Land Subsidence in the Venetian area: known and recent aspects

The paper reviews three major factors responsible for the relative land settlement occurred in the Venice lagoon area over the XX century. The anthropogenic geomechanical subsidence, induced by groundwater over-exploitation, the geological subsidence, and the eustatic sea level rise have lowered Venice of about 23 cm with respect to the m.s.l.. Other causes deeply studied over the last years are: a) land sinking due to the expected gas production from the Chioggia-Mare reservoir, but the development project is to date shelved despite the reassuring results obtained by a modeling analysis, and b) geochemical subsidence due to peat oxidation and salinisation of clayey sediments taking place in the southern catchment of the Venice lagoon. Finally, an integrated subsidence monitoring system, based on leveling, GPS, and InSAR techniques, has been elaborated and used to provide a comprehensive image of the land displacements in the Venice region over the past decade.