Événements à Venise et alentours : détail
Du 25 Décembre 2009 au 31 Décembre 2011
High water "Acqua alta" Venezia is not a dangerous phenomenon
What to do in Venice when there is "acqua alta" high water?
You can find all follows information on the web site of Municipality of Venice, where is possibile to find more and see how the tide is gone:
http://www.comune.venezia.it/flex/cm/pages/ServeBLOB.php/L/EN/IDPagina/22795#4e46e6
"Acqua alta" is not a dangerous phenomenon: it is important to understand that most of the time high tides cause very limited inconvenience to Venetians and tourists. In these cases, the only thing to do is to be patient and wait a few hours for the following ebb. Otherwise, a suggestion for the most curious people is to buy a pair of boots and visit the town in a quite unusual way.
High water depends on the tide cycle (the alternation of high and low tides happens every 6 hours): when there is "acqua alta" on the streets this lasts only a few hours during the peak of the high tide (usually 3 to 4 hours maximum). Once water goes down again, things go back to normality.
"Acqua alta" (high water) is a phenomenon which generally takes place in Venice in winter time, when a combination of astronomical tide, strong south wind (scirocco) and seiche (see glossary below) can cause a larger inflow of water into the Venetian Lagoon. But even in these months, high waters usually affect only the lowest parts of the town, such as St. Mark's Square, whereas exceptional high tides statistically occur only once every 5 years.
No, only exceptional high waters affect the whole town and even on those occasions the water-line is really remarkable only in the lowest areas. These are the flooding rates of the town in relation to high water levels (measured on the mareographic zero): +100 cm: 3,56%; +110 cm: 11,74%; +120 cm: 35,18%; +130 cm: 68,75%; over +140 cm 90% of the town is covered by water.
Venice and Venetians have always been used to coping with "acqua alta". These are the City Administration's measures in case of high tide: if there's a sea level forecast of +110 cm on the mareographic zero, the population is alerted by acoustic signals and with text messages (for those registered at the free high tide information service of the City Tide Centre - Centro Maree Comunale). At the same time, elevated platforms are set along the main streets to allow passage. Public waterbuses keep on working, although some lines may be subject to changes. In any case access to most of the town is guaranteed. Only when exceptional high waters occur (higher than 120 cm on the mareographic zero) the famous "acqua alta boots" are really needed, but even on these occasions the inconvenience last just as long as it takes for the water to go down again, which usually happens in a few hours.
Glossary:
seiche: the periodic movement of sea waters, a sort of long wave which washes all Adriatic coasts
mareographic zero: the conventional reference level for measuring water-lines
scirocco: warm south-east wind pushing Adriatic waters towards the Venetian Gulf
subsidence: slow, but progressive shift downwards of a sea basin or a continental area
eustasy: fluctuation of sea levels, caused by global climate change.
Retour