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Cross sections for the backwater analyses were digitized from 1982 aerial photography (Reference,6). Since the cross sections for the White River did not include any below-water geometry, adjusted discharge values were used in the HEC-2 analysis for that stream. The adjusted discharge values were determined by reducing the peak discharges, as shown in Table 1, by the flow in the White River at the time of the aerial photogfaphy. The flow in the river at the time of the photography was obtained from records at the USGS gaging station No. 0906300. The State Highway 64 and South White Avenue bridges over the White River and all culverts along College Canyon Draw and Coal Mine Draw were field surveyed to obtain elevation data and structural geometry. Locations of selected cross sections used in the hydraulic analyses are shown on the Flood Profiles (Exhibit 1). For stream segments for which a floodway was comp~ted (Section 4.2), selected cross section locations are also shpwn on the Flood Boundary and Floodway Map (Exhibit 2). Roughness coefficients (Manning's IOn") were determined by field observation. The coefficients used were 0.040 for the main channel and 0.060 for the overbank areas on the White River, and 0.040 for both the main stream and overbank areas of Coal Mine Draw. Rough- ness coefficients for the main channel and overbank areas of College Canyon Draw varied from 0.040; to 0.045. A slope area normal-depth computation was used to deter~ine starting water-surface elevations for all floods. The effect of ice jams on flood hazards within Rangely were not reflected in the hydraulic analyses for this study. 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 tail. Two culverts at street crossipgs along College Canyon Draw limit the stream carrying capacity. Limited culvert capacity at South White Avenue causes 50-, 100-, and 500-year flows to escape the channel along the right overbank. These flows result in shallow flooding extending north along South White Avenue and east along East Main Street. Limited cu~vert capacity at Prospect Street causes 10-, 50-, 100-, and SOb-year flows to escape the channel along the right overbank and ~o flow north to the White River. Normal-depth analyses were used to determine the depth of flooding resulting from the overflows from College Canyon Draw. The shallow 100-year overflows occurring at South White Avenue and Prospect Street were determined to have depths averaging less than 1.0 foot. ) 0