"Venice is on its knees," Mayor Luigi Brugnaro says, as the lagoon city is suffering some of the worst floods in its history. The highest tide in 50 years brought seawater that is threatening monuments and works of art in the historic city.

With more than 85 percent of the city flooded, Brugnaro says the Italian city is in a state of emergency. He's now asking Italy's central government for help, saying the damage to Venice is huge.

The water overwhelmed seawalls and smashed brick docks, shoving boats into streets and putting portions of landmarks such as St. Mark's Basilica and La Fenice Opera House underwater. While the crypt at St. Mark's was flooded, a member of its management board tells Italian news agency ANSA that the main concern is that water may have damaged the basilica's support columns.

At least one death has been reported: "A 78-year-old man was electrocuted due a short circuit, apparently linked to the flooding" in his home, ANSA reports.

"These are the effects of climate changes," Brugnaro said via Twitter as he surveyed the damage to Venice Tuesday night.

Topping 6 feet, the tide inflicted "a wound that leaves indelible marks" on the low-lying city, the mayor said.

Venice has often suffered its worst tidal flooding — or acqua alta — in the winter, when strong winds funnel water in from the northern Adriatic Sea. The 1966 high-water mark was also set in November.

"A long and dramatic night for Venice," the city said on its Facebook page. It added that the flooding is comparable only to the tragic floods of 1966 — and the city says it's the second-worst case of flooding since it started keeping official records.

"Built centuries ago on tiny islands, the city has always been subject to flooding," Sylvia Poggioli reports from Rome. "An ambitious project of movable undersea barriers called Mose is yet unfinished due to cost overruns and corruption scandals. Experts say once completed, it will be insufficient to deal with rising sea levels."

Poggioli tweeted several videos sent from Venice by her niece, who is attending college in the city. One piece of footage shows water rushing out of a toilet, seemingly driven back through the pipes by the floods.

Because of the high water and strong winds from a winter storm, the city has lost nearly a third of the 1,100 raised walkways it relies on to help people navigate through high water, according to the city's public utility, Gruppo Veritas.

While the worst of the flooding may have passed by Wednesday, Venice's weather forecast office says the tide will stay at "very high" levels in the coming days.

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