Manas Dasgupta
NEW DELHI, Oct 5: Fourteen people have died and 102 others, including 22 Army personnel, are still missing after the cloud burst over Lhonak Lake in North Sikkim triggered a flash flood in the Teesta river basin which has also washed away 14 bridges causing total traffic disruption, officials said on Thursday.
The lake outburst also resulted in the breach of the Chungthang dam, which is the largest hydropower project in the State.
Search and rescue efforts are continuing to locate the 22 missing soldiers in Sikkim, and the family members of the missing soldiers have been contacted and informed about the situation, the Defence Spokesperson in Guwahati said on Thursday.
“Continued efforts are on to dig out the vehicles submerged under the slush at Burdang near Singtam. The search for the missing persons now focuses on the areas downstream of Teesta River, the Spokesperson said in a statement. Of the 23 soldiers initially missing, one was rescued alive on Wednesday evening. “All other Indian Army personnel posted in Sikkim and North Bengal are safe, and they are unable to contact their family members due to disruptions of mobile communication,” the statement said.
The National Remote Sensing Centre, one of the ISRO centres, has conducted a satellite-based study on the outburst of the South Lhonak Lake in Sikkim by obtaining temporal satellite images (before & after) over the water body. “It is observed that Lake is Burst and about 105 hectares area has been drained out (28 September 2023 image versus 04 October 2023) which might have created a flash flood downstream,” an ISRO statement said on Wednesday.
The National Disaster Management Authority on Wednesday said the possible cause of the flash flood in Sikkim could be a combination of excess rainfall and a Glacial Lake Outburst Flood (GLOF) event at South Lhonak lake in North Sikkim. A glacial lake outburst flood, or GLOF, usually results in more damage and destruction than a flood caused by excess rainfall alone. GLOFs occur when lakes formed by melting glaciers suddenly burst open. This can happen due to various reasons, such as excessive water accumulation in the lake or triggers like earthquakes.
Official sources said around 1 am on Wednesday, the South Lhonak Lake, a glacial lake in the upper reaches of Sikkim, burst its banks following a cloudburst in the area. The lake is around 17,000 feet above sea level and satellite images showed that nearly 65% of its water was drained, flooding the Teesta River.
All of this water flowed downhill, leaving destruction in its wake, and reached Sikkim’s biggest hydropower project – the Teesta-III project in Chungthang – about 5,000 feet above sea level. The water, with all the debris it picked up along the way, rammed into the dam, causing parts of it to give way.
This led to massive flooding downstream. The Central Water Commission said the Teesta was flowing below the danger mark before the dam burst and then breached the mark in a matter of six hours. Severe damage was reported in all downstream areas of the river, including Mangan, Dikchu, Singtam and Rangpo. Bardang, the town where the 23 Army personnel were washed away and went missing, is also on the banks of the Teesta river. Road links to Gangtok have been cut off because sections of National Highway 10 have been washed away.
As many as 14 bridges have been washed away in the state and over 3,000 tourists are reported to be stranded. Mobile networks and broadband connections have been disrupted in Chungthang and most of North Sikkim due to fibre cable lines being destroyed by the flash floods in Sangkalan and Toong in Mangan district.
The Army is laying down Bailey bridges so that essential items can reach all affected areas. The state government has also set up relief camps in various places, including Singtam, Rangpo, Dikchu and Adarsh Gaon.
Troops are extending medical aid and telephone connectivity to civilians and tourists stranded in the areas of Chungthang, Lachung and Lachen in North Sikkim, the Spokesperson added. All government and private schools, colleges and universities in Sikkim will remain closed till October 15 due to the prevalence of inclement weather, according to a revised circular by the State Education Department on Thursday.
The circular comes within hours of Chief Minister Prem Singh Tamang’s directive for the closure of schools, colleges and universities in Sikkim till further notice due to the unprecedented disaster caused by flash floods in the Teesta river basin.
Army and NDRF search teams continued to work their way through the slush in the Teesta basin and downstream north Bengal for a second day in search of people who were swept away by a flash flood, officials said on Thursday. Fourteen bodies have been found so far while 102 people, including 22 Army personnel, remained missing.
So far, 2,011 people have been rescued, while the calamity that happened on Wednesday affected 22,034 people, the Sikkim State Disaster Management Authority (SSDMA) said in its latest bulletin. The State government has set up 26 relief camps in the four affected districts, it said. A total of 1,025 people are taking shelter in the eight relief camps in Gangtok district, while the number of inmates at the 18 other relief camps was not available immediately.
