Nepal disaster exposes growing challenge of monitoring Himalayan hazards
The deadly Aug 26 disaster in Nepal shows how a warming Hindu Kush Himalaya is creating complex, cascading hazards that scientists are racing to understand and monitor.
The Himalayan region is highly tectonically-active and heavily impacted by global warming. (Photo: CNA/Jack Board)
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KATHMANDU: As the first images of a deadly torrent ripping through Nepal’s Trishuli River valley emerged on Aug 26, some of the region’s leading glaciologists were sitting in a conference room across the Chinese border in Sichuan province, watching in dismay.
Some of the scientists who know the Himalayas best were discussing the gaps in monitoring and understanding cryosphere hazards at a regional scientific network meeting.
And the mountains had just demonstrated their staggering power.
“It was really very shocking, and I think nobody who has been working in cryospheric science for decades ever anticipated this scale of disaster,” said Dibas Shrestha, an assistant professor at Tribhuvan University’s Central Department of Hydrology and Meteorology.
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The cryosphere refers to parts of the Earth system where water is frozen.
In the same venue was Miriam Jackson, a glaciologist and climate scientist with vast experience examining Himalayan glaciers and hazards. She immediately recognised the type of high-mountain hazard scientists have long been concerned about.
“It was very clear that this was a huge event, and there were going to be many fatalities and a lot of damage. I was certainly very shocked, but to be honest, not really surprised,” said Jackson, a research scientist at the Norwegian Water Resources and Energy Directorate.
A bedrock failure high in the mountains had brought down a section of rock and ice, which became a destructive flow travelling more than 100km downstream, something experts have labelled a multi-hazard cascade.
As of Sep 12, 1,386 people were killed and 5,130 are officially recorded as missing.
The disaster comes amid profound changes across the Hindu Kush Himalayan region, a massive 3,500-km mountain system spanning eight countries. It covers all of Nepal and Bhutan, and parts of India, China, Bangladesh, Afghanistan, Pakistan and Myanmar.
Global warming is fast changing the dynamics in a region known as the Third Pole, due to it having the largest concentration of snow and ice outside the Arctic and Antarctic polar regions.
Rising temperatures here – about twice the global average – and other climate change impacts are affecting glaciers, snow, permafrost and exposed slopes simultaneously, creating combinations of hazards that are difficult to anticipate, monitor and respond to, experts told CNA.
Research published this year found the glacier-covered upper reaches of Nepal’s Langtang catchment have been warming more than three times faster than lower elevations.
The transformation of the Third Pole also threatens to bring more violent disasters at the same time as it erodes the natural water storage on which huge populations downstream depend.
It means Asia’s great mountains are becoming a source of growing uncertainty.
Snow and glaciers act as natural reservoirs, regulating when and how reliably water flows, explained Benjamin Horton, the dean of the School of Energy and Environment at City University of Hong Kong.
Nearly two billion people depend to varying degrees on river systems originating in the Hindu Kush Himalaya, including the Ganges, Brahmaputra, Indus, Mekong and Yangtze.
“The transformation of the Third Pole is fundamentally a transformation of Asia’s water system,” he said.
“We should be extremely concerned because this is not a smooth transition from too much water to too little. It is likely to be an increasingly unstable period.”
Snow and glacier melt contribution is expected to increase towards mid-century before declining as the frozen reserves diminish, said Mohd Farooq Azam, a senior cryosphere specialist at the International Centre for Integrated Mountain Development (ICIMOD), a regional knowledge institution working across the Hindu Kush Himalaya.
Depending on future warming and location, scientists project the region could lose roughly a-third to more than three-quarters of its current glacier volume by 2100.
Even the eventual disappearance of glaciers would not remove the danger, said Tobias Bolch, glaciologist and professor at Graz University of Technology in Austria, as newly exposed rock would create different hazards.
Glacier loss, extreme heat, heavier rainfall, drought, ocean warming and sea-level rise are all converging as interacting hazards affecting the same people, supply chains and infrastructure systems throughout Asia, Horton added.
“The Third Pole is sometimes described as remote, but there is nothing remote about its consequences.”
UNDERSTANDING THIS DISASTER
On the morning of Aug 26, scientists found that a mass of bedrock and overlying glacial ice broke off Langtang-Lirung mountain and plunged from a height of about 5,200 m more than 2 km down to the valley floor.
It resulted in a ground impact significant enough for the United States Geological Survey to report a 5.2 magnitude earthquake.
A rush of melting ice, rock and debris entered the high altitude Lhende Khola river in Tibet, from where a large lake briefly formed before breaking and surging downstream, carrying all in its path.
Research is continuing into the exact mechanics of this particular failure, but scientists believe the mountain may have been weakened by a combination of long-term geological processes and a warming climate.
As glaciers and snow retreat, more rock is exposed to heat, while warming can degrade the permafrost that helps bind high mountain slopes together, Azam said.
Bolch has spent years studying glaciers across the Hindu Kush Himalaya. As they have retreated, he has observed some pulling back from valley floors towards steeper mountain slopes.
In areas of permafrost, ice can be frozen firmly to the rock beneath it. As temperatures rise, that bond can weaken, while meltwater seeping into cracks can further destabilise the glacier, Bolch said.
“This is for sure an impact of the changing climate and the increased temperatures. It’s hard to predict, but I’m pretty sure we will see something similar happening in the next couple of years around the world,” he said.
While scientists can observe glacier surfaces, they know little about what is happening at the glacier bed or internally, including the subtle processes that might precede this kind of failure, Shrestha said.
“There are several hidden stories and hidden signs,” he said of the unseen interior and bottom of glaciers.
“These are the things that we need to know better to anticipate these kinds of disasters in future.”
For years, much research attention and active observation has focused on large, visibly expanding glacial lakes. When they suddenly release their water, they can produce what is known as glacial lake outburst floods (GLOFs), which can be highly dangerous for communities below them.
Recent GLOFs have devastated Sikkim’s Teesta Valley in 2023 and Nepal’s Thame village the following year, where the failure of a relatively small lake triggered another downstream.
Still, the Aug 26 disaster is prompting scientists to look even beyond these relatively easier-to-monitor risks to the slow-moving threat from hanging glaciers, unstable rock slopes and thawing permafrost.
With an estimated 54,000 glaciers across the Hindu Kush Himalaya, identifying at-risk areas with unstable mountain slopes in future will rely upon cutting-edge technology and research, the experts agreed.
It is a “needle in a haystack problem”, said Simon Allen, a geoscientist and senior research associate at the Universities of Geneva and Zurich.
He explained that the latest analyses of the Aug 26 event showed movement in the area as early as 2018, which accelerated in the weeks before the disaster.
“This is easy in hindsight,” he said. “But how should authorities or scientists have known to look at this slope beforehand?”
These types of hazards are not new. But, as Jackson observed, the challenge is that they may become more frequent or intense, or occur in places where they did not before.
“In a changing environment, it becomes hard to say which areas are safe. Those that historically were safe, may be quickly becoming some of the most dangerous areas to live,” she said.
WHAT’S PREVENTING BETTER MONITORING?
Satellites can watch almost every glacier in the Himalayas. But there are scale, data and money problems stymying the most precise and real-time monitoring that could identify dangers before disaster strikes.
The challenge, Jackson said, is that while scientists can identify growing hazards in the mountains, they often cannot say when a catastrophic event will occur.
“When you can’t put a timeline on when things will happen, then the warnings aren’t always taken seriously,” she said.
Azam argued that governments should invest in highly precise commercial imagery and shift from post-disaster investigation towards pre-disaster assessment.
High-resolution imagery often becomes freely available after a disaster, like in the Aug 26 event, which helps explain what happened but not prevent it, Bolch said.
“In a perfect world”, regular high-resolution stereoscopic satellite imagery, using images taken from different angles to track changes in the mountains in three dimensions, could significantly improve monitoring, he said.
The situation is urgent, given the cryosphere is changing much faster than scientists’ ability to understand these processes and develop early warning systems, Azam added.
“It’s like we are trying to catch a train that has already started running on the platform. The train is going faster and faster, and we are trying to catch it,” he said. “There is a big lag.”
Automated space-based monitoring that could detect and alert small movements and changes in the mountains is being developed, but the technology is not ready to be used over large regions like the Hindu Kush Himalaya, said Allen.
“I’d say operationalising such approaches in the Alps is the first step, and then scaling to other larger, more challenging regions,” he said.
Another limit is political. Mountains and rivers frequently cross borders, demanding much better transboundary communication, Jackson said.
Meanwhile, human exposure is growing as tourism, hydropower and other infrastructure expand further into mountain environments. During peak trekking seasons, tourists now outnumber residents in parts of the Langtang Valley.
“In between these extreme events, which are probably going to bring more and more disasters to this region, this is a very tricky situation for the region,” Azam said.
At the same time, Nepal, for example, cannot afford to abandon its rivers, settlements or hydropower. Its steep terrain leaves limited space for settlements and infrastructure, while the country relies overwhelmingly on its rivers for electricity generation.
The latest disaster will force a rethink of how sustainable development could go ahead in mountain regions, Allen said.
“Buzz phrases like ‘building resilient infrastructure’ hold little value when you see the power of an event of that size. You simply cannot engineer solutions for events of this type,” he said.
Infrastructure designed to last 50 or 100 years is still being planned around historical climate conditions that may no longer hold, Horton said.
“The climate of the past has already gone. The danger is that too much of Asia is still being built as though it has not,” he said.
Nepal estimates it will need about US$4.8 billion to rebuild and has appealed for international climate finance and compensation, including from the global Fund for Responding to Loss and Damage.
The government is mapping settlements considered no longer habitable and drawing up plans to rebuild some communities outside flood-risk zones.
Better science and preparedness can reduce the risks, but they cannot make the Himalayas completely danger-free. Scientists say limiting future warming remains critical to slowing the changes already transforming the Third Pole.
“To be honest, I think we cannot avoid these kinds of disasters,” Shrestha said.
“The only way is to adapt and be better prepared. Nowhere in the high mountains is safe.”
Source: CNA/jb
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