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

Not even the world’s fastest sprinters could have outrun the devastating floodwaters that struck a border crossing between China and Nepal last week, according to one of the first peer-reviewed assessments of the disaster.

Researchers from the Chinese Academy of Sciences (CAS) calculated that the surface velocity of the debris flow was 19 metres per second (62 feet per second) when it struck the checkpoint at Gyirong Port in Tibet.

This is almost twice Usain Bolt’s average speed when he set the 100 metres world record of 9.58 seconds in 2009 and 50 per cent higher than his top speed.

In a paper posted online on Tuesday by the Chinese-language journal Yangtze River, the team used digital models and frame-by-frame analysis to reconstruct the event, which was triggered by the collapse of a high-altitude glacier in Nepal.

“This disaster involved a continuous transition from ice avalanche to debris flow, then to mudslide and finally to flood,” wrote the team from CAS Institute of Mountain Hazards and Environment.

“The time from the occurrence of the ice avalanche to its impact on the Gyirong Port was extremely short, and the effective response time was limited, which put forward higher requirements for rapid identification, information transmission and emergency decision-making.”