Satellite Images Point to Landslide as Cause of Deadly Nepal-Tibet Floods

As rescue teams continue to search for survivors after catastrophic flooding along the Nepal-China border, earth scientists are using satellite imagery to piece together what caused the disaster that killed hundreds on Wednesday.

Initial images were obscured by clouds and dust, but clearer views from Thursday revealed that a large section of bedrock beneath the Langtang Lirung peak had collapsed, taking a massive chunk of glacier with it. The debris — boulders and ice — thundered into the valley below.

“You have this big bedrock failure that took part of the glacier with it,” said Dan Shugar, an associate professor at the University of Calgary. He described the scene downstream as heart-wrenching, with villages buried under debris.

Geomorphologist Kristen Cook of the Université Grenoble Alpes explained that after slamming into the valley floor, the debris continued moving through the steep, narrow valley as ice melted, sending water and mud several stories high through communities.

Satellite images show the Trishuli River has widened significantly and turned brown with sediment. Towns like Syapru Besi, a popular trekking gateway, have been devastated, with buildings toppled and swept away.

Alton Byers, a mountain geographer at the University of Colorado at Boulder, called it the largest glacier flood he has ever seen. He believes climate change is a likely factor, as warming melts permafrost that has held high-altitude rock and ice together for millennia, making slopes unstable.

While Cook and Shugar caution that a direct link to climate change cannot yet be confirmed, they agree that such events may become more frequent as the climate warms. “Not this big, hopefully not this big,” Cook said.