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Acqua alta

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.

acqua alta

More challenging here. I was trying to go to San Giorgio degli Schiavoni,and I had to come back later.

acqua alta

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.

acqua alta

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.

acqua alta 1966

acqua alta 1966

A bit of water and passerelle-in-waiting on the Zattere~

Venice2010 395

Acqua alta and a stack of passerelle in the Rialto Market area~

acqua alta in Rialto

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.

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Comments (6)

Kathy (Trekcapri):

Hi Annie, this is a very informative post explaining Aqua Alta. It was very interesting to learn about the sound types for the sirens. I remember them waking me up one morning and wondering what it was. I had no idea that sirens went off to help the residents to know that there was aqua alta and also the level to expect to see.

The height of the 1966 water level is really incredible. Your photo collection showing the different levels of how aqua alta looks like is very useful information too. Before my trip in November 2007, I remember trying to imagine what aqua alta looks like so I would know what to expect. This is very helpful information.


Wonderful information and great photos, Annie. It's hard to imagine the water getting as high as almost 200 cm! I've also experienced some acqua alta and it wasn't pleasant (especially because, foolishly, I went out without boots!)

I've wondered how comfortable locals are with the passerelle? Especially older folks. When I had to use them, it was great to be that high off the flooded pavement, tricky when you met someone walking the other way, but getting on and off was a real scramble.


Hi Annie Your blog made me look for a recording of the siren which I've heard before. Very haunting noise. I found this clip on Youtube. It's called Acqua Alta Venice 30th November 2009 ( including siren). Worth a look. Sorry can't do proper links!


Andrew, thanks! I found it and will add the link. Going to go watch it now. Annie


Andrew, thanks for the link. It does sound haunting on that video, more than I remember when I've heard it in real life. Maybe I was so happy to be in Venice, I couldn't be haunted!

Sandra, agree with you about climbing on and off the passarelle. It can be an ordeal!

Kathy, thanks. I remember that you experienced some pretty serious acqua alta the last time you were there.

I wonder if my stivali will be high enough this winter? I'd better make sure I have plenty of food and vino for emergencies! :-)


Yvonne, that sounds like a great plan to me!

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This page contains a single entry from the blog posted on August 15, 2011 2:27 PM.

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