Was the landslide on the banks of Sikkim Lake the cause of the deadly flood? What do satellite images show?


Was the landslide on the banks of Sikkim Lake the cause of the deadly flood?  What do satellite images show?

Maxar’s photos show the site of cracks, broken ice, and landslides in the lake. High Race: Here

New Delhi:

New high-resolution satellite imagery obtained by NDTV on Friday shows the exact location of the breach in the high-altitude South Lonak Lake in Sikkim that led to the devastating floods, which claimed at least 50 lives.

Importantly, the images show exposed parts of the lake’s shores, indicating that the water level is dropping significantly after exiting the fissure, and down along the Teesta River basin. leading to massive flooding.

There is also evidence of landslides, which may have been an important factor in the erosion of the lake’s banks.

Arup R. Dasgupta, managing editor of Geospatial World (formerly GIS Development) magazine, said, “There is a lot of snow on the glacier right now, and this snowpack must have put a lot of pressure on the mouth of the lake, which has given birth to this rift.” Experienced ISRO Imagery Expert.

South Lehnak Lake is located in the highlands of North Sikkim at an altitude of 17,100 feet, not far from the India-China border.

The new images show the exact area where the glacial lake cracked. One of the images indicated that water was still gushing out of the lake on Friday, three days after the eruption.

An Oct. 6 Mexar satellite image shows the location of the South Lehnak Lake breach, where water continues to flow.  A low water level in the lake reveals an exposed shoreline.

An Oct. 6 Mexar satellite image shows the location of the South Lehnak Lake breach, where water continues to flow. A low water level in the lake reveals an exposed shoreline. Hi res here

As a result of the receding water level in the lake, a large area of ​​the coastline is now exposed, an area that was under water just three days ago.

In fact, scientists at the Indian Space Research Organization (ISRO) have already said that the area covered by the lake has shrunk by more than half, with only an estimated 60.3 hectares of water.

This February 7, 2023, photo shows the lake completely frozen, and under an ice sheet.  Hi res here

This February 7, 2023, photo shows the lake completely frozen, and under an ice sheet. Hi res here

South Lunak Lake was also filled by glacial runoff from the retreating North Lunak Glacier and Central Lunak Glacier. This increased the surface area of ​​the lake by 500 meters and the average depth by 50 meters, said lead scientist on the 2013 paper, Dr SN Remiya.

Photos from February this year show that the lake was completely frozen, although a fracture pattern is clearly visible on the surface of the ice.

Another photo from February 7, 2023 shows a fracture pattern in the ice sheet covering the lake.

Another photo from February 7, 2023 shows a fracture pattern in the ice sheet covering the lake. Hi res here

However, Friday’s photo shows a large amount of broken ice, and ice floes (floating ice sheets) on the surface of the lake. It is not clear whether the ice gave way due to downstream water flow that reached the breach or whether it melted substantially during the summer months.

An old satellite image from that day shows piles of snow and broken ice on the surface of the lake.

An old satellite image from that day shows piles of snow and broken ice on the surface of the lake. Hi res here

“The ice cover on the lake in the first images shows a regular fracture pattern, indicating that the ice sheet was likely under pressure from the glacier. This pressure was probably increased by fresh snow on the glacier. was as seen in the second image. This may have led to the breach,” said Mr. Dasgupta.

The images show the breakup pattern of the lake on February 7 and the broken ice on it on Friday.  Hi res here

The images show the breakup pattern of the lake on February 7 and the broken ice on it on Friday. Hi res here

The October 6 photo also shows clear evidence of landslides on one side of South Lahnak Lake. It is unclear whether the landside resulted in water displacement and was a contributing factor, resulting in the lake breaching its banks.

Satellite images from October 6 show clear evidence of landslides on the shores of the lake.

Satellite images from October 6 show clear evidence of landslides on the shores of the lake. Hi res here

“In Sikkim, the glaciers draining the lakes have shown rapid growth… South Lonak Glacier is no different. It is one of the fastest retreating glaciers and the associated South Lonak Lake State. has become the largest and fastest-growing lake in the world. . . . This has raised concerns about the potential for danger because the downstream (areas) are heavily populated…” Journal of Geomorphology in 2021. A study published in

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