InSAR data for detection and modelling of overexploitation-induced subsidence: application in the industrial area of Prato (Italy)

Abstract

Spaceborne-based monitoring for environmental purposes has become a well-established practice. The recent progress of synthetic aperture radar (SAR) sensors, including through the European Space Agency's (ESA) Sentinel-1 constellation, has enabled the scientific community to identify and monitor several geohazards, including subsidence ground deformations. A case study in the Tuscany Region, Italy, highlights the effectiveness of interferometric synthetic aperture radar (InSAR) in detecting abrupt increases in ground deformation rates in an industrial area of Montemurlo municipality. In this case, InSAR data enabled prompt identification of the phenomenon, supporting the authorities in charge of environmental management to thoroughly investigate the situation. First, an on-site validation was performed via field surveys confirming the presence of cracks and fissures on some edifices. Further analysis, including water pumping rates, settlement gauge and topographic levelling, corroborated the InSAR data's findings regarding vertical deformation. Integration of collected data allowed for spatial identification and assessment of the subsidence bowl and its source depth recognized by the remote sensing data. The Montemurlo case offers a procedural guideline for managing abrupt accelerations, identified by InSAR data in subsidence-prone areas due to fluid overexploitation. In fact, these data proved useful in helping local authorities responsible for hydrogeomorphological risk management. With the exacerbation of deformation issues in subsidence-prone regions due to climate change, early detection and monitoring of such phenomena are increasingly crucial, with InSAR data playing a central role in achieving this goal.

Keywords: Field surveys; GBIS model; InSAR; Sentinel-1; Subsidence; Tuscany.

Figure 1

Localization of the area of interest and of the ground deformation. Ground deformation maps of the period 2015–2022 of continuous monitoring in the Tuscany region and characteristics of the Sentinel-1 data.

Figure 2

Flowchart for monitoring detected deformation areas by InSAR continuous monitoring.

Figure 3

Spatial analysis of the ground deformation of Montemurlo. Ground horizontal (a) and vertical (b) velocity components of deformation in the industrial area of Montemurlo. Vertical ground deformation maps (× 10 exaggerated) by year (c) and time series of measurement points cross-correlated with nearby levelling points (d).

Figure 4

Spatial (a) and temporal distribution of anomalies in the area of interest. Spatial localization of the MPs showing acceleration or deceleration in the ascending or descending (APs) orbits and temporal distribution compared with a time series per orbit.

Figure 5

Vertical distortion close to the Wa measured by the vertical gauge in the borehole (a) and GBIS assessed results of depth and volume changes (b).

Figure 6

Section A-A’ (Fig. 3a), including all the involved subsidence analysis data and the GBIS-assessed source depth of the area of interest. The section shows the piezometric levels at different times, i.e., 2010 (pre-event), and 2019 and 2020 (post-event), on the geological background and the vertical and horizontal components recorded by the MPs.