Venice is not sinking!

Oct 27, 2017 | geography, lagoon and islands, society, Venetian lagoon | 0 comments

An up-date about the complex issue of high tides and frequent floods in the city.

First of all, let us debunk the myth that Venice is sliding into the sea drastically. In fact the city does sink…but at a rate of approximately 4 cms per century, and that is a common and natural phenomenon known as subsidence, the compaction of the soil.

However the reason why Venice gets flooded on a regular basis is due to more complex circumstances than simple compaction.

Venice is a group of islets connected by bridges located in the centre of a vast lagoon that is separated from the Adriatic Sea by barrier islands called Lidi. Three natural channels connect the lagoon to the sea, and also create the access that made it possible for Venice to become a major port and a wealthy maritime trade centre.

Venice and its lagoon with the 3 inlets

Venice and its lagoon with the 3 inlets

It’s through these 3 inlets that the sea tides ebb and flow every 12 hours, with a tidal range of 30 cms. However, this is not always the case. Between September and February the tidal range can vary consistently, especially in stormy weather and when there is a full or a new moon. Strong winds and persistent rain are crucial and when all these circumstances occur, the city gets flooded. This has always happened from time immemorial and Venetians simply address to it as acqua alta, high water. People are often curious to know how locals handle a major raising tide… Well, they carry on with their routine, go to work, go to school…with some important adjustments though!

A typical day of acqua alta in Venice,156 centimetres, 1st Dicember 2008

A typical day of acqua alta in Venice,156 centimetres, 1st Dicember 2008

The Venice Tide Forecast Centre can monitor and anticipate any slight variation of the tide with extreme precision and alert all residents even with a text message. When a severe high tide is expected, a system of raised walkways enables the circulation of pedestrains and sirens sound to alert people in the city. Venetians get ready to face the day (or night), goods in the shops are moved to a safe level, rubber boots get ready to be worn. It all lasts approximately 3 or 4 hrs and then the tide recedes.

A typical day of acqua alta in Venice,156 centimetres, 1st Dicember 2008, photo by Marta Buso/Arici

A typical day of acqua alta in Venice,156 centimetres, 1st Dicember 2008, photo by Marta Buso/Arici

However, following the tragic flood of November 4th, 1966 when the tide reached 1 mt 94 cms above sea level, the Italian State outlined an integrated project to safeguard Venice and its lagoon. Understanding that the main threat is not so much subsidence as it is eustasy (that is the rise of sea level due to global warming) the project has also comprised the construction of 78 mobile barriers anchored within the 3 inlets, a complex water-engineering system estimated to start functioning around 2018. A pharaonic project which has been entirely designed by Italian experts and has cost the Italian State  5.493 million Euros. A real challenge!

The Mose System with the Barriers up

The Mose System with the Barriers up

 

Laura Sabbadin
BestVeniceGuides.it
www.venice-revisited.com