The Himalaya is undergoing profound environmental transformation. Rising temperatures, retreating glaciers, degrading permafrost and changing precipitation patterns are reshaping mountain landscapes and increasing the potential for cascading hazards. Rock and ice avalanches, glacial lake outburst floods (GLOFs), glacier detachments and extreme floods are no longer distant possibilities. They are immediate concerns for mountain communities, infrastructure planners and disaster management authorities.

The catastrophic rock and ice avalanche at Chamoli, Uttarakhand, in February 2021 involved approximately 26 million m³ of material, comprising nearly 80% rock and 20% glacier ice, with the detached mass reaching a thickness of about 180 m. The collapse transformed into a destructive debris flow that swept through downstream valleys, destroying the Rishiganga hydropower project and severely damaging the Tapovan Vishnugad project, while claiming more than 200 lives or leaving people missing. A similar but much larger disaster struck the Rasuwa region of Nepal on 26 August 2026, when a rock and ice avalanche, preliminarily estimated at around 100 million m³, triggered a devastating flood that travelled more than 180 km downstream. The disaster affected 12 hydropower projects and resulted in at least 1,455 reported deaths, with hundreds more people missing in the aftermath. Originating near the Nepal-China border, the event also highlights the transboundary dimensions of mountain hazards, with consequences extending across interconnected river systems and infrastructure networks. Together, these disasters underscore the capacity of high mountain mass movements to trigger cascading impacts far downstream, often leaving communities and infrastructure with little time to respond.

The October 2023 South........

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