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where n = Manning's roughness coefficient; A = flow area; and R = hydraulic radius. Increasing conveyance in a reach decreases stage while decreasing conveyance has the opposite effect. Increasing the storage capacity of a reach delays the arrival of a flood wave at a downstream location, while decreasing storage reduces the wave's travel time through a reach. For the 37 surveyed cross sections in the vicinity of the Ouray National Wildlife Refuge, bed roughnesses from the Green River Flooded Bottomlands Investigation (FLO Engineering, Inc. 1996) were used. For the remaining upstream reaches, an estimated roughness of 0.035 was used to represent a gravel-bedded river with minor surface irregularity and gradual variation in cross sectional geometry (Chow 1964). Ice cover thickness, roughness, and spatial extent for the steady flow period were selected to represent the pre-peaking conditions observed during 23-24 January 1997. An ice cover with a thickness of 21 cm and a roughness of 0.025 was applied to the reach from the Ouray Bridge to the Jensen Bridge in order to represent a cover composed of thermally grown sheet ice and juxtaposed frazil pans. From the Jensen Bridge up to the leading edge of the ice cover near Razorback Island, an ice thickness of 24 cm with a roughness of 0.03 was used, representing an ice cover composed mainly of juxtaposed and slightly shoved frazil pans and floes. Table 1 summarizes the calibration parameters used in the UNET model; cross-section location and type are shown graphically in Figure 6, along with ice cover extent. The UNET model was calibrated to observed stage hydrographs at the seven locations indicated in Figure 6. Simulated and observed stage hydrographs for these seven locations are presented in Figures 7 through 13. Calibration results were generally quite good with a few exceptions. The measured stage hydrograph at the Chew Bridge location (RM 316.3) is more peaked than the reported stage hydrograph for the nearby Jensen gage (RM 316.6) (Figure 7), possibly because the channel is more narrow at the bridge than at the gage location a short distance upstream. Similarly, the observed hydrograph at the Jensen Bridge location (RM 302.3) is more peaked than the simulated result (Figure 9). The simulated and observed hydrographs agree quite well in terms of total wave height and timing of the peak at Dinosaur Bend (RM 307.1; Figure 8), Bonanza Bridge (RM 294.0; Figure 10), and Horseshoe Bend (RM 279.4; Figure 11). At the Ouray National Wildlife Refuge (RM 254.6; Figure 12) and the Ouray Bridge (RM 248.0; Figure 13), the timing of the first hydrograph peak and the total wave height are simulated fairly well. The simulated falling limbs of these hydrographs are less steep than the observed falling limbs, however. Resolution may be a problem in this part of the river because observed wave height is small, on the order of 0.3-0.4 ft. Also, these downstream sites are more than 60 miles from the location of the observed inflow hydrograph at the Jensen gage (RM 316.6), the upstream boundary of the model. -12-