Persistent Scatterer Interferometry in the post-event monitoring of the Idukki Landslides

The monitoring of pre-failure movements and their evolution over time is necessary to assess the predisposing and triggering factors. This research focusses on assessing terrain displacements in the Idukki district (Kerala, India) over a year before the deadly disaster, which occurred in August 2018; this disaster was claimed to be a dreadful one as it took off hundreds of human lives and properties. The post-event Persistent Scatterers interferometric analysis on a stack of 20 Sentinel-1 images was performed to analyse the precursory deformations of the landslides. From the results obtained, the study region is estimated to have undergone a displacement of -26 to +19 mm/year, which indicates the instability of the terrain. Also it is evident that the occurrence of the landslides in August 2018, has been due to the effect of the torrential rainfall and the increase in the pore water inducing instability, thereby causing displacement in the region.