Back to news
4 Feb 2025 | Press releases

New scientific study confirms climate change played key role in deadly 2023 lake outburst in Sikkim

Massive collapse of moraine into South Lhonak lake in October 2023 sparked a 20-metre-high ‘tsunami-like’ wave that sent 20,000 Olympic swimming pools’ worth of water downstream – making it one of the most catastrophic to hit the Himalayas in recent decades.

3 mins Read

70% Complete

Key findings:

Kathmandu – A newly published scientific study provides the first comprehensive analysis of October 2023’s devasting Glacial Lake outburst flood (GLOF) for South Lhonak Lake in Sikkim, India.

The disaster resulted in 55 casualties, with 70 people still missing and caused extensive damage to critical infrastructure including hydropower facilities, bridges, highways, and buildings in the Teesta Valley. This event ranks among the most catastrophic GLOFs to hit the Himalaya in recent decades.

The research, led by a team of international scientists from nine countries, examines the triggers, dynamics, and cascading impacts of the flood, offering critical insight for Himalayan communities vulnerable to climate-induced disasters.

Using high-resolution satellite imagery and modelling techniques, the study reveals that the GLOF was triggered by a collapse of up to 14.7 million cubic meters of frozen moraine material into the South Lhonak Lake. This collapse generated a tsunami-like wave approximately 20 meters high, which eroded the lake’s frontal moraine dam, releasing about 50 million cubic meters of water – equivalent to 20,000 Olympic sized swimming pools.

“The South Lhonak GLOF serves as a grim reminder for similar high-risk lakes across the region,” said Ashim Sattar, Assistant Professor at Indian Institute of Technology Bhubaneswar and lead author of the study. “We urgently need a multi-faceted approach, including early warning systems, strengthened regulatory frameworks, and community education, to mitigate these risks.”

The flood severely impacted settlements and infrastructure along the Teesta River, breaching the Teesta III dam in Chunthang district. The study highlights the role of cascading hazards, where initial flooding triggered secondary landslides and debris flows, compounding the destruction.

Key recommendations from the study underscores:

  1. Enhanced Early Warning Systems: Urgent implementation of improved hazard detection and response systems across the Himalaya.
  2. Advanced GLOF Modelling: Current models often underestimate risks by failing to account for sediment entrainment and riverbank collapses. Improved techniques are critical for effective risk management.
  3. Adaptative Risk Management: The recent disaster shows the need for urgent, adaptive plans, particular for basin-scale early warning systems.
  4. Resilient Infrastructure: Strengthening regulations and risk assessments for hydropower projects near glacier lakes to safeguard communities and investments.

“This research paper exemplifies global collaboration among Earth scientists, using cutting-edge satellite imagery and modelling techniques to unravel the complexities of cryospheric hazards.” said Mohd. Farooq Azam, Intervention Manager, Cryosphere, ICIMOD, and a co-author of the study.

GLOFs occur when lakes fed by glacier melt release large volumes of water due to dam failures triggered by glacier calving, heavy rainfall, avalanche. These events pose increasing threats to mountain communities as climate change accelerates glacial retreat and destabilises moraine dams.

“This study reveals how climate change is amplifying glacial hazards, with the 2023 Sikkim GLOF triggering an unprecedented cascade of destruction. It underscores the urgent need for better early warning systems, resilient infrastructure, stronger regional cooperation to mitigate future risks, and, most of all, faster action to switch to renewable energy especially among high emitting economies,” said Arun Shrestha, Senior Climate Change Specialist, ICIMOD.

Published in the journal science, this study is a significant contribution to the growing body of research on climate change-driven cryosphere hazards. It provides crucial insights for policymakers, disaster response agencies and researchers to safeguard vulnerable mountain communities.


For media inquiries, please contact:

Neraz Tuladhar (Raz), Media Officer
Email: media@icimod.org

12 Dec 2018 Press releases
Koshi DRR knowledge hub to strengthen transboundary collaboration

At the launch of the 24th Conference of the Parties (COP) meeting, UN Secretary General Antonio Guterres called for greater ...

10 Dec 2024 Press releases
Region’s disaster experts unite in response to rising numbers and intensity of climate-driven hazards in mountains

Kathmandu, 10 December 2024 Senior Disaster Management experts from six Hindu Kush ...

14 Mar 2018 Press releases
Tackling poverty in a rapidly changing world: Experts recommend a collective response to common ecosystem risks

South Asia faces the challenge of tackling persistent poverty at a time of rapid and large-scale changes in social, environmental, ...

2 May 2023 Press releases
Global Alliance for a Sustainable Planet and ICIMOD to Drive Social and Environmental Change in the Hindu Kush Himalaya

Kathmandu - The International Centre for Integrated Mountain Development (ICIMOD) and the Global Alliance for a Sustainable Planet (GASP) are ...

24 Jul 2015 Press releases
Policy conference produces recommendations to support action on adaptation

Political leaders, scientists, and people from the Indus basin stress the need for knowledge sharing and the promotion of local ...

5 Dec 2010 Press releases
Challenges of climate change in the mountains highlighted in Cancun

Experts from leading institutions and government organisations working in the field of climate change in the Himalayan region called attention ...

24 Feb 2015 Press releases
Climate and Clean Air Coalition (CCAC) meets in Kathmandu to tackle air pollution

Over 100 state and non-state partners of the Climate and Clean Air Coalition (CCAC) met in Kathmandu to develop a ...

21 Jun 2024 Press releases
Development Alternatives and ICIMOD forge long-term partnership to build climate-resilient Hindu Kush Himalaya

New Delhi, India/ Kathmandu, Nepal – 21 June 2024 The impacts of climate change are increasingly being felt across the Hindu ...