An engineering marvel just saved Venice from a flood. What about when seas rise?

Three years ago, a historic rush of water surged into this city, inundating restaurants and churches, tossing boats onto streets, and leaving Venetians distressed about a future with ever more extreme events. But this past week, one of those events arrived — a tide nearly as large as 2019’s — and residents barely noticed, aside from some wind and rain. The city was spared from disaster.

That’s because of a $6 billion engineering project designed to protect Venice from mass flooding and the exhausting cycle of cleanup and recovery. The lagoon city’s inlets are now guarded by 78 rectangular metal barriers, each the height of a five-story building, that are pumped with air and raised from the sea floor any time high waters threaten it.

It’s a landmark climate change solution, one requiring 30 years of planning and 20 years of construction, that has reduced fears of Venice turning into a modern-day Atlantis.

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The system that safeguards Venice could become stressed with even a 30-centimeter sea-level rise, its operator says — something that middle-of-the-road projections indicate could come by mid-century. With luck, and if major nations dramatically cut back emissions, the MOSE, as the system is known, could yet work for 100 years as designed, scientists say. But more dire scenarios would trim the system’s life span by decades.

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In contrast with the permanently visible dams and dikes constructed in places such as the Netherlands, the raisable gates of the MOSE are hidden away on the sea floor. That allows the lagoon on most days to operate as normal. Ships can come and go. And crucially, so can the tides, with saltwater from the Adriatic helping to flush out the lagoon and prevent it from becoming a fetid petri dish.

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