Integrated landslide analysis using petrological investigation and drone based high resolution geospatial assessment: Irshalwadi landslide- A case study from Western Ghats of India

Landslides are global hazards and occur instantaneously with large destructions in terms of life and property. The present work is a case study of a large debris flow triggered by an intense rainfall event at Irshalwadi village on 19 July 2023 in Raigad district, Maharashtra, Western Ghats, India. The objective of this research is to study the large landslide using UAV data to get details information of the case of landslide trigger and geological information of Landslide. The rationale for this research is to enhance the understanding of landslide dynamics in basaltic terrain, which is essential for disaster preparedness and mitigation. UAV survey was performed using structure from motion (SFM) photogrammetry to generate high resolution orthomosaic images and digital elevation model (DEM) which were processed in a GIS environment. The methodology involved conducting a detailed geological study using high-resolution optical images (5 cm) from the UAV survey, along with field sampling and petrographic analysis of the sampled landslide material. The crown of the Irshalwadi landslide was situated in contact with the weathered basalt and compact basalt. Our observations revealed that the cracks in the compact basalt facilitated the transfer of rainwater to weathered basalt, promoting slope failure conditions. Validation using filed survey showed that the lithology and petrographic properties were crucial in landslide initiation. This study shows that UAV-based remote sensing in combination with petrographic analyses allows us to map and characterize the landslides with accurate dimensions, which is useful in analyzing the parameters that trigger landslides and this will help in the preparedness and mitigation of extensive landslide disasters globally in basaltic terrain.