Why Uttarakhand avalanche killed 200 & similar Switzerland disaster saw only 1 death

DEHRADUN: When a massive wall of ice and rock collapsed into the Rishiganga valley in Chamoli in Feb 2021, it triggered a devastating torrent that destroyed hydropower projects, swept away bridges and killed more than 200 people -- many of whom are still reported missing. Four years later, in the summer of 2025, a similarly large ice-rock avalanche struck the alpine village of Blatten in Switzerland. Although most of the settlement was buried, the disaster claimed only one life. The stark difference, experts said, lay in preparedness and early-warning systems.An international team of scientists compared the two disasters and concluded that the contrasting outcomes were "not a matter of luck but the result of monitoring, early warnings, timely evacuation and coordinated risk management". Their findings are detailed in a paper titled ‘Ice-rock avalanches in a warming Himalaya indicate pathways toward effective preparedness', published in the journal Communications Earth & Environment. The study was conducted by Rayees Ahmed of the Indian Institute of Science, Bengaluru, Anshuman Bhardwaj and Lydia Sam of the University of Aberdeen in the UK and Lander Van Tricht of the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) in Switzerland.According to the research, the avalanche above Blatten was preceded by clear warning signs of slope instability. Swiss scientists monitored the mountain using instruments that track glacier movement, rock fractures, temperature changes and ground deformation. When these indicators showed increasing instability, authorities assessed the risk and ordered the evacuation of the village, which had about 300 residents at the time. As a result, when the slope eventually collapsed, most people had already moved to safety. "This coordinated approach, combining scientific monitoring, rapid communication and community response, prevented a large natural event from becoming a major human tragedy," the authors said.In contrast, the disaster in Chamoli unfolded without warning for communities downstream. The sudden collapse of ice and rock high in the mountains sent a fast-moving debris flow through the Rishiganga valley, destroying infrastructure and trapping workers inside tunnels at hydropower projects. At the time, there was little real-time monitoring of unstable slopes in the region and no effective early-warning system to alert people in the valley, the study noted.The researchers also pointed out that hazards such as ice-rock avalanches are often overlooked in the Himalayan region. Compared with other glacial hazards, these events remain under-documented in hazard assessments and policy frameworks, partly because they occur relatively rarely. Yet their impacts can be far more destructive and far-reaching than many other types of landslides, as the Chamoli disaster demonstrated.The paper further stated that climate change is increasing these risks, as rapid glacier retreat and thawing permafrost are destabilising high-mountain slopes across the Himalaya and making sudden collapses of ice and rock more likely.Although some progress has been made since the Chamoli disaster such as expanded glacier monitoring and greater use of satellite observations, "significant gaps remain", the study said, adding that the vast and remote terrain of the Himalayan region makes monitoring difficult, while coordination between scientists, authorities and local communities remains limited in many areas.The scientists said the Swiss experience offers valuable lessons for the Himalayan region. "In Switzerland, hazard monitoring forms part of a broader risk-management system that integrates scientific data, govt action and community awareness. Continuous monitoring allows experts to detect early signs of instability, while authorities maintain clear protocols for issuing warnings and carrying out evacuations," they said.The research suggested that elements of this model could be adapted for the Himalaya. Satellite-based monitoring, combined with strategically placed ground sensors in high-risk valleys, could help identify unstable slopes, while stronger communication systems would ensure that warnings reach communities quickly. "The rising frequency and complexity of cryospheric hazards in the Himalaya highlight the need to shift from reactive disaster response to proactive risk management and anticipatory governance, similar to the integrated risk management model used in Switzerland," the authors concluded.They added that many glacier-fed valleys in the Himalayan region still rely on outdated hazard zonation maps, while environmental impact assessments for infrastructure projects often fail to adequately consider cryospheric slope failures, including permafrost thaw and cascading hazards. "The 2021 Chamoli disaster exposed this gap. Despite satellite data indicating precursor signs, the absence of focused monitoring, integrated analysis and response protocols turned a potentially predictable event into a catastrophe," the researchers said.By contrast, the avalanche in Blatten demonstrated how anticipatory governance can reduce disaster impacts. Decades of monitoring and institutional preparedness enabled authorities to quickly deploy radar instruments after unusual slope activity was detected in 2025, confirm accelerating movement and carry out a precautionary evacuation before the collapse, the study highlighted.