The two main mechanisms of Glacier Lake Outburst Flood in Tibet, China

With the global warming, the disasters of Glacier Lake Outburst Flood (GLOF) have taken place frequently in Tibet in recent years and attracted more and more attention. A systematic survey was conducted on the 19 GLOFs in Tibet to study their two main mechanisms. Investigations indicated that all the events occurred in end-moraine lakes, and the outburst occurred partially and instantly. And the breach had the shape of an arc or a trapezoid in overflow outburst and its top width was 3-5 times more than the height. The two main mechanisms of GLOFs in Tibetan end-moraine Lake were overflow and piping, and the overflow mechanism caused by iceberg collapse was dominated in most cases. A formula was proposed to calculate the critical thickness of iceberg tongue that determines the collapse. Granular analysis of the moraine materials revealed that seepage deformation is crucial in the outburst process. Finally, we conducted a case study of the Guangxiecuo Lake to show its possible process of outburst and estimated the peak discharge of the resulted flood.