Modelling confluence dynamics in large sand-bed braided rivers

Abstract. Confluences are key morphological nodes in braided rivers where flow converges, creating complex flow patterns and rapid bed deformation. Field survey and laboratory experimental studies have been carried out to investigate the morphodynamic features in individual confluences, but few have investigated the evolution process of confluences in large braided rivers. In the current study a physics-based numerical model was applied to simulate a large lowland braided river dominated by suspended sediment transport, and analyzed the morphologic changes at confluences and their controlling factors. It was found that the confluences in large braided rivers exhibit some dynamic processes and geometric characteristics that are similar to those observed in individual confluences arising from two tributaries. However, they also show some unique characteristics that are result from the influence of the overall braided pattern and especially of neighboring upstream channels.