Abstract A series of natural landslide dams commonly form in a river valley in mountainous areas. Their failures are frequently triggered by intense rainfall, which may result in severe flash flooding or debris flow in a short period. It is important for risk mitigation to develop greater evidence-based understanding of flood dynamics due to cascading dam failures. Based on detailed hydro-morphodynamic modeling of various scenarios, this study systematically evaluates the formation and evolution of flash floods due to a cascading failure of natural landslide dams. The hydro-morphodynamic model has been shown to be capable of simulating shock-captured flows and resultant morphological changes. In this study, we first calibrate the dynamic model with dedicated experimental data, and then apply it to simulate a variety of designed flash flood scenarios caused by cascading dam failures. Moreover, process-based flood dynamics and their evolution are explored in detail. Results indicate that cascading dam failures in a sloping channel cause an overall amplification of flash flood dynamics in the flow direction, but fluctuation of key hydraulic parameters occurs around each dam. Also, bigger landslide dams prevent upstream flood propagation better, but the blockage of the flows raises the potential flow energy. This implies a higher potential hazard risk in case of ‘sudden-onset’ failure of the dam. Moreover, the shape characteristic of a channel (straight or with bends) influences the evolution of the flash flood along the sloping channel. The findings enhance the understanding of the formation and evolution mechanisms of flash floods due to cascading failures of natural landslide dams, and hence are beneficial for assessing hazard risk and developing mitigation strategies for flash flooding in mountainous areas.

中文翻译：

---

天然滑坡大坝级联破坏引起的山洪动力学数值研究

摘要 山区河谷中普遍形成一系列天然滑坡坝。它们的故障经常由强降雨引发，这可能会在短时间内导致严重的山洪暴发或泥石流。对因级联大坝溃坝而导致的洪水动态进行更深入的循证理解对于降低风险非常重要。本研究基于各种情景的详细水文形态动力学模型，系统地评估了由于天然滑坡大坝的级联故障引起的山洪暴发的形成和演变。流体形态动力学模型已被证明能够模拟激波捕获的流动和由此产生的形态变化。在这项研究中，我们首先用专用的实验数据校准动态模型，然后将其应用于模拟由级联大坝故障引起的各种设计的山洪场景。此外，还详细探讨了基于过程的洪水动力学及其演变。结果表明，斜坡河道中的级联大坝破坏会导致流向的山洪动力学整体放大，但每个大坝周围都会发生关键水力参数的波动。此外，更大的滑坡坝可以更好地阻止上游洪水的传播，但水流的阻塞会提高潜在的水流能量。这意味着在大坝“突然发生”故障的情况下具有更高的潜在危害风险。此外，水道的形状特征（直的或弯的）会影响山洪沿倾斜水道的演变。