MOSE and Venice’s 50-year fight against floods

Libreria Acqua Alta is Instagram famous. More than 30,000 people have tagged themselves visiting the enchanting bookstore, but unlike other popular buildings in Venice, Libreria Acqua Alta isn’t a church or canalside palazzo. It’s quintessentially Venice in another way: It’s designed to outsmart the floods that have plagued the city for centuries.

Inside you’ll find books on Venetian cuisine stacked within bathtubs. English and Italian fiction titles are wedged beside each other, packed tightly in a gondola stretching from one side of the cramped shop to the other. They aren’t just there to add atmosphere. When the Italian city floods, as it does dozens of times a year, the bathtubs and gondola float, safeguarding the books inside. 

Libreria Acqua Alta gets its name from this phenomenon: Acqua Alta, which means “high water,” refers to the high tides from the Adriatic Sea that blow into the Venetian Lagoon. These floods have been a fact of life for Venice since the fifth century, but due to rising sea levels caused by climate change, they now pose a destructive threat. 

There were 34 instances of acqua alta between 2014 and 2018 that exceeded 110 centimeters (43 inches), enough to flood chunks of the city and cause chronic damage to its infrastructure. There were just 30 such events between 1875 and 1951.

The city’s residents, historic buildings and irreplaceable art are at risk. Some contend Venice itself will be unlivable by the end of the century. Several solutions have been proposed, such as pumping water or liquid cement under Venice to raise the city, as well as further fortifying the lagoon’s natural defenses.

Venice’s Libreria Acqua Alta suffered flooding in November 2019.


Instead, the Italian government is thinking on a grander scale. It’s spent the past 17 years building MOSE, a multibillion-euro infrastructure project revolving around 78 remote-controlled gates that would rise when necessary to block high tides from entering the Venetian Lagoon. 

On Oct. 3, after previously being tested in fair whether, MOSE was used to protect Venice against an actual acqua alta. It was a success. While tides in the lagoon rose to 120 centimetres, local media reported, Venice itself remained dry. This came as a shock to Venetian citizens. 

Beset by corruption and delays, MOSE over the last 17 years has itself has become a problem. Critics say that the gates won’t be as effective as the government envisions and that they’ll have to be raised so frequently that Venice’s sewage will be trapped in the Lagoon, killing off its ecosystem. 

“This is the death of Venice,” Fabrizio Antonioli, a geologist at sustainable development firm ENEA, said of MOSE earlier this year.

Though October’s successful test is a good sign, Venetians have reason to remain skeptical. If everything had gone to plan, the MOSE gates would have been ready in 2011. But nine years later, and 4 billion euros over the original 1.6 billion ($1.8 billion) euro budget, some worry that MOSE might never rise to the challenge of saving Venice. 

The biggest acqua alta in history came in 1966, reaching 1.94 meters.


Climate catastrophe

Resting at the northern end of the Adriatic Sea atop 118 islands that are linked by bridges and separated by canals, Venice is defined by water. After centuries of Venice ruling portions of the Mediterranean Sea as a maritime power, the city’s iconic canals now attract around 20 million tourists a year. Yet the water that protected its first settlers from invasions has become the city’s most troubling liability. A high tide and a strong wind from the sea, blowing the Adriatic’s water into the shallow lagoon, is all that’s needed to flood Venice’s lower districts.

Robert Rodriguez/CNET

Like Libreria Acqua Alta, Venice is designed to work with flooding. Electrical junction boxes are kept where even the highest of tides can’t reach. Elevated wooden walkways, or “duckboards,” are set up quickly to connect buildings when sidewalks are submerged. Gondolas are designed so that their heads can be removed (and later reattached) to ensure safe passage under bridges as water levels rise. But last year one large acqua alta arrived so quickly the city had no time to react. 

“It started out of the blue,” recalls Diana Zamda, an employee at Libreria Acqua Alta. “I’ve never seen anything like that.” All it took was “40 or 50 minutes” for a normal day in Venice to transition into chaos.

Zamda is describing Nov. 12, 2019, when Venice was ravaged by catastrophic floods. Water rose as high as 1.87 meters (6.1 feet), half a meter more than expected, causing an estimated $1.1 billion in damage. Historic buildings were deluged, hotels were shut and two people were killed. And Libreria Acqua Alta’s defenses were overwhelmed, with hundreds of books damaged or lost. 

St. Mark’s Square, the tourist and historical centerpiece of the city.


Only one flood in the city’s recorded history was more destructive than 2019’s, back in 1966. A 1.94-meter acqua alta, known as the Acqua Granda, ravaged the city. Thousands of citizens were forced to evacuate their homes, an estimated 75% of shops were damaged and $3 billion in artwork was lost.

Since then, Venice’s inundations have skyrocketed with no sign of abating. St. Mark’s Square, the city’s historical and tourist centerpiece, flooded less than 10 times a year in the first decade of the 20th century. In each of the past five years, it’s flooded 60 times. 

One of Venice’s lower points, St. Mark’s Square now floods around 60 times a year.


Venice’s floods aren’t caused by climate change, but global warming is a major factor. Just as climate change provokes bushfires in Australia by worsening preexisting conditions like drought and dry soil, it magnifies Venice’s inherent vulnerability to floods through rising sea levels — from 2.5 millimeters a year in the 20th century to around 6 millimeters a year in recent decades. 

Venice’s method of water-level measurement evinces the extent to which climate change has magnified the issue. Base level, zero centimeters, refers to the water level of 1872, when the first tide gauge was installed. When officials note that the city begins to flood as sea levels reach 80 centimeters, they mean 80 centimeters above the 1872 level. But the sea level has risen by around 30 centimeters, or 12 inches, in the 150 years since. With this raised sea level, the new unofficial average, tides only need to rise 50 centimeters before parts of the city begin to flood. 

Local human activity is exacerbating the city’s water woes, too. A post-World War II plot to industrialize a nearby town led to excessive pumping of Venice’s groundwater from the ’50s to the ’70s, causing the city to sink 12 centimeters and positioning it even more precariously. (And due to tectonic activity, the city continues to sink a few millimeters each year.)

“Flooding of Venice has occurred many times during its history,” wrote Caroline Fletcher and Tom Spencer in their 2005 book on Venice, but “the last 50 years represents an unprecedented period of frequent and intense events.”

Duckboards are kept on hand for quick construction so citizens can go about their day during mild floods, which occur dozens of times a year.


Venice’s government has been actively combating flood conditions since 1966’s Acqua Granda. In the years that followed, explains Carl Amos, Southampton University’s professor emeritus of earth and ocean sciences, the local government bolstered the city’s defenses. Canals were dried out so the city’s foundations could be fortified, walkways were raised to withstand higher tides, and salt marshes and mudflats in the Venetian Lagoon were cultivated to block incoming ocean water.

“A lot of the work was done by the municipality of Venice. It was all local,” says Amos, who’s been studying Venice for over 25 years. He said these renovations, though not spectacular, were effective. Unfortunately, many remedies can be enacted only up to a point. You can raise pavement but not doorways, for example, so further elevating walkways would mean citizens crouching through doors. (One of the more commonly proposed alternatives to MOSE is to continue working on the Lagoon’s mudflats and salt marshes.)

In the 1980s, Italy’s national government decided it would fix Venice’s water problems once and for all. It conceived a project called MOSE, short for Modulo Sperimentale Elettromeccanico (Electromechanical Experimental Module), and Italian for Moses. It may be named after a biblical figure, but now, almost 40 years later, many unconvinced that MOSE is the answer to Venice’s prayers. 

MOSE woes

The idea sounds plausible. MOSE’s 78 mobile gates would be constructed along the three inlets that connect the Adriatic Sea to the Venetian Lagoon. Like London’s Thames Barrier or the Maeslantkering protecting Rotterdam from the North Sea, the gates will be remotely erected when tides rise, blocking water from entering the Lagoon and saving Venice from heavy floods. The gates are then remotely retracted once the sea level lowers.

A simple plan, but a gargantuan project. Consorzio Venezia Nuova, the body set up to manage the scheme, had to build something that could protect Venice from floods without endangering its ecosystem or creating a large structure that would blight its beauty. That meant, unlike the Thames Barrier or the Maeslantkering, the gates would have to live underwater.

The MOSE gates are the three entrances to the Venetian Lagoon.

Robert Rodriguez/CNET

“MOSE is the only solution to this impossible problem,” argues Giovanni Cecconi, an engineer who worked on MOSE for 28 years. 

The first feasibility study for mobile dams as a solution to Venice’s floods was submitted in 1971, with legislation passing on the proposal two years later. Politicians and engineers argued over and modified the project for 30 years before construction began in 2003. At that time, its cost was estimated to reach 1.6 billion euros over an eight-year construction period.

That forecast proved to be extravagantly optimistic. Nine years after the scheduled completion date, work on MOSE continues. In 2014 the updated cost was €5.5 billion, 343% over the original budget. Now some estimate MOSE’s true building costs to be around 8 billion euros. Following the successful test in October, the current estimate is for the gates to be regularly operational in 2021. This cuts a chunk out of MOSE’s planned lifespan. 

“It was supposed to be finished in 2011,” says Jane da Mosto, an environmental scientist and co-founder of We Are Here Venice, an NGO dedicated to the city’s preservation. She notes that Italy’s government designed MOSE to last for a century. “We’ve already lost 10 years of the so-called 100 years operating time,” she sighs.

Tardiness is far from MOSE’s only issue. While deployed, the gates would block ships from reaching and leaving ports, a vital part of the city’s economy. More importantly, they would trap sewage, which flows out from the city into the Adriatic Sea, in the Venetian Lagoon.

Due to these side effects, MOSE is only intended for “very intense high tides,” the official categorization of those that reach 110 centimeters. These cause the most deleterious floods, but are rare enough, occurring only a handful of times a year, for MOSE to not seriously harm the lagoon’s ecosystem.

Or at least, they were rare enough. There’s another problem the project’s designers didn’t anticipate: A woeful underestimation of sea level rise means the gates will be deployed far more frequently than originally planned. The engineers accounted for a 20 centimeter rise over MOSE’s 100-year lifespan, according to da Mosto. A 2019 report by the International Panel on Climate Change says a 60 centimeter rise is more likely.

“MOSE must be used not two or three times a year [as officials thought]” says ENEA’s Antonioli, “but for example 25, 30 times a year.” Others estimate the gates will eventually have to be deployed hundreds of times a year.

This would ruin the city’s ecosystem. Sewage from Venice would be trapped inside the lagoon for extended periods of time, causing heavy algae growth. This algae would suck in all the oxygen, killing everything else. 

“If you go around the lagoon, there is a vibrant fishing community, a clam industry, a fishery, there are fish farms south of Venice,” Amos explained. “You’re looking at [hundreds of millions of euros] a year in value in the fisheries. … All of that is likely to be in danger.”

Experts have other gripes, too. Lower areas like St. Mark’s Square can flood with tides as low as 80 centimeters, for instance, meaning MOSE will mostly leave it vulnerable by design. This was the case on Oct. 3, when MOSE’s deployment didn’t save St. Mark’s Square from inundation. Similarly, parts of Venice flood from below due to antiquated piping methods, another problem MOSE won’t solve.

Concept art that shows how each gate erects from its underwater lodging.

Consorzio Venezia Nuova

Cecconi acknowledges the complication of a rising sea level, but says this doesn’t reduce MOSE’s necessity. He concedes that MOSE may not last for its 100 intended years, but says the system will be more valuable to Venice during its years of operation, since it’ll be needed more frequently than anticipated. He’s not a stalwart defender of the project, but rejects those who suppose that MOSE is designed to fix all of Venice’s problems.

“If you are oversimplistic and you just say ‘this final solution is going to last forever or it will fail,’ oh yes, it will fail,” he says. “It has never been said that this is the final solution. This is insurance to gain time for another solution. This is the meaning of adaptation.”

However, early tests of some of the project’s gates reveal a more deflating concern. MOSE may not be able to operate as intended without exorbitant maintenance costs. Several distorted hinges at the base of gates were found during June 2019 trials near Lido, one of the islands of the Venetian Lagoon. They had mostly been corroded by salt, according to La Nuova Venezia. More rusting and salt corrosion was discovered in May.

“If you distort the hinges, then clearly they will not rise properly,” explains Amos. “Essentially, they’re rendered useless.”

Consorzio Venezia Nuova did not reply to multiple requests for comment. Alessandro Soru, MOSE’s current project manager, last year told the Wall Street Journal: “It’s a long process that takes tweaking, and based on the tests we have done there is absolutely no indication that MOSE won’t work.” 

Giuseppe Conte, Italy’s prime minister, watches the MOSE gates rise on July 10.

Anadolu Agency/Getty

Watergate scandal

With doubt mounting over MOSE, the consortium sought some vindication on July 10. In a ceremony attended by Giuseppe Conte, Italy’s prime minister, all 78 MOSE gates were lifted in a public test designed to demonstrate the system’s competence. Consorzio Venezia Nuova had previously tested sections of MOSE, but never before had the entire set of gates been raised simultaneously. 

With the disclaimer that weather conditions will be far more violent when MOSE is needed — winds were four times as strong during last November’s Acqua Alta — the demo went off without a hitch. Yet even the prime minister was cautious about being too optimistic.

“We must all hope it works,” Conte said to reporters, after acknowledging the project’s history of “corruption and malfeasance.” 

MOSE’s bad reputation is not just a matter of poor planning, but venality too. In 2014, MOSE became the center of a huge corruption case. Consorzio Venezia Nuova is accused of funneling money away from the project and using it to bribe dozens of politicians and officials in exchange for supporting the increasingly scrutinized project.

Venice’s mayor, Giorgio Orsoni, was accused of misusing funds embezzled from MOSE to finance party activities. In June 2014, he was placed under house arrest and forced to step down, but not before blaming his Democratic Party, saying it advised him to accept the funds and claiming other mayors before him had done so too. Giovanni Mazzacurati, head of the Consorzio until 2013, was charged with bribing politicians, reaching a plea deal before dying at 87 last year. 

July 10’s ceremony got the attention of many citizens who are against MOSE. The project has seen large-scale protests on several occasions. 

Stefano Mazzola/Awakening/GETTY

“The engineering and the construction and the materials used are very worrying,” explains da Mosto, “but even worse than all of that is how the whole project has, and is being, managed.”

Cecconi blames many of the project’s delays on “the bottleneck of bureaucracy.” After the corruption scandal in 2014, work on the project became glacial. The Italian government tasked a commission with running the consortium, a turnover which lost a year of construction. In 2018 the consortium’s commissioner said MOSE was 93% completed, up just 8% from the reported completion rate in 2013.

“There’s a big lobby by Venetians against this whole project,” says Amos. “Not only is it siphoning money from other projects around Italy, but it means that there’s not enough money left for doing the day-to-day business within Venice. At some stages, there wasn’t even enough money for garbage disposal.”

Critics charge that MOSE is more about politics than problem solving, a stigma predating its construction. Cecconi notes that, even in the 90s, the project was a “political flag” for people who were for or against it. This has poisoned discussion.

“There are two parties, they don’t speak to each other. One that says MOSE is big business, useful only to the people that invented it at the detriment of the citizens. The other is the party of doing, [who say] MOSE will be the final solution for the city. Both of them are wrong.”

The lagoon that saved Venice’s first settlers from invasions could now be its undoing.

Kent German/CNET

Opposed by environmental groups, Italy’s influential national green party and the Venice City Council (one of several bureaus related to the project), MOSE had been mired in political quagmire for nearly two decades — since the Consorzio Venezia Nuova was tasked with safeguarding Venice in 1984 — before the first brick was laid in 2003. The gridlock was broken by Silvio Berlusconi who, after becoming prime minister in 2001, enacted an infrastructure law that enabled him to sidestep the bureaucracy that slows down important national projects. 

Amos describes MOSE as a Berlusconi “vanity project” and says that the prime minister was aware of the red flags but insisted it be built “come hell or high water.” The project has never been universally popular: As Berlusconi inaugurated construction with a ceremony in 2003, environmentalists on small boats attempted to disrupt the festivities. A hydrologist brought to Venice to evaluate MOSE was asked in 2003 by CBS (CNET and CBS have the same parent company, ViacomCBS) whether he thought the scheme would work. “I don’t think so,” he answered. “I don’t think you’re going to march forward, not an inch.”

Even after construction began in 2003, there was a significant push to shelve the project. In April 2005, after an anti-MOSE mayor came into power, Venice’s city council ordered police to halt construction, and environmentalists began protesting with renewed zest. But Berlusconi rejected the mayor’s request to pause the project. “The last doubts have vanished,” he said at the time. “MOSE will be made.”

Berlusconi’s office was reached for comment but did not respond.

Silvio Berlusconi (second from right in the front) returns to Venice after 2019’s floods, demanding MOSE be completed.

Filippo Monteforte/Getty

Da Mosto says there’s more than enough blame to go around. “All the governments that came after [Berlusconi’s] could have done something to change it,” she says. “You can change these huge infrastructure projects, or stop them or reverse them if you get new information and realize it’s the wrong thing to be doing.”

The flooding problem will only get more urgent in the next few decades. Over 5,500 square kilometers of land, including Venice, will be underwater by 2100 if climate change isn’t halted, according to a 2017 study led by ENEA’s Antonioli. (Cecconi disputes the methodology of the study, which looked at abandoned millstone quarries across the Mediterranean coast to ascertain sea level rise over the last millennium and extrapolate expected sea level rise over the next century.) Unlike most other coastal cities, Venice’s woes will get global attention. But there’s still a risk that it’ll take too long for MOSE to be proven an empty solution. 

“Until people wake up to the fact that MOSE isn’t going to solve Venice’s problem, other options are not going to be taken seriously,” says Amos. “But to really be able to demonstrate [that MOSE isn’t going to work] will take another 20 or 30 years, by which time it’s going to be too late for Venice.”

Despite looming problems, Oct. 3’s successful test has brought hope to Venice. “Today is an historic day because we should have been full of water by now and instead we are dry,” a local cafe owner said to Reuters. Citizens took to Twitter to exclaim their relief, including one who called it “possibly the best ‘happy birthday’ message I could have received.” The city’s mayor, Luigi Brugnaro, proclaimed that Venice “stopped the sea.” 

“Lots of bad things have happened here, but now something wonderful has happened,” he said to reporters on Oct. 3.

Now the city braces for November and December, when acqua alta are most frequent and often most fierce. Venice’s 2020 flood season has just begun. 

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