acqua alta

Acqua alta: some thoughts

Last Monday’s acqua alta

29 October 2018 saw most of the city of Venice flooded with an acqua alta of 156cm above sea level. This is the fourth highest flooding on record and so has attracted a lot of attention on social media and in the world’s press. Although there has been some accurate reporting, much of what I’ve seen has been sensationalist, inaccurate, and at worst, to use a phrase of the day, fake news. I wanted therefore, to add my voice to the debate.

Non violent

First of all, acqua alta is not violent. On a TV news report about the situation, they used footage of a wall of water flooding into a street, that patently was not Venice. Anyone who has seen the acqua alta knows that it rises slowly and steadily over a period of hours, although if there is a strong wind, the water can be quite choppy around the edges of the city. A British newspaper report that waters had ‘washed away’ most of the mosaic floors of the Basilica di San Marco is wrong. That’s not how it works.

acqua alta
People cross the Piazza San Marco on passerelle during an episode of acqua alta.

Acqua alta and global warming

Secondly, acqua alta is not caused by global warming and to claim otherwise is misleading and unhelpful. Acqua alta is a natural phenomenon known at Venice since it was built. It’s caused when there is a confluence of high tides, augmented by higher levels of water being emptied into the lagoon by the rivers, and exacerbated by the southerly scirocco wind which blows the water exiting the lagoon the back towards the city.


It’s true that this Monday’s super-high tide was the fourth highest on record, but records only began in 1872 so we have no idea how high tides were before that. However, although precise heights are not mentioned, there are plenty of descriptions of acqua alta before that from which we can make a very good guess.

acqua alta
The Rialto bridge during acqua alta.

A thousand years of acqua alta

Beginning in the year 782, we read that the water was so high that almost all the islands were submerged, as they were on Monday. In September 1240, we are told, the water was so high that it entered all the houses and churches. August 1410, there an acqua alta in which  boats were turned over, and more than 1,000 people drowned on their way back from a festival in Mestre. Chimneys collapsed all over the city, and two campanili fell, destroying houses around them. There are records of about 50 such events between 1200 and 1800.

When you read, as in 1522, that the Piazza was only accessible from the Canal Grande, the implication is that all the surrounding streets were impassible. This would suggest water at about 2 metres above sea level, like the disastrous acqua alta of 1966.

These documents describe exceptional acque alte. The ordinary ones, when the water reaches about 110 cm above sea level are not recorded so we don’t know how frequent they were. But it’s very telling that almost no buildings in the centre of Venice, high or low status, were built with living accommodation on the ground floor from the middle ages onwards.

Detrimental to Venice

I’m not saying that acqua alta is not something to worry about. It is and it’s certainly detrimental to the city. The very fact that this has happened frequently in the past means that every time it happens more and more damage is wreaked. The city gets older, and therefore less able to stand up to the ravages of acqua alta, every year. What I am saying, however, is that understanding the real causes of it help us to understand what to do and what can be done.

acqua alta
The Basilica di San Marco

Increased frequency

There is, of course, a probability, but one which we can’t prove, that acqua alta is more frequent today, and this could very well be linked to global warming. Certainly studies of the more recent records suggest that this might be so. However, increased frequency could equally be caused by the fact that the canals are dredged much less frequently now than in the past. But that’s not the point.

The point is that saying it’s all the fault of global warming is to pass the buck. It’s to say that Venice’s plight is part of a larger, international, and possibly insoluble problem, when in fact, it’s not the case. It’s gives people the excuse to do nothing specific but to wait and hope for the world to come to its senses and to collectively save the environment.

acaua alta

What can be done?

In the past, technology didn’t exist to stop the aqua alta, which causes damage to the Venice’s buildings as well as wrecking the lives of the shopkeepers and residents of the city. It might be fun for tourists to experience, but for Venetians, to quote long-term Venice resident and author Gregory Dowling, it’s ‘a real nuisance’.

The Doges of Venice could only look King Canute-like out of the windows of the Palazzo Ducale and hope for the best, while their merchants lost huge amounts of money in ruined goods. Today is a different matter. Technology exists. London, the Netherlands, Saint Petersburg, have all been saved from the frequent flooding that used to plague them by barriers.

Flood defences

So why doesn’t Venice have a flood defence? Well, it does, only it’s not finished. (I remember seeing an exhibition about proposed defences in the city in around 1987 so it’s been on the cards for a very long time.) Venice would have been protected from this week’s floods, if the now infamous MOSE project had been handled well. After almost 25 years of planning, debate, delays, and so on, Venice’s flood defences are still not in place. The project has already cost over a billion euros more than the initial forecast which was criticized at the time for being too high, and still it is unfinished and unable to protect Venice. Although the project is due to be finished in 2022, many people think that it won’t work. I’m not going to go into details about MOSE—you can read those elsewhere on the Internet—but the point is that Venice should have flood defences by now and the fact that it doesn’t is somebody’s fault.

What we need

Defences that work, have to be finished, and soon. They delay of the defences is the real problem which is threatening Venice. But saying it’s all the fault of global warming let’s those responsible for those delays and lack of action off the hook and takes the pressure off them, when actually the future of Venice is in their hands.




9 thoughts on “Acqua alta: some thoughts”

  1. Thank you for sharing this information, Luca. I had always believed global warming was a cause of acqua alta, so I am happy to be correctly informed now. Sending lots of prayers to my favorite city in the world.

    1. My pleasure. While I am sure that the acqua alta is probably being made worse by global warming it’s been happening since before the city was built. What were my ancestors thinking?

  2. interesting article…leaving tomorrow for Sicily and Puglia and haven’t had the pleasure of experiencing the aqua alta but wouldn’t think it fun at all although somehow i doubt it would diminish Venice’s grandeur

    1. Acqua alta at night in the Piazza is an incredibly poignant, and beautiful thing that reinforces the idea of the link between Venice and the sea. Have a great journey down south.

    1. Ciao Cristina! The cruise ships have no affect at all on the acqua alta. They cause pollution, backwash, vibrations, and increased footfall, which are also causing damage but we can’t pin this one on them.

  3. Luca, thank you for the very informative article. I arrived to Venice on Monday 29 October, via Marco Polo airport. I am not new to Venice, this being my 5th visit, but, it was quite an adventure indeed getting to our apartment near SS Giovani e Paolo. As luck had it, I chose a place to stay that has a very low elevation and the water was very high, reaching to my fingertips (and I’m tall!). We were there Monday through Friday and had a grand time; we planned every day around the water levels and times. The acqua alta did not diminish my love for Venice and I look forward to returning!

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