New Delhi, India – On the morning of August 26, the Himalayan landscape above Nepal’s Rasuwa district changed in minutes. A mass of ice and rock broke loose high in the mountains and sent a violent surge of water, mud and debris down the Lhende Khola River. The torrent travelled through valleys, swept away settlements and infrastructure and eventually reached the Nepal-China border.
By mid-September, more than 1,400 people had been reported dead and at least 6,000 remained missing in Nepal and across the border in Tibet. Twelve hydropower plants were destroyed, while roads, bridges and homes were buried or washed away. The scale of the destruction has left scientists and disaster managers confronting a difficult question: How do you warn communities about a disaster whose trigger may occur high above them, in terrain that is difficult to monitor and where there may be only minutes to react?
Basanta Raj Adhikari, director of the Centre for Disaster Studies at Tribhuvan University in Kathmandu, described the event to Al Jazeera as unprecedented in size, affected area and mechanism. His estimate suggested that the energy involved was greater than that released by the Hiroshima atomic bomb, a comparison intended to illustrate the scale of the physical forces involved rather than suggest that the event was equivalent to a nuclear explosion. For scientists who study the Himalayas, the disaster demonstrated how quickly an event originating in a remote, high-altitude environment can become a regional catastrophe.
A warming climate is altering glaciers, snow cover, permafrost and high-altitude lakes. At the same time, roads, hydropower projects, tourist facilities and settlements have pushed deeper into mountain valleys. That combination is creating a new risk landscape in which one hazard can trigger another.
An avalanche can block a river. A blocked river can form a temporary lake. A sudden release can become a debris flow.
That debris can destroy a road or bridge, block another river and create another flood downstream. The August disaster in Nepal showed how quickly such a sequence can unfold. It also exposed a weakness in the way early-warning systems are often designed.
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