Venice’s Controversial Inflatable Floodgates Save City for the Second Time

On October 3, Venice’s new barrier system protected the city for the first time from high tides and severe flooding by blocking the water from surging into the lagoon and over the island. But last Thursday, the barriers once again shielded Venice from a 4.6-foot tide that could have flooded half the city, reports Angela Giuffrida for the Guardian.

Last year, Venice declared a state of emergency when it experienced its worst floods in 50 years. The flooding caused more than $1 billion in damage, and parts of the city were left under six feet of water, including St. Mark’s Basilica, a nearly thousand-year old cathedral. This time, the high tide could have wreaked havoc on the small island, but the barrier system of 78 floodgates—known as Mose—successfully kept Venice’s winding alleyways and historic squares clear. Instead of flooding, the tide within the lagoon only rose by 1.7 feet, reports Reuters.

The barriers are designed to stay at the bottom of the lagoon until they are activated, at which point they fill with air and then rise to the surface. The large yellow walls then seal off three of the lagoon’s inlets, shielding the island from high tides. The barriers can handle floods of up to ten feet, reports Jonathan Hilburg for the Architect’s Newspaper.

The floodgates had been tested before in less threatening conditions, but October 3 was the first time authorities “raised them to defend Venice,” Alberto Scotti, the engineer who designed the floodgates, told Elisabetta Povoledo for the New York Times earlier this month.

The construction firm has until the end of 2021 to finish the floodgates. Until then, they will be used when the tide is estimated to be higher than 3.5 feet; after it is fully operational, it will protect against 4-foot tides.

Mose has been in the works since the 1980s and was supposed to be completed by 2011. Cost overruns, corruption and pushback from environmental groups delayed the highly anticipated project. However, time is running out for Venice as it simultaneously sinks and battles rising sea levels. The city was originally built on a muddy lagoon using weak foundations, causing it to slowly sink into the sea. Plus, rising tides as a result of climate change have flooded the city repeatedly, damaging its historic buildings, quaint shops and packed rows of homes.

Despite the success of the floodgates so far, some say that they aren't a sustainable solution and that it could have serious environmental ramifications. For example, when the barriers rise, they seal off the lagoon from the rest of the ocean, turning a free-flowing channel into a closed-off swamp. This barrier will deplete the water’s oxygen levels and prevent pollution from flowing out of the channels.

“With climate change, there’s a chance that the floodgates could be employed 150 to 180 days a year, becoming an almost fixed barrier and severing the lagoon’s relation to the sea,” Cristiano Gasparetto, an architect who opposes the project, told the New York Times earlier this month. “If the lagoon is cut off from the sea for long periods, it dies, because the natural exchange of waters stops, and all of its organic life risks decaying. If the lagoon dies, Venice dies.”

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Rasha Aridi is a science journalist based in Richmond, Virginia. She has written for Science magazine and Science News for Students. You can find her portfolio at rashaaridi.com.