Introduction:
Several roads and over 600 houses in Joshimath in Uttarakhand, the gateway town to the Badrinath temple have developed cracks over the past few weeks, causing panic and protests among the local population. While a high level meeting of officials from Centre, state govt and agencies like NDMA, GIS and NIH took stock of the situation on Sunday, the Supreme Court declined an urgent hearing on a plea relating to the incident. Based on recommendations by an expert panel tasked by the centre to assess the sinking of the ground surface in Joshimath, the authorities began demolition process of two hotels. Affected families are also being provided shelter by the state govt. According to experts, 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.
- Land subsidence occurs when large amounts of groundwaterhave been withdrawn from certain types of rocks, such as fine-grained sediments.
- Land subsidence is the lowering of the land-surface elevation due to changes that take place underground.
- Throughout, subsidence has damaged buildings, aqueducts, well casings, bridges and highways. Common causes include pumping water, oil or gas, dissolution of limestone aquifers known as sinkholes, drainage of organic soils and initial wetting of dry soils.
- As the land sinks, flooding problems are aggravated. Subtle changes in land gradient can adversely impact sewer lines and storm drainage. In all, subsidence has resulted in millions of dollars in damage.
- In general, the groundwater system responds to the climate. In wetter periods, water goes into storage, while in drier periods, or droughts, water is removed from storage.
- Long-term overdraft or excessive pumping of a groundwater aquifer, can also result in subsidence and sinking ground surface.
Causes of it:
- Joshimath falls in Zone V of the Seismic Zonation Map and has witnessed several earthquakes of magnitude of less than 5 on the Richter scale.
- It was found that a gradual settling or sudden sinking of the earth’s surface due to the removal or displacement of subsurface materials — has induced structural defects and damage in almost all wards of the city.
- According to the 1976 Mishra Committee report, Joshimath lies on a deposit of sand and stone, it’s not on the main rock. It lies on an ancient landslide.
- The report added that undercutting by river currents of Alaknanda and Dhauliganga are also playing their part in bringing landslides.
- Scattered rocks in the area are covered with old landslide debris comprising boulders, gneissic rocks, and loose soil, with a low bearing capacity.
- The area is a seismic zone, which makes it prone to frequent earthquakes.
- These gneissic rocks are highly weathered and have a low cohesive value with a tendency of high pore pressure when saturated with water, especially during monsoons.
- Increased construction, Overpopulation, hydroelectric projects, obstruction of the natural flow of water and the widening of the NH have made the slopes highly unstable in the last couple of decades.
Impacts of it:
- Cracks appeared in many roads and houses.
- 68 families have been evacuated to temporary relief centres and around 90 more will be evacuated soon, according to officials.
- It could affect the Char Dham project
- It could affect the tourism which was one of the major revenue generator for Uttarakhand.
- Livelihoods of many families involved in Tourism and allied activities could be impacted.
Way forward:
- Experts recommend a complete shutdown of development and hydroelectric projects in the region. But the urgent need is to relocate the residents to a safer place and then reimagine the town’s planning to accommodate the new variables and the changing geographical factors.
- Drainage planning is one of the biggest factors that needs to be studied and redeveloped. The city is suffering from poor drainage and sewer management as more and more waste is 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.
- The committee had recommended that restrictions be placed on heavy construction work, blasting or digging to remove boulders for road repairs and other construction, felling of trees.
- Experts have also suggested replantation in the region, especially at the vulnerable sites to retain soil capacity.
- While the state already has weather forecasting technology that can warn people of local events, its coverage needs to be improved.
