INVESTIGATION OF THE CAUSE OF SAND DEPOSITION IN UPSTREAM AREA OF MOVABLE WEIR

Abstract

 The problem of large amounts of sand deposition at movable weir often occurs both upstream and downstream of weir at the time of flood, and investigation of the cause is an important issue for river management. Sand deposition at movable weir at the time of flood is especially remarkable in downstream area, and is often considered to be a problem. However, there are few studies on sand deposition at upstream side, and there are many unclear points. In this study, a hydraulic model experiment using a model weir in an experimental channel was conducted with reference to the Heisei Grand Weir.The results showed that increase tractive force in upstream of the weir promoted sand movement and deposition. In addition, the water surface dropped below the lower edge of weir at high flow rates, and suggested that this is caused by the formation and movement of dune.