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 devastating floods that have swept through the Nepal–Tibet border region are first and foremost a human tragedy. Hundreds of people have died or remain missing.
But as scientists begin to reconstruct what happened, the event also exposes something fundamental about the way we understand natural hazards in high mountain regions. Mountains and rivers do not reset after an extreme event. A landslide changes a slope.
A flood rearranges a river. A retreating glacier exposes sediment and unstable ground. Each disturbance changes the conditions in which the next one occurs.
In the Himalayas, those connections can turn individual hazards into destructive hazard cascades. Early satellite and seismic evidence indicates that this disaster began high in the mountains with the collapse of part of a slope and steep glacier in Tibet. A huge mass of ice and rock traveled rapidly into the valley below, mobilizing water, sediment and debris that then spread through the river system and into Nepal.
The precise mechanics of the event will take time to establish. But describing it simply as a flood captures only the final stage of a much longer process. I am involved in a UK–Indian academic project that starts from a simple proposition: hazard risk in the Himalayas is not static.
For instance, retreating glaciers can leave behind unstable slopes and large stores of loose sediment. Some have been described as "sediment bombs" because huge quantities of material can remain in a valley until released by another landslide, severe rainfall or a flood. The first hazard therefore changes the landscape in which the next one happens.
Extract — continue reading at the source.
