Numerical study on landslide dam breach and its induced morphological change
(2023) 40th IAHR World Congress — Location: Vienna, Austria (21.August.2023)
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- Abstract
- Landslide dams are natural dams that are formed by the blockage of river channel with landslides, rockfalls or debris flows. Due to their unconsolidated earth material composition, landslide dams are vulnerable to overtopping failure resulting in floods with mega discharge after their formation, posing great threaten to people and infrastructures downstream, and further changing the local morphology. One of the key characteristics of such landslide dams is the complex material composition, which was investigated experimentally by conducting flume experiments. In this paper, numerical simulations of these experiments are presented using a finite-volume model solving the shallow-water and Exner equations, complemented with a bank failure operator to reproduce the progressive breach formation, considering the natural angle of stability of the dam material. As regards the numerical resolution of the system of shallow-water and Exner equations, both coupled and weakly-coupled approaches are used: coupled approaches are known to be well suited for fast transient flows, but weakly coupled approaches improve the results accuracy as they are less diffusive. The material composition is represented by a specific parameter such as d50 that differs for the different experimental configurations. Applications of the numerical models with different sediment transport equations show that the overall breaching process is well reproduced by the models. However, it was also observed in the experiments that the material composition has a significant impact on the erosion-deposition process, thus further impacting the dam breach process and local morphological change. Here, despite the different modelling options, there is an over-estimation of the erosion depth during the simulation of dam breaching, resulting in a larger discharge as well as a larger deposition depth in the downstream part of the flume. This tends to show that the single d50 is not sufficient to represent the behavior of the complex landslide dam material. This work thus focuses on the improvement of the model by considering a bi-modal material composition in the resolution of the Exner equation to better represent the breach evolution.
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Yang, J., Soares Frazao, S., Shi, Z., & et al. (2023). Numerical study on landslide dam breach and its induced morphological change. 40th IAHR World Congress, Vienna, Austria. https://hdl.handle.net/2078.5/216579