Downstream Scour of Broad-Crested Weir with Sloping Sides

Every year، in order to control the downstream scour of hydraulic structures and prevent destruction of them so many costs are spent. Therefore، scouring in hydraulic structures and its forecasting before building any hydraulic structure are of great importance. Development of this process may be dangerous for the structure stabilty. In this research the most important factors، which affect the local scour processes at downstream of horizontal apron of a Broad-Crested weir with sides slopes are identified and grouped by dimensional analysis to obtain the dimensionless parameters. The results obtained were used to introduce dimensionless relationships and diagrams in order to determine characteristic length of the scour hole (i. e. maximum scour depth and its position، height of sand bars and its distance from the end of apron، and longitudinal development of scour hole). By using the introduced simple relationship the geometry of the sour hole may be predicted and proper action may be taken to reduce the probable losses.