This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The deadly flash flood in Nepal on Wednesday was likely caused by a huge chunk of a glacier that broke off and temporarily dammed a river, according to preliminary investigations by scientists. That may have led to the backed-up water surging downstream with enormous force a few hours later, they suggested.
Scientists are still piecing together information from satellite and ground-level data to figure out exactly what happened to cause the flood, which killed at least 353 people and left more than 1,300 missing, including foreigners and pilgrims. Geological Survey on Wednesday reported a magnitude 5.2 glacier collapse that sent debris flowing downstream with catastrophic impact on communities. It said its determination was based on data from nearby seismic stations, long period seismic waves and satellite imagery.
"A lower part of a glacier has really come off," said Jakob Steiner, a geoscientist at the University of Graz in Austria who is currently based in Bangladesh. "If you look at the imagery it's like someone cut with a huge knife through the whole lower part and it fell off." Steiner said a mass of glacial ice dropping from a great height could have felt like a bomb exploding, resulting in the chaos that followed. Scientists said it is too early to draw a direct connection between global warming and Wednesday's catastrophe.
However, they said that as Earth's temperature rises because of human activities such as burning oil, gas and coal, the chances of such disasters increase, especially in the Himalayan mountains, which are warming considerably faster than many other parts of the world. "We have to be cautious and not draw a connection yet. However, rising temperatures are changing the Hindu Kush Himalaya region and melting glaciers," said Saswat Sanyal, a disaster risk reduction specialist at the Kathmandu-based climate research group International Centre for Integrated Mountain Development.
Hundreds have lost their homes across the Himalayan region, and officials reported large-scale damage to critical infrastructure, including hydropower dams, roads, buildings and bridges in the region. Water levels in rivers across the flood-affected region rose by as much as 9 meters (29.5 feet) in 30 minutes as a result of the surge from the glacial detachment upstream, researchers at the Kathmandu-based climate research group said. "It was a huge rise, a huge surge of water that happened suddenly," said Sanyal.
Preliminary evidence suggests a large volume of ice and rock may have plunged into the Lhende Khola, a tributary of the Bhote Koshi River. Researchers said the collapse could have displaced water and picked up loose sediment and boulders, producing a powerful surge downstream. Researchers are also examining whether debris temporarily dammed the river before the impounded water burst through, magnifying the flood.
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