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摘要
An analytical model is proposed to describe lake drainage and downstream flooding due to the gradual breaching of natural and manmade earthen dams. Erodible triangular dams are considered, undergoing gradual incision by a breaching channel of constant effective width. Adopting a simple stream power law for dam material transport, the long profile evolution of the breaching channel is governed by a diffusion equation with variable diffusion rate, proportional to the water discharge. The resulting flood is routed downstream using the kinematic wave equation. Moving boundary problems are obtained due to retrogression of the breach crest, and to the downstream propagation of the flood wavefront. For both the dam breaching and flood routing problems, explicit analytical solutions are derived. They depict a breaching process that is at first self-accelerating, then becomes self-limiting. Results include boundary paths, long profiles, and stage and discharge hydrographs. In particular, the breaching solution yields a discharge hydrograph of simple analytical shape that turns out to be ideally suited for kinematic wave routing. The model is applied to the well-documented breaching of the Tangjiashan landslide dam, Sichuan, in June 2008. Calculated results for this and other cases are in reasonably good agreement with the measured data. As the model is simple to apply, with minimal computational and data requirements, it could prove useful as a tool for rapid risk assessment. The proposed analytical approach also complements numerical models by providing more transparent links between solution outcomes and the problem data.
- 出版日期2013-4
