| Debris flows and floods caused by outburst of glacial lake have occurred frequently in the Himalaya of South Asia. The outburst of glacial lakes typically occurs due to moraine dam failure caused by glacier mass movement leading to a rapid rise of water level, seepage flow, earthquake, landslides, ice/rock fall and a surge. The debris-flows and floods caused by glacial lake outburst events can cause catastrophic sediment disasters and flooding in the downstream areas along the river valley. The risk of these disasters has been increasing tremendously by global climate change. It is thus necessary to investigate debris-flow and flood characteristics from potentially dangerous glacial lakes in order to manage the hazards and risk in the areas. In this study, numerical and experimental analyses are carried out to predict debris-flow and flood characteristics caused by outburst of glacial lake due to moraine dam failure. The moraine dam failure due to seepage flow and water overtopping has also been investigated. The relationships between peak outburst discharges with the volumes of lake water have also been analyzed. As a case study, debris-flow and flood characteristics caused by potential outburst floods from the Imja glacial lake in the Himalaya of Nepal have been computed by using numerical model. The Imja glacial lake is the rapidly developing and most dangerous lake in Nepal. The characteristics of debris flows and floods caused by potential outburst of the Imja glacial lake due to moraine dam failure by water overtopping are analyzed. The erosion and deposition processes along the river valley are also considered in the analyses. The predicted results of debris-flow and flood characteristics such as outburst discharge, peak flow, maximum flow depth, sediment concentrations and riverbed variations can be useful for effective preventive measures, river basin management and infrastructure planning in the river basin. Moreover, it can be also useful to raise awareness of local peopleand preparedness for outburst flood disasters. |
