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<br />EXPERIMENTAL RESULTS AND DISCUSSIONS <br /> <br />Weirs A and B <br /> <br />The results of studies with weirs A and B showed no readily <br /> <br />evident effect on the discharge coefficient due to changes in slope of <br /> <br />the upstream and downstream faces of the weir. The results are shown <br /> <br />in Fig. 9 with coefficient of discharge C as a function of unit model <br /> <br />discharge. The coefficient C was calculated from <br /> <br />Q = CL!l3/2 <br /> <br />where <br /> <br />H = specific head above the weir <br /> <br />Observations were made on the transport of sediment at the weir <br /> <br />during these tests. There appeared to be no observable difference in the <br /> <br />movement of stream bed material over the structure whether at a slope of <br /> <br />2:1 as for Weir A or at a flatter slope of 3:1 as for Weir B. As the <br /> <br />sand dunes which formed on the bed of the flume, moved downstream onto <br /> <br />the structure, the dunes deteriorated in form in the region of accelerat- <br /> <br />ing velocity and the sediment washed over the structure. There was no <br /> <br />deposition of sand on the weir crest. <br /> <br />Simulated step-wise hydrographs were run to investigate the effects <br /> <br />of rising and falling river stage on the aggradation of the channel up- <br /> <br />stream of the structure. No attempt was made to relate this artificial <br /> <br />hydrograph with runoff that might occur in the Rio Grande. The results <br /> <br />shown in Figs. 10 and 11 indicate that in the recirculating flume the bed <br /> <br />. - , <br />l " 1. ~. .~ .,) <br /> <br />-13- <br />