Experimental Investigation on the Effect of the Bendway Weir Angle on the Erosion and Sedimentation Pattern in Meandering River

Bank erosion is one of the important management issues, especially in meandering rivers. Bendway weirs have recently become among the most popular structures in erosion control along the meanders. Bendway weirs are the stone structures constructed in outer bank to change the flow direction from outer bank to the center of the channel so as to prevent erosion. In this study it has been attempted to investigate the effect of angle of bendway weirs on the pattern of erosion and sedimentation. Three angles of 60°, 75° and 90° and three flow rates of 120, 180 and 230 liter per second were examined. Other structural parameters such as length, height, and distance were kept constant. Continuous injection of sediment with d50= 1.6 mm formed a live bed. The results of this study showed that the cross-section area of sedimentary bar in the inner bank decreased by an order of 13 to 48 percents as a result to the construction of weirs. The minimum and maximum of decrease were corresponded to the angles of 90° and 60°, respectively. The maximum scour depth to weir height ratio in the outer bank wall was very evident for the angle of but not so noticeable for other two angles. The maximum amount of this ratio was 4.6 at 90°. Sedimentation and scouring patterns showed that the sedimentation between weirs and thereby protecting the outer bank were better for the angles of 60° and 75°. Angle of 90° is not recommended for construction of bendway weirs.