India, Aug. 29 -- We are living through another great crisis in the Himalaya. On August 26, a mass of rock and ice collapsed high above the Nepal-Tibet border and became a devastating debris flow along the Bhote Koshi-Trishuli river system. Homes, roads, bridges and hydropower facilities were swept away, while hundreds of people were killed or remain missing. The exact sequence is still being reconstructed, and scientists have cautioned that there is not yet evidence to call it a conventional glacial-lake outburst flood or GLOF. What is clear is that this was not one event in the ordinary sense. It was a cascade: collapse, acceleration, entrainment of debris and destruction far downstream.

The disaster is therefore not only a warning abo...