- 1School of Earth Ocean and Climate, IIT Bhubaneswar (ashim.sattar@gmail.com)
- *A full list of authors appears at the end of the abstract
On October 3, 2023, a glacial lake outburst flood (GLOF) occurred at South Lhonak Lake in Northern Sikkim, India, resulting in extensive downstream destruction with transboundary effects extending hundreds of kilometers. The GLOF was triggered by the failure of the lake's perennially frozen and rapidly creeping North lateral moraine, leading to a displacement wave that overtopped and breached the frontal moraine dam. The resulting flood wave severely impacted the downstream valley, claiming lives and damaging infrastructure, including numerous buildings, bridges, roads, and hydropower plants. It completely destroyed the Teesta III hydropower project, at Chungthang located 63 km downstream of the lake. In our study, we employ a multi-model approach to reconstruct the GLOF process chain and analyze its associated geomorphic processes. We utilized various proxies, including flood marks, changes in lake volume before and after the GLOF, and flow velocity measurements to calibrate our models. Our calculations indicate that the erosion and deposition volumes from this event classify it among the most devastating GLOFs recorded to date. Additionally, we identify landslides triggered by the GLOF and assess their impacts on local infrastructure. Our study underscores the urgent need for improved monitoring and risk management strategies in mountain regions exposed to such extreme cascading events.
Ashim Sattar 1, Kristen L. Cook 2,3, Shashi Kant Rai 4, Etienne Berthier 5, Simon Allen 6,7, Sonam Rinzin 8, Maximillian Van Wyk De Vries 9,10, Wilfried Haeberli 6, Pradeep Kushwaha 11, Dan H. Shugar 12, Adam Emmer 13, Umesh K. Haritashya 14,15, Holger Frey 6, Praful Rao 16, Kori Sanjay Kumar 17,18, Prabhakar Rai 19, Rajeev Rajak 20, Faruk Hossain 21, Christian Huggel 6, Martin Mergilli 13, Mohd. Farooq Azam 22, Simon Gascoin 23, Jonathan L. Carrivick 24, Louie Elliot Bell 25, Rakesh Kumar Ranjan 20, Irfan Rashid 26, Anil. V. Kulkarni 27, Dave Petley 28, Wolfgang Schwanghart 29, C. Scott Watson 30, Nazimul Islam 31, Moushumi Das Gupta 32, Stuart N. Lane 31, Shahid Younis Bhat 26 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, Jammu and Kashmir, India 5 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, Alberta, Canada 13 Department 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, NGO, Kalimpong, West Bengal, India 17 Indo-Tibet Border Police, Ministry of Home Affairs, Government of India 18 Department of Psychology, Banaras Hindu University (BHU), Varanasi, India 19 Sikkim State Disaster Management Authority, Government of Sikkim, Sikkim, India 20Department 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, IISc, 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, Switzerland 32 Journalist, The Print, New Delhi, India
How to cite: Sattar, A. and the SLL GLOF investigating team: The South Lhonak GLOF Cascade of October 2023, Sikkim Himalaya, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-768, https://doi.org/10.5194/egusphere-egu25-768, 2025.
