Explained: Why is Joshimath sinking

New Delhi, Jan 07: The Uttarakhand government banned construction work in and around Joshimath over land subsidence which resulted in cracks in 561 homes.

Joshimath is a town in the Garwhal Himalayas and is an altitude of 1890 meters. It is also an important way station on both the pilgrimage and trekking circuits. This town however is on a fragile mountain sloped houses 20,000 people. Moreover the problem has become immense due to unplanned and indiscriminate development.

A study by the Uttarakhand State Disaster Management Authority says that the town is located in an area that is prone to landslides. The first instance of subsidence was reported in the Mishra Commission report in 1976.

Piyoosh Rautela, executive director USDMA according to Hindustan Times said that the Joshimath town is covered with a thick layer of overburden material. Large boulders of gneisses and fragments of basics and schistose rocks are embedded in grey-coloured, silty-sandy matrix. This makes the town highly vulnerable to sinking, he also said.

The study said that the perennial streams, appreciable snow in the upper reaches and highly weathered gneissic rocks with low cohesive characteristics make the area prone to landslides.

"Flood events of June 2013 and February 2021 had adverse impact on the landslide zone with toe erosion and sliding along Ravigram Nala and the Nau Ganga Nala having increased since the February 7, 2021, flooding of Rishi Ganga," the study added.

Huge volume of debris-laden water brought down by the Dhauliganga during a previous flood event (February 2021) has also aggravated the toe erosion along the left bank of the Alaknanda, downstream of its confluence with the Dhauliganga river at Vishnuprayag. This adversely impacted the stability of the slope on which Joshimath town is situated," the study also added.

Further the study said that the eco-tectonic and geomorphic factors along with meteorological characteristics render Joshimath region highly vulnerable to subsidence.

Joshimath sits on the Vaikrita Thurst (VT), a tectonic fault line and the town is also very close to the main geological fault lines, the Main Central Thrust and Pandukeshwar Thrust (PT). The MCT passes below Halang, a little south of Joshimath town and juxtaposes with the rocks of the Garhwal Group and this brings the town under the impact zone of any tectonic activity on the MCT.

Hemant Dhyani, environmentalist and member of the Supreme Court appointed High Powered Committee said that the despite being fly aware of geological vulnerability of the area, hydroelectric schemes have been sanctioned around Joshimath and Tapovan, including the Vishnugad HE project.

The locals say that in the past 10 years, several new multi-storey buildings have come up in and around Joshimath town.One such building tilted due to subsidence activity.

The HT report citing Kailash Joshwal, a resident of Joshimath said that the blame is on the construction work on the hydropower project run by the National Thermal Power Corporation. This has worsened the situation with water from the power tunnels seeping into the houses.

The USDMA said that the reasons for the increase in ground seepage of water from surface could also be a cause for subsidence. Also, Joshimath town does not have sewage and wastewater disposal system.