Unstable Tibetan Plateau risks cascading disasters as glacier losses mount in Nepal, China

Glaciers on the Tibetan Plateau are likely to become more unstable, which may lead to more collapses and collateral disasters, a senior climate official warns as the death toll from last week’s catastrophic landslide and flood on the China-Nepal border continues to rise.
“Over the past 60 years, the glacier area on the Tibetan Plateau has shrunk by around 24 per cent, with around 7,000 small glaciers disappearing completely,” Gao Rong, deputy director of China’s National Climate Centre, told a press briefing on Wednesday.
“Looking ahead, the structural stability of glaciers across the Tibetan Plateau will decline further. Glacial disasters are likely to become more frequent and could amplify in destruction and reach through cascading effects.”

China has reported 21 deaths and 541 people missing as of Wednesday after a glacier collapsed at Langtang Lirung on the Nepalese side of the border on August 26. In Nepal, the death toll rose to 1,114 by Wednesday afternoon, with about 3,900 people still missing.
Beijing has stepped up cross-border support to its neighbour. Guo Jiakun, a spokesman for the foreign ministry, said on Wednesday that China’s second batch of emergency supplies had arrived in Kathmandu on Tuesday afternoon, accompanied by five DNA identification experts. A third shipment and a second expert team were being prepared.
After working for seven days, Beijing on Wednesday cleared the road to Gyirong Port, which was hit hardest on the Chinese side by the mudslide. Heavy machinery has reached the checkpoint area to aid a deeper search.

The mudslide created by the glacier collapse travelled 22km (13.7 miles) along the valley and reached the Gyirong Port border crossing in just seven minutes, according to an initial assessment last week.
Scientists stress that hazard evaluations can no longer rely solely on measuring initial collapses.
A study released on Tuesday, led by the Institute of Tibetan Plateau Research at the Chinese Academy of Sciences, alongside the Chinese University of Hong Kong, Wuhan University and other institutions, found that downstream erosion was critical to the scale of destruction.
Analysing satellite and field data from Gyirong County, researchers found that collapsing ice and rock swept down the 22km valley, scouring the riverbed, entraining bank debris, and mixing with water, turning a high-elevation collapse into a devastating mudslide.

Therefore, the Chinese research suggested, disaster risk assessment in the high-mountain cryosphere must look beyond the initial failure volume of material breaking away from the mountain, and include the valley bulking potential – the capacity to increase the size of a landslide as it travels downhill – and downstream exposure.
“What truly determines risk is not just how much collapsed on the mountain, but how much can be entrained in the gully, and what critical infrastructure and populations downstream are exposed to the hazard chain,” it said.
An article published in Nature on Wednesday highlighted the urgent need to upgrade future monitoring and forecasting systems.

The disaster proved difficult to predict because it was triggered by the sudden failure of a high-altitude glacier-rock system rather than typical signals, such as extreme rainfall or rising glacial lakes, according to the article.
Manoochehr Shirzaei, a geophysicist at Virginia Tech in Blacksburg, told Nature that conventional monitoring tools fell short in predicting such disasters, and stressed the need to have better integrated detection systems.
The article said: “What is still largely missing is a regional satellite-based system that routinely searches for accelerating glacier and rock-slope deformation and then connects that information directly to downstream flood and avalanche modelling”.