Climate change is directly linked to flood disasters in mountain communities

In the morning hours of October 3, the serene South Lhonak Lake transformed into an agent of destruction. What followed was a catastrophic flood disaster that would leave an indelible mark on India’s Sikkim region, claiming dozens of lives and reshaping the landscape of the Teesta River valley.

In a recent study, experts have pieced together the dramatic sequence of events during this disaster.

The research was led by Dr. Ashim Sattar of the Indian Institute of Technology in Bhubaneswar and Dr. Christian Huggel from the University of Zurich’s Environment and Climate research group.

The findings paint a sobering picture of the escalating impact of climate change on mountain communities.

Impacts of the flood disaster

On October 3, 2023, a sudden and catastrophic event triggered the flood. Approximately 14.7 million cubic meters of frozen moraine collapsed into South Lhonak Lake.

This collapse caused a massive wave, similar to a tsunami, that reached up to 20 meters in height. The force of this wave breached the moraine, allowing nearly 50 million cubic meters of water to escape.

This volume is equivalent to filling 20,000 Olympic-sized swimming pools, demonstrating the sheer scale of the disaster.

As the water surged downstream, it carved through the 385-kilometer-long valley, causing unprecedented destruction. Sediment, estimated at around 270 million cubic meters, was displaced along the river’s course.

Vulnerability of high mountain communities

Roads, bridges, and hydroelectric power plants on the Teesta River were washed away, cutting off communities and crippling local economies. The impact extended beyond infrastructure, affecting ecosystems and farmlands that depended on stable water sources.

At least 55 people lost their lives in the disaster, while another 70 were reported missing. The suddenness of the event left little time for evacuation, increasing the human toll. Survivors faced immediate hardships as homes, livelihoods, and access to essential resources were swept away.

“This event is a stark reminder of the vulnerability of high mountain regions to the effects of climate change,” said Dr. Huggel. “The thawing of permafrost and the instability of rock, ice, and moraine structures pose major risks.”

Understanding the flood disaster

To analyze the flood’s impact, the researchers relied on advanced scientific methods. High-resolution satellite images captured the affected regions before and after the event, allowing scientists to compare structural changes in the landscape.

Digital elevation models helped reconstruct the terrain’s shifting contours, offering insights into how the floodwaters moved through the valley.

Seismic data played a crucial role in pinpointing the exact moment of the moraine collapse. The tremors generated by the falling ice and debris provided a time marker for the sequence of events.

Geomorphological studies further determined the volume of water and sediment released, helping scientists understand the flood’s full magnitude.

By integrating satellite technology and physical modeling, the researchers created a detailed picture of the disaster’s progression. These insights are invaluable for predicting similar events in other glacial regions, where climate change continues to threaten landscape stability.

“The use of high-resolution remote sensing data was crucial to understanding the complex processes and cascading effects of the flood in detail,” noted Dr. Sattar. “Collaboration among researchers from different disciplines was key in gaging the full extent of this event.”

Need for early warning systems

The flood not only destroyed critical infrastructure but also caused extensive environmental damage.

Sedimentation and erosion altered the course of the Teesta River, affecting farmlands and water supplies. Communities that relied on stable river conditions for agriculture and fisheries faced major disruptions.

The study highlights an urgent need for early warning systems. The researchers found that the moraine had shown signs of instability for years before the collapse.

Satellite observations recorded shifts of up to 15 meters per year, indicating gradual weakening of the structure. If these warning signs had been monitored closely, preventive measures might have reduced the impact.

“Our findings highlight the urgent need for early warning systems and international cooperation to address such challenges,” said Dr. Sattar.

Scientists advocate for a network of real-time monitoring stations that track glacial lake conditions and provide alerts when risks increase.

Such systems would allow authorities to issue timely warnings, giving local communities a chance to evacuate or reinforce protective barriers before a disastrous flood strikes.

Climate change plays a major role

The researchers warn that similar flood disasters are likely to become more common as global temperatures rise. Melting glaciers contribute to the expansion of glacial lakes, increasing the risk of outburst floods.

High-altitude regions, already vulnerable to extreme weather, will face growing challenges in managing these threats.

“The case of South Lhonak Lake is a reminder to take climate risks in mountain regions worldwide more seriously,” said Dr. Huggel.

Rising temperatures weaken the stability of ice, rock, and moraine structures, making high-altitude environments increasingly unpredictable. The consequences extend beyond localized floods, as sediment displacement and altered river courses impact larger ecological systems.

“We need better risk modeling and assessment, as well as robust adaptation strategies, to minimize future disasters,” said Dr. Sattar.

Scientists emphasize the importance of integrating climate projections into risk assessments. More accurate models will help policymakers develop targeted strategies to reduce vulnerabilities in glacial regions.

Strengthening regulation and preparedness

The research team calls for stricter regulation of hydropower development in high-risk areas.

Many of the destroyed hydroelectric plants had been built in locations susceptible to floods and landslides. Strengthening oversight in infrastructure planning could prevent future losses and improve resilience.

Improved monitoring of glacial lakes is another key recommendation. By using satellite imagery, drones, and ground-based sensors, scientists can track changes in lake size, moraine stability, and surrounding permafrost conditions.

Regular assessments would allow authorities to take preemptive action when warning signs appear.

Early warning systems must be integrated with disaster response plans. Communities in high-altitude regions need access to evacuation routes, emergency shelters, and rapid communication networks. Governments and international agencies must collaborate to provide funding and expertise for these initiatives.

The study provides valuable insights that could help mountain communities prepare for the challenges of climate change. With better risk assessment, stronger regulations, and proactive disaster response strategies, the impact of future floods can be minimized.

Scientists stress the need for immediate action, as delaying preventive measures could lead to more catastrophic events in the years ahead.

The study is published in the journal Science.

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