Visuals of flash flood in Sikkim.
Credit: Defence sources
A massive flash flood triggered by the bursting of a major lake in north Sikkim killed at least five persons, caused widespread devastation and wiped off a part of a major national highway even as 23 personnel of the Indian Army, struck by the deluge, remained missing so far.
According to the satellite images shared by the Indian Space Research Organisation, the lake lost an area of more than 100 ha when it burst, inundating ten downstream districts in Sikkim and West Bengal.
The pre and post view of the South Lhonak lake shows that the glacier-fed water body had a size of 167.4 ha on Sept 28, but shrunk to 60.3 ha on Wednesday morning.
“It is observed that the lake has burst and about 105 ha area has been drained out, which might have caused the flash flood downstream,” the National Remote Sensing Centre, one of the ISRO units, said.
While the lake burst was caused by incessant rains since yesterday, the situation was compounded by the release of a large volume of water from a dam, which in the past had attracted criticism for its potential to harm the fragile Himalayan ecology.
Defence sources said 23 army personnel were missing in north Sikkim following a flash flood caused by a lake burst at Chungthang area in north Sikkim.
“Due to the sudden cloudburst over Lhonak Lake, a flash flood occurred in the Teesta River in Lachen valley. Release of water from the Chungthang dam led to a sudden increase in water level up to 15-20 feet high downstream,” said an official.
“This has led to Army vehicles parked at Bardang near Singtam getting affected and 23 personnel have been reported missing. A few vehicles are reported submerged under the slush. Search operations are underway,” he added. Army establishments along the valley have also been affected.
Gangtok Sub-Divisional Magistrate Mahendra Chettri said five bodies were recovered from Golitar and Singtam region. The National Disaster Response Force has pressed three teams in the rescue operation and managed to rescue seven persons so far. More than 40 vehicles remained submerged in the slush.
Prime Minister Narendra Modi spoke to Sikkim Chief Minister Prem Singh Tamang to take stock of the situation and assured him of all possible support.
According to the Central Water Commission, the flood occurred at midnight on October 3. The situation turned worse by the release of water from the breaching of Chungthang dam, which lies at the core of 1200 MW Teesta-III hydro-power project.
More than 8000 cubic metre per second of water has been released from Teesta barrage, resulting in flood like situations in the downstream districts of Kalimpong, Darjeeling, Jalpaiguri and Cooch Behar of West Bengal.
“The National Highway 10, connecting Gangtok to Siliguri has been completely washed away near the Likhuvir-Sijhora stretch,” the West Bengal government said in a statement.
The Sikkim State Disaster Management Authority said the lake outburst in portions of Lhonak Lake in north Sikkim caused a rise in water levels with a very high velocity of nearly 15m/sec.