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Science

Venice continues work on massive flood protection project

The MOSE flood gates aim to stave off potential disaster in the city and the larger Venice lagoon when the Adriatic Sea surges. Local scientists say that such events are on the rise in recent years.

Venice scientists say high water events are increasing

Venice scientists say high water events are increasing

Last month, under the bright summer Italian sun, tourists rolled up their trousers and waded through water in front of the centuries-old Basilica on Venice's famous Piazza San Marco.

This was one of the most recent occurances of "acqua alta," or "high water," a term used in the Veneto region for the exceptional tide peaks occurring in the Adriatic Sea, which reaching their maximum in the Venetian Lagoon, invade the foundations and inundate the older and lower parts of Venice.

According to the technicians at the city's Tide Monitoring and Forecast Center, these high water events are becoming more frequent and last a longer time.

"The worry is that the increase in the frequency of these high water events doesn't show any sign of slowing down," said Paolo Canestrelli, the Center's director said in a recent interview with Deutsche Welle. "It's increasing at an almost exponential rate."

Canestrelli cited various reasons for this, one of which he says is climate change. He added that the fluctuating environment has caused rising sea levels and more frequent storm surges. Plus, he noted, the land the city sits on is also sinking - it's estimated Venice has sunk at least 23 centimeters (9.05 inches) in the past century.

But whatever the reason, the data speaks for itself.

Venice's Tide Monitoring and Forecast Center said that 2009 was a record year for high water

Venice's Tide Monitoring and Forecast Center said that 2009 was a record year for high water

A 'record' year

According to Canestrelli, 2009 was a record flood year in Venice - the worst in more than a century. The tide reached 80 centimeters, flooding large parts of Piazza San Marco, more than 125 times. It reached 110 centimeters, and so invaded large parts of city 16 times.

In the decades since Venice began officially recording the "acqua alta" measurements in the early twentieth century, tides of greater than 110 centimeters occurred on an average three or four times a year.

This year, 2010, Canestrelli says, already promises to be worse.

"I think that this year we'll reach a record higher than that of last year," he warned in September. "We've already had 102 cases of water higher than 80 cm. So already 102 times, Piazza San Marco has seen water and there's still four months to go."

A decades-old plan

The MOSE project encompasses 78 floodgates to block the inlets when the tide reaches over 110 centimeters

The MOSE project encompasses 78 floodgates to block the inlets when the tide reaches over 110 centimeters

That's why now, more than ever, the city needs a huge barrier to protect itself.

The MOSE project, an Italian acronym for "Experimental Electromechanical Module" - and an allusion to Moses, who parted the Red Sea - is intended to protect the city from exceptional high water events. Work has been underway on the project since 2003 and engineers recently estimated that it still won't be completed for a number of years to come.

MOSE provides for 78 floodgates that will rise and block the three inlets connecting Venice with the Adriatic Sea, when a tide of 110 centimetres or more is forecast.

When the alarm sounds, compressed air will fill the gates and empty them of water. They'll rotate around their hinges, emerge from the depths and cut off the lagoon from the sea, stopping the tidal flow.

At the Lido inlet, the widest of Venice's three entrances to the sea, workers are building the concrete "caissons" or containers that will house 20 of those floodgates, each larger than the wing of a 747.

But it will be four more years before MOSE is able to protect Venice – two years longer than originally expected, and Venetians have been waiting for decades before that.

It was the great flood of 1966, causing the lagoon to rise almost two meters above its normal levels, which focused attention on the danger to the city. In 1987, a consortium of Italian companies, the Consorzio Venezia Nuova, was entrusted with finding a solution. But it wasn't until 2003 that construction actually began.

"Two thirds of the work has been completed now and we're waiting for remaining 25 percent of the money to do the remaining," said Giovanni Cecconi, a Consorzio hydrologist.

"From a technical point of view we are pretty much on schedule, and the only risk of delay can come from financing. By the year 2014, all the four barriers will start operation, if the money will come."

A multi-billion euro project

The budget of this massive construction project has ballooned to over 4.5 billion euros

The budget of this massive construction project has ballooned to over 4.5 billion euros

MOSE is the largest public works scheme in Italian history, involving 3,000 workers spread over several sites. Its budget has blown out from three billion to more than four and half billion euros. Critics fear it could cost taxpayers close to double that in the end.

At the Lido inlet construction site, Cecconi is also keen to trumpet MOSE's green credentials as the project has long been the target of conservationists. They say the lagoon is one of the most important wetlands in Western Europe and the tidal exchange with the sea is essential to its well-being.

Cecconi pointed out that the gates can be deployed just partially to minimise the effect on the environment.

"We leave the tidal flow in and out of the lagoon available all the time, but not during the storm surges, so (we'll deploy them) just three to five times a year, for three to four hours," he said.

But Cecconi's comments don't mollify Guido Ortalli of Italia Nostra, a group of citizens concerned to protect Italy's cultural heritage. He describes the project as "very heavy, very costly and technically complicated" and involving "really high maintenance costs."

Whatever the objections, most people agree that something must be done, or one of civilization's most beautiful locations may simply sink beneath the waves. Still, for many in Venice, the work on defending the city can't finish soon enough.

Author: Jean Di Marino, Venice
Editor: Cyrus Farivar

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