Scores feared dead in flash floods in Sikkim

New Delhi At least 11 people were killed and over a hundred were missing in a remote region of Sikkim on Wednesday as a glacial lake overflowed after torrential showers, triggering flash floods down the Teesta that washed away homes and highways, and smashed through a crucial dam that powers the region.

Though some officials on the ground indicated the toll had already hit 40, the administration said it was waiting for more reports from the region to ascertain the cost to human life.

A senior official with the state’s disaster management said torrents of water that began coursing downstream around 1.30am on Wednesday,effectively cutting north Sikkim off from the rest of the state and marooning hundreds of people.

“We rushed out, and in 30 minutes, everything was gone. Our entire three storey home was washed away,” said Mina Tamang, a 70-year-old resident of Singtam town who barely escaped the cascading waters.

A Sikkim government statement said 120 people — including 22 army personnel — were still missing as night fell on Wednesday, as 15-feet-high columns of water swept away six bridges and chunks of National Highway 10 that connects the northern state to West Bengal.

Prime Minister Narendra Modi spoke to Sikkim chief minister Prem Singh Tamang and assured him of all possible help.

“Spoke to Sikkim CM Shri @PSTamangGolay and took stock of the situation in the wake of the unfortunate natural calamity in parts of the state. Assured all possible support in addressing the challenge. I pray for the safety and well-being of all those affected”, he posted on X.

“Emergency services have been mobilised to the affected areas, and I personally visited Singtam to assess the damages and engage with the local community,” Tamang wrote on X.

“At least 11 people have died and 120 are missing,” said Prabhakar Rai, director of Sikkim’s disaster management department.

Experts pinned the floods on unusually intense showers — the weather office said the remoteness of the terrain meant it didn’t have an accurate reading of the rainfall — and a glacial lake outburst flood (GLOF) in the South Lhonak Lake in northwestern Sikkim around 1am but stressed that the climate crisis had left the Himalayan region more vulnerable to such stresses and disasters than ever. The Indian Space Research Organisation (Isro) in a statement said its satellites observed “that the lake had burst”.

A GLOF is caused when the moraine (debris accumulated over the years by a glacier) that usually functions as a dam, creating a lake, is breached. It was not immediately clear as to what may have triggered the GLOF on Lhonak lake, although the risk has loomed large for at least a decade, said experts who had flagged the possibility.

“It was probably an avalanche that had a massive impact on the lake water, which in turn ultimately breached the moraine wall,” said Ashim Sattar, a scientist with IISc Bengaluru, who has studied the lake and the glacier extensively.

Sikkim declared the floods a disaster and authorities warned that the toll is expected to mount dramatically, with the possibility of missing people being found alive remote. With the Teesta flowing through four districts of West Bengal before entering Bangladesh, a flood alert was also sounded in north Bengal and the neighbouring country.

Officials said 45 people were rescued till Wednesday evening; 18 were hospitalised with critical injuries.

Visuals showed a swollen Teesta roaring through sparsely populated towns and villages, caking every inch of its path in mud and debris, and leaving little standing.

State disaster relief officials said around 4,000 people were evacuated from areas downstream of the dam early on Wednesday and moved to shelter homes.

Rai, director of Sikkim’s disaster management department said “the scale of the damage was still being assessed”.

Isro, in its statement, said the lake reduced in area from 167.4 hectare on September 28 to 60.3 hectare on October 4

Rescue operations began early on Wednesday morning, with four National Disaster Rescue Force (NDRF) and army personnel pressed into action to help the local administration in relief and rescue in Sikkim.

The India Meteorological Department (IMD) said north Sikkim received around 39mm rain between Tuesday morning and Wednesday morning, possibly triggering an avalanche that in turn led to the GLOF in the lake.

However, the weather office said it has no automatic weather stations in the affected region, rendering it nearly impossible to estimate how much rain pounded South Lhonak Lake.

“The flood water reached the Chungthang dam around 1am and triggered heavy damage in the Teesta 3 dam. By around 2.30pm, the low-lying areas in the districts downstream were flooded,” said an official, adding that the Teesta 5 dam downstream was partially damaged.̣

“The region where the GLOF occurred is extremely remote and we do not have automatic weather stations there so it’s very difficult to tell how much it rained there.”

As showers battered the remote mountain region, the water in the lake swelled, spilled beyond its edges and swept down the Teesta basin, wreaking havoc in downstream Mangan, Gangtok, Pakyong, and Namchi districts.

“As huge volumes of water and debris comprising boulders came gushing down, they hit the hydro dam in Chunthang,” said Sattar.

Experts underlined that the climate crisis had exponentially worsened the situation, and focused on the moraines — banks of rocks and sediment that are carried down by glaciers that settle along its edges.

As the earth warms, glaciers melt faster, and essentially recede, exposing these rocks and the sediment and pushing more water into the glacial lake — in this case, the South Lhonak. Spells of excess rain over these water bodies create a cascading effect, where the lakes, already filled to the brim, are fed with more water than they can hold, causing them to overflow and race downstream.

Jakob Steiner, hydrology expert and fellow of ICIMOD’s Himalaya University Consortium said, “It is possible that strong permafrost degradation in the vicinity of the lake may have destabilised the dam, which may have then failed upon an exceptionally strong rainfall event.

Some experts also pointed out that parts of northeastern India were jolted by an earthquake on Monday, and parts of northern India, by another on Tuesday.

Teesta Urja, the second biggest run-of-the-river hydro power project in India, suffered massive damage due to flooding caused by the breach in Lhonak lake.

The 1,200MW power project on Teesta river, one of the most dammed rivers in the country, is located between Chungthang and Mangan in Mangan district in North Sikkim and is the biggest of nine working hydro projects on the river in Sikkim.

The Indian Army in a statement said it rescued one person on Wednesday, even as 22 of its personnel remained missing.

West Bengal chief minister Mamata Banerjee instructed state officials to begin rescue operations.

“On the instructions of chief minister Mamata Banerjee, a team comprising state ministers and bureaucrats rushed to north Bengal to oversee rescue operations,” said an official with the West Bengal government.

Around 5,800 people have been rescued from the four districts of north Bengal and shifted to safer places. One column of the army was requisitioned to rescue a family stranded in Rangpo area.