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Climate change challenges sinking city of Venice

July 23, 2017 at 4:46 PM EDT
The Italian city of Venice is prone to frequent flooding because it has sunk five inches over the last century, but it is also grappling with a new challenge: sea-level rise, caused by climate change, which increases the severity. NewsHour Weekend Special Correspondent Christopher Livesay reports on the risks, and Italy's plans to mitigate them, as part of our series “Peril and Promise,” on the challenge of climate change.

CHRISTOPHER LIVESAY: Venice is a world class wonder. A city built on more than 100 small islands, connected by a maze of bridges and canals. The largest is the Grand Canal with its famous Rialto Bridge. Over the centuries, Venice has stood the test of time, but today this island city is under siege like never before…from “rising” seas and a “flood” of tourists.

MONICA CHOJNACKA: The fact that we are still waiting for any kind of solution of these problems of tourism and flooding is deeply depressing.

CHRISTOPHER LIVESAY: Historian Monica Chojnacka was born in Venice and proudly calls this city her home.

MONICA CHOJNACKA: That was the step you got on when you got off of your gondola or your boat to get into the house.

CHRISTOPHER LIVESAY: But she’s concerned about its future.

MONICA CHOJNACKA: This is a step that, of course, when it was built was never designed to be submerged in water. Now it’s always underwater even in this relatively low tide.

CHRISTOPHER LIVESAY: “Acqua Alta,” meaning high water, has always been a fact of life here. Several times a year, high tides and storm surges flood the city, especially the famous Piazza San Marco. The worst flood occurred in November 1966, when the Venice lagoon rose more than six feet above sea level.

CHRISTOPHER LIVESAY: After the deluge, the city designed an alert system which has kept pace with the times.

MONICA CHOJNACKA: What happens is we are alerted via an app as well as text messages and in addition, we have sirens that are blasted through the city.

CHRISTOPHER LIVESAY: Those warning sirens are coordinated from this command center on the Grand Canal. A siren is followed by pitched whistles. One whistle means about 12% of the city will be flooded, water is ankle deep, and shopkeepers barricade their doors. Two whistles means the water will be higher. Almost one-third of the city will be flooded.

MONICA CHOJNACKA: Three means run for the hills, because it’s going to be high!

CHRISTOPHER LIVESAY: Venetians generally take “Acqua Alta” in stride. Like the manager of the Gran Caffe Lavena, Massimo Milanese. He showed us pictures of his cafe during a recent flood. Tables and chairs sitting in the water.

MASSIMO MILANESE: See the special doors here.

CHRISTOPHER LIVESAY: Like others in the Piazza, he has flood doors to protect his business. He took us behind the cafe, where those flood doors are stored.

CHRISTOPHER LIVESAY: So the water can actually get this high?

MASSIMO MILANESE: The maximum that I saw — this.

CHRISTOPHER LIVESAY: Whoa. So just a couple of inches more, and this would have been useless.

CHRISTOPHER LIVESAY: He also keeps waterproof boots on hand for his employees.

CHRISTOPHER LIVESAY: Acqua Alta events are usually less than boot high, last just a few hours, and the city cleans up and goes back to normal. But floods also eat away at the soft, permeable bricks that sit above the foundations of the buildings. Over time, Venetians have raised their doorways and in some cases abandoned their ground floors. But the flooding is getting worse as the water level in the Adriatic Sea and Venice Lagoon rises due to climate change. The sea level alone has risen five and half inches since 1900, according to city officials.

CHRISTOPHER LIVESAY: The Italian government does have a plan to protect Venice. It’s called the MOSE project. Conceived in the 1970s, it’s a series of 78 underwater gates secured to the floor of the Venice lagoon. During especially high tides, they will be pumped with air and rise to the surface to block rising water from reaching the city. Four giant barriers across three inlets are scheduled to be operational by 2019.

CHRISTOPHER LIVESAY: Is MOSE able to defend Venice?

DARIO BERTI: Yes, MOSE will be able to protect the city of Venice from exceptionally high water. That means water that exceeds three-and-half feet above sea level.

CHRISTOPHER LIVESAY: So this is what the gate looks like when it’s down?

DARIO BERTI: Yes, this is the gate when it it standing on the bottom of the inlet.

CHRISTOPHER LIVESAY: Dario Berti is engineering and production manager with the company building the MOSE project. Construction began in 2003, testing, in 2013.

CHRISTOPHER LIVESAY: If this is the first project of its kind, how can you be so sure that it’s going to work?

DARIO BERTI: Well, this is the result of years and years of planning and experiments on models, trials in tanks. It’s been tested in all possible conditions. So, we’re certain it will work.

MONICA CHOJNACKA: One question about the MOSE project, these seawalls is whether it will be effective?

CHRISTOPHER LIVESAY: If it will be effective? They’ve spent billions of Euros on it. Shouldn’t it be effective?

MONICA CHOJNACKA: Yes, the latest estimates are between 5 and 6 billion Euros having been spent on this project. Certainly a portion of that money has not gone towards the building of the project but rather towards payoffs to local and regional politicians and business folk. Three years ago, about 35 of our leading citizens were arrested along with our mayor.

CHRISTOPHER LIVESAY: The mayor of Venice was arrested?

MONICA CHOJNACKA: The mayor of Venice was arrested as well on charges of corruption connected to this project.

CHRISTOPHER LIVESAY: A verdict on the case of that former mayor is expected this fall. Considering the corruption scandals, environmental scientist Jane Da Mosto says the Italian government should have gone back and reviewed the engineering and scientific basis for MOSE.

JANE DA MOSTO: There hasn’t been any kind of technical review about whether or not they are doing the right thing, and that I do find seriously alarming.

CHRISTOPHER LIVESAY: Da Mosto is executive director of a nonprofit group called “We are here Venice,” which is trying to raise awareness of the challenges facing Venice.

CHRISTOPHER LIVESAY: So there’s a lot of concern among Venetians that the work at MOSE isn’t being done properly?

JANE DA MOSTO: It’s not just amongst Venetians. Articles have been published in national newspapers, international journals. They have a problem about sand going into the indentations in the lagoon floor, where the panels then have to lie back down again. They found that the hinges, they’ve started corroding much sooner than they thought they would. They also keep delaying when they say it’s going to be ready. Not a good sign.

CHRISTOPHER LIVESAY: MOSE engineers say they are addressing the issues of sand obstructing the barriers and of rusting hinges.

CHRISTOPHER LIVESAY: But Luca Zaggia, from the Institute of Marine Sciences National Research Council of Italy, warns assuming they work, there’s a limit to how many times the defensive flood barriers can be deployed before they damage the lagoon.

CHRISTOPHER LIVESAY: How many times can you raise the flood barriers in a year?

LUCA ZAGGIA: We say 10 times a year is the best amount. Maybe 15 or 20 but no more.

CHRISTOPHER LIVESAY: But the climate is changing. The water level is rising. What happens 20 years from now, 30 years from now? Is that still going still to be the case?

LUCA ZAGGIA: No. Sure. We will close more frequently. Up 100 times a year.

CHRISTOPHER LIVESAY: 100 times a year? What is that going to do to the lagoon?

LUCA ZAGGIA: It will be a terrible disaster for the ecosystem. Stagnation first and then contamination and growth of microalgae.

CHRISTOPHER LIVESAY: It sounds very harmful.

LUCA ZAGGIA: Yeah, it is. You can have massive deaths of fishes in summer.

CHRISTOPHER LIVESAY: Most tourists are oblivious to the barrier system and seriousness of the flooding problem. They are busy taking selfies, marveling at the beauty of this car-free city, or trying to escape from the summer heat, like these tourists from Ireland we found in the shade of the tower in Piazza San Marco. They had no idea, until we told them, this plaque marks the historic flood of 1966, when the water level was so high, their children would have been neck deep.

CHRISTOPHER LIVESAY: The 25 million tourists who visit every year are actually another major threat to Venice. Souvenir shops and high-end boutiques catering to them have replaced vegetable stands, hardware stores, and other shops necessary for daily life. Housing prices have soared with speculators buying up property to rent to tourists. As a result, Venetians are moving away. At the end World War Two, there were 150,000 full-time residents of Venice. Now, there are only 54,000.

CHRISTOPHER LIVESAY: On some days, there are actually more tourists than residents, and that upsets Venetians like Matteo Secchi.

MATTEO SECCHI: The Venetian way of life is at risk, simply because we’re vanishing. There’s always fewer of us. We’re losing our culture. Because when a Venetian leaves the city, he doesn’t just leave the city, he leaves a way of life and culture.

CHRISTOPHER LIVESAY: In this fragile city, some residents say huge tourist cruise ships are making matters worse. Tommaso Cacciari is the founder of the group “No Grandi Navi,” meaning ‘No Large Ships.” It wants to ban large cruise ships from entering the Venice lagoon.

TOMMASO CACCIARI: There’s a mass amount of water that pushes back and forth. It’s called siphoning. It’s like an accordion that sucks the foundation of the city. There’s no concrete under here. There’s mud, soft material that gets sucked out.

CHRISTOPHER LIVESAY: This pier, he says, rebuilt seven years ago is already showing signs of damage from the cruise ships.

CHRISTOPHER LIVESAY: When they pass by, they create this huge pressure that basically sucks the sediment out from underneath us and actually lowers the foundation. You can see it really right before your eyes here with these bricks here.

CHRISTOPHER LIVESAY: The cruise ships employ five thousand Venetians, but the Venice Port Authority says only about a quarter of their passengers get off them and spend money in the city. Reining in the ships and the tourists is one challenge humans can control. Controlling the seas is not. Which is why Marine scientist Luca Zaggia is putting his faith in the MOSE project to save Venice for future generations.

CHRISTOPHER LIVESAY: So the system must work. The alternative is what?

LUCA ZAGGIA: The system must work. We have no alternatives at this point. It has to work.

Peril and Promise is an ongoing series of reports on the human impact of, and solutions for, Climate Change. Lead funding for Peril and Promise is provided by Dr. P. Roy Vagelos and Diana T. Vagelos. Major support is provided by Marc Haas Foundation.