Aqua alta is a high tide which occurs regularly in the northern Adriatic, especially in autumn and winter when it is reinforced by the sirocco winds and the rain.
When this phenomenon occurs (it’s one the Venetians are used to), before Venice (or to be exact, a part of Venice) becomes submerged by the high tide, the citizens are alerted by audible alerts courtesy of the City of Venice‘s tides information service, the Centro Maree, which also gives advanced notice of the probable height of the tide.
However, you shouldn't let the figures worry you: the height of the tide is measured using level zero on the tide gauge of the Punta della Salute as a reference. What this means is, as Venice is about 100 cm above sea level, an exceptional tide of 140 cm actually means another 40 cm of water (or 60 at the lowest points of the city, such as Piazza San Marco) and flooding in more than half of the historical centre.
The water, however, follows the cycle of the tides (rising for 6 hours and dropping for 6 hours), thus the flooding only occurs during the central hours of the rising phase, typically lasting about 3-4 hours. Once it has dropped, Venice returns to normal. In the meantime, boardwalks are provided to ensure that the main routes are passable.
Firstly; make inquiries in advance. An excellent source of information on the expected tides is, as mentioned, the Centro Maree of the City of Venice or – our concierge!
Secondly: if you do need (or want) to go out when the tide is rising, it is always best to either wear or take wellington boots with you so that your shoes are not irreversibly ruined.
Thirdly: where you can, take advantage of the boardwalks. When walking along them remember to respect the two-way circulation of traffic and note that you will probably not be able to stop, as that would impede the passage of other pedestrians.
If the high water does catch you out and you have not prepared yourself for your journey, always ask whether there are alternative routes – there often are.
“Aqua alta” is also the name of an unusual and fascinating bookshop which is located close to Campo Santa Maria Formosa, a 5-minute’ walk from the Hotel Londra Palace (actually at Calle Longa Santa Maria Formosa 5176).
It’s a labyrinth where you can happily lose yourself among publications on Venice in every language and by every publisher, plus second hand books, ancient and modern literature, essays, comic books and monographs; all piled up in boats, gondolas and bathtubs. Its name is no accident: it’s located below street level and at high tide the water comes in through the “Emergency Exit“, a doorway at the back of the bookshop. During the hours of high tide, even the fish, which come in with the water, are given a cultural tour!