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.
The announcement came after a high-level meeting took place among the senior officials of the Central government, Uttarakhand state officials, and top officers from agencies including the National Disaster Management Authority (NDMA), Geological Survey of India (GSI) and the National Institute of Hydrology (NIH).
As of Sunday, 68 families have been evacuated to temporary relief centres and around 90 more will be evacuated soon, according to officials.
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 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.
According to a report by the Mishra Committee in 1976, Joshimath lies on an ancient landslide deposit of sand and stone, and not on the main rock. So, this means that it resides on landslide debris. The report also highlighted the undercutting by river currents of Alaknanda and Dhauliganga as contributing factors to the landslides.
Geographically, the area is characterized by scattered rocks covered with old landslide debris consisting of boulders, gneissic rocks, and loose soil, with a low bearing capacity as per the report. These gneissic rocks are highly weathered and have a low cohesive value, making them susceptible to high pore pressure when saturated with water, particularly during monsoons.
The situation in Joshimath has been exacerbated by increased construction activities, hydroelectric projects, and the widening of the National Highway in the past couple of decades. These activities have made the slopes highly unstable and vulnerable to landslides. The running streams from Vishnuprayag and sliding along natural streams are also cited as other reasons for the city’s fate.
Several experts said that a complete shutdown of development and hydroelectric projects in the region would be the suitable step now. However, the immediate need is to relocate the residents to a safer place and then reimagine the town’s planning to accommodate the new variables and changing geographical factors.
Drainage planning is one of the most critical issues that need to be studied and redeveloped. The city is suffering from poor drainage and sewer management, leading to more waste seeping into the soil, loosening it from within. The irrigation department has been asked by the state government to look into the issue and create a new plan for the drainage system.
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”, according to a report to the media.