Nepal's hydropower bet wrecked by Himalayan rock-ice avalanche

A massive rock-ice avalanche on 26 August killed over 1,400 people and destroyed nearly a dozen hydropower plants along Nepal's Trishuli river corridor. The disaster, triggered by a mountain collapse at 5,200 metres, has exposed how climate-driven permafrost thaw and glacier retreat are creating hazards that exceed the design assumptions of Nepal's energy infrastructure, per the Hindustan Times and WSJ.

Bottom line — The collapse generated seismic energy equivalent to a magnitude 5.7 earthquake, per scientists at Grenoble Alpes University and Columbia University.

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• The initial failure was a bedrock collapse, not a glacial lake outburst or earthquake, according to seismic analysis by Dr Kristen Cook of Grenoble Alpes University and Dr Göran Ekström of Columbia University. The USGS had initially reported a magnitude 4.4 earthquake.
• The debris flow travelled at roughly 50 metres per second, reaching the Chinese border checkpoint at Gyirong within six to seven minutes, per Chinese state media cited by the Peoples' Review.
• At least 13 hydropower projects were affected, including the 216 MW Upper Trishuli 1, whose 2018 environmental assessment flagged flood risk but whose early-warning system failed on 26 August, a World Bank spokesman told the Hindustan Times.
• The Langtang Khola Hydro project was engineered for a 100-year flood raising river levels by 6 metres; the August surge reached 20 times that height, its managing director told the Hindustan Times.
• Scientists estimate the avalanche volume was roughly 10 times that of the 2023 Blatten collapse in the Swiss Alps, per geomorphologist Wolfgang Schwanghart of Freie University Berlin.
• No formal attribution study has quantified climate change's role in this specific event, but researchers note that rising temperatures, glacier retreat and permafrost thaw may have destabilised the slope, per the HiRisk scientific consortium.
• Nepal's installed hydropower capacity has quadrupled over the past decade, with 210 projects under construction that would expand it by 150%, per industry estimates cited by the Hindustan Times.
• The disaster has prompted calls for a permanent trans-Himalayan scientific monitoring mechanism between China and Nepal, according to the Peoples' Review, and for a South Asia-wide early warning architecture, per Dawn.

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