Unveiling Vulnerabilities: Assessing Subsidence Risks in Himachal Pradesh's Monsoon Season

The South Asian monsoon, which spans from June to September, brings about 80% of annual precipitation to the region. In 2023, this same monsoon period poured unprecedented rains in Himachal Pradesh causing havoc and loss (https://reliefweb.int/report/india/local-situation-report-0122023-16082023). For instance, the state witnessed 224.1mm of rainfall during five days between July 8 to July 12, which is a deviation of 431% increase from average rainfall, the highest since 1980. According to reports, on July 9, the Kullu district saw 131mm of rainfall in a single day which is the highest since 1971 causing loss of road infrastructure and lives. A monsoon surge, coupled with a western disturbance has led to extreme events resulting in flash floods, cloudbursts and associated landslides, subsidence and sinking of land(https://environicsindia.in/2023/09/08/preliminary-analysis-of-2023-disaster-across-himachal-pradesh/#:~:text=Three%20extreme%20spells%20(8%20to,some%20of%20the%20worst%20affected). Intense rainfall than normal tends to make more infiltration providing more water into the soil and below lying rock layers. This extra water when spills into nearby channels causing slow creep readjustment of the whole area in the form of subsidence. Similar subsidence events were reported in Sainj-Gushaini village where the permanent structure showed huge cracks and associated deformation. The members of the DExtER lab(IIT Mandi), visited the site in the Kullu district for a related study. The site intercepted deformation in the form of cracks in the houses, sinking of road etc. State of art PS-InSAR, SAR interferometry was performed in the area to decipher the rate of displacement. The results showed a high displacement rate (from -58mm/yr to 68mm/yr) at various locations of the village . Thus, It is concluded that the population dealing in the valley is vulnerable which will subsequently increase in the coming monsoon !

Fate of Parashar Landslide

Landslides and other related phenomena are detrimental to the economy as well as the population of Mandi district. The district has faced unprecedented amounts of rainfall, which in turn have led to the occurrence of landslides in the district. Last year, the region experienced cloudburst and flash flood situations in and around Baggi area. These increased precipitation have led to a massive landslide in Parashar area thereby causing damage to the existing bridge.

The destroyed bridge served as a main source of communication between the higher elevation village and Mandi main town. Further, it was reported by many commuters that cracks were developed along the existing landslides. Recent visit on 21st January by member of lab (Dr. Dericks, NItesh, Kirti and Nishant) conducted a drone survey around the affected areas. The drone survey revealed about the development of new cracks in the crown part of the existing landslide which can lead to development of potential slip surface in near surface if not warned timely. Thus, it is required that these areas should be kept under strict supervision. 

Landslide Susceptibility Mapping of Kangra district

Ankit Singh

Landslides have posed a significant threat to the nation's economy. To minimize the losses caused due to it, a landslide susceptibility mapping (LSM) is important for future planning and management. In this article, Probable landslide locations in the Kangra district were identified using an integrated approach of landslide dataset, geoenvironmental factors, and statistical method. Results showed that the popular tourist location Dharmashala is under a zone of very high susceptibility. Thus, it is important to analyse the reasons and implement suitable measures to avoid any loss of property and lives.