Previous studies had shown water-levels in the former capital of the Maritime Venetian Republic had stabilized. New research claims it has actually submerged, and tilted to the east, by an unprecedented 2mm per year over the last decade. Earlier studies had suggested it was submerging at just 0.04mm per year. The patches of land in Venice's 117 island lagoon are also sinking. Northern sections are dropping between 2 to 3mm per year, while the southern lagoon is subsiding by 3 to 4mm over the same period.
A study to be published in the American Geophysical Union's journal Geochemistry, Geophysics, Geosystems said the current subsidence was due to natural causes, such as plate tectonics. The Adriatic plate, which includes Venice, sub ducts beneath the Apennines Mountains and causes the city and its environs to drop slightly in elevation. About four or five times each year, residents and tourists must walk on wooden planks to stay above the floodwaters in large parts of the city. The city has invested billions of dollars into a flood defense system to prevent the city from sinking. A system of flood prevention walls that can be raised to block incoming tides is nearing completion.