Updating landslide inventory maps using Persistent Scatterer Interferometry (PSI)

This work illustrates the contribution of persistent scatterer interferometry (PSI) from radar satellites ERS (European Remote Sensing satellite) and ENVISAT (Environmental Satellite) for the updating of a pre-existing landslide inventory (LSI) map: the main purpose is to change or confirm the landslide state of activity and geometry and to identify new landslides. Radar data have been integrated with optical images and ancillary data in a 1320 km² wide river basin (Biferno Basin) located in the central-eastern part of Italy. The geological setting of the area is characterized by clay and alternated clayey, silt and sandy formations that are affected by slow landslides. Field validation confirmed the results and the capabilities of multi-interferometric synthetic aperture radar data, integrated and coupled with conventional techniques, to support landslide investigation at the regional scale thanks to the available archive of repeated satellite data, which provides measurements of ground displacements with a millimetre-scale accuracy. In the study area, about 9% of the pre-existing LSI has been modified by means of permanent scatterer (PS) information, 15% of which have changed the state of activity from dormant to active and 95 new landslides were detected. The radar interpretation method applied in Biferno Basin confirms its high capability of detecting and mapping landslides at basin the scale: the information acquired from radar interpretation is the basis of the proposed method to evaluate the state of activity and the intensity of slow landslides. However, it is clear that limitations exist and this method does not always support the updating of LSI for the whole study area. We consider this methodology and procedure as a portable and suitable one for different geological and geomorphological environments.