In 2017, Venetians witnessed the lowest tides in Venice in 16 years
Many people know that Venice, at times, can be flooded. It’s a natural phenomenon, known as “acqua alta”, that lasts for a couple of hours and during which a certain area of the city is flooded.
What many people do not know about, however, is the opposite phenomenon, called “acqua bassa”: a particularly low tide.
The same way floodings are a natural phenomenon which usually does not cause particular damages, “acqua bassa” is also a natural phenomenon connected to the movement of the tides.
What is the consequence of extremely low tides?
Low tides do not cause as many headaches as extremely high tides as they do not impact residents homes or shops. However, they do cause a problem, too.
The main issue with extremely low tides is the fact that boats can no longer navigate in a number of canals.
This means that ambulance or firefighters boats can no longer reach certain areas of the city. In case of emergency, that can be a serious problem!
How long does acqua bassa last?
Like the “acqua alta”, the “acqua bassa” last for few hours, the time for the tide to grow again.
What are the different 'tide' hights?
Venice’s “Istituzione Centro Maree” puts tides in a category depending on their height.
The different categories and relative heights are:
- Exceptional High Tide: Equal to or higher than +140
- Very High Tide : from +110 to +139
- High Tide: from +80 to +109
- Normal Tide: from – 5o to +79
- Tide under the normal level: from -51 to -90
- Exceptional low tides: Lower than -90
How low were the tides in Venice in the past years?
Since 2016, Venice witnesses a few very low tides every year, in particular between the end of December and the end of January.
In 2016, the “acqua bassa” hit a record of – 66 cm below the average sea level. In 2017, -52 cm, and in 2018 again -65 cm.
In 2020, just two months after the worst flooding in 53 years that hit Venice on the 12th of November, tides can be as low as 50 cm below the average sea level.
How does Venice look with low tides?
Canals in Venice have an average depth of 2 to 3 meters, but narrower canals are often much shallower.
During these days, tides are so exceptionally low, that some smaller canals end up completely dry, and even some main canals can become a hazard for bigger boats.
Transportations of people and goods can, therefore, be impaired or interrupted, potentially temporary impacting many of the city’s businesses, which rely on waterways.
How low was the greatest acqua bassa ever recorded in Venice?
The lowest “acqua bassa” ever recorded in Venice was, to our knowledge, -121cm. It happened on the 14th of February 1934.
Is such an acqua bassa common? When was the latest important 'acqua bassa'?
Really low tides are not a common phenomenon: before the “acqua bassa” of December 2016, the latest recorded “acqua bassa” happened in 2008, 8 years before.
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