Based on the shape of the braided river in the middle reaches of the Yalu Tsangpo River, the study established a mathematical model for the simulation of sediment transport in braided rivers. The numerical calculation used a two-dimensional hydrodynamic and non-viscous sediment coupling model to simulate the sediment transport in the braided river. The model is based on the incompressible Reynolds average N-S equation, which included continuous equations, momentum equations, riverbed deformation equations, and total sand transport equations. The mathematical model calculated the suspended sediment and the sediment transport rate through the theory of total sediment transport. When simulating flood peak flow, the peak of the sediment concentration process and the suspended sediment transport rate of the braided river lags was behind the inflow process, causing a phase difference. The smaller the sediment particle, the smaller the phase difference. The phase difference of sands, whose particle sizes were 0.01 mm and 0.02 mm, was about 0, and the phase difference caused by the rate of exit suspension sediment transport was less than that caused by sediment concentration. The sedimentation of 0.30 mm, 0.20 mm and 0.10 mm particle size in the braided river exceeded 50%. In the calculation of sediment transport, the topographic renewal caused by sediment start-up and sedimentation was considered, and the influence of the sediment flow on the topographic changes during the movement of the braided river was analyzed, which established a numerical simulation example for the research prediction of the natural braided river.
