Coupled modelling of flood due to natural landslide dam breach Available to Purchase

A coupled two-dimensional mathematical model is presented for a flood due to natural landslide dam breach. A new numerical algorithm is developed, preserving the well-balanced property between the flux and source terms of the momentum conservation equations over a mobile bed. It allows for the wetting–drying transition to be properly resolved. Equally importantly, the spatially variable size of the sediments of natural landslide dams is taken into account in estimating bed sediment entrainment flux. The model is first tested against flume experiments and then applied to a case study of the Tangjiashan landslide dam, the largest of its kind generated by the 2008 Wenchuan earthquake in Sichuan Province, China. Compared with field observations, the widening and deepening of the breach along with the flood hydrographs are reproduced fairly well by the present model as the heterogeneity of the dam material is incorporated. In contrast, when the heterogeneous composition of the natural landslide dam is ignored using a fixed sediment size, the model fails even if the parameters related to roughness, entrainment flux and mass collapse are largely tuned. An appropriate account of the heterogeneous composition of natural dams is therefore significant.