Venice is seeking a backup flood protection plan just five years after the Mose barriers were launched. The barriers have prevented flooding 154 times but are increasingly raised due to rising sea levels, harming the lagoon's ecosystem.
Key points
Venice is seeking a backup flood protection plan.
The Mose flood barriers have been operational since 2020.
The barriers have prevented flooding 154 times.
Rising sea levels are increasing the frequency of barrier use.
Frequent use of the barriers harms the lagoon's ecosystem.
Mentioned in this story
Venice
Mose
The Arsenale, the colossal shipyard that was the engine of the Venetian Republic’s domination for seven centuries, remains the nucleus of the city’s control over the water. Its northern section is made up of cavernous brick warehouses called capannoni, which in the 16th century could produce a warship a day through a rigorously ordered assembly line.
Now, one of them houses the operations centre of the Mose, the sprawling flood defence system that protects the city.
The name stands for modulo sperimentale elettromeccanico (experimental electromechanic module) and is a nod to the biblical character who parted the seas. For Venetians who have seen their city devastated by storm surges they call acque alte, there is something miraculous about it: the massive, luridly coloured flood barriers sunk into the seabed at three inlets between the lagoon and the Adriatic have saved Venice from potential flooding 154 times since they were inaugurated in 2020.
But, despite the Mose having been in operation for only five years, city authorities are already looking for a plan B. Rising sea levels due to the climate crisis mean engineers are forced to raise the flood barriers more frequently, which damages the lagoon’s ecosystem.
Buildings on the bank the San Marco basin in Venice
The San Marco basin in Venice. Closing the flood barriers costs the city upwards of €200,000 a time Photograph: Emanuele Cremaschi/Getty Images
An alarming acceleration in sea level rise – an estimated extra metre by the end of the century – represents a “death knell for the city”, says Andrea Rinaldo, the head of the scientific committee of the newly appointed Lagoon Authority, the organisation that manages the Mose and is now also charged with working out what could succeed it.
“With a metre more, you would have to close the Mose barriers on average 200 times a year, which means it’s practically always closed,” Rinaldo says. “When this happens, the lagoon loses its nature of being a transitional environment. It would become a filthy pond.”
The tides create a natural exchange of water and sediment between the Venice lagoon and the Adriatic. The raised flood barriers block the flow of water, which encourages an excess growth of algae. When the algae die, they decompose, sucking out all the oxygen in the water and killing off fish and other marine flora.
Q&A
What is the Mose flood defense system in Venice?
The Mose is a flood defense system consisting of barriers designed to protect Venice from storm surges, operational since 2020.
Why is Venice looking for a plan B for flood protection?
City authorities are concerned that rising sea levels require more frequent use of the Mose barriers, which negatively impacts the lagoon's ecosystem.
How many times has the Mose system prevented flooding in Venice?
The Mose flood barriers have saved Venice from flooding 154 times since their inauguration in 2020.
What are the environmental concerns related to the Mose barriers?
Frequent raising of the Mose barriers due to climate change is damaging the lagoon's ecosystem, prompting the search for alternative flood protection solutions.
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Rinaldo insists the Mose is not poorly designed. It was envisioned as a project for the future, but that future came far sooner than its engineers expected. He is urging immediate action. “You won’t have a lagoon. You won’t have a city. And all of this could happen in a timeframe that is comparable with the time that we had to design and build the Mose. We can’t wait.”
Yellow flood barrier raised across two islets
The Mose is keeping Venice dry but its frequent use is encouraging an excess growth of algae in the lagoon. Photograph: PR Image
It took five decades for the Mose to be designed and brought into operation, after Venice suffered the worst flood in its history on 4 November 1966. The idea for flood barriers was fleshed out in the 1970s and the module was built in the 1980s, but bureaucracy and concerns over its environmental impact delayed its implementation.
In 2014, the then mayor of Venice, Giorgio Orsoni, was arrested on suspicion of corruption. His arrest tugged on a thread that revealed a network of cronyism and bribery that had swelled the cost of the project by millions of euros. Many Venetians were initially against the Mose because of its ballooning budget, its impact on the lagoon, and a certain cynicism that it would ever work. But then it did – and Venice has stayed dry ever since.
The inside of the Mose operations centre in the northern Arsenale looks like a Bond villain’s hideout, or perhaps a Silicon Valley tech startup: glass staircases, gleaming white walls and offices hidden in frosted Perspex cubes. The control room has the feel of a war room with its curving wall of screens, which display a panoply of meteorological conditions that could combine to create a storm surge.
The control room of the Mose flood defence system.
The control room of the Mose flood defence system. Photograph: PR Image
One screen shows a satellite image of Venice, boats appearing as flecks of white spittle in the grey lagoon. Giovanni Zarotti, the Mose technical director, explains that the tides never go unmonitored. The control room even has an exact replica elsewhere in the Arsenale complex, in case of a power cut or another technical issue.
It is a well-oiled operation but mistakes still happen. Zarotti says the decision is made to close the barriers three hours before the water level is expected to reach the height that would cause flooding.
“We’re relying on God, statistically speaking. We have a margin of error of 10cm. If we forecast 110cm and order the closure, there could be a sudden drop in wind and the water only rises 98cm,” he says.
Activating the Mose has a significant economic impact, not only because closing the barriers costs the city upwards of €200,000 (£175,000) each time, but also because it puts a halt to maritime traffic going through the Malamocco inlet on its way to the Marghera port. During the Venice carnival this year, the barriers were raised 26 times in just three weeks, costing the city more than €5m.
Aerial view of Venice lagoon
The sea level in Venice is predicted to rise by a metre by the end of the century. Photograph: Giorgio Marcoaldi /CVN
Zarotti says the team is experimenting with raising the barriers at each inlet consecutively, to stagger the impact, and is considering raising the activation level to 130cm. He admits, however, that Venetians have grown accustomed to the Mose and are far less tolerant of even light flooding. The last devastating acqua alta the city experienced was in 2019, when the city was engulfed by 187cm of water, flooding 80% of the city.
“Venetians now take the Mose for granted,” he says. “Many don’t even own waders any more. Imagine, if you’re six years old, you’ve never heard the sound of flood sirens.”
What the next project will be still needs to be defined. Rinaldo is enthusiastic about the intellectual possibilities of the challenge at hand. He plans to put out a global call for ideas from leading thinkers across a variety of different disciplines, from art and economics to history and science. Each group of experts would be given a grant and a year to devise a proposal, which would then be assessed by a scientific advisory board. The chosen projects would then be given to city authorities to put into action.
“Venice is a test bed for how we cope with these systems in the future,” he says, adding that it is a problem that can’t be solved by science and engineering alone.
He believes it is vital the city is entirely reimagined, in particular redirecting Venice’s economy away from its reliance on tourism, which is just as much a threat to the city as rising waters. Otherwise, what he calls a jewel of artistic heritage would be lost. He lets out a laugh. “Over my dead body!”
