# The Flood Barriers That Could Save Venice > How Venice's MOSE flood defense system works, why it draws criticism, and what the future holds for the project. Here's the big picture, explained simply. - URL: https://langandtrip.com.ua/en/article/venetsianska-systema-zakhystu-vid-povenei-mose-iak-pratsiuie-krytyka-ta-maibutnie-proektu/ - Language: en - Published: 2024-05-21 - Categories: Culture, Historic Sites, Museums, Tours, Italy, Seas & Oceans --- Your first impression is that this private, man-made island, sitting between the Adriatic Sea and the Venetian Lagoon, looks like a Bond villain's lair. Your second is that mooring at the private pontoon, walking past the brutalist concrete facade, and stepping into a "control room" where staff watch monitors around the clock, tracking the waters around the island, feels like something out of "Squid Game." In truth, as sinister as it may sound, this 144,000-square-meter (35.6-acre) island, which keeps its silent watch over Venice 24 hours a day, is no evil force. It exists to protect one of the world's most fragile cities. The nameless island, positioned between the Cavallino-Treporti peninsula (which curves out from the Italian mainland to form a protective arm around the Venetian Lagoon) and the island of Lido, a giant sandbar that separates most of Venice's historic center from the Adriatic Sea, is the heart of MOSE: the flood barrier system that, after 1,200 years, has finally allowed the floating city to stand up to rising sea levels. It has been a long time coming. MOSE, Moses in Italian and short for Modulo Sperimentale Elettromeccanico, or Experimental Electromechanical Model, has been in development since 1984. But it took nearly four decades to build, dogged by delays and corruption to such a degree (a former mayor stood trial for embezzling money from the project) that many Venetians believed it would never actually work. Their fears proved unfounded on October 3, 2020, when, as happens regularly in winter, Venice faced an unusually high tide. The tide, which rose 135 centimeters (53 inches) above the normal level, bore down on Venice. Ordinarily this would have flooded roughly half the city, but this time Venice stayed dry. It was the first time MOSE had been raised in adverse weather. As one Venetian put it at the time, it was "historic... like Armstrong's first step on the Moon." Fourteen months later, MOSE had been raised 33 times: 13 times in 2020 and 20 times in 2021. (The flood season typically runs from October through March.) The skeptics, it seemed, had been proven wrong. Not once had it failed to protect the city when raised. The yellow fins, barely breaking the surface of the sea, usually look fragile against the churning Adriatic in footage shot as they rise, typically during storms driven by the harsh sirocco winds that batter the city from the south. But get closer and you realize looks can be deceiving. Each of these enormous barriers is 20 to 30 meters (66 to 98 feet) long and 20 meters wide. They are set into the seabed inside concrete caissons that are 40 meters wide, 60 meters long, and 10 meters high. Oh, and there are 78 of them, arranged in four rows across the three entrances to the Venetian Lagoon. As a piece of infrastructure, MOSE is a giant. And yet, when the barriers aren't in use, you see nothing at all. Unlike the flood barriers of Northern Europe, and at far greater expense, MOSE was designed to be invisible when the barriers aren't needed. ## A Bond-style island on no man's land ![](/storage/image/prev/july-article-image-59-1-2024.jpg) At the center of the project is a purpose-built island floating in the middle of the lagoon's northernmost entrance. Looking out over the bucolic island of Sant'Erasmo, with the snow-capped Dolomites on the horizon, it is a "no man's land between the sea and the lagoon," where the waters of the lagoon and the Adriatic meet, according to engineer and site director Alessandro Soru. "Bocca di Treporti," or the Treporti inlet ("bocca" means "mouth" in Italian), is a nearly kilometer-long channel between Punta Sabbioni (the tip of Cavallino-Treporti) and the northernmost point of the island of Lido. There are two other entrances to the lagoon: at Malamocco, on the southern edge of Lido, and another at Chioggia, a fishing town at the southernmost point of the lagoon. Treporti, however, is the widest channel, and the seabed here ranges from 20 to 40 feet deep. So, rather than building a single massive barrier of varying height, an island was created to split the inlet in two. It also provides space for MOSE's headquarters, which might otherwise have disturbed tourists at the campgrounds and beaches of Punta Sabbioni. ## 'A real James Bond' ![](/storage/image/prev/july-article-image-59-2-2024.jpg) Inside, a wall of monitors in the control room streams live feeds from the CCTV cameras, showing boats passing through the three channels. It also relays weather data and tide levels, and keeps watch over the barriers when they are raised. One screen displays the lagoon level and the sea level: blue for the former, red for the latter. On ordinary days, the blue and red lines rise and fall together like a heartbeat monitor, climbing during high tide and then bottoming out at low tide. On a recent date, however, December 8, 2021, the lines diverged sharply. The red line, marking the tide level in the Adriatic, climbed high, 130 centimeters (51 inches) above average, while the blue lagoon line followed it for a while, then dropped abruptly, then leveled off far below the red line before finally sinking back down alongside it. On that day, at 8:58 p.m., MOSE was raised when the tide reached 80 centimeters. That rapid drop? Physics, or more precisely, the hydrodynamics of Bernoulli's principle, which meant the lagoon level fell rapidly to 50 centimeters before stabilizing at 80 centimeters for the next 12 hours. MOSE was lowered at 8:44 a.m. the following day, when the two lines converged again. In good weather, a couple of people work the day shift here, along with a team of four in the tunnel, 62 feet down, where half-mile tunnels inside the concrete caissons beneath the fins connect the island to Lido and Punta Sabbioni, and the underwater damp settles into your bones. ![](/storage/image/prev/july-article-image-59-3-2024.jpg) Mazes of pipes carrying air to fill the barriers run underfoot in the tunnel, while chambers branching off to the side hold the valves that connect the fins to the concrete bunkers. Each one can be sealed off from the main corridor at the push of a button, and can keep working even if water gets inside during a disaster. Soru points to a porthole in the corner of the room: "That's so you can get in here by submarine if it floods, a real James Bond," he says. But when the tides run high, this becomes the round-the-clock nerve center of the whole operation, with a team of 100 working in the control room, in the underwater tunnels, and out on the lagoon, where boats ferry workers to the island since there is no public transport. There is even lodging here so staff can sleep between shifts. ## How MOSE works ![](/storage/image/prev/july-article-image-59-4-2024.jpg) After decades of early controversy, construction of MOSE began in 2009, and the final "fin" was installed in June 2019 on the Lido side of the Treporti island. The Venetian Lagoon is known for being shallow, with an average depth of just 1 meter (3.3 feet). But the entrances from the Adriatic Sea are far deeper: Malamocco, for instance, the entrance to the industrial port, is 14 meters (46 feet) deep. Although the engineers did not change the depth of the entrances, they dredged the seabed along all three to make room for the concrete "housings" that sit flush with the seabed. The 14,000-ton housings were cast in concrete on the mainland, then floated into position and sunk underwater, while the debris removed from the seabed was used to build the island at Treporti, a "working citadel," as Soru calls it. Inside the concrete housings are metal gates that are treated every three months with an anti-corrosion agent, non-toxic because of the lagoon's ecosystem. Each of the 78 barriers has the same width of 20 meters (65 feet) and ranges from 20 to 30 meters in length, depending on the water depth. They can withstand waves up to 3 meters above the normal tide level, far more than even the record tide of 194 centimeters (76 inches) that devastated the city in 1966. ![](/storage/image/prev/july-article-image-59-5-2024.jpg) The way they work is based on a surprisingly simple hydraulic method. Lying dormant on the seabed, the hollow barriers are filled with water to hold them down. To raise them, air is pumped into the fins and the water drains out. They float upward until they emerge above the water, at which point they form a barrier, with the Adriatic raging on one side and the relatively calm, low lagoon on the other. When the tide recedes, water is pumped back into the fins and the air is released, which forces them to sink again and settle into their housings. Raising them takes just 32 minutes, and lowering them roughly half that, less than the 91 minutes it took last year, according to Elisabetta Spitz, the "extraordinary commissioner" in charge of the project, who reports to the Italian government. ![](/storage/image/prev/july-article-image-59-6-2024.jpg) The process seems simple, but it has been fine-tuned to precision. There is a gap of nearly 3 inches between each barrier to ease the intense pressure on the fins as they hold back the Adriatic. For the same reason, they rise four or five at a time rather than all at once. They can also operate independently of one another, so engineers can choose to raise only some of the barriers to slow the flow of water into the lagoon, or lower them temporarily at Malamocco to let an industrial ship pass through to the Venetian port, the second busiest in Italy and fifth in the Mediterranean. It also means, Soru says, that if, as people fear, a single barrier ever fails to rise, it won't cripple MOSE as a whole. Not that it has happened during the year it has been protecting the city. ## Finger on the button ![](/storage/image/prev/july-article-image-59-7-2024.jpg) The decision to raise the barriers is a complex process. Two agencies study the weather forecasts: Centro Maree di Venezia, which monitors tide levels for the city, and Sala Operativa Consorzio Venezia Nuova, which is responsible for MOSE. Both use different models and compare their forecasts. Spitz describes the process as "a series of warnings, from 48 hours before the tide down to three hours before it." It isn't only MOSE's operators who receive them. "It informs everyone working in the lagoon so they can start to act, because everyone has something to do, from the driver of a garbage-collection boat who needs to change course, to ships that need to come in and out," she explains. Fifteen minutes before that three-hour warning, Spitz and a government representative receive an email "summarizing everything that happened in the previous hours and asking for confirmation to proceed. "For example, if a ship is running late because it hit bad weather, we can decide to leave part of the barrier open to let it through. "We only step in for exceptional events that mean we need to deviate from the procedure. If not, the procedure continues without intervention." It isn't only the sea level and wind speed that have to be taken into account. Rainfall raises the water level around the city, as do the swollen rivers that flow into the lagoon. "Even if a tide of 95 cm is forecast, we don't know whether the barriers will go up," Soru says. Last year, on December 8, Venice was hit by a 138 cm flood that caused significant damage to the city, just weeks after MOSE had shown this should never happen again. The reason? Only 125 cm had been predicted, but wind, rain, and river water pushed the sea level up. ![](/storage/image/prev/july-article-image-59-8-2024.jpg) "I take responsibility for that," Spitz says. "It was one of the first activations, we had a procedure that was a bit more complicated, and because the acqua alta \[flood\] hadn't been forecast, we made the decision not to mobilize it. "But it was one of our first attempts, and we realized the process needed to be made more automatic, so we updated the procedure. It was our fault. But today it wouldn't happen." "It was catastrophic, but we learn from experience. Now we raise the barriers a few centimeters earlier," Soru says. When MOSE is fully operational in 2023, the barriers will rise once the water level reaches 110 cm (43 inches) above the usual level. This won't help the city's lowest-lying areas, such as St. Mark's Square, which floods at around 90 cm, but it will protect roughly 86% of Venice, including most residential areas. In fact, Soru says, the barriers will rise when it looks as though the tide will reach 100 cm, to account for the wind and rain that push the water level up. For now, though, while the barriers are in the final stage of testing, they rise when the tide is forecast to reach 130 cm. ## The criticism ![](/storage/image/prev/july-article-image-59-9-2024.jpg) Of course, projects on this scale are rarely without their critics. One of the main criticisms leveled at MOSE is that the barriers interfere with the lagoon's ecosystem, turning it into a pond rather than a living lagoon. But as Spitz says, when the barriers were raised for 48 hours last year, it was a test to check their durability. In the future, even in periods when the barriers go up every day, it will only be for a few hours at a time. They have also installed locks at Chioggia and Malamocco so that some fishing boats and industrial ships can pass through while the barriers are raised. "When it goes up, it's three or four hours at most," she says. "And then you don't necessarily raise all the barriers. There are lots of options and a lot of flexibility. We're testing them all to better tailor our choices to the needs that will gradually emerge. Every time we do a lift, we prepare dozens of tests to get the answers we need, understand the function, and make it better." And while St. Mark's Square floods at a level well below the point at which MOSE kicks in, another project, though delayed, is meant to build a glass barrier around the famous Byzantine basilica. Protection for the businesses on the square, however, such as the historic Quadri cafe, is still a long way off. Its manager, Roberto Pepe, previously said that MOSE's 110-centimeter threshold "changes nothing and leaves a bitter taste" for those whose livelihoods depend on the square. Spitz insists she did not choose the threshold points. A committee of local and national government did, and port access was also taken into account. ![](/storage/image/prev/july-article-image-59-10-2024.jpg) "We need to save Venice, Chioggia, the islands. Murano, Burano, and countless small islands are in an even worse position when faced with high tides," she says. "But above all, we need to find a middle ground between economic needs, those of the people who work in the lagoon, and the need for protection. It's a big question we'll have to grapple with in the future." Another criticism of MOSE? The excessive overheads. Building MOSE cost roughly $8 billion, and first-year reports suggest each raising costs $328,000, nearly double the original estimates. The fins have to be treated with an anti-corrosion agent every three months, and their containers cleaned twice a season, after a buildup of sand inside them meant six fins could not be lowered during the 2020 tests. The containers need a thorough cleaning every five years. ## Coping with climate change ![](/storage/image/prev/july-article-image-59-11-2024.jpg) The big question, of course, is how MOSE will hold up against climate change. After the December 2020 flood, Claudio Vernier, president of the Associazione Piazza San Marco, which represents business owners on St. Mark's Square, said that when MOSE was first planned, it was expected to reach 110 centimeters only a couple of times a year. "Now, with the climate crisis worsening, the water level is always higher, and we see this tide level 20 times a year. What will it be like in 30 years?" he asked. Spitz and Soru, however, insist the barriers will outlast that. "A corrosion study we carried out a few months ago showed it could last 100 years, but it has to be maintained every three months," Soru says. "If in 100 years the barriers aren't enough, and we can't hold back 3-meter tides, I can tell you the problem won't be in Venice," Spitz adds. "The lagoon is closed now. The protection is more than enough, the barriers are what they are. But you'd have to think about protecting other areas. The problem would be far bigger in the Po Delta \[which covers much of northern Italy\]. "If climate change turns out to be dramatic, the serious problems will be elsewhere. You'll need to look somewhere else, not Venice." In the meantime, plans have been floated to partly power MOSE with solar panels. Installing them at Malamocco could provide 20% of the energy, but Spitz hopes to make the project carbon-neutral within three years to prepare it for the future. Spitz arrived in 2019, after MOSE's corruption trials were already underway. "I know there were scandals, I read about them, and it's right that they've been stigmatized and the people who did it were punished," she says. "But despite everything that happened with MOSE, I say: long live MOSE. Because it protects Venice." If she is right, the devastating flood of November 2019, which killed two people and caused $1 billion in damage to local businesses that have yet to recover, may become a thing of the past. And La Serenissima can rest a little more, well, serenely.