Eustacy and land subsidence in the Venice Lagoon at the beginning of the new millennium

Venetian land subsidence, both natural and induced by groundwater withdrawal, and northern Adriatic Sea eustasy have caused 23 cm of relative land subsidence referred to as the mean sea level over the last 100 years. This relative elevation loss has been vital for Veniceʹs existence, inasmuch as Venice lives in the water. After a short overview of the process during the past decades, the actual trend of relative ground-sea movement is presented by integrating high precision leveling, remote sensing measurements and tide gauge records. Geodetic and Interferometric Synthetic Aperture Radar (InSAR) data evidence the present ground stability of the central part of the lagoon, where the city of Venice is located, and slight sinking rates at the northern and southern extremities of the lagoon edges (3–5 mm/year) and at some places in the central and northern littorals (1–3 mm/year). At the same time, the latest tide gauge records indicate a renewal in the sea-level rising trend. Within the average secular eustatic rate of 1.13 mm/year, the value of −0.89 mm/year, observed near Venice during the period 1971–1993, increased to 1.53 mm/year when adding the records up to 2002.