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There was a major landslide at a hydroelectric dam in India.


Satellite image of the site of the Subansiri Lower Hydroelectric Dam, after the landslide. Image copyright Planet, used with permission. Image dated 29 October 2023.

The author of The Landslide Blog is Dave Petley, a renowned expert in the field of landslide research and control.

Image of a landslide partially covered with a transparent sand-colored overlay and the words “The Landslide Blog,” centered, in white

A major landslide took place on October 27, 2023 at the Subansiri Lower Hydroelectric Power facility in Assam, northern India. This event is significant as it has obstructed the only remaining diversion tunnel that was being used to redirect the river’s flow during the construction of the dam.

At least two videos of the landslide have been recorded and shared on Youtube.

The obstruction in the diversion tunnel resulted in a halt of water flow at the site. An article from Northeast Now, an Indian news site, provides a thorough coverage of the incident, including information about the Subansiri River blockage.

The coordinates for the site are [27.55482, 94.26049]. This is an image of the dam taken by Planet Labs on October 26, 2023.

Satellite image of the site of the Subansiri Lower Hydroelectric Dam, before the landslide.

The satellite picture shows the location of the Subansiri Lower Hydroelectric Dam prior to the landslide. The image is copyrighted by Planet Labs and was taken on October 26, 2023.

Notice the area of land where a landslide occurred to the northeast of the dam. This is where the most recent failure happened. Also, observe the water coming out from the tunnels beneath the dam on the eastern side of the channel.

In comparison, this is a picture taken on October 29, 2023, following the landslide.

Satellite image of the site of the Subansiri Lower Hydroelectric Dam, after the landslide. Image copyright Planet, used with permission. Image dated 29 October 2023.
The image of the Subansiri Lower Hydroelectric Dam site after the landslide, captured by a satellite. This image is copyrighted by Planet Labs and used with their permission. It was taken on October 28, 2023.

The water level behind the dam rose significantly on October 28, 2023, and is now overflowing over the spillway. While there is currently no urgent crisis, the period of no flow may have resulted in ecological harm.

One concerning issue with this occurrence is the lack of slope management. There have been reports of eight diversion tunnels being obstructed due to slope failures, and footage of additional landslides at the location.

An article from NDTV details the significant landslides that have occurred at this location and the resulting protests that took place over the weekend.

Reference

The Planet Team (2023) developed the Planet Application Program Interface to support the mission of improving life on Earth through space technology. It is based in San Francisco, CA and can be accessed at https://www.planet.com/.

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Text © 2023. The authors. CC BY-NC-ND 3.0

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