Effect of sediment load from main canal on maximum scour depth at river confluence

River confluence is an important element of river system. At this place، because of complex three dimensional flow structure، scour and sedimentation is occur which can damage the surrounding area، change river morphology and can be harmful to navigation. Many variables can effect the sedimentation pattern at river confluence such as bed load coming from the main channel which has not been studied in the past. Therefore it is the main goal of this study to experimentally investigated the effect of bed load. To do so first a general non dimensional relation was developed، then a sediment feeder was designed and calibrated. Afterwards، series of experimental tests were conducted in various hydraulic conditions and sediment discharge. The results indicate that increasing the amount of bed load sediment، reducing the maximum scour depth from up to 35 percent. Also it was observed that bed scour and sedimentation patterns can change when the bed load is presented. Finally، an equation was developed to predict the scour depth in terms of sediment load. The accuracy of the new is within 95 percent. The sensitivity analysis of this equation shows that it is more sensitive to Densimetric Froude. The new relation was compare with Ghobadian and Shafai Bejestan (2007).