Joshimath crisis: What is land subsidence and why does it happen?

Source: The post is based on the article “Joshimath crisis: What is land subsidence and why does it happen?” published in Indian Express on 9th January 2023

What is the News?

Joshimath, Uttarakhand has been declared as a landslide and subsidence-hit zone.

What is Land Subsidence?

According to the National Oceanic and Atmospheric Administration(NOAA), subsidence is the sinking of the ground because of underground material movement. 

It can happen for a host of reasons, man-made or natural, such as the removal of water, oil, or natural resources, along with mining activities. Earthquakes, soil erosion, and soil compaction are also some of the well-known causes of subsidence.

The subsidence can happen over very large areas like whole states or provinces, or very small areas like the corner of your yard.

What can be the reasons behind Joshimath’s subsidence?

Firstly, Joshimath city has been built on an ancient landslide material — meaning it rests on a deposit of sand and stone, not rock, which doesn’t have high load-bearing capacity. This makes the area extremely vulnerable to ever-burgeoning infrastructure and population.

Secondly, the lack of a proper drainage system might have contributed to the sinking of the area. Experts say that unplanned and unauthorized construction has led to the blocking of the natural flow of water, which eventually results in frequent landslides.

Thirdly, subsidence might have been triggered by the reactivation of a geographic fault — defined as a fracture or zone of fractures between two blocks of rock — where the Indian Plate has pushed under the Eurasian Plate along the Himalayas.

Fourthly, the incident might have occurred because of unplanned construction, over-population, and obstruction of the natural flow of water and hydel power activities.

Fifthly, residents have blamed NTPC’s Tapovan Vishnugad Hydro Power Project for the incident. They allege that the tunnel had water seepage from a punctured aquifer, leading to the drying of water sources in Joshimath.