A novel workflow to map differential land subsidence risk using EGMS InSAR and urban settlement data: national scale assessment in Italy

Differential land subsidence affects many world metropolises, impacting their public and private infrastructure, including housing, transport and utility networks, social, healthcare and education facilities and, in turn, causing socio-economic impacts. This work showcases an innovative workflow based on geospatial data for exposure-vulnerability rating, hazard quantification and risk assessment. The methodology integrates Interferometric Synthetic Aperture Radar (InSAR)-derived information on ground displacement from Copernicus European Ground Motion Service (EGMS), with land cover and settlement characteristics from freely and openly available global datasets including the Copernicus Global Human Settlement Layer (GHSL) and DLR’s World Settlement Footprint (WSF). Such an integrated approach represents a significant step forward from InSAR displacement velocity-based approaches that are nowadays common in the specialist literature, to actionable risk information that are still rare. Land subsidence-induced deformation and structural stress on urban assets are quantified within the 15 metropolitan cities of Italy, along with the distribution and amount of residential/non-residential infrastructure and population exposed. Deformation-induced risk is assessed via the implementation of a tailored risk matrix enabling the geospatial intersection of four hazard (H1 to H4) and four exposure-vulnerability (EV1 to EV4) classes into 16 combinations of likelihood and impact (or also, probability and severity), and the consequent classification of risk in three levels (R1 to R3). The analysis shows that a total of 1.44 out of 2665 km² urbanised land within the 15 cities is at high risk (R3) due to significant angular distortions (and, sometimes, additive threat from horizontal strain) affecting very high exposure-vulnerability infrastructure. Moreover, it is estimated that, for more than 2700 buildings within the 15 cities, there is high likelihood of already occurred/incipient structural damage. The reference knowledge-base on present-day subsidence-induced risk can inform land and risk management at national scale, and provides a baseline for future assessments to build upon with a look to the next decades and sustainable urban development.

This work is funded by the European Union – Next Generation EU, component M4C2; project SubRISK+ (https://www.subrisk.eu/), 2023–2026 (CUP B53D23033400001). Value-added risk mapping outputs and statistics are openly available via the SubRISK+ ‘Control Room’ web platform (https://controlroom.subrisk.eu/).

Full details about the workflow and results are available in the full paper: Cigna F., Paranunzio R., Bonì R., Teatini P. 2025. Present-day land subsidence risk in the metropolitan cities of Italy. Scientific Reports, 15, 34999 (https://doi.org/10.1038/s41598-025-18941-8).