SAR interferometry for landslides risk assessment at local scale: The case study of castagnola (northern Apennines, Italy)

In this work we describe the application of remote monitoring techniques based on radar interferometry (PSI and GB-InSAR) to assess the state of activity and the associated risks of the Castagnola landslide located in Northern Apennines (Liguria, Italy). The ongoing slope instability affecting the Castagnola area is a complex and still poorly understood phenomenon which in the last few decades has undergone numerous reactivations leading to damage to buildings and civil infrastructures. Following a geomorphological field characterization and an aerial photo interpretation of the site, we have analyzed and compared the past long term evolution of the ground movements using Persistent Scatterers Interferometry technique (PSI) from a set of ERS 1/ERS2 space-borne data acquired between 1992 and 2001 and the recent landslide displacements obtained from Ground- Based Interferometric Synthetic Aperture Radar (GB-InSAR) surveys. The results of the space-borne inteferometric data analysis have been compared both with the deformation measured at the head of 10 inclinometric tubes and with the openings of some cracks on buildings. The GB-InSAR monitoring has been carried out in three distinct campaigns from October 2008 to March 2009. The interpretation of the results has allowed to derive a multitemporal deformation maps of the landslide, showing the up-to-date displacement field and the mean landslide velocity. On the basis of the outcomes of GB-InSAR monitoring, the pre-existent boundaries of the Castagnola landslide have been modified.