Five years ago, Venice spent more than 5 billion on a system of barriers against the sea. Now look for a plan B

There was a time when Venice looked at the Adriatic with ambition. The sea not only shaped the city, permeating its DNA, it also propelled it until it became a naval power who fought for dominance of the Mediterranean. Today things are different. The Serennissima (turned into tourist power) observes with increasing concern the coming and going of the tides, the same ones that in 2019 submerged it under 187 cm of water, flooding 80% of the city.

The reason is very simple. Everything indicates that the multimillion-dollar system that Venice was equipped with a few years ago to protect itself from the threat of high water It won’t take long for it to become obsolete. And it is not very clear what the alternative is.

One figure: 18. The threat of flooding is not new in Venice. In fact, one of the worst in memory was suffered six decades ago, in November 1966when an intense storm caused the water to reach 194 cm, flooding much of the city. However, experts have been detecting worrying signs for some time. It is not just that Venice sink or the sea level rising (which too). There are increasingly clear signs that suggest that floods will become more frequent in the future.

Recently, a group of researchers dedicated themselves to analyzing the “extreme” episodes suffered by the city, those in which 60% of its surface was flooded. Throughout the last century and a half, it counted 28 incidents of those characteristics. The surprising thing is that the vast majority of them (18) were concentrated during the last 23 years.

One measurement: 0.42 m. Today more than half of Venice is alone between 80 and 120 cm above the average sea level and projections show that this scenario will soon worsen: in the best of cases, if we manage to drastically reduce our polluting emissions, the sea will rise 0.42m by 2100. In the worst case, it will be 1.8 m, which would greatly complicate the outlook for the Serennissima. In fact, now the high tide already leaves St. Mark’s Square only 30 cm above the water level.

One name: Mose. Aware of how much is at stake in Venice, the Italian Government has long been looking for a way to protect itself from floods. The result was Mose (experimental elettromechanical module)a system made up of four barriers and 78 independent mobile gates that allow authorities to protect the Venetian lagoon from what is known as high watertides that flood the city.

The objective: to temporarily isolate the Adriatic lagoon and thus protect Venice from the most dangerous tides. To achieve this, the barriers were strategically installed in the inlets of Lido, Malamocco and Chioggia. Each gate also measures 20m wide and between 18.6 and 29.6 m long.

An investment: 5,000 million. It is said that the project mobilized an investment of more than 5.5 billion of euros (its execution was marred by corruption). Its work began in 2003 and after several delays it carried out a first test in October 2020, in an event led by the then Prime Minister Giuseppe Conte. A year earlier, Venice had suffered a of the worst floods that are remembered, during which the water reached 187 cm, flooding part of the entrance to the Basilica of Saint Mark.

An indicator: frequency. The problem is that the authorities are turning to Mose much more often than expected. EuroWeekly assures that in less than a month, between January 28 and February 19, the system was activated 30 times. Other media report that since their inauguration at the end of 2020, the barriers have saved Venice from flooding in 154 occasions. The problem is that the use of Mose does not come free to the region, neither in economic terms nor on a social and environmental level.

Setting up the enormous Mose floodgates has a direct cost, but it also has another indirect cost: by isolating the lagoon, the system alters, for example, the activity of the port sector and interrupts maritime traffic with the port of Marghera. Guardian points out that pressing Mose’s button has an economic impact of more than 200,000 euros for Venice. For this year’s Carnival alone the total bill would be around five million euros.

An extra concern: the lagoon. Not everything is measured in operational cost, maritime traffic and economic impact. Altering the tides in the area also has an impact on its ecosystem and that is something that worries experts like Andrea Rinaldo, from the scientific committee of the Lagoon Authority. Especially if two fundamental data are taken into account: first, the frequency of use in recent years; second, the forecasts for sea level rise.

“With one more meter, the Mose barriers would have to be closed an average of 200 times a year, which means that they would practically always be blocked,” explains Roinaldo. “When this happens, the lagoon loses its function as a transitional environment. It would become a pond.”

A victim: the lagoon itself. As explains GuardianBy blocking the flow of water, the barriers encourage the growth of algae. The problem is that when these die and decompose they directly affect the quality of the water and the rest of the flora and fauna. Does that mean Mose was a mistake? Rinaldo thinks not. The changes are simply happening much faster than engineers expected, forcing authorities and technicians to think about the future in the medium and long term. At the end of the day, if Mose taught anything, it is that projects of his importance are not approved and executed overnight.

One question: What to do? The great unknown. Those responsible for Mose are looking for ways to reduce its impact, but it is not an easy decision. Among other things because the Venetians themselves have become accustomed to the barriers and gates coming into operation at the slightest risk, points out Giovanni Zaroti, one of the system technicians.

Rinaldo mentions the possibility of launching an international call so that technicians from different fields can propose solutions. There are those who have already gone ahead and are putting options on the table, like the researchers who published a few days ago an article in Scientific Reports reflecting on “long-term adaptation path” for Venice in the face of rising oceans.

A warning: “Unsustainable”. One of its authors, Piero Lionello, professor of atmospheric physics and oceanography at the University of Salento, recognized recently told ABC News that the rate of flooding in recent decades has been “pretty impressive.” The expert remember that the possible effects that climate change will have on the region are clear and emphasizes that we cannot sit idly by.

“A rise of 75 cm would mean that Mose would be at wave height six months a year, something unsustainable, a turning point, since it would damage the lagoon ecosystem,” he warns,

One threat… four strategies. The article by Lionello and his colleagues is interesting because it does not limit itself to diagnosing the problem and warning of the risks that loom on the horizon. They also outline several strategies to deal with it, although none of them are simple or cost-free.

One of them would be to reinforce the efficiency of Mose by gradually raising the lagoon and the city thanks to the injection of water into the aquifers located under Venice. In that case the barriers would be effective, even if the sea level rises up to 1.25 meters. The problem is if (as they warn some projections) this new mark is surpassed in the long term, around 2300.

Another solution would be the use of dikes and constructions that allow the lagoon to be closed. Of course it also has ‘buts’: it would completely change the spirit of the city, affecting its port, traffic and the life of the lagoon. There is also its very high economic cost, the deadlines it would require and its social risks. “If the barrier were broken, the time to save the local population would be practically non-existent,” collect the reportcited by The Times.

An extreme way out: moving. There would be another solution, in the authors’ opinion, even more radical. imitate in a certain way what was done at Abu Simbel (Egypt) and relocate large monuments to protected areas.

“Faced with an extreme rise in sea level, the relocation of monuments to suitable inland areas and their abandonment would be the only possible strategy, which could be inevitable in the 22nd century if current climate policies are maintained and a collapse of the Antarctic ice sheet occurs,” he slips. the article. In addition to its historical and emotional impact, this measure would also have an enormous cost: around 118 billion dollars.

Images | Dan Novac (Unsplash), Ludovico Lovisetto (Unsplash) and Wikipedia

In Xataka | Venice has been building walls to protect itself from water for centuries. For one researcher it was the wrong strategy