Understanding the 2023 Sikkim Multihazard Flood Cascade

• Post by: Randy Muñoz
• May 5, 2025
• Comments off

A landmark international study sheds new light on the devastating multihazard cascade that struck the Indian Himalayas in October 2023. The paper, “The Sikkim flood of October 2023: Drivers, causes, and impacts of a multihazard cascade,” presents a detailed analysis of one of the region’s most destructive recent events, tracing its origins to a permafrost landslide that triggered a glacial lake outburst flood (GLOF), sediment erosion, secondary landslides, and widespread downstream destruction.

EClim members Simon Allen, Heinz Frey, and Christian Huggel played active roles in this collaborative effort, which demonstrates the power of global scientific partnerships to inform disaster risk reduction and policy in High Mountain Asia.

Key findings include:

• Collapse of ~14.7 million m³ of frozen moraine into South Lhonak Lake generated a 20-m wave, breaching the dam.
• Sudden release of ~50 million m³ of water triggered a 385-km flood cascade down the Teesta River to Bangladesh.
• Over 25,900 buildings were damaged or destroyed; 31 bridges lost; hydropower infrastructure devastated.
• The study stresses the need for improved modeling of cascading hazards and urgent investments in early warning, risk transfer, and resilience-building.

This event underscores the compounding impacts of climate and development pressures in the Himalayas—and the urgent need for forward-looking risk management strategies.

📘 Access the full paper here: https://www.science.org/doi/10.1126/sciadv.adn5280