Flood hydraulics due to cascade landslide dam failure

Abstract

Landslide dams are usually unconsolidated and when they act to impound water, they are subjected to failure that triggers catastrophic flooding downstream. However, the flood hydraulics due to landslide dam failure has remained poorly understood and cannot be reliably predicted at present. Inevitably, this militates against effective flood risk management in areas prone to landslides. Extending the recent investigation of a single landslide dam failure and the resulting flood, here, we present an experimental and computational study on the flood flow induced by cascade landslide dam failure. A total of 12 runs of experiments are conducted in a flume of 80 m × 1.2 m × 0.8 m, with differing inflow discharge and dam composition. An array of 12 automatic water‐level probes is deployed to measure the stage hydrographs along the flume. The coupled shallow water hydrodynamic model calibrated for cases of a single landslide dam failure is demonstrated to perform reasonably well for cascade landslide dam failure. Most notably, under appropriate conditions, the occurrence of streamwise progressive enhancement of the flood induced by cascade landslide dam failure is demonstrated. This features a higher risk of flooding downstream and therefore warrants careful consideration in flood risk management.

A double layer-averaged model for dam-break flows over mobile bed

“…A Runge-Kutta scheme is applied to solve the ordinary differential equations composed of the source terms. The new model is tested against a series of cases, including laboratory experiments on flows induced by instant and full dam break (Spinewine 2005a) and also flows due to progressive failure of a single and cascade landslide dams (Cao et al 2011a, 2011b, Schmocker and Hager 2012. The model has also been compared with two existing models, including the SDL model of Spinewine (2005a) and the SL model by Cao et al (2004).…”

“…In general, strong interactions exist between the flow, sediment transport and channel morphology. Since the pioneering work of Capart and Young (1998), laboratory experiments have contributed significantly to the understanding of dam-break hydraulics over mobile bed (Spinewine 2005a, Cao et al 2011a, 2011b, Schmocker and Hager 2012. However, flume experiments are usually constrained by the comparatively small spatial scales in laboratories and may not be sufficient for fully unraveling the complex mechanisms of dambreak flows.…”

“…Computational study is an attractive alternative for enhancing the understanding of mobile bed dam-break flows. Indeed, the work of Capart and Young (1998) acted as a catalyst for the development of many numerical models (Cao et al 2004, 2011a, 2011c, Spinewine 2005a, Leal et al 2006, 2010a, 2010b, Spinewine and Zech 2007, Wu and Wang 2007, Xia et al 2010, Goutière et al 2011, Soares-Frazão et al 2012.…”

Coupled modelling of flood due to natural landslide dam breach

“…Over the last few decades, researchers have strived to enhance understanding of the mechanisms of landslide dam failure and the hydraulics of the resulting floods (Cao et al, 2011c). In particular, the breaching process has received considerable attention as it dictates the generation and propagation of the downstream flood wave and subsequent inundation, and is the most challenging process to model.…”

“…The erosion rate was used to calculate the bed change while the deposition in the breach area was not considered. Cao et al (2011bCao et al ( , 2011c developed a 2D coupled model to simulate landslide dam breach for both single and cascade dams composed of single-size sediment. In this model, the entire dam breaching process was modelled, which included the stage rise in the reservoir due to inflow, the breaching process of the landslide dam and the flood propagation downstream of the dam.…”