Space-borne and ground-based SAR interferometry for landslide activity analysis and monitoring in the appennines of Emilia Romagna (Italy): Review of methods and preliminary results

This work concerns the application of SAR interferometry for the assessment of the long-term analysis of the state of activity of deep seated mass movements affecting some urban areas in the northern Appennines of Emilia Romagna region (from 1994-2001 space-borne ERS data) and for the real-time monitoring of active flow-like landslides in year 2002 (from ground-based system). These activities are part of an ongoing research project supported by civil protection authorities of the Emilia-Romagna region that involves several research institutes with diverse expertises. A set of test sites characterized by a high landslide risk have been selected mainly taking into account phenomena characteristics such as deformation rates and vegetation coverage, with respect to the employed techniques. After a preliminary detailed geomorphologic characterization of the sites, the interferometric analyses, still in progress, have been implemented. In particular space-borne DInSAR has been applied for 10 unstable areas using a set of ERS1/ERS2 data acquired in the last 7 years. From 9 interferograms, the line-of-sight displacement maps have been calculated and, later on, post processed in GIS environment in order to have on-slope-direction displacement maps that could fully be integrated with geomorphologic and ancillary data and that could semi-quantitatively be compared with other traditional monitoring data. The results obtained have been rather satisfactory, especially in some test sites where entire villages are settled on the mass movement, as in the case of Berceto (Parma) presented in the paper, and post-processed products have proved a significant amelioration of basic interferometric ones. Moreover, in order to measure terrain displacements induced by landslide characterized by high deformation rates and little urbanisation, ground-based SAR interferometry (GBInSAR) has been used for the monitoring of a test site located in the province of Bologna. This application proved that the LISA system adopted performs well even in clayey wet material, where signal attenuation is generally very strong.