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Satellite data archives reveal unrecorded Himalayan floods

08 May 2018

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Almost 30 years' worth of Landsat observations created a comprehensive inventory of catastrophic floods caused by glacial lakes bursting through their rock dams.

A flood that tore through central Nepal in July 2016, destroying houses and roads, came from a seemingly placid source: a glacier. The Himalaya region encompasses thousands of glaciers, so glacial lake outburst floods like that summer 2016 torrent are a perennial problem. Glacial lake outburst floods occur when large bodies of glacial run-off water suddenly breach the fragile, naturally formed piles of rocks and other glacial debris, referred to as moraine dams, that held them in place. But monitoring these deluges using ground-based observations is often impractical because of challenging mountainous terrain and harsh weather conditions.

Now researchers have used satellite data spanning nearly 3 decades to assemble a census of glacial lake outburst floods across India, Nepal, Bhutan, and China. The team's algorithm identified all but one of the region's 11 previously reported floods as well as 10 previously undocumented events, observations that shed light on the prevalence of these unpredictable—and sometimes deadly—torrents.

Source: Eos - American Geophysical Union

Image credit: Jeffrey S. Kargel, Planetary Science Institute, Tucson, Ariz - Imja Lake — the long, silty lake in this 2010 photo — has grown in front of Imja and Lhotse Shar glaciers (top right) in the Himalayas. In 2016, engineers lowered Imja Lake by 3.5 meters to reduce the chances of a large glacial lake outburst flood.

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