Flooding: Sinking Land and Rising Seas
The flooding in Venice is not entirely caused by the strong winter winds, additional factors including: subsidence, groundwater extraction, and rising sea levels are contributing to the sinking of Venice and the increased occurances of acqua alta. Subsidence is a natural occurring process resulting from the settling of coastal sediments, an inevitable process in the specific area of Venice. Additionally, the Earth’s tectonic plates are continually shifting, which in turn is driving the Italian plate beneath the Alps. The sedimentary settling and movement of plates are the causes as to why Venice is sinking by 0.5mm each year. Further sinking was caused in the 1920s when industry developed in Marghera and the Port of Venice. In order for these factories to function, mass quantities of fresh water were pumped from deep aquifers located beneath the lagoon. This system continued for decades until it was realized that the aquifers were vital cushions, helping to keep Venice buoyant. Between the years 1950 until 1970, Venice had sunk a total of 50cm. Once the Venetian government was made aware of the issue by geotechnical specialists, bans were placed on water pumping. An accompanying issue to subsidence and groundwater extraction is rising sea levels. As global temperatures increase, the heat causes land based ice to melt and seawater volume to expand, both of which together raise the sea levels across the world, this process is known as eustasy. It is predicted that by the year 2100, the global sea level will have risen by about 8-88cm.
 Fletcher, Caroline and Jane Da Mosto. The Science of Saving Venice. Turin: Umberto Allemandi & Co., 2004. p. 34.
 Carbognin, Laura, Teatini, Pietro, and Luigi Tosi. “Eustacy and Land Subsidence in the Venice Lagoon at the Beginning of the New Millennium.” Journal of Marine Systems. no. 1-4 (2004): 345-353.