Bhutan glacial lake burst: Sankosh on red alert, 10,000+ moved in Alipurduar, flood advisory for Bengal, Assam

The flood destroyed facilities at Gasa Tshachu, a hot spring tourist site near the Mo Chhu river. People had been moved out beforehand, and no deaths or injuries were reported there. A solar-powered irrigation system in the Dochhukha–Dzomlingthang–Ritsa area of Punakha was partly damaged, and debris affected the Punakha–Gasa highway near Dzomlingthang. Because the surge came late at night, with darkness and strong floodwater, the full extent of the damage was not known, according to Bhutan's state broadcaster.

Sirens were sounded along the Mochu river and downstream on the Punatsangchhu. The Punatsangchhu II hydropower plant halted generation and opened its spillway gates to flush out floodwater and debris. Bhutan's National Centre for Hydrology and Meteorology is monitoring its stations at Tashithang and Yebesa.

The Central Water Commission's special advisory said that the surge in the Punatsangchhu basin could cause a sudden rise in water levels in Alipurduar in West Bengal and Dhubri in Assam. It estimated at first that the floodwater would reach the India–Bhutan border within six to eight hours. The commission is watching its stations at Barobisha, Sankosh LRP, Golakganj and Baladoba. The advisory named Kumargram, Chengmari, Pakriguri and Bholka, forest settlements and other low-lying areas as being at risk.

Evacuations in Alipurduar

Alipurduar's Superintendent of Police, Amit Kumar Shaw, said that between 4,000 and 5,000 people are in temporary shelters, many of them in school buildings, and that more than 6,000 others have been moved to safer ground. Schools and community buildings were turned into relief centres, and the administration arranged drinking water, dry food and sanitation. Shaw appealed for calm, saying that there was no need to panic and that the situation was under control.

Officials said that the intensity of the flow had eased slightly, but the red alert on the Sankosh river system remained in force. Warnings extend to parts of Alipurduar, Jalpaiguri, Cooch Behar and the Darjeeling region in West Bengal, and in Assam the district of Dhubri has been identified as vulnerable. The Assam chief minister was tracking the situation, according to one report, which put the time for the flood to reach Dhubri at six to eight hours.

State Disaster Response Force personnel have been deployed in West Bengal, and National Disaster Response Force teams have been mobilised to help the district administration. Civil Defence and local officials are also involved. West Bengal's forest minister, Manoj Kumar Oraon, who is the MLA for Kumargram, urged villagers and tea garden workers along the riverbank to move out. Darjeeling MP Raju Bista asked people living in the affected river catchments to relocate to safer ground, and state minister Nisith Pramanik said that disaster management personnel had been activated.

One report says the India Meteorological Department has forecast heavy rain in Alipurduar on Friday, which could complicate relief work.

A glacial lake outburst flood happens when a lake held back by ice or loose moraine gives way and releases a large volume of water at once. In mountain valleys such floods can carry boulders and debris far downstream, and they can arrive with little warning. Rivers that start in Bhutan, such as the Sankosh, run through the plains of North Bengal and Assam, where they spread out, and the effects can be felt many kilometres from the source.

Officials said the intensity of the flow had eased slightly, but the red alert on the Sankosh river system remained in force when the reports were filed. The cause of the burst, the full damage in Bhutan and the number of people who will need relief in India are still to be established.