Regional and local land subsidence at the Venice coastland by TerraSAR-X PSI

Land subsidence occurred at the Venice coastland over the 2008-2011 period has been investigated by Persistent Scatterer Interferometry (PSI) using a stack of 90 TerraSAR-X stripmap images with a 3m resolution and a 11-day revisiting time. The regular X-band SAR acquisitions over more than three years coupled with the very-high image resolution has significantly improved the monitoring of ground displacements at regional and local scales, e. g., the entire lagoon, especially the historical palaces, the MoSE large structures under construction at the lagoon inlets to disconnect the lagoon from the Adriatic Sea during high tides, and single small structures scattered within the lagoon environments. Our results show that subsidence is characterized by a certain variability at the regional scale with superimposed important local displacements. The movements range from a gentle uplift to subsidence rates of up to 35 mm yr(-1). For instance, settlements of 30-35 mm yr(-1) have been detected at the three lagoon inlets in correspondence of the MoSE works, and local sinking bowls up to 10 mm yr(-1) connected with the construction of new large buildings or restoration works have been measured in the Venice and Chioggia historical centers. Focusing on the city of Venice, the mean subsidence of 1.1 +/- 1.0 mm yr(-1) confirms the general stability of the historical center.