The Sikkim flood of October 2023: Drivers, causes, and impacts of a multihazard cascade

Ashim Sattar¹, Kristen L Cook^{2

3}, Shashi Kant Rai⁴, Etienne Berthier⁵, Simon Allen^{6

7}, Sonam Rinzin⁸, Maximillian Van Wyk de Vries^{9

10}, Wilfried Haeberli⁶, Pradeep Kushwaha¹¹, Dan H Shugar¹², Adam Emmer¹³, Umesh K Haritashya^{14

15}, Holger Frey⁶, Praful Rao¹⁶, Kori Sanjay Kumar Gurudin^{17

18}, Prabhakar Rai¹⁹, Rajeev Rajak²⁰, Faruk Hossain²¹, Christian Huggel⁶, Martin Mergili¹³, Mohd Farooq Azam²², Simon Gascoin²³, Jonathan L Carrivick²⁴, Louie Elliot Bell²⁵, Rakesh Kumar Ranjan²⁰, Irfan Rashid²⁶, Anil V Kulkarni²⁷, Dave Petley²⁸, Wolfgang Schwanghart²⁹, C Scott Watson³⁰, Nazimul Islam³¹, Moushumi Das Gupta³², Stuart N Lane³¹, Shahid Younis Bhat²⁶

Affiliations

¹ School of Earth, Ocean and Climate Sciences, Indian Institute of Technology Bhubaneswar, Odisha, India.
² Institut de Recherche pour le Développement, University Grenoble Alpes, Grenoble, France.
³ Institut des Sciences de la Terre, University Grenoble Alpes, Grenoble, France.
⁴ Department of Environmental Sciences, Central University of Jammu, Jammu and Kashmir, India.
⁵ Observatoire Midi-Pyrénées, Université de Toulouse, LEGOS (CNES/CNRS/IRD/UT3), Toulouse, France.
⁶ Department of Geography, University of Zurich, Zurich, Switzerland.
⁷ Institute of Environmental Sciences, University of Geneva, Geneva, Switzerland.
⁸ School of Geography, Politics, and Sociology, Newcastle University, Newcastle, UK.
⁹ Department of Geography, University of Cambridge, Cambridge, UK.
¹⁰ Department of Earth Sciences, University of Cambridge, Cambridge, UK.
¹¹ Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India.
¹² Water, Sediment, Hazards, and Earth-surface Dynamics (waterSHED) Laboratory, Department of Earth, Energy, and Environment, University of Calgary, Calgary, AB, Canada.
¹³ Institute of Geography and Regional Science, University of Graz, Graz, Austria.
¹⁴ Department of Geology and Environmental Geosciences, University of Dayton, Dayton, OH, USA.
¹⁵ Sustainability Program, University of Dayton, Dayton, OH, USA.
¹⁶ Save The Hills, Kalimpong, West Bengal, India.
¹⁷ Indo-Tibet Border Police, Ministry of Home Affairs, Government of India, Lucknow, India.
¹⁸ Department of Psychology, Banaras Hindu University (BHU), Varanasi, India.
¹⁹ Sikkim State Disaster Management Authority, Government of Sikkim, Sikkim, India.
²⁰ Department of Geology, Sikkim University, Gangtok, Sikkim, India.
²¹ Geological Survey of Bangladesh, Segunbagicha, Dhaka, Bangladesh.
²² Department of Civil Engineering, Indian Institute of Technology Indore, Indore, India.
²³ Centre d'Etudes Spatiales de la Biosphère (CESBIO), CNES/CNRS/INRAE/IRD/UT3-Paul Sabatier, Toulouse, France.
²⁴ School of Geography and water@leeds, University of Leeds, Leeds, UK.
²⁵ Scott Polar Research Institute, University of Cambridge, Cambridge, UK.
²⁶ Department of Geoinformatics, University of Kashmir, Srinagar, India.
²⁷ DST Centre for Excellence in Climate Change, Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, India.
²⁸ School of Environmental Sciences, University of Hull, Hull, UK.
²⁹ Institute of Environmental Science and Geography, University of Potsdam, Potsdam-Golm, Germany.
³⁰ COMET, School of Earth and Environment, University of Leeds, Leeds, UK.
³¹ Institute of Earth Surface Dynamics (IDYST), University of Lausanne, Lausanne, Switzerland.
³² ThePrint, New Delhi, India.

PMID: 39883788
DOI: 10.1126/science.ads2659

Free article

The Sikkim flood of October 2023: Drivers, causes, and impacts of a multihazard cascade

Ashim Sattar et al. Science. 2025.

Free article

. 2025 Mar 21;387(6740):eads2659.

doi: 10.1126/science.ads2659. Epub 2025 Mar 21.

Authors

Affiliations

¹ School of Earth, Ocean and Climate Sciences, Indian Institute of Technology Bhubaneswar, Odisha, India.
² Institut de Recherche pour le Développement, University Grenoble Alpes, Grenoble, France.
³ Institut des Sciences de la Terre, University Grenoble Alpes, Grenoble, France.
⁴ Department of Environmental Sciences, Central University of Jammu, Jammu and Kashmir, India.
⁵ Observatoire Midi-Pyrénées, Université de Toulouse, LEGOS (CNES/CNRS/IRD/UT3), Toulouse, France.
⁶ Department of Geography, University of Zurich, Zurich, Switzerland.
⁷ Institute of Environmental Sciences, University of Geneva, Geneva, Switzerland.
⁸ School of Geography, Politics, and Sociology, Newcastle University, Newcastle, UK.
⁹ Department of Geography, University of Cambridge, Cambridge, UK.
¹⁰ Department of Earth Sciences, University of Cambridge, Cambridge, UK.
¹¹ Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India.
¹² Water, Sediment, Hazards, and Earth-surface Dynamics (waterSHED) Laboratory, Department of Earth, Energy, and Environment, University of Calgary, Calgary, AB, Canada.
¹³ Institute of Geography and Regional Science, University of Graz, Graz, Austria.
¹⁴ Department of Geology and Environmental Geosciences, University of Dayton, Dayton, OH, USA.
¹⁵ Sustainability Program, University of Dayton, Dayton, OH, USA.
¹⁶ Save The Hills, Kalimpong, West Bengal, India.
¹⁷ Indo-Tibet Border Police, Ministry of Home Affairs, Government of India, Lucknow, India.
¹⁸ Department of Psychology, Banaras Hindu University (BHU), Varanasi, India.
¹⁹ Sikkim State Disaster Management Authority, Government of Sikkim, Sikkim, India.
²⁰ Department of Geology, Sikkim University, Gangtok, Sikkim, India.
²¹ Geological Survey of Bangladesh, Segunbagicha, Dhaka, Bangladesh.
²² Department of Civil Engineering, Indian Institute of Technology Indore, Indore, India.
²³ Centre d'Etudes Spatiales de la Biosphère (CESBIO), CNES/CNRS/INRAE/IRD/UT3-Paul Sabatier, Toulouse, France.
²⁴ School of Geography and water@leeds, University of Leeds, Leeds, UK.
²⁵ Scott Polar Research Institute, University of Cambridge, Cambridge, UK.
²⁶ Department of Geoinformatics, University of Kashmir, Srinagar, India.
²⁷ DST Centre for Excellence in Climate Change, Divecha Centre for Climate Change, Indian Institute of Science, Bangalore, India.
²⁸ School of Environmental Sciences, University of Hull, Hull, UK.
²⁹ Institute of Environmental Science and Geography, University of Potsdam, Potsdam-Golm, Germany.
³⁰ COMET, School of Earth and Environment, University of Leeds, Leeds, UK.
³¹ Institute of Earth Surface Dynamics (IDYST), University of Lausanne, Lausanne, Switzerland.
³² ThePrint, New Delhi, India.

PMID: 39883788
DOI: 10.1126/science.ads2659

Abstract

On 3 October 2023, a multihazard cascade in the Sikkim Himalaya, India, was triggered by 14.7 million cubic meters of frozen lateral moraine collapsing into South Lhonak Lake. The impact generated an ~20-meter tsunami-like impact wave, which breached the moraine and drained ~50 million cubic meters of the lake's water. The ensuing glacial lake outburst flood (GLOF) eroded ~270 million cubic meters of sediment, which overwhelmed infrastructure, including hydropower installations along the Teesta River. The physical scale and human and economic impacts of this event prompt urgent reflection on the role of climate change and human activities in exacerbating such disasters. Insights into multihazard evolution are pivotal for informing policy development, enhancing early warning systems (EWS), and spurring paradigm shifts in GLOF risk management strategies in the Himalaya and other mountain environments.

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The Sikkim flood of October 2023: Drivers, causes, and impacts of a multihazard cascade

Affiliations

The Sikkim flood of October 2023: Drivers, causes, and impacts of a multihazard cascade

Authors

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Abstract

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