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<br /> Table 2. Summary of Discharges <br />Fl oodi ng Source Ora i nage Area Peak Discharge (cfs) <br />and Location (Square Miles) 10-Year 50-Year 100-Year 500- Year <br />Arkansas River <br />At Canon City 3,117 8,850 16,500 20,500 32,200 <br />Forked Gulch <br />At Canon Ci ty 3.76 960 2,290 2,790 5,490 <br />West Forked Gulch <br />At Canon Ci ty 2.61 760 1,790 2,220 4,100 <br />Sand Creek <br />A t Canon City 12.8 1,660 4,060 5,400 9,800 <br />Southea st Canon <br />A t Canon City 1.27 170 400 500 920 <br />Northeast Canon Drainage <br />At Canon City 6 1,485 2,275 2,380 3,575 <br />3,2 Hydraulic Anal yses <br /> <br />Analyses of the hydraul ic characteristics of the flooding sources <br />studied in detail in the community were carried out to provide esti- <br />mates of the elevations of floods of the selected recurrence inter- <br />val s along each of the flood sources. <br /> <br />Water-surface elevations for the 10-,50-,100- and 500-year floods <br />for the Arkansas River, Forked Gulch, Sand Creek, Northeast Canon <br />Drainage, and Southeast Canon Drainage, were computed using the U,S. <br />Amy Corps of Engineers HEC-2 Water-Surface Profiles Program (Refer- <br />ence 12). Cross sections for this analysis were obtained from aerial <br />topographic mapping flown in April 1979, coupled with appropriate <br />fi el d verifi cation (Reference 13). All bridges and cul verts were <br />measured in the field to obtain elevation data and structural <br />geometry. <br /> <br />Locations of sel ected cross sections used in the hydraul ic analyses <br />are shown on the Flood Profiles (Exhibit 1). For stream segments in <br />which a floodway is computed (Section 4.2), selected cross section <br />locations are al so shown on the Flood Boundary and Floodway Map. <br />Roughness val ues (Manning's "n") were determined by fiel d inspection. <br />Ground 1 evel photography aided in the sel ection of roughness factors <br />and aerial photography was used to determine the 1 imits of each <br />roughness zone. Roughness val ues along the Arkansas River ranged <br />from 0.025 to 0.065 for the flood plain and 0.03 for the channel for <br />all recurrence intervals. Roughness values for the tributaries <br />ranged from 0.03 to 0.06 for the flood plain and 0,016 to 0,06 for <br />the channel. <br /> <br />8 <br />