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Andrews and Nelson Q-50 Maximum value -172 cm/s - - - - - - :::: - - ~~~:::-, :=:~g~g~~...... -~::-~=~~ :::- ~ ~ = F .:-- E - Q-275 Maximum va1ue -104.6 em! 5 ~ :: - ~ - - ... ~~~~~~ ;::~~~~~~...... ~~~~=~~ ::-~~:= , ::- g g - Q - 475 Maximum va1ue -lZl.7 an/s Fig. 5. Distribution of vertically_veragedvelocity in the Ouray reach at diseharges of 50 m3/s. 275 m3/s, and 475 m3/s. the same 3 discharges are compared in Figure 5. The bankfull dischar,;e in this reach is about 475 m3/s, and the mean annual discharge is about 130 m3/s. The same bankfull channel topography, shown in Figure 2, was used for the calculations compared in Figures 4 and 5. Channel curvature through the Ouray reach, as indicated by the channel banks or centerline, is moderate. Curvature of the streamlines as indicated by the vertically-averaged velocity vectors shown in Figure 5, however, is appreciably larger. The greater curvature of the streamlines compared to the banks is due to the very substantial influence of channel topography. Steering of flow around the bar is shown by the divergence of the boundary shear stress arld vertical Ii-averaged velocity beginning near cross section 13. Topographic steering is also significant further downstream where the point-bar on the left bank forces the high velocity core to the right bank. Streamline curvature increases as discharge decreases, especially in the vicinity of the bar. The apex of the bar is within 20 em of the water surface at a discharge of 275 m3/s. Consequently, there is very little flow over the top of the bar at this discharge, and most of the flow must go around the bar. Lateral convective accelerations are especially large between cross sections 15 to 18. Topographic steering of the flow has a substantial influence on the spatial distribution of sediment transport rates. In the vicinity of cross section 9, the 475