Venice, Italy (1985-2003)
Eighteen years separate these two Landsat thematic mapper images of the city of Venice, Italy.
Venice, the city of canals, is the capital of the region of Veneto. The city stretches across a number of small islands in a marshy lagoon along the Adriatic Sea in northeast Italy. The saltwater lagoon runs along the shoreline between the mouths of the Po (South) and the Piave (North) Rivers.
The lagoon has a surface area of around 550km². It is around 8% land and about 11% is permanently water while around 80% is flat mud and salty marsh. It is connected to the Adriatic Sea by three inlets: Lido Inlet, Malamocco Inlet and Chioggia Inlet. The Lido Inlet represents the main entrance from the sea and is clearly visible in the two images as the funnel-shaped channel to the East of the city. Being at the end of a closed sea, the lagoon is subject to high variations in water level, the most extreme being the spring tides, which are better known as the acqua alta (high water), regularly flooding much of Venice.
Venice lies at the centre of the two images, right in the middle of the lagoon, with the Canal Grande (Grand Canal), the city's largest water way, cutting through it from North West to East. Its banks are lined with some of the most beautiful buildings in the city: amongst the many palazzos and churches are the Ca' Rezzonico, Ca' d'Oro, Ca' Foscari, Palazzo Barbarigo and the Palazzo Venier dei Leoni, housing the Peggy Guggenheim Collection. Due to the fact that most of the city's traffic goes along the Canal rather than across it, there are only three bridges, the most famous of which is the covered Rialto Bridge.
The Canale della Giudecca canal is also visible in the images, separating the city of Venice from the island of Giudecca to the South. Murano, famous for its glass making, particularly lampworking, is the small white island a mile north of Venice. The 5 km long Ponte della Liberta Bridge joins Venice to the city of Mestre, on the mainland.
The first Landsat-5 image was acquired on 23 September 1985 – This is a Landsat thematic mapper image of Venice, Italy, and its marshy lagoon in 1985. Venice was founded as a result of the influx of refugees into the marshes of the Po estuary following the invasion of northern Italy by the Lombard's in 568. It was built on more than 100 islands forming the archipelago of the Venetian Lagoon. Every means of transport is on water or on foot, with the countless canals serving the function of roads. The only causeways in Venice are the railroad station and the surrounding car parking lot which were added in the 19th and 20th centuries, respectively. Beyond these two land entrances at the North Western edge of the city, transportation within the city remains, as it was in past, entirely on water or on foot.
Venice is also served by the Marco Polo International Airport, or Aeroporto di Venezia Marco Polo, named in honour of its famous citizen. The airport is on the mainland and was rebuilt away from the coast.
The second Landsat-5 image was acquired on 21 February 2003 – The buildings of Venice are constructed on closely spaced wooden poles which penetrate alternating layers of clay and sand. The lack of oxygen in the clay layers preserved these pilings for centuries, allowing buildings of brick or stone sitting above these footings to remain intact. The buildings are often threatened by flood tides pushing in from the Adriatic between autumn and early spring.
The sink of Venice started in the twenties, when a whealth of artesian wells were dug into the periphery of the lagoon to draw water for the local industry. Although the sinking process has slowed markedly since artesian wells were banned in the sixties, the city is still threatened by more frequent low-level floods (so-called acqua alta, "high water") that regularly follow the autumn and spring tides.
To tackle the issue, in May 2003 the "Moses" project was inaugurated. Moses is the name given to a device made of a series of 79 inflatable pontoons lying across the sea bed at the three main entrances to the lagoon. When tides are predicted to rise above 110 centimetres, the pontoons are filled with air and block the incoming water from the Adriatic Sea. This challenging engineering work is planned to be completed by 2011.