Glacial Lake Outburst Flood Evolution Simulation Under Different Breach Mechanisms

Glacial lake outburst flood (GLOF) is one of the glacier disasters in Tibet. The characteristic of GLOF is wide range, long duration time, great harm and often accompanied by mudslides. The typical dangerous glacial lake------Huanghu and relevant region, located in Nianchu River Basin, Tibet, China were selected as the study area for this paper. The information of the meteorological, hydrological, topographical and geomorphological was investigated. Based on DEM data and rectangular mesh, a two-dimensional dam-break flood numerical model was used to simulate outburst flood evolution under different breach mechanisms. The result shows that the breach mechanism has a larger influence on peak flow discharge, maximum water depth and maximum flow velocity in upstream channel. It has a smaller influence in midstream and downstream channel. In upstream channel, the peak flow discharge of small breach scenario is greater than that of large breach scenario. The peak flow discharge of gradually breach scenario is less than that of instantaneously breach scenario. In midstream and downstream channel, the peak flow discharge of the gradually small breach scenario is the maximum.Gyantse is one of the important population and economic centers in NianChu River upstream. According to different simulation scenarios, we have got the basic results when the outburst flood arrived at Gyantse. For the worst scenario2, the arrival time of flood in Gyantse was about33.5h and the peak discharge in Gyantse was about1914.8m3/s. For the best scenario6, the arrival time of flood in Gyantse was about34.0h and the peak discharge in Gyantse was about1758.4m3/s. Both of them were greater than the peak discharge of the design flood with recurrence interval of ten thousand years (less than1000m3/s). Obviously, if the glacial lake dam break, the outburst flood may cause serious damage on downstream, especially in Gyantse county.There are two main innovations of this study.1) This study considered different breach mechanism of glacial lake.2) The simulated potential dangerous glacial lake has not been studied by hydrological models before. The results have important practical significance to improve the potentially dangerous glacial lakes databases of Gyantse and develop flood warning strategies scientifically.