ROME — After decades of bureaucratic delays, corruption and resistance from environmental groups, sea walls designed to defend Venice from “acqua alta,” or high water, went up on Saturday, testing their ability to battle the city’s increasingly menacing floods.

By 10 a.m., all 78 floodgates barricading three inlets to the Venetian lagoon had been raised, and even when the tide reached as high as four feet, water levels inside the lagoon remained steady, officials said.
“There wasn’t even a puddle in St. Mark’s Square,” said Alvise Papa, the director of the Venice department that monitors high tides.
Had the flood barriers not been raised, about half the city’s streets would have been under water, and visitors to St. Mark’s Square — which floods when the tide nears three feet — would have been wading in a foot and a half of water, he said….
The floodgates have been tested several times over the past summer, but under less threatening weather conditions than those on Saturday.
“This time we raised them to defend Venice,” said Alberto Scotti, the engineer who designed them.
The system is not fully operational yet. Some infrastructure still needs to be completed, and workers haven’t been fully trained, so Saturday’s operation was technically a test.
“But it’s a test that had an objective, to guarantee the safety of the city, and it did,” Mr. Scotti said.