Thursday, 28 SEPTEMBER 2023 | PNS | DEHRADUN
The Wadia Institute of Himalayan Geology (WIHG) has attributed hydrological or groundwater imbalance at the high slope areas as the main reason for the landslide and development of cracks in Joshimath. WIHG was among the eight institutes roped in by the Uttarakhand State Disaster Management Authority (USDMA) to find the cause of land subsidence in Joshimath town earlier this year. In its conclusive report submitted to the National Disaster Management Authority (NDMA) and USDMA the WIHG said that it found a water saturated zone in the Manohar Bagh region that extended from five metre below surface to a depth of 30 metres with the help of the resistivity and magneto telluric surveys which confirmed that the slide is being facilitated by the presence of water. The WIHG scientists pointed out the presence of many natural drains flowing down the slope and absence of proper drainage system as the causes of the hydrological imbalance in the Joshimath. “The household water might have also penetrated down and the loose debris materials were soaked with water. The structural, geomorphological and crack mapping along with water discharge at Jaypee Colony were carried out throughout the month of January, 2023. The joints and fractures on structural mapping are observed that might have provided a sliding plane for the Joshimath slope,’’ the report states.
The WIHG also acquired the LiDAR data on behalf of USDMA, which provided very high-resolution topographic images of the Joshimath area.
“The LiDAR- mapped topography shows moderate to high slope angles facilitating slow displacement, which has been active since decades and aggravated further by recent extreme events like rainfall coupled with the anthropogenic activities, which might have saturated the top soil to the threshold for initiating the sudden slide in January 2023,’’ the report further states.
A network of seismic stations, operated by WIHG, has recorded micro-earthquakes in and around Joshimath but it said that it is too early to state that the landslide in Joshimath was caused by any seismic activity.
