Nieuws

Hidden flood barrier to protect Venice during high tides

Gepubliceerd op
16 oktober 2013

Over the next few years, 78 steel ‘swing doors’ will be installed in the Lagoon of Venice. Most of the time these swing doors will remain out of sight, lying flat on the sea bed. At high tide they will swing upwards, closing off coastal inlets. Venice will then be protected against the storm tides in the Adriatic Sea. Alterra researcher Professor Pier Vellinga has been closely associated with this project for many years.

Over the next few years, 78 steel ‘swing doors’ will be installed in the Lagoon of Venice. Most of the time these swing doors will remain out of sight, lying flat on the sea bed. At high tide they will swing upwards, closing off coastal inlets. Venice will then be protected against the storm tides in the Adriatic Sea. Alterra researcher Professor Pier Vellinga has been closely associated with this project for many years.

Venice is afflicted by acqua alta, high tides, several times a year. Flooding started to occur more frequently in the twentieth century because of rising sea levels and settlement in the city. That is why Venice is working hard to find ways of preventing further flood damage. "For a long time there was resistance to any technical solutions,” says Pier Vellinga, who has been associated with this research for more than 30 years. "There were also concerns about what the temporary closures would do to the ecological quality of the lagoon. However, the effect of the barrier on the lagoon is limited, I believe, because it is only closed a few times in winter. As a result of our advice, the decision was taken to go ahead with the project and free up the necessary financing.”

Vensluizen

The solution, consisting of movable gates that pivot on the seabed, was developed in the 1980s after the enormous 1966 floods. Alternative solutions were investigated at the time, such as completely shutting off the lagoon, turning it into a polder, or closing it off in a way similar to the dam at Oosterschelde. However, Venice wanted to avoid any pollution of the horizon and to retain the idea that the city had an open connection with the sea. Hence the solution with hidden flood barriers.

In 2004, work began on the final design and specific details. Pier Vellinga is a member of the Ufficio di Piano, the committee overseeing the implementation of the plans. "Our committee meets every two months to advise the government in Rome on progress, planning and priorities. We expect the flood barrier to be officially ready for use in 2017. It is estimated the project will cost €5.4 million. In addition, approximately the same amount will be spent on restoring the ecological quality of the lagoon and on work in and around the city, such as raising the pavements and adapting historical buildings. It is the only large infrastructure project that is going ahead in Italy at present. The taxpayer is prepared to make sacrifices for Venice.”

The flood barrier now being built is revolutionary, as well as complex and expensive, but it is important to safeguard the city and its stream of tourists. Pier Vellinga: “Piazza San Marco is flooded 30 to 40 times a year. The new barrier won't prevent flooding completely because the tourists like seeing it happen. However, as soon as the water is 10-20 centimetres deep in the square, the barrier will be shut. The barrier is bright yellow – typically Italian. You could regard it as a Ferrari that is protecting Venetian heritage. For the next hundred years, anyway.”