Why the glacier collapse behind Nepal’s flash flood is a warning sign for the Himalayas

Nepal is still reeling from the aftermath of the deadly flash floods that claimed over 350 lives on Wednesday. Hundreds are still missing and rescue teams are racing against time to look for survivors amid the mountain of debris left behind by the flash floods in Nepal's Nuwakot and Rasuwa districts.

According to scientists, the flash flood in the Trishuli River was caused by a glacier collapse across the border in Tibet, not by an earthquake, as initially believed. Based on seismic and satellite data, as well as videos of the event, scientists say the chain of events began after the bedrock beneath gave way, leading to the collapse of a very large section of a glacier.

Seismic waves equivalent to a 5.2 earthquake

According to the US Geological Survey, the impact generated seismic waves equivalent to a 5.2-magnitude earthquake, and a large volume of ice and rock may have plunged into the Lhende Khola, a tributary of the Bhote Koshi River.

“What we’ve certainly confirmed — there was a large ice avalanche, probably a mixture of ice and rock, which detached and then became fluid and then transformed into this devastating flood,” Simon Allen, a research associate at the University of Zurich who studies glacial hazards in the Himalayas, told Bloomberg.

Rijan Bhakta Kayastha, a climate researcher and professor at Kathmandu University, told The Kantipur Post that an avalanche appeared to have blocked the Lhende river before the blockage gave way.

“We suspect an avalanche on the Nepal side blocked the Lhende river,” Kayastha said. “An earthquake occurred at around the same time, but we do not yet know whether it helped trigger the avalanche.”

Climate change behind increase in natural disasters

In recent years, Nepal and adjoining countries, including India, Bhutan, China, and Pakistan, which share the Himalayas, have seen an increase in natural disasters linked to global warming and climate change.

The Himalayas, the youngest mountain system on Earth, are highly susceptible to global warming, leading to the rapid loss of their snow cover.

In March this year, the International Centre for Integrated Mountain Development (ICIMOD)stated in a report that glaciers across the Hindu Kush Himalaya (HKH) are melting at an accelerating rate, with ice loss rates doubling since 2000.

“HKH holds the largest volume of ice outside the poles, with an inventory of over 63,700 glaciers covering nearly 55,782 square kilometres. These glaciers are the source of at least ten major Asian river systems, supporting the food, water, energy, and livelihood security of billions. However, around 78% of this glacier area, located between 4,500 and 6,000 metres above sea level, is highly exposed to elevation-dependent warming,” it noted.

China warns of more floods

Following the glacier collapse in Nepal, China’s Ministry of Water Resources on Thursday issued a warning that a significant barrier lake has formed near the confluence of the Chhochen Khola and Purepu Tsangpo rivers.

According to China Central Television, another 3 million cubic meters of water is expected to flow into the lake over the next three days, posing a high risk of a breach.