 20, and 40 feet (References 29, 3D, and 31, respectively). Flood plain boundaries for Cherry Creek were determined by a COE report entitled Flood Plain Information, Cherry Creek-Cherry Creek Lake through Franktown, Colorado (Reference 14). This report was also used to determine the boundaries at the confluences with Cherry Creek tributaries included in this study. The 100- and SOD-year flood plain boundaries are shown on the Flood Insurance Rate Map (Exhibit 2). On this map, the 100-year flood plain boundary corresponds to the boundary of the areas of special flood hazards (ZOnes A and AE); and the SOD-year flood plain boundary corresponds to the boundary of areas of moderate flood hazards. In cases where the 100- and SOD-year flood plain boundaries are close together, only the 100-year flood plain boundary has been shown. Small areas within the flood plain 26