A dual finite volume method scheme for catastrophic flash floods in channel networks

This paper develops a new numerical scheme for flash floods based on the one-dimensional shallow water equations in channel networks, referred to as the dual finite volume method (DFVM) scheme. The scheme uses an upwind spatial discretization based on staggered meshes so that the flows in multiply connected channel networks are consistently handled without complicated treatment at junctions. The scheme is firstly examined with a series of test cases including idealized and experimental dam break problems to demonstrate its accuracy and versatility. The scheme is then applied to numerical simulation of a flash flood resulting from an earthquake-induced complete dam failure in Japan. Channels from a reservoir to the downstream rivers are modelled as a multiply connected channel network with non-prismatic cross-sections, steep slopes, and bends. The computational results agree well with the field observations and eyewitness reports. Numerical simulation of alternative scenarios as possible cases is also performed to analyze potential risks of the downstream area.