Numerical investigation of effect of flow stages and vegetation on bed morphology at a large river confluence

River confluences are important locations in drainage systems where there are abrupt changes in flow structure, sediment transport, and bed morphology. A problem to be resolved is how bed morphology at a large river confluence responds to different flow stages. Moreover, the role of lateral (in) stability through bank-vegetation effects on flow dynamics and bed morphology at a river confluence is not clearly understood. This paper presents an integrated depth-averaged 2D model to investigate these aspects. The computed results indicate that bed morphology at a large river confluence is substantially affected by flow rate rather than discharge/momentum ratio. Response of bed morphology to different flow stages has a periodic tendency depending upon flow rate. Additionally, the presence of vegetation over the confluence bar (if any) has significant influence on bed morphology within and downstream the river confluence.