Depth‐averaged 2‐D calculation of flow and sediment transport in the lower Yellow River

Abstract

Because of the complexities of hyper‐concentrated flow and compound‐channel topography, the numerical simulation of flow and sediment transport in the lower Yellow River is extremely difficult. In this study, the depth‐averaged 2‐D model, CCHE2Dfvm, is applied to calculate the flood routing and sediment transport in the 100km‐long reach between Huayuankou and Jiahetan gauging stations in the lower Yellow River. The model solves the two‐dimensional shallow water equations by using the finite volume method with the SIMPLEC algorithm and Rhie and Chow's momentum interpolation technique on a curvilinear, non‐staggered grid. The sediment transport equations are also solved by the finite volume method on the same grid. The flow and sediment are calculated in a decoupled form, but the three components of the sediment module: sediment transport, bed changes and bed material sorting are computed in a coupled fashion. The computations of the 1982 and 1996 floods show that the CCHE2Dfvm model is capable of efficiently simulating the flow and sediment transport with low and middle concentrations (<200kg/m3) in the widely wandering Yellow River with very complex topography and rapidly wetting and drying processes. The computational time step is 15 minutes. The simulated flow discharges, water elevations and sediment discharges are in reasonably good agreement with the measured data. The applicability of this model in the situations of high sediment concentration (>200kg/m3) needs to be investigated further.