Abstract
The Po River Delta (PRD, Northern Italy) has been historically affected by land subsidence due to natural processes and human activities, with strong impacts on the stability of the natural ecosystems and significant socio-economic consequences. This paper is aimed to highlight the spatial and temporal evolution of the land subsidence in the PRD area analyzing the geodetic observations acquired in the last decade. The analysis performed using a moving window approach on Continuous Global Navigation Satellite System (CGNSS) time-series indicates that the velocities, in the order of 6 mm/year, are not affected by significant changes in the analyzed period. Furthermore, the use of non-permanent sites belonging to a new GNSS network (measured in 2016 and 2018) integrated with InSAR data (from 2014 to 2017) allowed us to improve the spatial coverage of data points in the PRD area. The results suggest that the land subsidence velocities in the easternmost part of the area of interest are characterized by values greater than the ones located in the western sectors. In particular, the sites located on the sandy beach ridge in the western sector of the study area are characterized by values greater than −5 mm/year, while rates of about −10 mm/year or lower have been observed at the eastern sites located in the Po river mouths. The morphological analysis indicates that the land subsidence observed in the PRD area is mainly due to the compaction of the shallow layers characterized by organic-rich clay and fresh-water peat.
Highlights
Among the available InSAR datasets, only the Sentinel-1A/B entirely overlaps with the Global Navigation Satellite System (GNSS) observations obtained from the Continuous Global Navigation Satellite System (CGNSS) stations and the PODELNET network
Land subsidence processes can introduce not negligible local E-W movements that can provide a significant contribution to the measured InSAR LOS velocity: in this case, the information inferred from the observations acquired by a ground-based GNSS network can help to detect the areas not covered by InSAR, and/or to remove possible biases in the InSAR
Direction shows differences lower than 10 mm/year (Figure 8b): it can be noted that the Non-Permanent Sites (NPS) sites located on the complex sandy beach ridge of the PRD area (Figures 1 and 4a) are characterized by positive velocities or low/moderate negative rates, whereas the ones on the land reclamation and sedimentary areas are characterized by more heterogeneous velocity patterns, with land subsidence rates lower than 5 mm/year (Figure 4a)
Summary
Land subsidence afflicts many areas of the world, in particular the ones located along transitional environments, such as coastal areas, deltas, wetlands, and lagoons, which are becoming increasingly vulnerable to flooding, storm surges, salinization, and permanent inundation [6,7,8,9]. In these areas, subsidence can be usually considered as a consequence of a complex combination of natural and anthropogenic factors: the compaction of Holocene sediments, tectonic movements, sinkholes formation, volcanism, thawing permafrost, and the Glacial Isostatic Adjustment (GIA), are generally considered as the main natural sources of land subsidence [10,11,12]; aquifer-system compaction associated with groundwater/oil/natural gas depletion and storage, drainage of organic soils, underground mining, hydro-compaction and stress given by new constructions, are the principal drivers of the anthropogenic land subsidence [13,14,15,16,17,18,19]. The effects of climate change can dramatically increase the subsidence-related problems due to the rising of sea levels: the 2012
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
