Effects of Confluence Angle on Erosion and Sedimentation Pattern at River Confluence by Physical Model

River confluence is an important element of river system. The entrance flow from the minor branch to the main channel causes extensive variation in flow pattern which result a deep scour hole and formation of point bar. These phenomena can accelerate the rate of bank erosion, bring problems for navigation and may causes failure of the bridges or structure nearby. Despite of these, due to three dimensional structures of flow and sediment at river confluence, systematic study for understanding the mechanism of flow and sediments are very few. There for the main purpose of this study to conduct a comprehensive literature review and experimental program to study the effects of confluence angle on erosion and sedimentation pattern. To reach such goals first using the dimensional analysis, general non- dimensional equations were developed. Then many experimental tests were conducted for three confluence angles of 60, 75 and 90 degree and different hydraulic conditions. The experimental tests showed that as the confluence angle is increase, the scour hole and point bar dimensions increases. Using the experimental data, the effects of each non-dimensional parameters on scour hole depth were investigated and finally relations were developed for prediction the scour and point bar dimensions.