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Soares-Frazo S.,Catholic University of Louvain | Canelas R.,University of Lisbon | Cao Z.,Wuhan University | Cea L.,University of La Coruna | And 22 more authors.
Journal of Hydraulic Research | Year: 2012

In this paper, the results of a benchmark test launched within the framework of the NSF-PIRE project Modelling of Flood Hazards and Geomorphic Impacts of Levee Breach and Dam Failure are presented. Experiments of two-dimensional dam-break flows over a sand bed were conducted at Université catholique de Louvain, Belgium. The water level evolution at eight gauging points was measured as well as the final bed topography. Intense scour occurred close to the failed dam, while significant deposition was observed further downstream. From these experiments, a benchmark was proposed to the scientific community, consisting of blind test simulations, that is, without any prior knowledge of the measurements. Twelve different teams of modellers from eight countries participated in the study. Here, the numerical models used in this test are briefly presented. The results are commented upon, in view of evaluating the modelling capabilities and identifying the challenges that may open pathways for further research. © 2012 Copyright International Association for Hydro-Environment Engineering and Research. Source


Cao Z.,Wuhan University | Cao Z.,Heriot - Watt University | Yue Z.,Yangtze River Waterway Research Institute | Pender G.,Heriot - Watt University
Natural Hazards | Year: 2011

Landslide dam failure can trigger catastrophic flooding in the downstream. However, field observation of such flooding is rarely available, while laboratory experimental studies are sparse. The mechanism of landslide dam failure and the flood has so far remained insufficiently understood. Here, we present an experimental investigation of landslide dam failure and the flood. A total of 28 runs of experiments are carried out in a flume of 80 m × 1.2 m × 0.8 m, with differing inflow discharge, dam composition, dam geometry, and initial breach dimension. An array of twelve automatic water-level probes is deployed to measure the stage hydrographs along the flume, and the video recording of the dam failure processes facilitates an estimation of the widening of initial breach. Under the present experimental conditions with dams composed of homogeneous materials, landslide dam failure is primarily caused by erosion of overtopping flow, and lateral mass collapse is also considerable during the cause of breach widening. Cohesive clay may act to mitigate the seepage through the dam and thus its subsidence and appreciably modulate the dam failure process and the flood. However, the impacts of clay may be readily overwhelmed by a large inflow discharge and initial breach. Gravels in the dam may appreciably depress the rate of the dam failure process and thus modify the flood. The present work provides new experimental data set for testing mathematical models of the flood flow due to landslide dam failure. © 2011 Springer Science+Business Media B.V. Source


Cao Z.,Wuhan University | Cao Z.,Heriot - Watt University | Yue Z.,Wuhan University | Yue Z.,Yangtze River Waterway Research Institute | Pender G.,Heriot - Watt University
Journal of Flood Risk Management | Year: 2011

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 80m × 1.2m × 0.8m, 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. © 2011 The Authors. Journal of Flood Risk Management © 2011 The Chartered Institution of Water and Environmental Management. Source


Cao Z.,Wuhan University | Cao Z.,Heriot - Watt University | Yue Z.,Yangtze River Waterway Research Institute | Pender G.,Heriot - Watt University
Natural Hazards | Year: 2011

A coupled 2D mathematical modelling study of landslide dam failure and flood is presented, complementing our experimental investigation presented in the companion paper. The model is built upon the shallow water hydrodynamic equations. The governing equations are numerically solved using the total-variation-diminishing version of the second-order weighted-average-flux method along with the HLLC (Harten, Lax and van Leer with Contact wave restored) approximate Riemann solver. Two parameters related to bed-load sediment transport and critical slope stability are calibrated using the measured stage hydrographs from two runs of the flume experiments. The calibrated model is then applied to other independent runs of the experiments featuring different inflow discharges, dam geometry, dam composition and initial breach dimensions. It is found to be able to satisfactorily reproduce the measured stage hydrographs and the widening of initial breach. The experimental observation of the prime role of the inflow discharge and initial breach in dictating the dam failure process and flood is unequivocally resolved, along with the impacts of dam geometry as well the content of cohesive clay and gravel in the dam. Interestingly, the downstream peak discharge and stage of the flood are substantially reduced by initial breach, which clearly exemplifies its role in modulating the flooding. © 2011 Springer Science+Business Media B.V. Source


Yue Z.-Y.,Yangtze River Waterway Research Institute | Cao Z.-X.,Wuhan University | Li Y.-W.,Yangtze River Waterway Research Institute | Fu Z.-M.,Yangtze River Waterway Research Institute | Yan J.,Yangtze River Waterway Research Institute
Shuidonglixue Yanjiu yu Jinzhan/Chinese Journal of Hydrodynamics Ser. A | Year: 2011

This paper presents a high-resolution two-dimensional finite-volume numerical model based on unstructured grids for unsteady two-dimensional shallow-water flow over topography with wetting and drying. The bed elevation is defined at triangle grid nodes and bed slope source is solved by DFB (divergence from for bed slope source term) method, which balanced correctly the flux gradient and source terms in Godunov-type finite volume shock-capturing schemes and by the moving wet-dry boundary as the flood rises or falls. To alleviate the problems associated with numerical instabilities due to small water depths near a wet/dry boundary, the friction source terms are treated in a fully implicit way. Finally, four tests are used to validate the solver of the present model. Results of the numerical simulation indicate that present model may accurately capture flow processes over irregular topography. Source

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