Daily Weird News Report
Satellite imagery reviewed after deadly flooding along the Nepal-China border shows that the disaster may have begun with the collapse of both a glacier and the mountain bedrock supporting it.
The failure occurred near Langtang Lirung peak, close to the border with Tibet. According to geomorphologists Kristen Cook and Dan Shugar, early images were partly obscured by clouds and dust. Clearer imagery obtained Thursday showed that the event involved more than a broken section of ice: a much larger portion of the mountainside had also given way.
The collapse sent boulders and ice into a steep, narrow valley. As the ice melted, the debris continued moving downstream, according to Cook of Université Grenoble Alpes. Water and mud several stories high then swept through nearby communities.
The Trishuli River rose dramatically. Before-and-after satellite images of Kolpurtar, Betrawati and Syapru Besi show a river that is wider and heavily discolored by sediment. In some places, it overtopped its banks; in others, debris filled the channel. Villages and towns along the river appear buried beneath brown mud and rubble, although some buildings remained visible in Betrawati.
Floodwaters and debris destroyed or swept away buildings in Syapru Besi, a tourist destination associated with the trek to Langtang. Imagery also showed a widened side river, apparently pushed upstream by the force of the flow.
The flooding killed hundreds of people in Nepal and Tibet, while hundreds more were reported missing, including foreigners and pilgrims, the report said. Rescue teams were searching affected areas as scientists examined the satellite evidence.
Mountain geographer Alton Byers called it the largest glacier flood he had seen and said warming-related glacier and permafrost loss could be involved. He argued that weakening permafrost may make high-altitude rock, ice and soil less stable.
Cook and Shugar cautioned that there is not yet enough evidence to directly connect this particular collapse to climate change. Cook said slope failures and landslides occur naturally, although a warmer climate could make similar events more likely.
