Assessing Long-Term Land Subsidence Hazard in Bologna City Using PSInSAR Data

Land Subsidence (LS) poses a significant geological hazard in urban areas worldwide, driven by both natural processes and human activities. In this paper, LS is investigated in the city of Bologna, Italy, focusing on its evolution over the past three decades. The spatial and temporal patterns of LS are analyzed using satellite Synthetic Aperture Radar (SAR) data processed with Persistent Scatterer Interferometry (PSInSAR) algorithms to assess subsidence magnitude, evolution and hazard levels, emphasizing the importance of integrating multi-temporal ground deformation datasets for a comprehensive understanding of LS processes and their induced hazard. The results for Bologna show a notable reduction in LS rates over time from the early 1990s to 2022, along with changes in the distribution of hazard zones. While in the 1990s LS rates reached over 55 mm/year and hazard levels were high or medium across 12 km² of the 150 km² administrative area, as of 2022, high hazard levels became null, medium hazard levels reduced to 0.23 km² and LS rates under 15 mm/year, classified as low hazard, extended across 92 km². Overall, this study highlights the importance of monitoring and understanding LS dynamics in urban areas for effective hazard mitigation and urban planning.