LAND SUBSIDENCE
1. Context
Almost a week after cracks appeared in many roads and hundreds of houses of Joshimath, Uttarakhand, authorities on Sunday declared it a landslide and subsidence-hit zone.
2. About 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 US-based agency’s website also mentions that this phenomenon can “happen over very large areas like whole states or provinces, or very small areas like the corner of your yard.”
3. The reasons behind Joshimath subsidence
|
The exact reason behind Joshimath land subsidence is still unknown but experts suggest that the incident might have occurred because of unplanned construction, over-population, obstruction of the natural flow of water and hydel power activities.
Not only this, the area is a seismic zone, which makes it prone to frequent earthquakes.
|
- The possibility of such an incident happening in the region was first highlighted around 50 years when the MC Mishra committee report was published and it cautioned against “unplanned development in this area, and identified the natural vulnerabilities.”
- 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 everburgeoning infrastructure and population.
- Moreover, the lack of a proper drainage system might have also contributed to the sinking of the area.
- Experts say that unplanned and unauthorised construction has led to the blocking of the natural flow of water, which eventually results in frequent landslides.
4. Tapovan Vishnugad Hydro Power Project
- As per the reports, residents have also 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.”
- Experts suggest that it could be one of the reasons for the collapse of the area.
- However, NTPC denied the allegations and in a statement said, “The tunnel built by NTPC does not pass under Joshimath town.
- This tunnel is dug by a tunnel boring machine (TBM) and no blasting is being carried out presently.
5. Conclusion
Apart from the aforementioned possible reasons, reports have pointed out that subsidence in Joshimath 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.
For Prelims & Mains
|
For Prelims: Land subsidence, Eurasian Plate, NTPC, MC Mishra committee, National Oceanic and Atmospheric Administration (NOAA),
For Mains:
1. What is land subsidence and discuss the reasons behind Joshimath subsidence and suggest remedial measures. (250 words)
|
Source: The Indian Express
