INVESTIGATING THE POSSIBLE ROLES OF CAUSATIVE FACTORS LIKE ANTECEDENT RAINFALL, SATURATION AND GROUNDWATER IN LANDSLIDE OCCURRENCES OVER MAHARASHTRA

Abstract

The western ghats of Maharashtra, India experiences severe rainfall each summer monsoon during the month of June-September. The occurrence of rainfall Induced landslides accompanied by several other factors, are very common in the region. However, in July 2021, an unprecedented number of landslides occurred in the region, possibly due to heavy rainfall as its primary triggering factor. This work aims to comprehensively examine the cause of such large number of landslides and focus on the mechanism causing slope instability. In the study, we used the event-based landslide inventory developed by NRSC (National Remote Sensing Centre) to gather information about the landslide in the study area (Taliye Village) and developed our own landslide inventory using the Google earth imagery and ArcGIS 10.8 for the Mahabaleshwar landslide of Satara district. The Satellite based precipitation GPM product, namely GSMaP Global Satellite Mapping of Precipitation v6 hourly rainfall data of July 2021 was analyzed to identify the anomaly in rainfall intensity in the study area and the control of rain rate in landslide occurrence. Additionally, the Ground based IMD gridded Rainfall data is employed to assess the impact of 2-, 3- and 5-days antecedent rainfall on the landslide occurrence in the taliye village through comparative analysis with the two other time stamped landslides i.e Jui landslide (2005) and Malin Landslide (2014). For Mahabaleshwar region, we did landslide mapping in Google earth engine using the Sentinel- 1 and Sentinel-2 Satellite imagery along with the NASA Digital Elevation Model (DEM) data. This methodology identifies the potential landslide zones by calculating the backscatter intensity ratio (I_ratio) from pre and post event SAR data, refining it with slope and curvature thresholds and creating heat maps to visualize the landslide zones.