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<br />Base Map Source <br /> <br />Streams Covered <br /> <br />Northway-Gestalt Company, Lena Gulch <br />Plans (Reference 39) <br /> <br />Lena Gu lch 1 <br /> <br />1 <br />2Supplemented with field survey <br />Supplemented with construction drawings <br /> <br />The cross sectiona used in the backwater analyses of the streams <br />added from the City of Golden Flood Insurance Study (Reference 1) <br />were obtained from a number of sources. Cross sections on Clear <br />Creek were compiled by the Bell Mapping Company using photogram- <br />metric methods for the 1979 Flood Hazard Area Delineation (FHAD) <br />report (Reference 40). Cross sect10ns on Kenneys Run were <br />digitized by photogrammetric methods using aerial photographs at a <br />scale of 1 :6,000 (Reference 41). Cross sections on Jackson snd <br />Lena Gulches were compiled by Olympus Aerial Surveys for a report <br />by Wright-McLaughlin Engineers, by photogrammetric methods, using <br />maps at a scale of 1 :1,200, with a contour interval of 2 feet <br />(Reference 19). <br /> <br />The cross section data for the South Platte River, as adopted <br />the Douglas County Flood Insurance Study (Reference 2), <br />obtained by field survey. <br /> <br />from <br />were <br /> <br />Locations of selected cross sections used in the hydraulic <br />analyses are shown on the Flood Profiles (Exhibit 1). <br /> <br />Roughness coefficients (Manning's "n") for the flooding sources <br />were estimated by field inspection. The channel and overbank <br />roughness value ranges for each stream are given in Table 2. <br /> <br />Starting water-surface elevations were determ1ned as listed in <br />Table 3. <br /> <br />On Clear Creek at Golden, water-surface elevat10ns were computed <br />based on results from the UDFCD FHAD report (Reference 40). These <br />results were modified at Ford Street and downstream through the <br />Coors brewery, where the topographical configuration has changed. <br />At Ford Street, for example, the channel and overbank flows were <br />handled separately. The resulting water-surface elevations in the <br />channel at Ford Street and Washington Avenue were input to the <br />HEC-2 model considering only the channel as an effective flow area <br />and modifying the discharges accordingly. The 50- and 500-year <br />flood water-surface elevations were extrapolated from the 10- and <br />100-year flood elevations. Other changes have been made to the <br />FHAD report, with UDFCD approval, upstream of U.S. Highway 6. <br /> <br />Br1dges, dams, and culverts were measured to obtain elevation data <br />and structural geometry. <br /> <br />21 <br />