Mario Floris

From ERS-1/2 to Sentinel-1: two decades of subsidence monitored through A-DInSAR techniques in the Ravenna area (Italy)

Land subsidence due to underground resources exploitation is a well-known problem that affects many cities in the world, especially the ones located along the coastal areas where the combined effect of subsidence and sea level rise increases the flooding risk. In this study, 25 years of land subsidence affecting the Municipality of Ravenna (Italy) are monitored using Advanced Differential Interferometric Synthetic Aperture Radar (A-DInSAR) techniques. In particular, the exploitation of the new Sentinel-1A SAR data allowed us to extend the monitoring period till 2016, giving a better understanding of the temporal evolution of the phenomenon in the area. Two statistical approaches are applied to fully exploit the informative potential of the A-DInSAR results in a fast and systematic way. Thanks to the applied analyses, we described the behavior of the subsidence during the monitored period along with the relationship between the occurrence of the displacement and its main driving factors.

Variation in the Occurrence of Rainfall Events Triggering Landslides

We analyze the climatic features of the Vicenza Province (NE Italy) and the characteristics of the exceptional rainfall event that hit the area in November 2010, triggering a huge number of landslides. Our analysis aims at identifying the hydrological variable related to the triggering of the recorded instabilities and the recent variation in the occurrence of rainfall events inducing landslides.

Phase and amplitude analyses of SAR data for landslide detection and monitoring in non-urban areas located in the North-Eastern Italian pre-Alps

Abstract The main aim of this paper is to exploit information obtained from satellite SAR data to detect and monitor instability phenomena affecting hilly and scarcely urbanized areas, overtaking some of the restrictions due to the presence of thick vegetation. To this end, phase and amplitude analyses of COSMO-SkyMed SAR data were carried out on two landslides located in the North-Eastern Italian pre-Alps: Cischele roto-translational slide and Val Maso rotational slide—earth flow. In the first case, the careful choice of processing parameters allowed to evaluate landslide displacement fields considering the phase difference between SAR acquisitions. In the second case, the speed of movement and the deep changes in morphology and vegetation induced by the landslide did not allow to apply DInSAR techniques; in this case the variation in the amplitude between SAR acquisitions allowed to detect the area affected by the instability. Obtained results show that methods and techniques to analyse satellite SAR data could be further refined in order to provide useful tools for landslide mapping and monitoring.

Using Data from Multiple SAR Sensors in Landslide Characterization: Case Studies from Different Geomorphological Contexts in Italy

An application of Differential Interferometry SAR (DInSAR) technique based upon C- and X-band SAR imagery is here presented. The aim of this study was to assess SAR technology’s applicability and reliability for landslide detection and monitoring. To this purpose, two test sites have been selected, both located in Italy, which are affected by slow-moving landslides: Rovegliana, falling within the North-Eastern sector of Italian Alps, and Varco d’Izzo, which belongs to the Southern Apennines. Results from C-band (ERS and EnviSat) and X-band (COSMO-SkyMed and TerraSAR-X) imagery data allowed to identify several unstable areas previously undetected for the Rovegliana site, while the state of activity of Varco d’Izzo landslides was confirmed.

Testing Sentinel-1A Data in Landslide Monitoring: A Case Study from North-Eastern Italian Pre-Alps

Open image in new window The main aim of this study is to test the effectiveness of Sentinel-1A Synthetic Aperture Radar (SAR) data in monitoring scarcely urbanized slopes affected by slow-moving instabilities. To this end, geological and geomorphological surveys were carried out, satellite SAR data were processed and a GPS network system was installed. The study area, named Rovegliana, is located in the North-Eastern sector of the Italian pre-Alps. Rovegliana slopes are covered by eluvial, colluvial and landslide debris deposits which are mainly affected by superficial phenomena such as creep and soil slips. In situ surveys and Advanced Differential SAR Interferometry (A-DInSAR) processing of ERS, ENVISAT and COSMO Sky-MED SAR data pointed out that the instabilities are active with constant velocities up to 10 mm/year. Only the central and eastern sectors of the area were subjected to an acceleration after an exceptional rainfall event occurred in November 2010. GPS monitoring started in October 2015 and has been implemented through four campaigns made up of high precision geodetic measures of possible soil deformations of 22 vertices of a Global Navigation Satellite System (GNSS) static network. These vertices have been connected by a network to obtain a robust system. Comparing results from historical interferometric data, GPS measurements and interferometry processing of Sentinel SAR data acquired in the period 2015–2016, make it possible to verify if Sentinel data, characterized by short revisiting time, can be used as useful tool to define the spatio-temporal evolution of the recorded instabilities, overcoming the limits of applying interferometric techniques caused by temporal decorrelation due to the presence of vegetation cover, increasing the possibility to obtain significant information about landslide dynamics from SAR data. Moreover, we expect that the high number of planned acquisitions will improve the accuracy of deformation measurements.

Estimation of land subsidence in deltaic areas through differential SAR interferometry: the Po River Delta case study (Northeast Italy)

ABSTRACT River deltas are very complex environments vulnerable to flooding. Most of the world’s deltas are facing the immediate threat of land subsidence that jeopardizes the safety of millions of people worldwide. In Italy, the Po River Delta (PRD) (Northeast Italy) is an area historically affected by high rate of subsidence due to natural and anthropic factors. Even if the subsidence rates remarkably reduced during the last three decades, this process continues to be alarming in particular in low-lying sectors and along the coastline, where the loss of elevation, combined with the sea-level rise, increases the risk related to flooding. In this study, we monitored the subsidence affecting the entire PRD area with advanced differential interferometric synthetic aperture radar (A-DInSAR) techniques applied to three C-band SAR data sets acquired by the European Remote Sensing satellites, Environmental Satellite, and Sentinel-1A satellite in the last 25 years (from 1992 to 2017). The results of the interferometric processing, consisting of both mean velocity and displacement time series along the satellite line of sight, validated by comparison with levelling and global positioning system measurements, show increasing subsidence moving from the inland to the coastline, with maximum deformation velocities, for the most recent data, in the order of −30 mm year−1. In particular, many embankments near the coastal area are affected by high values of subsidence, which increase the flooding hazard of the entire deltaic territory. This work shows the importance of adopting A-DInSAR techniques to update the knowledge of the extent and rates of deformation of subsiding areas in low-lying territories such as river deltas. The outputs of such monitoring can be of primary importance for the future protection of the territory and the flooding risk mitigation.

The Ligosullo (UD, Italy) Landslide, Revisiting of Past Data and Prospects from Monitoring Activities

The paper focuses on the analysis of a landslide, located in the northern sector of the Friuli Venezia-Giulia Region (North-Eastern Italy) affecting the village of Ligosullo. Field surveys, geophysical investigations and interferometric analyses, financed by the Geological Survey of Friuli Venezia-Giulia Region in the last 15 years let to recognize a sliding surface up to 70 m deep, causing the mobilization of 7 millions m3 of material. A new phase of studies including geological and geomechanical surveys and monitoring activities has been recently undertaken by the University of Padua (Department of Geoscience) and NHAZCA S.r.l. (Spin-off of “Sapienza University of Rome”). The first results we obtained and the future goals are discussed in this paper.

Caratterizzazione geotecnica e mineralogica di depositi vulcanici alterati soggetti a fenomeni di scivolamento nell'area pedemontana della Provincia di Vicenza

The main aim of this study is to investigate triggering mechanism of landslides which widely affect altered volcanic rocks outcropping in the Italian pre-Alps of Vicenza province. To this end, geotechnical and mineralogical tests were performed. The results show how the variation of mineralogical properties of the soils influences the stability of the involved slopes. Based on this finding, numerical simulations have been carried on to evaluate the influence of mineralogical properties on the decay of strength parameters.