More than a week after devastating flash floods triggered by a glacier collapse engulfed the Himalayan border region of Nepal and China’s autonomous region of Tibet, authorities were still trying to identify the bodies of victims of the disaster. Meanwhile, Nepal said it would have to rebuild at least 20,000 homes in the affected areas.
According to the latest provisional toll, the floods left more than 1,270 people dead and more than 4,700 missing.
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But while the region is slowly recovering from the catastrophe, questions are emerging about Nepal’s prevention and early warning systems. With global warming increasingly melting glaciers across the world, experts warn that such collapses will become more common and that more effective monitoring technologies are urgently needed.
A disaster too fast to predict
A report by the HiRISK consortium of experts – a body that provides risk data related to the High Mountain Asia (HMA) region – detailed that on August 26, the glacier situated in Langtang Lirung, which comprises a Nepal peak of 7,234 metres (23,734 feet) in height and underlying bedrock, collapsed at 8:37am local time.
The collapse led to a flash flood that travelled at an average speed of 193 kilometers per hour (120 mph) down the Trisuli river valley, a cross-border river that originates in Tibet and is one of the main tributaries of the Gandaki river basin in central Nepal.
The Kathmandu Post reported that the chief district officer of the Rasuwa district informed Nepal’s Department of Hydrology and Meteorology of the flood 23 minutes later, and that alerts to the communities across the four local districts of Rasuwa, Nuwakot, Dhading and Chitwan came only 38 minutes after the glacier collapsed. The notifications warned them to move to higher ground, at which point the flood had already travelled downstream.
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The region is accustomed to monsoon-related floods, but typically these rise more gradually, leaving sufficient time to warn and evacuate the population. Another risk that tends to be watched more closely is the potential breaking of glacier lakes, but glacier collapse itself is harder to predict.
According to the HiRISK report, early-warning systems had been set up recently in the region, focusing on several glacial lakes in China, but no operational early-warning system had been installed for glacier-related risks.
“Given the rapid speed of the initial avalanche, warning time from conventional in-channel systems would have been minimal and likely insufficient for successful evacuation,” the report noted.
Manoochehr Shirzaei, a geophysicist at Virginia Tech, said that satellite images taken of the glacier and the surrounding rocks a few days before the event already showed an acceleration in their movement.
“What we think happened is that this glacier had probably been moving for years – possibly decades – and then, over the past few months, its motion accelerated,” Shirzaei said. “That acceleration could be linked to climate warming, more runoff at the base, or a change in slope. We don’t yet know if the failure was only within the ice or also involved the bedrock. But the mass detached, travelled a long distance and created the disaster downstream.”
The HiRISK report states that, in hindsight, there were certain warning signs indicating that the ice surface had accelerated just before the event and that “melt water had turned visibly brown” by August 24.
The report also details that the mass movement “caused a seismic signal at a magnitude larger than four, suggesting that such seismological systems could be used in future in seismic-based early warning setups across large scales”.
In an article in The Conversation, Prashidha Khatiwada, a structural and seismic engineer at Swinburne University of Technology in Melbourne, wrote that the event highlighted the limitations of Nepal’s current warning systems.
“For communities close to the source, flood warnings simply came too late,” he shared.
What could early-warning systems look like?
Khatiwada argues the country must make monitoring systems more resilient, map risks more effectively and automate warning systems – not only via cellphones but also through back-up systems such as “sirens, radio and trained local task forces”.
Technologies for measuring the early warning signs of glacier collapse and risk mitigation already exist, as was the case with the Birch glacier collapse in the Swiss Alps in 2025, where glacier movements had been detected and the village of Blatten below was evacuated before a massive and unprecedented landslide engulfed most of it.
But for Philip Prince, a geologist at Virginia Tech, although the equipment used to detect the early warning signs in this instance had been relatively straightforward to install in the Alps, this would not have been the case in the Himalayas, where the terrain is much more challenging and the area is simply much too vast.
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According to Shirzaei, existing monitoring technologies are insufficient to predict events such as that of August 26 and systems with a layered approach are needed in order to prevent not only glacier and rock collapses, but also their cascading effects.
Such could include wider satellite monitoring to identify hotspots and changes in motion or acceleration, scenario testing and local monitoring when possible, but these would need to come hand in hand with more effective alert warnings to the surrounding communities.
“We have the technology to build a reliable early‑warning system, but it has to be layered,” he said. “And all of this only works if it’s paired with planning and routine training so communities know exactly what to do and where to go when an alert comes.”
For Prince, however, the kind of localised, high-precision monitoring that would be needed is almost impossible faced with the realities of the Himalayas.
“If you compare it to the European Alps, for example, it’s a mountain range that is simply more accessible for study than the Himalayas,” he said. “The ability to get that kind of monitoring and precise movement measurements in this terrain is just almost impossible.”
Melting Himalayas? Nepal disaster exposes growing risk of glacial flooding
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On top of this, Prince argues that the sheer scope of the highest mountain range in the world makes it particularly hard for scientists to know which area to focus on among the hundreds of sites that could be at risk.
“We can absolutely look back and learn from the event,” he said. “But the amount of resources that would be required to monitor all of the possible dangerous features like that throughout the Himalayas is absolutely incredible.”
Shirzaei said that disaster management in the shared mountain region would also require more cross-border cooperation and open data.
“This is a transboundary issue that requires cooperation between neighbouring countries and open access to data,” he said. “I’ve heard reports that Chinese authorities did not share key information after the event, and that needs to be resolved. Data that protects communities should be accessible.”
For experts, the threat that climate change could accelerate risk of glacier collapse makes comprehensive monitoring and emergency systems all the more urgent.
According to the HiRIKS report, the glacier had greatly receded in previous decades and “more recent glacial recession potentially facilitated eventual failure processes”.
“Warming temperatures certainly can contribute to the conditions that will cause a collapse like this and that’s something we will have to think a lot about in coming years,” Prince said.
This story originally appeared on France24
