Venice, the iconic lagoon city, has been experiencing an unusually high number of extreme high tides at the start of the year, sparking growing concerns about rising sea levels and the long-term vulnerability of the city. With 15 high tides in just nine days, ten of which exceeded 110 centimeters, the city has reached what the director of the Venice Tides Centre, Alvise Papa, described as “a record for the period”.
Understanding the Causes of High Tides in Venice
According to Papa, the spike in high tides is closely linked to the steady rise in average sea level, which he attributed to climate change. “Today we are at about 40 centimeters,” he told ANSA, referring to the baseline sea level, “while in the early 2000s it was around 21 to 23 centimeters.” This increase in sea level has made the city more vulnerable to flooding, even in moderate weather conditions.
As a result, much weaker weather systems are now capable of producing dangerously high tides. “In the past, very strong winds were needed to raise the tide by 80 centimeters,” Papa said. “Now much weaker ones are enough to reach one meter.” The figures mark a sharp increase compared with recent years, with only one high tide recorded during the same period last year.
The Impact of Recent Weather Conditions
Recent weather conditions have not been particularly severe, making the data more striking. Sea levels remained above one meter for a record 42 hours, compared with just four hours during the same period last year. In 2024, the figure stood at 13 hours, while in 2023 it was 16. This trend is expected to worsen, with increasingly modest disturbances capable of flooding large parts of the city.
The MOSE system, a flood barrier designed to protect Venice from high tides, has been activated repeatedly to prevent acqua alta from flooding the historic centre. The system consists of 78 mobile barriers installed at the three inlets connecting the Venetian Lagoon to the Adriatic Sea: Lido, Malamocco, and Chioggia.
The MOSE System: A Vital Defense Against Flooding
The MOSE system was first successfully tested during a severe tide event in October 2020 and has since been used repeatedly to prevent acqua alta from flooding the historic centre. Its activation has spared Venice from damage during several high-tide events that would previously have inundated St Mark’s Square and surrounding districts.
Despite its effectiveness, the system has been controversial, with costs rising to over five billion euros and concerns over maintenance and environmental impact. However, city officials see MOSE as indispensable, with Papa noting that keeping water levels below one meter is now essential to protect Venice.
As high tides become more frequent, MOSE is being activated far more often than originally envisaged. Experts warn that this could accelerate wear on the system and raise questions about its long-term sustainability. For now, however, the MOSE system remains the city’s primary defense against increasingly frequent flooding.
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