AP: Nepal flooding linked to mountain slope collapse

A catastrophic flood in Nepal near the Tibetan border was caused not only by a glacier collapse but also by the failure of a section of the mountain slope beneath the glacier on Langtang Lirung peak, according to geomorphologists cited by the Associated Press.

Kristen Cook of the University of Grenoble Alpes and Dan Shugar of the University of Calgary examined satellite images taken before and after the disaster. While the initial images were obscured by clouds and dust, images captured the following day showed that part of the mountain slope beneath the glacier had collapsed.

Millions of tonnes of rock and ice fell into a narrow valley and moved rapidly downhill. As the ice melted, it mixed with water, soil and debris, forming a powerful debris flow that reached several storeys in height in some areas.

The flow entered the Trishuli River valley, where satellite images showed the river had widened significantly around Kolpurtar, Betrawati and Syapru Besi. The river water also changed from greenish to brown and almost black because of the large amount of soil and debris carried downstream.

Syapru Besi, a tourist centre and starting point for treks to Langtang, was particularly badly affected. The flow destroyed and swept away buildings, while debris altered the river channel in some areas.

Scientists described the event as one of the largest observed glacial floods. However, researchers have not established a direct link between the disaster and climate change.

Mountain slopes can collapse naturally, although permafrost thawing may weaken high-altitude rock and increase the risk of such collapses. Researchers therefore regard climate change as a possible factor contributing to mountain slope instability, rather than a proven sole cause of the flooding.

By Aghakazim Guliyev