DEHRADUN: The devastating flash flood that tore through Nepal on Wednesday, sweeping away homes, bridges and other infrastructure, bears striking similarities to the 2013 Kedarnath disaster, according to Himalayan geologists.
Scientists say the catastrophe may have been triggered by an ice avalanche, rockfall or debris flow that temporarily blocked a narrow valley before the natural dam burst. The possibility of seismic activity is also under investigation.
The scale and force of the deluge have renewed concerns over global warming, rapidly retreating glaciers and the growing instability of the Himalayan region. Rainfall is now increasingly being recorded at elevations of up to 4,000 metres, where precipitation earlier occurred largely as snow, experts said.
Speaking to TNIE, Dr Manish Mehta, senior scientist at the Wadia Institute of Himalayan Geology, said satellite images of the affected area were being analysed. “The Indian Space Research Organisation has also studied the disaster. Its preliminary assessment suggests that an ice avalanche or debris flow may have triggered the flash flood,” Mehta said.
Satellite imagery indicates that the region is highly vulnerable, with glaciers retreating rapidly. The disaster site is located in a narrow valley in a downstream area, conditions that could have amplified the destructive force of the water.
“One possibility is that a major landslide or avalanche created a temporary dam. Its subsequent collapse may have unleashed the flood on settlements downstream,” Mehta said.
Reports of strong tremors before the disaster have also prompted speculation about a possible earthquake. Mehta, however, said it was too early to reach a definitive conclusion.
“Two theories are currently being examined. The first points to an ice avalanche, rockfall or debris flow, while the second considers seismic activity as a possible trigger. A clearer picture should emerge after detailed studies over the next two or three days,” he said.
Experts are also comparing pre- and post-disaster satellite images to determine whether exceptionally heavy rainfall destabilised rocks and carried debris into the valley. “The Himalayan conditions in Uttarakhand and Nepal are broadly similar. From the northwest to the northeast, the mountain chain faces comparable geological and climatic vulnerabilities,” Mehta told TNIE.
He added that intense rainfall in a region that traditionally received little rain could have fractured unstable rock formations and triggered a massive debris-laden torrent.
Based on the initial images, Mehta said the Nepal event appeared “two to three times larger” than the 2013 Kedarnath tragedy, largely because of its extensive catchment and the presence of several glaciers.
The Nepal disaster has revived memories of June 16-17, 2013, when torrential rain and raging waters from the Mandakini and Saraswati rivers devastated Kedarnath valley. A massive surge from behind the shrine swept away buildings and roads, leaving thousands dead or missing in one of Uttarakhand’s worst natural disasters.