Explained | What is Land Subsidence and its connection with a Joshimath-like crisis

By Manjori Borkotoky and Aayushi Sharma

Joshimath is a town in the Garhwal Himalayas, situated at an altitude of 1890 metres in Uttarakhand. With a population of about 20,000, this town that grew on a fragile mountain slope is giving in to the effects of unplanned and indiscriminate development. The incidence of land subsidence has disrupted Joshimath recently.

The town area is prone to landslides and highly vulnerable to sinking due to scattered and highly weathered gneissic rocks with a low bearing capacity and loose soil due to seepage from streams uphill.

The exact reason behind Joshimath’s land subsidence is still unknown. Still, experts cite unplanned construction, over-population, obstruction of the natural flow of water, and hydel power activities as possible causes.

Who has been affected by the incident?

It is reported that more than 600 houses across Joshimath have developed cracks, and the most-affected families have been evacuated, so far. Residents have been petitioning in protest against the government to stop all the construction in the town.

All the developmental projects including the hydropower project are halted in and around the town with immediate effect.  Over 60 families have been evacuated to temporary relief centres and, officials said, another 90 families have to be evacuated. 

A meeting called by the Prime Minister’s Office decided that the immediate priority in Joshimath’s case, hit by land subsidence, should be the safety of people living in the affected area. Further, the state government should establish a clear and continuous communication channel with the residents, the PMO is learnt to have told senior state government officials.

Joshimath declared a land subsidence site

Joshimath, Uttarakhand has been declared as a landslide and subsidence hit zone by the authorities. The development came almost a week after the cracks started appearing in many roads and houses of Joshimath.

The decision to declare it a landslide and subsidence-hit zone was reached during the high-level meeting which took place among the top officials of the Central government, the state government officials, and officers from agencies like the National Disaster Management Authority (NDMA), the National Institute of Hydrology (NIH) and Geological Survey of India (GSI).

ISRO’s Report on Joshimath Subsidence

Meanwhile, news reports claim that Satellite images released by ISRO on Friday last showed that the Himalayan town sank 5.4 cm in 12 days. The Wire has reported that Joshimath, faced two subsidence events between April 2022 and January 2023, according to preliminary results released by the Indian Space Research Organisation’s National Remote Sensing Centre (NRSC). The report was, however, taken down with the organisation stating that the cause was that it was being misinterpreted negatively.

What is the phenomenon of Land subsidence?

The United States Geological Survey describes land subsidence as a gradual settling or sudden sinking of the Earth’s surface due to the removal or displacement of subsurface earth materials. According to the American body, subsidence is a global problem. Subsidence is most often caused by the removal of water, natural gas, oil or mineral resources out of the ground by the process of pumping, fracking, or mining activities. Natural events responsible for land subsidence are soil compaction, erosion, earthquakes and sinkhole formation.

The National Oceanic and Atmospheric Administration notes that subsidence can occur over very large areas such as whole states or even small corners such as a person’s garden.

Effects of land subsidence

Land subsidence can cause the settlement of clay on the upper levels which leads to damage to infrastructure and floods due to ineffective drainage systems in the area. According to some experts, this impacts houses and other infrastructure like roads by making them weaker and also leads to the weakening of foundations of buildings and develops cracks in them, similar to what is happening in the Joshimath region. This phenomenon can also cause earthquakes. Land subsidence can cause substantial economic damage in the area.

Cases of land subsidence in India

Land subsidence was observed in certain parts of Delhi like Kapashera, near the Indira Gandhi International Airport, with the specific land sinking at the rate of 11 cm per year during 2014-2016, which grew to more than 17 cm per year during the two years that followed.

In India, the prime cause of subsidence is the unregulated pumping of groundwater and the rapid pace of urbanisation. Such is the severity of land subsidence that experts estimate that by 2040, land subsidence will affect eight per cent of the world’s surface and approximately 1.2 billion people living in 21 per cent of the major cities across the globe. Studies report that “During the next decades, global population and economic growth will continue to increase groundwater demand and accompanying groundwater depletion and, when exacerbated by droughts, will probably increase land subsidence occurrence and related damages or impacts.” 

What are the possible reasons behind Joshimath’s subsidence?

The exact reason behind Joshimath land subsidence is still not known 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.
• Also, the area is a seismic zone, which makes it prone to frequent earthquakes.

 As per reports, the possibility of such an incident happening in the Joshimath region was first highlighted about 50 years ago 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 ancient landslide material. It rests on a deposit of sand and stone and is not rocky terrain, which reduces its high load-bearing capacity. This makes the area vulnerable to disaster due to ever-burgeoning infrastructure and population.

“The incidents of subsidence, fissuring, and cracking in the land surface of Joshimath, Chamoli District in Uttarakhand is fundamentally a result of geomorphological destabilisation of that region in the Garhwal Himalayas. Over the last four decades, intensive and indiscriminate infrastructure development has caused extensive upheaval and manipulation of the fragile landscape that rests on a stratum of overburden formed of soft soil, sand and debris that originated from glaciers and landslides in the geological past. The entire state is in a geo-tectonically unstable and seismically active zone. Notwithstanding such information being available to scientists, technocrats and policymakers, rampant destruction of natural ecosystems followed by aggressive construction activities for development infrastructure (roads, dams, tunnels, multi-storied buildings) continued beyond the tipping point,” said Dr Partha Jyoti Das, Senior Climate and Environmental Scientist and also Inhouse Consultant of CFC. 

He added that the probable environmental and social impact of many of these projects were not properly assessed. Critical opinions of some experts who thought the large-scale manipulation of the geo-ecologically susceptible hillscapes would invite disasters and jeopardise the ecological sustainability of the central Himalayan region, were ignored. He says that such a mindless approach to development defies all scientific logic and policy pragmatism on the part of the successive political governance concerned.

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. Experts suggest that NTPC’s Tapovan Vishnugad Hydro Power Project could be one of the reasons for the collapse of the area. 

Apart from all the mentioned reasons, reports have also noted that subsidence in Joshimath might also have been triggered due to 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.