Why ice-rock avalanches are the new unseen threat

On March 6, the scientific journal Nature published a well-researched article under its Perspective section titled ‘Ice-rock avalanches in a warming Himalaya indicate pathways toward effective preparedness’. In retrospect, it was an uncannily prescient prognosis of the probability of such disasters and the dire need of specific preparedness to handle them.

The current disaster in Nepal and the Chamoli disaster in Uttarakhand on February 7, 2021, offer striking parallels. Both can serve as reminders to urgently reconfigure long- and short-term disaster governance in the fragile Himalayan mountain ecosystem. The emerging consensus is to categorise them as ‘ice and rock avalanches’, as a distinct typology meriting specific preparation, like using high-tech, AI-driven early warning systems (EWS), besides appropriate policy and governance measures. These include robust trans-border cooperation regimes, which acknowledge that in a multi-nation fragile Himalayan geography, a landslide in the jurisdiction of one country may do disastrous downstream damage in another country.

It is significant to note that the disaster in Nepal does not fall neatly into any of the more recognised high-altitude disaster categories like GLOF (glacial lake outburst floods), landslide, snow avalanche or flash floods. Sure enough, it contained some elements of each, but its potential frequency as a distinct hazard category requires particular policy response frameworks, cooperative risk governance and scientific research in the vulnerable countries in Asia.

India, with its vast Himalayan geography and river systems that originate there, is particularly vulnerable to such avalanches and consequent flash floods downstream, already exemplified in Chamoli.

During that disaster, I was serving as the director general of the National Disaster Response Force (NDRF), which was immediately pressed into service and eventually stayed in Chamoli for a considerable period, helping in post-disaster operations. Reconstruction of the sequence of events suggested that the trigger phenomenon was the breaking away of a 500m wide wedge of ice-covered rock from the more than 6,000m high Ronti Peak in the Garhwal Himalayas in Uttarakhand. The structural failure on the steep mountainside generated a cascading torrent of pulverised rock and ice that completely destroyed two hydropower projects (Rishiganga and Tapovan), and severely damaged infrastructure and settlements, leading to the loss of more than 200 lives.

After some initial confusion, now it is established that in Nepal, too, the disaster was triggered when a massive portion of a glacier sheared off in the mountains on the Nepal-Tibet border and collapsed suddenly, creating a rapidly cascading ‘ice-rock avalanche’. Like in Chamoli, this super-kinetic debris-flow crashed deep down into narrow valleys with high-gradient river systems. The debris piled up in the valley, temporary damming fast-flowing rivers. This resulted in the backing up of rivers in the shape of massive temporary lakes, building enormous water pressure. Predictably, due to the mammoth pressure, the blocking debris of rock and ice gave way suddenly, leading to a furious flash flood that destroyed life and infrastructure downstream. The final tally of dead and missing, which is an ongoing concern, appears to be much more than that in Chamoli.

Experts are linking both events to increasing geological and climate vulnerability, exacerbated by aggressive infrastructure development, which can be considered ab initio risky in the fragile Himalayan ecosystem.

Both events offer lessons that must inform and be deeply integrated into risk and disaster governance, including regional development, infrastructure planning and strategic deployment of effective early warning symptoms.

Interestingly, there are good practices and precedents that can serve as a template. The ice-rock avalanche in Blatten, an alpine village in Switzerland, in May 2025 comes to mind. It caused severe damage to the settlement, burying most of Blatten under the debris. However, the entire population had been evacuated by authorities days before the avalanche struck. There was only one casualty. This timely response was due to an Integrated Risk Management (IRM) framework with constantly open communication channels between the community and all levels of governance, cantonal and federal.

Ground-based sensors were deployed, including radar interferometry (measurement technique that uses overlapping waves—light or sound—to extract information), GPS stations, and thermal and optical cameras, to track slope motion in real time. The observations confirmed accelerating deformation, prompting local authorities to issue an evacuation order for the 300 residents. The effective life-saving response owes much of its success to a human and technology-driven EWS regime aptly described in a leading newspaper editorial as ‘eyes on the ice’, which was an integral part of the IRM.

In Europe, Canada and China, disaster governance factors in real-time monitoring of glaciers, especially those identified as risky. It is high time the unstable ice-rock formations in the Himalayas are effectively risk-monitored. Thousands of glaciers in the region, many of them retreating and rendered precariously unstable due to rising temperatures and permafrost thawing, combine to present a potentially dangerous scenario.

It is imperative that disaster governance in countries of the region take an urgent call that factors in cooperation in scientific research and technology, as well as regional planning and development, especially mega projects. The only other sobering scenario is to be caught unprepared by more frequent, more tragic and more destructive Himalayan thunders in the foreseeable future.

The writer is former director-general of the National Disaster Response Force.