A flash flood surged down a river in Uttarakhand on February 7, killing at least 30 people and washing away two hydroelectric power stations. As rescue workers search for more than 150 people who are still missing, officials and scientists are trying to unravel the causes of the sudden flood.
Did a glacier high up in the mountains collapse, releasing a huge plug of frigid meltwater that spilled into the river? Or was the culprit a landslide that then triggered an avalanche? And what, if any, link might these events have to a changing climate?
Initial reports pointed towards a glacier burst as the possible reason for the disaster suggesting that a part of the Nanda Devi glacier in Uttarakhand’s Chamoli district broke off and triggered massive flash floods. However, more recent reports after studying satellite imagery say that the floods may have been triggered by a landslide and not a glacier burst.
A glacial lake outburst flood occurs when a natural lake is formed from a glacial ice melt and the lake is breached. However, available satellite images seemingly do not show the presence of a glacial lake before the flooding event. Instead, glaciologists and geologists identified a steeply hanging bit of a glacier which likely developed a crack and caused a landslide, triggering an avalanche and the subsequent flooding.
Located on the southern slope of the Himalayan range, Uttarakhand is one of the most disaster-prone states in India. The state faces the risk of calamitous events like flash floods/floods, cloudbursts, avalanches, landslides, mudflows, and earthquakes, among others, and has frequently been hit by them. The frequency and intensity of these hazards have increased over the last few decades. This has been due to many factors. The state’s topography, geological setting, and increasing level of tourism (leading to deforestation and commercialisation) have all been responsible for climate change.
A 2019 study, spanning 40 years of satellite observations, indicated that due to rising temperatures and climate change, the rate of melting of Himalayan snow has accelerated significantly since the beginning of the 21st century. This is leading to the weakening of glaciers and an increase in the water level in various river systems. Also, as per scientists glacier retreat, melting snow and thawing permafrost are making mountain slopes more unstable. They are increasing the number of glacial lakes and sudden, catastrophic failures are becoming more likely.