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<br />EXPERIMENTAL PROCEDURES <br /> <br />The slope of the 2-ft flume was varied during the preliminary <br /> <br />two-dimensional s~ies to determine its effect on the flow of water and <br /> <br />sedimeo.t; over the control structure. After these preliminary tests the <br /> <br />slope of the flume was maintained constant. <br /> <br />To establish a test run in the movable bed. flume, water was <br /> <br />introduced into the flume from a source outside of the recirculating <br /> <br />system and allowed to pond in the flume. Hhen a sufficient ponding depth <br /> <br />was developed, the pump was started and water and sediment were recircu- <br /> <br />lated. By this procedure it was possible to avoid excessive and unrealis- <br /> <br />tic channel bed movement during the initial starting stage. Hhen <br /> <br />recirculation was established, downstream flow depth was controlled by a <br /> <br />gate at the end of the flume. Hater surface elevations were measured <br /> <br />with a point gage on a travelling carriage, and flume slopes were deter- <br /> <br />mined by level measurements. <br /> <br />The same precautions were not necessary for the rigid-bed 2 ft flume <br /> <br />or the 8 ft flume. Hater surface elevations for these latter flumes were <br /> <br />also measured by point gage. <br /> <br />l: .' j.LA (" , <br />~. v v <br /> <br />-12- <br />