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Velocity Gradient <br /> 0.6 m/s/m <br /> 1 1 I I 1 1 <br /> . W- r �, <br /> -"Ili! y6. 2.1 -- <br /> m 2278.2- o 1.8 M - <br /> ii <br /> ::: "\\ 1.5 <br /> 0 2278- / - <br /> 0.6 1.2 <br /> cu <br /> ai 0.9 <br /> W 2277.8- 0.5 - <br /> 1 I I I I <br /> 0 1 2 3 4 5 6 7 8 9 10 <br /> Distance (meters) <br /> Figure 12. Velocity isovels of a J-Hook at Turkey Creek, CO (Velocity in meters/second) <br /> Applications <br /> Irrigation diversions. The use of a Cross-Vane for an irrigation diversion is shown in Figure 13. <br /> Cross-Vanes and W-Weirs have both been used successfully for irrigation structures. Both the <br /> Cross-Vane and W-Weir create a differential head in the near-bank region due to the flat slope of <br /> the vane leading to the bank. This condition provides the head to deliver water to the head gate <br /> at very low flows so that it is not necessary to construct sacrificial dams at low flows. When the <br /> head gate is closed during high flows, fine sediments often accumulate. To prevent the sediment <br /> deposition at the head gate and in the irrigation canal, a sediment sluice gate is installed so that <br /> the sediment is delivered back to the channel during normal high flows(Figure 13). <br /> Grade control. The Cross-Vane is used to maintain base level in both riffle/pool channels, <br /> rapids-dominated stream types and in step-pool channels (Figure 14). One aspect of river <br /> restoration is associated with the conversion of incised rivers G and F stream types to B stream <br /> types(Rosgen, 1994,1996,and 1997). The Cross-Vane; as used for grade control, maintains the <br /> new width/depth ratio, entrenchment ratio, reduces bank erosion, dissipates energy and improves <br /> fish habitat. Spacing of the structures is based on a negative power function relationship of the <br /> ratio of pool spacing/bankfull width as a function of slope. <br /> Ps=8.2513 S 0.9799 <br /> Where PS=the ratio of pool to pool spacing/bankfull width <br /> S=channel slope in percent <br /> This relationship was developed from natural channels and has a correlation coefficient(R2)of <br /> 0.92 and is shown in Figure 15. <br /> Bridge protection. Bridges constructed on a skew to the channel and/or placed on an outside <br /> bend often experience abutment scour and embankment erosion. This problem can be reduced <br /> by the placement of an offset Cross-Vane in the upstream reach. The vane on the outer bank in <br /> the bend has a flatter slope and smaller angle (200), while the vane arm on the inside bank has a <br /> steeper slope and a larger angle(30°) (Figure 16). W-Weirs are particularly useful for reducing <br /> 17 <br />