China-Nepal floods: first research shows that no one could have outrun debris flow

In a recent study, researchers from the Chinese Academy of Sciences estimated that the devastating debris flow that struck a border crossing between China and Nepal last week would have been impossible to outrun. The surface velocity of the flow reached 19 metres per second (62 feet per second) when it hit the checkpoint at Gyirong Port in Tibet, almost twice the speed of Usain Bolt's 100m world record and 50% faster than his top speed.

The disaster was triggered by the collapse of a high-altitude glacier in Nepal, leading to a sequence of events that included ice avalanche, debris flow, mudslide, and flood. The researchers emphasized the short response time, which put pressure on rapid identification, information transmission, and emergency decision-making. The flow continued downstream, taking between 46 and 75 minutes to reach a bridge on Nepal's Trishuli River 52km away, providing a potential window for disaster response.

However, the exact warning time for downstream areas remains uncertain due to numerous factors. Meanwhile, another study published in Science Bulletin described the catastrophe as a sudden failure stemming from long-term glacier dynamics rather than an immediate trigger like heavy rainfall. The study found seismic precursor signals hours before the collapse coincided with smaller-scale snow and ice activity.