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Abstract: Land subsidence and eustacy concurred to make the relative sea level in Venice (Italy) 23 cm higher over the last century. In order to protect the city and its lagoon environment from increased flooding, a series of mobile barriers are under construction at the three inlets of Lido, Malamocco, and Chioggia connecting the Adriatic Sea to the inner water body. Since 2003 work has been proceeding with the reinforcement and extension of the existing jetties and the construction of breakwaters, harbors, and a small island within the Lido inlet. We detected significant local settlements of a few centimeters between March 2008 and January 2009 at the three inlets induced by the construction works through an interferometric analysis of 30 satellite radar images acquired by the new German TerraSAR-X mission. On a more regional scale we observe that the city of Venice and the other major urban settlements on the lagoon littorals are not impacted by subsidence during this period. The very high spatial resolution of 3 m and the short repeat-time interval of 11 days of TerraSAR-X enable the investigation of displacements with an unprecedented observed level of details, opening new perspectives to geodynamic''s research and civil engineering sectors for the monitoring of large infrastructures with potential vulnerability to terrain motion. [Copyright &y& Elsevier]

Abstract: An original integrated monitoring method is designed to infer an accurate and reliable figure of regional land displacements in coastal areas where the presence of internal waters, wetlands, farmlands, urban and industrial centers usually reduces the efficiency of single ground-based and satellite-based measuring techniques. Five different methods, i.e. spirit leveling, Differential Global Positioning System (DGPS), Continuous GPS (CGPS), Interferometric Synthetic Aperture Radar (InSAR), and Interferometric Point Target Analysis (IPTA), are integrated into a Subsidence Integrated Monitoring System (SIMS) to overcome the limits characterizing each technique. The SIMS has been used over the past decade to provide a new image of the land displacements in the Venice region. The result exhibits a resolution never obtained before. The central lagoon, including the city of Venice, shows a general stability while the northern and southern lagoon extremities and their related catchment sectors sink with serious rates averaging 3 to 5 mm/year. The sinking rates increase up to 10–15 mm/year in the coastland south of the lagoon. Relatively small uplifts (less than 1 mm/year) are observed at the Alpine foothills and in a wide area comprised between the Euganean Hills and the lagoon. The observed land displacements have been associated to the geological features of the study region, i.e. tectonics, seismicity, differential consolidation of the middle–upper Pleistocene and Holocene deposits, and to anthropogenic activities, such as land reclamation and groundwater withdrawal. [Copyright &y& Elsevier]

The original morphology and hydrogeology of many low-lying coastlands worldwide have been significantly modified over the last century through river diversion, embankment built-up, and large-scale land reclamation projects. This led to a progressive shifting of the groundwater–surficial water exchanges from naturally to anthropogenically driven. In this human-influenced hydrologic landscape, the saltwater contamination usually jeopardizes the soil productivity. In the coastland south of Venice (Italy), several well log measurements, chemical and isotope analyses have been performed over the last decade to characterize the occurrence of the salt contamination. The processing of this huge dataset highlights a permanent variously-shaped saline contamination up to 20 km inland, with different conditions in relation with the various geomorphological features of the area. The results point out the important role of the land reclamation in shaping the present-day salt contamination and reveal the contribution of precipitation, river discharge, lagoon and sea water to the shallow groundwater in the various coastal sectors. Moreover, an original vulnerability map to salt contamination in relation to the farmland productivity has been developed taking into account the electrical conductivity of the upper aquifer in the worst condition, the ground elevation, and the distance from salt and fresh surface water sources. Finally, the study allows highlighting the limit of traditional investigations in monitoring saltwater contamination at the regional scale in managed Holocene coastal environments. Possible improvements are outlined. [ABSTRACT FROM AUTHOR]