Excess rainfall, glacial lake outburst likely cause of Sikkim flood: NDMA

The National Disaster Management Authority (NDMA) on Wednesday said the possible cause of the flash flood in Sikkim could be a combination of excessive rainfall and a Glacial Lake Outburst Flood (GLOF) event at the South Lhonak Lake in North Sikkim.

In a statement, the NDMA also said that the Himalayan mountain ranges are home to many glacial lakes, estimated to be around 7,500 using remote sensing techniques. Sikkim has about 10 percent of these, of which nearly 25 are considered endangered.

Giving details of the incident, the NDMA said in the early hours of Wednesday that there was a sudden increase in water flow in the Teesta river, which washed away several bridges, parts of NH-10 and Chungthang dam and destroyed several small villages affected. , towns and infrastructure projects in the upper river valley.

The main affected districts are Mangan, Gangtok, Pakyong and Namchi.

“While scientists are investigating the exact cause of the flash flood, the main reason for the sudden surge appears to be a likely combination of excessive rainfall and a GLOF (Glacial Lake Outburst Flood) event at South Lhonak Lake in North Sikkim,” said the report. in the statement.

The lake is located at an elevation of 5,200 meters, with a towering ice-covered spot about 6,800 meters north of and in close proximity to the lake.

Satellite images received from ISRO at 6 am on Wednesday show that more than half of the lake has emptied, most likely due to an avalanche from the ice-covered spot.

The Central Water Commission’s monitoring stations showed that the first wave of water was 19 meters above the maximum water level at Sangkalang at 1:30 am and 4 meters above the maximum water level at Melli at 4:00 am.

As soon as the news was received, the NDMA said, alerts were issued to downstream properties and relief and rescue operations were initiated by the NDRF, SDRF, ITBP, Army and Sikkim Civil Administration.

Several persons, including 23 army men, are missing, the report said.

Persistent snowfall in the upper reaches and rainfall and clouds in the lower reaches are hampering the deployment of helicopters and relief operations.

To mitigate the impact of a GLOF event in these lakes, an NDMA-led expedition recently surveyed two high-risk lakes in the first week of September 2023 to ultimately deploy early warning systems for real-time warnings.

In the next phase, the NDMA plans to install early warning systems for real-time alerts at most of the 56 endangered glacial lakes in India.

Efforts to expand the mitigation program are being accelerated while ongoing investigations into the causes of this event are conducted, the statement said.

Furthermore, the North Sikkim region is known for very localized heavy rainfall.

Therefore, efforts to improve predictive capabilities for such events will also be intensified in collaboration with relevant agencies, the NDMA said.