Last Saturday, October 3, was the first acqua alta of the season for Venice. Venice’s acque alte (“high waters”) is the regular flooding caused in the city by high tides, normally seen between October and March. This predominantly affects the two lowest-lying and most visited areas of the city- St Mark’s Square and the area around the Rialto- forcing closure of shops and disruption of normal life for Venice residents. In recent years the frequency and severity of acqua alta have witnessed an increase due to climate change. Last year on November 12, 2019, the acqua alta reached 187 centimeters, causing flooding in almost 90% of the city.

The 135-centimeter (53 inch) high tide forecast last Saturday would normally have seen flooding around half of the city. It was also the day Venice finally conducted its long-awaited trial of the flood barriers, after years of corruption controversies and delays. And while earlier trials did not manage to raise all 78 gates in the barriers, on October 3 at 12:05 PM – high tide, when there should have been knee-deep water at the St Mark’s Square, everything worked like clockwork. The square’s cafes and shops, which often have to close for hours during acqua alta, stayed open.

The defense system is called MOSE (Italian for Moses), a name derived from the more functional Modulo Sperimentale Elettromeccanico, meaning Experimental Electromechanical Module. It comprises 78 flood barriers set up in the seabed at the lagoon’s three main entrance points. During high tide, they rise to form a dam, stopping the Adriatic Sea from surging into the lagoon and flooding Venice.

And on Friday, when a full moon and high winds were predicted for the following morning, the city council asked permission to raise the barriers. The usual flood sirens rang throughout the city at 8 a.m and by 10:10 a.m., the barriers were fully raised, and while the water level rose to 132 centimeters outside the MOSE, inside the lagoon it remained at 70 centimeters- enough to keep San Marco dry.

“This was a historic day for Venice. There’s a huge satisfaction, having spent decades watching helplessly as the water arrived everywhere in the city, causing vast amounts of damage”, Mayor Luigi Brugnaro, who watched the raising of the barriers, told journalists. “We have shown, not only with a tide that would have flooded the city but also with a sirocco wind of 19 knots, that it works.” Calling it a “clear success,” MOSE commissioner Spitz emphasized that that this is “only a fundamental step towards protecting the city and the lagoon.” The MOSE project is due for completion in December 2021 and until then, it has been agreed that the barrier will be raised each time the tide hits 130 centimeters. Once the MOSE system is complete, the barriers will go up earlier, at 110 centimeters.