Two disasters, one Himalayan warning: Sikkim’s GLOF lessons for Nepal

Gangtok: The Himalayan disaster unfolding across Nepal is confronting the region with a stark reality: when ice, rock and water move together at high altitude, the warning window can shrink to minutes.

On August 26, a large section of glacier broke away near the Nepal-China border, triggering an ice-and-rock avalanche that temporarily blocked the Lhende Khola before unleashing a devastating surge into Nepal’s Bhotekoshi and Trishuli river systems. The Trishuli rose by as much as nine metres in just 30 minutes, sweeping away homes, roads, bridges and hydropower infrastructure.

The disaster has drawn an immediate comparison with Sikkim’s own South Lhonak Glacial Lake Outburst Flood (GLOF) of October 2023, and officials say the lessons learnt from that catastrophe could now help Nepal.

Sikkim State Relief Commissioner Rinzing Chewang Bhutia said the state has more than 400 glacial lakes, large and small, of which 16 have been classified as highly vulnerable: 13 in North Sikkim and three in West Sikkim.

“We are continuously monitoring the lakes,” Bhutia said, adding that sensors have been installed at most vulnerable sites to track changes in lake volume and water levels. The monitoring network has also been strengthened with early-warning systems and automated weather stations, particularly in North Sikkim.

This is perhaps the biggest difference between Sikkim today and Sikkim before October 2023: the state is no longer only studying the threat, but it is building systems to see it coming. Bhutia said the mechanism behind Nepal’s disaster bears similarities to what happened at South Lhonak.

At South Lhonak, a portion of the glacier fell into the glacial lake, displacing a huge volume of water and sending a destructive flood downstream. In Nepal, experts have found that a major glacier collapse and subsequent ice-rock debris flow triggered the catastrophic flooding along the Lhende-Bhotekoshi corridor.

The difference is critical.

Sikkim’s 2023 disaster was a GLOF triggered by a glacier impact on a lake; Nepal’s August 2026 disaster appears to have involved a glacier collapse, debris and temporary river blockage. Yet both demonstrate the same vulnerability of Himalayan settlements and infrastructure situated downstream of unstable high-altitude terrain.

And Nepal’s exposure is enormous. The country has more than 2,000 glacial lakes, with at least 21 identified as potentially dangerous, according to recent reporting.

For Sikkim, the South Lhonak disaster became a painful but important turning point. “After the October flood due to the South Lhonak incident, we had the opportunity to study the subject in detail. We have built up our own capacity on how to handle this kind of situation,” Bhutia said.

That capacity now includes scientific assessments of vulnerable lakes, real-time monitoring, early-warning systems and automated weather stations.

Chief Minister Prem Singh Tamang (Golay) said Sikkim is also working with the state’s Science and Technology Department and Central Government agencies to strengthen prevention and preparedness.

He said the Government of India has asked Sikkim to take forward the model it has developed. “We are working on the same model and taking it to the next stage,” Golay said.

The state is also working on particularly vulnerable low-lying areas, including relocation where necessary. Restoration and reconstruction of infrastructure damaged in the 2023 disaster are continuing, while damage to bridges and other infrastructure is being documented.

Nepal now faces the same question Sikkim once faced. The immediate challenge in Nepal remains rescue.

The August 26 flood destroyed critical infrastructure along the Bhotekoshi corridor and affected hydropower projects, with rescue teams now searching tunnels and debris for trapped workers. By August 31, Reuters reported 903 deaths in Nepal and more than 4,247 people missing, including hundreds of hydropower workers.

But once the rescue phase gives way to recovery, Nepal will face a much bigger question: How does a Himalayan region prepare for a disaster that can originate kilometres above its settlements and arrive with almost no warning? Sikkim believes part of the answer lies in what it has learnt the hard way.

Sikkim is not only sending relief to Nepal. It is offering something potentially more valuable for the future: experience.

For Sikkim, this is therefore more than a humanitarian mission.

It is one Himalayan disaster-affected region reaching out to another, not only with medicines and food, but with lessons written in its own scars.

The message from Sikkim is increasingly clear: in a warming Himalaya, disaster preparedness cannot begin after the water starts moving. It has to begin while the glacier is still being watched.

Views expressed are that of the author and do not reflect EastMojo’s stance on this or any other issue. The author is a journalist with News18 Assam & Northeast, covering Sikkim.

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