Previous Landslides Can Triple the Intensity of Glacial Lake Floods

Scientific Reports, 20 July 2022

Even small glacial lake outburst floods in the mountains can transform into huge debris flows, sweeping boulders across large regions as loose sediment triggers additional landslides. This study found that such debris flows can worsen the loss and damage caused by future such floods. Melting glaciers generate large meltwater lakes in mountain regions. When a large piece of ice or rock breaks away and tumbles down the side of a mountain, it can trigger a landslide or avalanche that bursts the dam restraining the glacial lake, draining all the water within a few hours. Such outburst floods flow down mountain slopes with enormous energy. In 2016, a small lake in the Poiqu basin of the Eastern Himalaya burst and flooded the valley, damaging major highways, a hydropower plant, and multiple buildings. As it entered the Bhotekoshi basin in Nepal, the flood accelerated and fanned outward into a severe debris flow that crossed the international border and produced more than 70 million USD in damage. The availability of loose debris in the path of the flood, likely from previous landslides, intensified the disaster by three orders of magnitude. Authors underscore the importance of curbing global emissions to slow the retreat of high-mountain glaciers, stabilize frozen regions to prevent additional landslides, and reduce the impact of future floods on vulnerable communities.

https://www.nature.com/articles/s41598-022-16337-6