Nov 18, 2013

Acqua Alta:The Periodic Flooding of Venice and Chioggia

By on Monday, November 18, 2013

Every year between autumn and spring, Venice and the neighboring costal town of Chioggia suffers from bouts of temporary flooding caused by exceptionally high tides that occur in the northern Adriatic Sea. The flooding is periodic, just like any high tides, and they reach their maximum in the Venetian Lagoon where they cause partial flooding of Venice and Chioggia. The phenomenon is locally known as acqua alta.

Acqua alta occurs when high tides caused by the moon's gravitational pull coincide with a strong scirocco, a warm wind blowing across the Mediterranean that forces water from the Adriatic into the Venetian lagoon. This coincidence happens from about the middle of October to the beginning of December. Since, acqua alta is a tidal phenomenon, it lasts three to four hours, during high tide. Once water goes down again, things go back to normality. The water may last a bit longer if there is a particularly strong scirocco, but is assured to drain away when the tide subsides, which happens every six hours.


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