Experimental Study of the Submerged Bendway Weirs Effect on Flow Resistance Coefficients

During the past two decades, bendway weirs have been used as erosion conrol structures in river bends. These structures are constructed for erosion control at the outer bank with suitable upstream angle. This research investigates the effect of the angle and length ratio of weirs on the resistance coeficients of the flow (f, n) in a sinusoidal channel and in different hydraulic conditions. Three angles (60°, 75° and 90°), three length ratios (0.2, 0.3 and 0.4) and three submergence ratios (2.6, 2.8 and 3) were used as variables. All experiments were performed in alive bed condition with a continuous sediment injection. The results showed that the Darcy-Weisbach’s f and Manning’s n coefficients decreased with increasing of the angle and length ratio. Flow resistance coefficients “f” and “n” increased 90% and 20%, respectively and “C” coefficient decreased 27% due to weirs construction.