Doda land subsidence: GSI report recommends avoiding habitation, no new construction on slope
A Geological Survey of India (GSI) report has attributed land subsidence at Doda’s Nai Basti village to a multitude of factors and has recommended some immediate reconciliatory measures to the J&K administration that includes avoiding habitation on unstable slope.
A Geological Survey of India (GSI) report has attributed land subsidence at Doda’s Nai Basti village to a multitude of factors and has recommended some immediate reconciliatory measures to the J&K administration that includes avoiding habitation on unstable slope.
In February’s first week, at least 22 houses were emptied out and 300 people moved from Nai Basti after cracks spread across several structures, leading to the collapse of at least three.
A similar incident was also reported from Duksar Dalwa in Gool tehsil of adjoining Ramban district in February itself where land subsidence had damaged 16 houses, 500 meters of road between Ramban and Gool and a 33 KV electricity transmission line.
The disturbing developments in the eco-fragile Himalayan region that falls between seismic zone 4 and 5 had raised concerns among the people. The two incidents had had drawn parallels with the recent crisis in Uttarakhand’s Joshimath.
GSI’s deputy director general Dr Harish Bahuguna has sent the report to Jammu divisional commissioner Ramesh Kumar Jangid. The 22-page report, prepared by senior geologist Parveen Kumar and geologist Imran Khan, dwelt at length the triggers behind the land subsidence at Nai Basti and has recommended some immediate reconciliatory measures.
“As an immediate precautionary measure, it is advised not to allow people to dwell in the houses, which are in close proximity to the slide scars or where the ground cracks are lying immediately on the back slope or front slope of any house or houses,” it reads.
The report stated that excavation at the toe of slope for construction purpose may be one of the factors, which might have disturbed the intrinsic stability scenario of the slope.
“Poor drainage network and steep slope played a significant role in inducing the instability on the slope. Seepage of water in the cohesion less material aggravated the stability condition of the slope,” it added.
The two geologists also stated that prima facie, saturation of the slope forming material due to rainfall (on January 30 and 31) and poor drainage arrangements in the affected slope might have triggered the slope failure.
The experts also concluded that the affected part of the slope falls in medium to high landslide susceptibility zone as per the National Landslide Susceptibility Mapping (NLSM) by the GSI.
“A moderate to heavy rainfall of 62.6 mm for two days (January 30 and 31) before the slope failure was reported in and around the area and prima facie it may have acted as a trigger for the incident on February 1,” they added.
The GSI team recommended that since the part of the slope was unstable hence no habitation should be allowed.
“It is advised to fix tell-tales in the houses, which are close to the most affected zone, so as to monitor the development of ground distress, if any, in the adjoining area. Immediate measures for diverting the surface runoff away from the affected part of the slope should be provided. Retaining structure, at the toe of the slope at road level in consultation with the design engineer need to be provided with proper weep holes and drainage holes,” read the report.
The report also recommended spot bolting in consultation with the design engineer in the rocky portion of the slope.
“No new construction of houses, cowsheds, civil amenity be permitted in the down slope area which falls in the run-out trajectory of the slide. Providing the gabion structure at the river level is suggested to avoid the erosion of the left bank. It will ensure long-term safety of the NH-244,” the report stated.
The report further recommended landslide zonation of the whole areas on a larger scale because the whole Thathri town was built up on the similar type of geological and geomorphologic setup.
“As per the seismic zonation map of India, Nai Basti, Thathri lies in the zone-IV, where quakes of magnitude 7 or more are anticipated. Therefore, the study area is assessed as having high seismic sensitivity,” the two geologists stated in their report.
However, a senior official, who insisted anonymity, said, “No action has been initiated on the GSI report so far. In fact, we also received another report from the geology and mining department and are now awaiting a report from National Institute of Disaster Management. Based upon the three reports, action will be initiated.”