If you mention “flooding” to a Venetian resident, they may correct you since acqua alta (high water) isn’t really a flood, it’s a high tide. Of course, high tides happen everyday in Venice, but the ones that fill the streets are elevated, usually because of sirocco winds, heavy rain, and/or the cycles of the moon. Venetians talk about acqua alta in terms of centimeters: “The forecast is for 100 centimeters,” they’ll tell you, “it won’t be that bad.”
100 cm: 5% of the city is flooded
110 cm: a siren will sound
130 cm: 43% of the city is covered with water
140 cm: an emergency situation (the December 1, 2008 acqua alta reached 156 cm).
I did hear the acqua alta sirens go off a few times while I was there last November, and I learned that the sirens themselves are part of the forecast.
110 cm: an extended sound of the same note
120 cm: two sounds in rising notes
130 cm: three sounds in rising notes
140 cm and over: four sounds in rising notes
I also learned the name of the walkways that I’ve always called “high-rise sidewalks” – passerelle. Many of the vaporetto stops have maps that show where the passerelle will be located during acqua alta.
Overall, the acqua alta wasn’t too bad when I was in Venice last year, nothing like what I experienced in May 2004 or December 2008 when I had to wear the dreaded rubber boots for extended periods. Last year, I was able to walk around the water most of the time, though there were a few times when I had to make a detour.
It was easy to walk around this; you can see how everyone was skirting the buildings on the right.
More challenging here. I was trying to go to San Giorgio degli Schiavoni,and I had to come back later.
A few inches of water in the Ca 'd'Oro courtyard. You almost can't see it except for the reflections of the columns in the water.
The most famous acqua alta was in November 1966 when the levels reached at least 194 cm. There’s a small plaque in the courtyard of San Giovanni Evangelista that shows how high the water was on that day. Pretty eerie.
A bit of water and passerelle-in-waiting on the Zattere~
Acqua alta and a stack of passerelle in the Rialto Market area~
Map showing where the passerelle will be located~
People who've never been to Venice have this idea that the water will rise and stay that way for the duration of their vacation. Not true, fortunately. The tide rises and then a few hours later, it goes back down.