Acqua alta, high water. It is a nuisance for Venetians, for sure.

Especially if one lives on a ground floor apartment or if he/she owns a shop. But seeing St. Mark’s Square filled with the water of the lagoon may be an unforgettable experience and I can remember how fascinating it was for me as a child. It reminds me of Istanbul’s mysterious Basilica Cistern or Bacoli’s Piscina Mirabilis, only on a larger scale.

It is important to know that it is not a dangerous event, water is not brought to the city by a swallen river, therefore it must not be confused with a flooding and it does not mean that the city is sinking. Most of the times it causes very limited inconvenience to Venetians and visitors. You just have to be patient and wait for a couple of hours for the following ebb.
Venice has been defined an ‘amphibian’ city, since water is one of its constituent elements.

WHAT IS ‘HIGH WATER’?

This phenomenon is determined by the sum of distintive elements, two of which are the astromical influence of the moon and the sun on the earth surface and special adverse metereological conditions, typically low preassure and a strong South wind (scirocco).

Conventionally, when the sea level reaches 100 cm above the local datum of Punta della Salute it is called ‘acqua alta’. When this happens, a few problems arise involving transports and pedestrian use of streets in lowest areas of the city, for example St. Mark’s Square.

When the tide exceeds 100 cm, the phenomenon affects larger sections of pedestrian areas. But Venetians know this also typical of their city, it happens only a 5 / 6 times a year in autumn and in winter and you can cope with it wearing a pair of rain boots or of disposable boots for a few hours (usually 3 to 4 hours).

The real problems arise when the level reaches +140 cm, as it happened on October 2018. But Venetians expect this to happen every 4 or 5 years.

WHAT HAPPENS IN VENICE WHEN THERE IS HIGH TIDE?

High tide can be forcast. In case of a forcast of + 100 cm, the population is alerted a few hours in advance by different acoustic signals depending on the expected tidal height. To allow pedestrian passage, raised elevated platforms are set along the main streets.

To know more about this phenomenon you can visit the Venice Municipality website and if you are visiting Venice in the high tide period you can download the useful free app Hi!Tide.