Nepal’s Disaster Is A Warning For Kerala: Report

The devastating disaster in Nepal could serve as a warning for Keralam, particularly the ecologically fragile Western Ghats, as a combination of avalanches, landslides, water, debris and gravity can turn mountain rivers into powerful forces of destruction.

In an article published by Mathrubhumi English, Dr D. Padmalal, former head of the Hydrology Division and a geologist, examines the science behind the Nepal disaster and compares it with the devastating landslide and debris flow that struck Wayanad in 2024.

The article, titled “Is Nepal’s disaster a warning for Kerala? Understanding destructive power of ‘hungry water’,” explains that the two disasters were triggered differently. In Wayanad, the devastation was caused by a landslide followed by a debris flow through the river.

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In Nepal, an avalanche was followed by a debris flow through the river.

However, both events demonstrate how enormous quantities of water and debris can gain destructive energy while moving through steep mountain valleys.

The disaster occurred in the upper reaches of the Narayani river basin, a major tributary system of the Ganga. Near the Tibetan border, parts of massive snow-covered mountains collapsed in an avalanche towards the source of the Lhende Khola river.

As ice and rocks rushed downhill, friction caused a significant amount of the ice to melt into water. Rocks, soil and ice accumulated in the narrow river valley, forming a natural dam.

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Within just 30 minutes, the water level behind the natural dam rose by around nine metres. As the pressure increased, the natural barrier eventually breached, releasing the stored water downhill with enormous force.

The floodwater travelled from an elevation of more than 5,000 metres through the Bhotekoshi and Trishuli river systems. It swept away structures built on the river’s floodplains, effectively reclaiming the natural space of the river.

What happened in Nepal was, in many ways, a much larger version of the process seen in other mountain disasters. The crucial difference was that the obstruction was a natural dam rather than a man-made one.

What is ‘hungry water’?

The scientific community uses the term “hungry water” to describe water carrying enormous energy and capable of scouring and transporting sediment, rocks and other material from a riverbed.

Water stored at a high elevation contains large amounts of potential energy because of gravity. When that water is suddenly released, the energy is converted into movement.

The resulting flow can tear away soil, rocks, trees and even sections of mountainsides before carrying the material downstream.

The process can also repeat itself. When ‘hungry water’ encounters an obstruction, the debris it carries can accumulate and create another natural dam. Water builds up behind it until the barrier eventually breaks, sending another surge downstream.

In steep river valleys with a high hydraulic gradient, this cycle can happen repeatedly, devastating downstream areas within minutes.

The phenomenon is not entirely unfamiliar to Keralam.

Water stored in reservoirs at high elevations contains enormous energy. This energy is harnessed by hydroelectric projects, where water is released through penstock pipes to generate electricity.

Many of Keralam’s major dams are located at elevations of more than 1,000 feet. But the destructive side of this stored energy became evident during the 2018 floods, when large quantities of reservoir water were released.

The situation around Ranni along the Pamba River remains a vivid example of the force that water can acquire as it moves rapidly downhill. The water was powerful enough to erode hillsides and cause extensive destruction.

The same principle also explains why there continues to be concern about the ageing Mullaperiyar dam, although repeated strengthening of the structure provides some reassurance.

The Himalayas themselves are a highly dynamic and unstable mountain system.

The range was formed around 40–50 million years ago, when the Indian and Eurasian tectonic plates collided, pushing up the floor of the ancient Tethys Sea.

The Himalayas continue to rise by around five millimetres every year.

The region lies in earthquake-prone Zone 5. The latest disaster, following the devastating 2015 earthquake, once again highlights the instability of the Himalayan region, both beneath the Earth’s surface and above it.

Climate change adds another layer of risk.

Studies indicate that the world has lost around 900 billion tonnes of ice over the past five decades. After the Arctic and Antarctic regions, the Tibetan-Himalayan mountain ranges contain the world’s largest reserves of freshwater stored as ice.

This is why the region is often called the “Third Pole.”

These glaciers, located among some of the world’s highest peaks, can act like nature’s “water bombs.” When global warming, climate change, unscientific human interventions and gravity interact, the consequences can be catastrophic.

The warning is not limited to the Himalayas.

Keralam’s Western Ghats are also made up of steep slopes, river valleys and settlements located close to natural drainage channels. Extreme rainfall combined with unstable slopes and human intervention can create conditions for destructive landslides and debris flows.

Dr Padmalal stresses the need for stronger disaster-prevention measures.

Floodplains must be protected. Natural flow channels in flood-prone river valleys may be used for agriculture, but settlements and major structures should be completely avoided in such areas.

Unscientific construction must stop. Human interventions in hilly regions and along riverbanks need to be substantially reduced, particularly in ecologically sensitive areas.

Monitoring systems must also be strengthened. Just as research and monitoring need to be improved in the Himalayan region, Keralam needs accurate real-time early-warning systems across the Western Ghats.