Lithological control of land subsidence induced by groundwater withdrawal in new urban AREAS (Granada Basin,SE Spain). Multiband DInSAR monitoring

Ground subsidence in the southeastern border of the Granada Basin (SE Spain) has been studied using remote sensing techniques. Over the last decades, the region has experienced a huge urban expansion, which has caused a substantial increase in water supply requirements. Water needs are exclusively met by groundwater by means of numerous pumping wells, which exploit a confined detrital aquifer of alluvial fan deposits with a heterogeneous facies distribution. A general piezometric level decline (up to 50 m) has been recorded in the aquifer during the past 30 years that has induced the generation of a subsiding area with oval shape oriented WNW‐ESE just where the new urban areas and pumping wells are located. Subsidence has been monitored by exploiting synthetic aperture radar (SAR) images from ENVISAT (2003–2009) and Cosmo‐SkyMed (2011–2014). A new approach, which combines A‐DInSAR and small‐area persistent scatterer interferometry (PSI) analysis, has been applied obtaining a good accuracy regarding temporal and spatial dimension of the subsidence. ENVISAT data (2003–2009) reveal subsidence rates up to 10–15 mm/year, and Cosmo‐SkyMed (2011–2014) values slightly lower; up to 10 mm/year. Temporal variations in the subsidence velocity are in accordance with the rainfall pattern and piezometric fluctuations in the aquifer. The sector with highest rates of subsidence does not correspond to the area with more intense groundwater exploitation but to the area with greater presence of clays in the confining layer of the aquifer. There is a clear lithological control in the spatial distribution of the ground subsidence. This work integrates detailed geological and hydrogeological data with differential SAR interferometry monitoring with the aim to better understand subsidence processes in detrital aquifers with small‐scale heterogeneity. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis with C- and X-band satellite SAR data of the Portalet landslide area

This paper describes the use of the Stable Point Network technique, a Persistent Scatterer Interferometry SAR technique, for the analysis of the Portalet landslide area (Central Pyrenees, Spain). For this purpose, different SAR datasets acquired by ERS-1, ERS-2, ENVISAT and TerraSAR-X satellites have been analysed. The use of different SAR images acquired by satellite radar sensors operating at different microwave lengths has allowed for a comparative assessment and illustration of the advantages and disadvantages of these satellites for landslide detection and monitoring. In the introduction, differential interferometry and the study area are briefly described. Then the specifics of the SPN processing and the results of the different datasets are described and compared. In Analysis of the results: the Portalet landslide area, the Portalet landslide area is introduced and the radar displacement measurements are analysed with available geo-information data. Additionally, X-band measurements are compared with those gathered by a ground-based SAR for a previous project. Finally, the most relevant conclusions of this work are discussed.     

A multidisciplinary investigation of deep-seated landslide reactivation triggered by an extreme rainfall event: a case study of the Monesi di Mendatica landslide,Ligurian Alps

Landslides - In November 2016, an extreme rainfall event affected the Ligurian Alps (NW Italy). Consequently, several landslides and debris flows occurred in the upper Tanarello stream basin. In...     

DInSAR analysis of ALOS PALSAR images for the assessment of very slow landslides: the Tena Valley case study

In this work we analyse the performance of advanced land observing satellite (ALOS) phased array type L-band syntetic aperture radar (PALSAR) images for mapping and monitoring of very slow landslides using conventional differential interferometry in the Tena Valley (Central Pyrenees, Spain). These results are compared with those retrieved in previous works where multi-band advanced differential interferometric synthetic aperture radar (DInSAR) analysis was performed for the same area using PSI techniques. The study area is largely underlain by slates (ca. 80 %) where large deep-seated very slow earth flows are dominant. The results reveal that DInSAR analysis is able to measure displacements of landslides with a greater spatial coverage than PSI analysis, but for a lower amount of them (nine against 51). Overall, the combination of the DInSAR and multi-band PSI analysis permitted to map and monitor 68 % of the landslides in Tena Valley. From this amount, 63 landslides are considered as active. The main advantage of DInSAR with respect to PSI analysis is the capability to detect faster movements (up to 145 cm?year^?1) derived from the 46 days interferograms. That is the case of Sextas and La Selva landslides where an acceleration of the moving mass was measured after intense rainfall periods producing major damages to linear infrastructures. The combination of measured displacement from ALOS interferograms, with the observed damages on the A-136 road, was useful to assess the potential damage that could cause these slow movements. In general, it is demonstrated that even though PSI analysis provides a better performance in terms of landslide mapping, L-band DInSAR analysis provides an added value for landslide hazard assessment through radar remote sensing. For this reason it is necessary to encourage the launch of new satellite missions similar to ALOS PALSAR that could operate with shorter revisiting time periods.     

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, for monitoring the impact of an offshore platform in the Adriatic Sea

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, was developed to evaluate the potential impact of an offshore gas platform in the central Adriatic Sea. Reference organisms were collected on a seasonal basis from an unpolluted site and transplanted for four weeks in both the sampling area and to the investigated platform. Chemical analyses of trace metals in mussel tissues were integrated with a multi-biomarker approach for the early detection of biological responses at several cellular targets. Induction of metallothioneins, peroxisomal proliferation and activity of acetylcholinesterase were measured as markers for specific classes of chemicals. Special attention was given to oxyradical metabolism and appearance of oxidative-mediated toxicity to reveal a more general onset of cellular disturbance. In addition to individual antioxidants (superoxide dismutase, catalase, glutathione S-transferases, glutathione reductase, Se-dependent and Se-independent glutathione peroxidases, and levels of total glutathione), the total oxyradical scavenging capacity (TOSC) allowed a quantification of the overall capability to neutralize specific forms of intracellular reactive oxygen species (ROS; i.e. peroxyl and hydroxyl radicals). Cellular damages were evaluated as lysosomal destabilization (membrane stability, accumulation of lipofuscin and neutral lipids), lipid peroxidation products (malondialdehyde) and DNA integrity (strand breaks and micronuclei); the air survival test was finally applied to evaluate the overall physiological condition of mussels. Concentration of trace metals (As, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn) revealed only limited variations in transplanted mussels during various experimental periods and such changes appeared partly related to natural fluctuations. Among biological responses, variations of antioxidants and lysosomal stability were confirmed as sensitive early warning signals for biological disturbance of both natural and anthropogenic origin. The presented protocol with caged mussels allowed marked biological effects caused by the investigated platform to be excluded, and represented a useful approach that is easy to extend for monitoring the impact of offshore activities in the Adriatic sea.