Understanding the subsidence process of a quaternary plain by combining geological and hydrogeological modelling with satellite InSAR data. The Acque Albule Plain case study

This paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages. The study area is located about 20 km east of Rome (Italy) and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level. Extensive processing at different scales of SAR satellite images (ERS and ENVISAT provided by ESA in the frame of a CAT-1 project) by means of A-DInSAR technique was performed. The time histories of ground displacements, have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades (as the response to the anthropic stress) based on a large piezometric dataset. This comprehensive dataset allowed us to describe the space and time distributions of the subsidence process. The spatial pattern and deformation rate change is attributed to the following causes: i) the changes in the groundwater levels due to the intensification of mine exploitation (requiring dewatering operations) and ii) the distribution and thickness of recent compressible deposits. Specifically, it is derived that the groundwater level variations drive the timing of subsidence triggering over the area, whereas the local geological conditions control the magnitude of the deformation process.