Well-balanced 2D Coupled Modelling of Dam-break Sediment-laden Flood Processes in a Real River Channel

The last two decades have seen development of numerous well-balanced Godunov-type finite volume models for shallow water modeling over irregular topographies, yet most are simply oriented for clear water flows, without considering the potential of sediment transport and bed morphological changes. Using unstructured triangular mesh to adapt complex boundary shapes, this paper presents a well-balanced 2D coupled non-capacity model, which accounts for not only the water flow evolution, but also the induced sediment transport and bed morphological evolution, as well as sediment adaptation. The well-balanced property is accomplished by defining bed elevation at triangle grid nodes and discretizing the geometric source term using the DFB (divergence from for bed slope source term) method. The friction source terms are treated in a fully implicit way to alleviate numerical instabilities. Validated by three representative laboratory-scale cases of dam-break flood process, the performance of the model is further demonstrated by its successful application to a field-scale dam-break sediment-laden flood process at the Najitan reservoir, Hubei province, China. Characteristics of field-scale dam-break flood process appear to appreciably differ from those generated in laboratory regular flume channels, indicating the necessity of more systematic efforts on dam-break sediment-laden flood process at field scales.