The disaster began high in the Himalayas, above remote villages in Nepal, where few could have anticipated what was about to unfold.
On August 26, an enormous mass of ice, rock and debris broke away near the Nepal-Tibet border and thundered down the mountainside. Within minutes, the isolated Himalayan terrain had been transformed by a deadly sequence of events.
The avalanche struck the Bhote Koshi river system, blocking and altering its flow before triggering a powerful surge downstream. The floodwater tore through mountain valleys at tremendous speed.
Bridges were swept away, roads became inaccessible and buildings were buried under mud, rocks and debris. In Betrawati, satellite images later showed sections of the town's commercial centre covered by debris, while power infrastructure and crucial connections to the outside world were also damaged.
But the most worrying discovery emerged only after the flood.
Satellite imagery of the affected region showed that the avalanche had created a new lake near the disaster's source. Water was accumulating at high altitude behind the debris, prompting concerns that another outburst could occur in an already severely damaged river system.
For India, the devastation in Nepal carries a troubling warning. The Himalayas do not stop at national borders.
The glaciers, unstable slopes and rapidly expanding high-altitude lakes that have raised alarm in Nepal are also present across the Indian Himalayas.
From Himachal Pradesh and Sikkim to Arunachal Pradesh, glaciers are shrinking, new lakes are appearing and existing water bodies are expanding.
Could a similar Himalayan disaster strike India?
INDIA ON ALERT AS THE HIMALAYAS BECOME MORE UNSTABLE
Scientists caution against assuming that India would experience an exact repeat of Nepal's disaster. Every Himalayan glacier, mountain and river valley has different geological conditions and potential triggers.
However, studies of the Indian Himalayas are revealing warning signs that are becoming increasingly difficult to overlook.
The concern is no longer limited to whether a glacial lake could burst.
The bigger danger lies in a chain reaction in an already fragile mountain environment: a glacier could collapse, an avalanche could plunge into a lake, a landslide could block a river, heavy rainfall could destabilise a slope, and millions of tonnes of water and debris could suddenly surge downhill.
In the narrow and increasingly populated Himalayan valleys, communities may have very little time to respond.
This has prompted a critical question across the Indian Himalayas: could India face a flash-flood catastrophe similar to Nepal?
COULD INDIA FACE A NEPAL-LIKE FLASH FLOOD?
Scientists do not have a straightforward yes-or-no answer.
There is no scientific basis for predicting that Nepal's disaster will simply be repeated in India. The glaciers, geology, triggers and river systems differ from one location to another. Nevertheless, the broader warning signs are becoming increasingly apparent.
Across the Himalayas, glaciers are retreating, lakes are expanding, slopes are becoming unstable and infrastructure is reaching deeper into narrow mountain valleys. The conditions capable of producing disasters are present.
The uncertainty is not about whether the mountains are changing, but about exactly when and where the next chain of events might begin.
Professor Dericks Praise Shukla, Professor of Remote Sensing and GIS at IIT Mandi, said the first priority is identifying where the greatest danger is concentrated.
His team studied Himachal Pradesh and identified around 2,000 lakes, comparing their sizes between 2015 and 2025. The lakes were categorised based on whether they remained directly connected to glaciers, had become disconnected or were close enough to potentially receive glacier-fed water.
Lakes that continue receiving water from melting glaciers are particularly significant because they constantly receive fresh inflows.
However, an expanding lake does not necessarily mean that a disaster is imminent.
That distinction is among the key findings of the research.
The IIT Mandi assessment looked beyond lake size and examined the material forming the natural barriers that contain the water. A lake held back by solid bedrock presents a very different hazard from one confined by loose debris. Moraine dams may be more stable than unconsolidated debris, but they are still weaker than bedrock.
Researchers also examined the dimensions of the natural barriers, including their height, width and length, as these characteristics can influence the likelihood of failure.
The study found that both the number and total area of glacial lakes in Himachal Pradesh increased over the past decade. Using several parameters and expert assessments, researchers ranked the lakes according to their potential danger, with around nine identified as highly critical.
However, a hazard does not automatically translate into risk.
COULD GLACIAL LAKES BREACH?
A lake may contain enough water to cause severe flooding if its natural barrier fails. But if there are no settlements, roads, hydropower facilities or other infrastructure downstream, the consequences could remain relatively limited.
On the other hand, even a smaller event can become catastrophic if it occurs in a densely populated valley filled with infrastructure.
Risk arises when people or infrastructure are exposed to the path of a hazard. Such vulnerable elements can include villages, roads, bridges, tunnels, dams, schools and healthcare facilities.
Therefore, an expanding lake becomes far more concerning when communities and critical infrastructure are located downstream.
This distinction is important when assessing lakes such as Samudra Tapu in Himachal Pradesh.
The lake is linked to the Tapu Glacier, is relatively large and has been expanding. A breach could potentially release a substantial flood. However, researchers assess its overall downstream risk as comparatively lower because settlements and other assets are located at a considerable distance and the downstream river gradient is relatively gentle.
That, however, does not mean India can afford to become complacent.
INDIA NEEDS STRONGER MONITORING
The Himalayan region is especially dangerous because disasters can trigger further disasters.
An avalanche involving ice and rock can plunge into a lake. A landslide can block a river, creating a temporary water body.
Heavy rainfall can destabilise slopes, while earthquakes can weaken natural dams. An expanding glacial lake can eventually breach.
One event can therefore set off another.
Nepal's disaster demonstrated this cascading nature. According to an analysis by Suhora Technologies, the event was triggered by an ice-rock avalanche rather than a conventional Glacial Lake Outburst Flood, or GLOF. The debris subsequently altered the river system and contributed to the formation of a new lake near the source of the disaster.
Satellite imagery from August 27 showed the newly formed water body in the Lhende Khola region, covering roughly 20.25 hectares. A lake created following an avalanche and debris-flow event could continue collecting water, making its stability an important focus for monitoring.
Union Home Secretary Govind Mohan reviewed the preparedness of Himalayan states and Union Territories for risks linked to Glacial Lake Outburst Floods and snow avalanches on Thursday.
The meeting examined state- and UT-specific vulnerabilities and preparedness measures, with an emphasis on converting mitigation plans into concrete action at district and local levels.
INDIA HAS ALREADY EXPERIENCED GLACIAL DISASTERS
India has witnessed the destructive potential of Himalayan cascading hazards before.
The 2021 Chamoli disaster, the South Lhonak Lake outburst in Sikkim in 2023, the Dharali deluge and several major landslides have shown how quickly mountain hazards can become devastating downstream events.
Scientists can identify areas that appear vulnerable, but determining precisely when a slope will collapse or a natural dam will fail remains extremely challenging.
For Himachal Pradesh, Professor Shukla said the next important scientific step is hydrodynamic modelling.
Identifying a potentially dangerous lake is only the starting point. Researchers must also determine how much water it contains and understand what could happen if the lake were to breach. Hydrodynamic models can help estimate flood depth, the extent of lateral spread and the speed and direction of a flood wave as it moves through a river valley.
However, reliable modelling depends on accurate estimates of lake volume.
Remote sensing can track changes in lake area with considerable precision, but calculating water volume using satellite-derived area measurements alone can carry substantial uncertainty. Empirical formulas can significantly overestimate volume, making it harder to accurately assess the potential consequences of a breach.
Some Himalayan lakes have already undergone more detailed studies. Research on Gepang Gath in Himachal Pradesh has indicated that a major outburst could affect downstream locations, including settlements around Sissu, with consequences potentially extending farther along the valley.
Even so, Professor Shukla warned against making exaggerated predictions.
It would not be scientifically accurate to claim that Himachal Pradesh will experience a disaster identical to Nepal's. The mechanisms behind Himalayan disasters differ across locations.
What researchers can establish is that potentially dangerous lakes exist, glaciers and mountain environments are changing, and disasters at certain locations could threaten downstream communities and infrastructure.
And the warning signs extend beyond Himachal Pradesh.
WARNING SIGNS ACROSS THE HIMALAYAS
An assessment by Suhora Technologies in Arunachal Pradesh's Tawang district found that four of five potentially hazardous glacial lakes in the Mago Chu Basin had expanded between 2016 and 2026.
These lakes had already been placed in high-risk categories, while satellite observations showed continuing changes in water accumulation.
Sanhapo Lake emerged as a particular concern. Satellite data showed its area increasing from 55.87 hectares in 2016 to 87.02 hectares in 2026, reaching 88.81 hectares in the latest observation from June 2026.
According to Suhora's analysis, the lake's size, continued expansion and existing high-risk classification make it a priority for detailed hazard modelling and continuous monitoring.
For Professor Shukla, the goal should not be attempting the impossible task of predicting the precise date of the next Himalayan disaster.
Instead, India needs to develop stronger systems capable of detecting danger early.
That would involve using satellites to monitor vast stretches of the mountains for changes in lakes and unstable terrain, followed by the deployment of ground-based sensors at the most critical sites. His research supports a two-level strategy: large-scale monitoring from space to identify potential hotspots, followed by focused ground monitoring and early-warning systems.
The Himalayas may never allow scientists to make perfectly accurate predictions.
But Nepal's tragedy has delivered a powerful warning: disasters in the mountains can begin with an unseen collapse high above a valley, leaving people below with little or no indication of what is coming.
India may never experience an identical event. It does not have to.
The Indian Himalayas have their own glaciers, lakes, valleys and vulnerabilities. Increasingly, they are providing signals that the time to understand and prepare for the next catastrophe is before the mountain begins to move.
