| Abstract Submission No. | ABS-3.1-0144 |
| Title of Abstract | Process Based Probabilistic Modeling of Shallow Landslides using Satellite Derived Inputs and Geotechnical Parameters in Himalayan Mountain Environment: A Case Study for Lahaul-Spiti Valley |
| Authors | Sudhanshu Raghubanshi*, Ritesh Agrawal, Jayaprasad P, Rajesh B Upadhyaya |
| Organisation | Space Applications Center (SAC), ISRO |
| Address | Building No. 43, Room No. 62, Space Applications Center, ISRO Anmedabad, Gujarat, India Pincode: 380015 E-mail: sraghubanshi@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | Shallow landslides represent a significant geohazard in mountainous terrains where intense rainfall, steep slopes, and variable soil-vegetation conditions interact to reduce slope stability. The proposed study involves a process-based probabilistic model for shallow landslide initiation in the Lahaul-Spiti district, Himachal Pradesh, using Landlab in Python. The model couples the infinite-slope stability equation with steady-state subsurface hydrogeology under varying groundwater recharge conditions. Spatially distributed raster datasets representing topography, soils, and vegetation properties were used to parameterize model inputs. The model computes grid-cell scale factor of safety from the Mohr-Coulomb law, balancing friction and cohesion against gravity accounting for pore-water pressure. Slope and specific contributing area were computed using Copernicus DEM, with thresholds of 170 slope and ≤1 km2 upslope area used to delineate potential slope failure regions. Geotechnical parameters such as root cohesion was derived using vegetation cover from LISS-3 data. Internal friction angle, soil density, and saturated hydraulic conductivity were estimated from downloaded gridded soil texture datasets. Transmissivity was calculated by combining soil depth (obtained from Bhuvan portal) with saturated hydraulic conductivity. Recharge forcing was introduced using downloaded (from CHRS portal) global rainfall data. In the study region, estimated geotechnical parameters varied within the ranges as root cohesion (12.1-24.9 kPa), internal friction angle (220-380), soil density (1015-1854 kg/m³), saturated hydraulic conductivity (0.77-12 m/day), and soil depth (0.25-1.48 m). Uniform recharge scenarios with minimum and maximum rainfall values (0.44-3.25 mm/day) were tested for the study region. Using these topographical, geotechnical and hydrogeological parameters slope failure probability map was generated. The relatively low mean probability but non-zero unstable fraction highlights that the landslide hazard is localized rather than widespread. The model generates spatial probabilities of shallow landslides, highlighting the role of topography, vegetation, soil, and rainfall patterns and provides process-based susceptibility maps for geohazard assessment and risk reduction in the Himalayan region. |
| Keywords | Shallow Landslides, Geohazard, Landlab, Digital Elevation Model, Groundwater Recharge, Geotechnical Parameters, LISS-3. |