An in-situ loading test was carried out in the Lazzaretto Nuovo salt-marsh in the Venice Lagoon, Italy. The test was aimed at characterizing the geotechnical properties of soils forming the marsh sedimentary body deposits. In fact porosity and compressibility are of paramount importance to quantify consolidation versus accretion and relative sea level rise. The fate of coastal marshlands in the next future will strongly depend of these processes.

The Venice coastland forms the major low-lying area in Italy and encompasses a variety of environments, such as farmlands, estuaries, deltas, lagoons and urbanized areas. Since most of the territory lies at a ground elevation below or slightly above the mean sea-level, also a few mm/yr of land subsidence can seriously impacts on the coastal system. In this study, we present an analysis of the vulnerability to relative sea-level rise (RSLR) considering an uneven land subsidence distribution.

We have depicted the continental and marine surficial water–groundwater interactions in a large portion of the coastland encompassing the southern Venice lagoon and the northern Po river delta. The saltwater-fresh water transition zone is very irregularly-shaped and mainly depends on the morphologic setting and the subsoil architecture. An over-consolidated Pleistocene clay layer and buried Holocene sandy paleo-channels and paleo-ridge systems controlled the saltwater-fresh water exchanges.

Eighty regular TerraSAR-X acquisitions over the 2008-2011 period significantly improve the subsidence monitoring at the Venice coastland. Settlements of 30-35 mm/yr have been detected at the three lagoon inlets in correspondence of the MoSE works. The Venice and Chioggia historical centers show local sinking bowls up to 10 mm/yr connected with the construction of new large buildings or restoration works. In the city of Venice, the mean subsidence of 1.1±1.0 mm/yr confirms its general stability.