Updating the subsidence map of Emilia-Romagna region (Italy) by integration of SAR interferometry and GNSS time series: the 2011–2016 period

Abstract

The analysis of the vertical movements of the soil in the Po River plane of the Emilia-Romagna Region (Italy) was updated through an interferometric analysis referred to the 2011-2016 time-span. This activity is a continuation of previous studies on the state of knowledge of vertical soil movements in the same area, analyzed firstly by levelling and GNSS and more recently by SAR interferometry for the periods 1992-2000, 2002-2006, 2006-2011, on behalf of the Emilia-Romagna Region. The survey area analysed was approximately 13 300 km 2 , which corresponds to the territory of the regional plain. The interferometric dataset was calibrated through the use of velocity time series of several permanent GNSS stations. Among the 36 stations analysed, 22 were included in the study area: 16 were used for the calibration and 6 as check points). The velocities required for the calibration of the SAR analysis were calculated in the period following the important seismic events that struck the territory of the Emilia Romagna Region in May 2012. The interferometric analysis was carried out by TRE ALTAMIRA using the SqueeSAR™ technology. In particular, in order to update the interferometric dataset to 2016, it was necessary to perform a joint processing of the available RADARSAT-1 data and of the data acquired by the RADARSAT-2 satellite using a specific operating mode of the SqueeSAR™ algorithm known as stitching; this approach allowed the joint processing of images acquired in the same geometry by these two satellites. The study of the time series of the GNSS permanent stations used to provide the velocity datum to the interferometric analysis, is described, and the results of the SqueeSAR™ interferometric processing are reported. Statistical analyses on the spatial distribution and the type of scatterers have been performed during the screening and validation procedures of the dataset, and for the identification and removal of the outliers. Finally, the resulting map is described in order to analyse the measured soil movements with respect to the results obtained in past analyses, and the possible geological and human-induced causes, which could have produced them.Published by Copernicus Publications on behalf of the International Association of Hydrological Sciences. 40 G. Bitelli et al.: Updating the subsidence map of Emilia-Romagna region (Italy)

Definition of the Local Geoid Undulation Using Non-contemporary GNSS-Levelling Data on Subsidence Area: Application on the Adriatic Coastline

“…Starting from the year 2006, the Emilia-Romagna region provides Subsidence Models for the area based on InSAR data every five years [12][13][14]: currently there is the availability of models for the periods 2006-2011 and 2011-2016. We extrapolated data of the later periods at epoch 2018.0 since the up-to-date model is still not available.…”

“…These benchmarks have been last measured through precise spirit levelling in 1999 and 2005 during campaigns for subsidence monitoring. In the following years Arpa, today Arpae, moved from spirit levelling to the InSAR technique for the monitoring of subsidence phenomena [12], therefore those gathered in 2005 are the most recent data about the orthometric height available for the coastal levelling networks.…”

Regression Analysis of Subsidence in the Como Basin (Northern Italy): New Insights on Natural and Anthropic Drivers from InSAR Data

“…To improve the spatial density of radar targets in non-cultivated or desert areas with moderate coherence due to small scattering objects, other techniques using Distributed Scatterers (DS) were then proposed, such as the Small BAseline Subset (SBAS) [17] and SqueeSAR [18] algorithms (for an overview, see [15]). Since their introduction, InSAR techniques have been largely applied for monitoring land subsidence, both in Italy [5,8,11,[19][20][21][22][23][24][25][26][27] and worldwide [2,6,12,13,[28][29][30][31][32][33][34][35][36]. The InSAR techniques allow the reconstruction of the deformation history of radar targets (PS) and for information about ground settlements to be obtained with high precision [23].…”

Remote Sensing Analysis of Surface Temperature from Heterogeneous Data in a Maize Field and Related Water Stress

“…The low-lying Ravenna coastal area has been historically affected by a widespread land subsidence process due to the superposition of natural processes, mainly the compaction of Quaternary deposits, and anthropogenic activities related to aquifer overexploitation, mechanical drainage, and gas withdrawal from a number of deep reservoirs scattered inland and offshore [15,16]. A recent survey of subsidence in the Emilia-Romagna plain carried out by the Regional Agency for Prevention, Environment and Energy (ARPAE) through interferometric data processing has quantified the subsidence of the study area over the period 2011-2016 being around 2-3 mm/year [17]. Combined with sea level rise, land subsidence significantly increases the exposure to flood risk of coastal areas and favors saltwater intrusion into the shallow coastal aquifer [18], seriously threatening groundwater quality, fertility and productivity of agricultural soils, and wetland biodiversity.…”