High tide in Venice, or “acqua alta,” can make Venice seem like Atlantis. It was at its worst in 1966, when floodwaters inundated the city with nearly two meters of salty lagoon water. It is possible to see the water splashing over the canal banks or gushing through the drains in St. Mark’s Square. Acqua alta is the term used for the annual flooding in Venice that occurs mostly in the winter months. It’s a natural phenomenon caused by a combination of factors including high tides, strong winds, and sometimes heavy rainfall.
This phenomenon is often mistaken as evidence that Venice is sinking. Although the city sank by about 10 cm in the 20th century due to industrial groundwater extraction, the subsidence was largely halted when artesian wells on the mainland were closed in the 1960s. Today, subsidence is estimated at 0.5 to 1 mm per year, mainly due to geological factors and compaction of the soil under the millions of wooden piles in the city.
A bigger problem is rising sea levels, which are becoming an even bigger threat as the Arctic ice caps melt due to global warming. Already, the frequency of acqua alta has risen from less than 10 times a year to more than 60 times a year in the last century, and the trend is rising.
Causes of flooding in Venice
The phenomenon occurs mainly in the period from autumn to spring and is caused by a combination of three factors.
Tidal Phenomena
The astronomical tide, that is, the rise of the sea level due to the attraction of the moon. The Adriatic Sea, where Venice is located, experiences two high tides and two low tides each day. When these tides are higher than usual, it can lead to flooding in the city.
Subsidence
Over the years, the ground level in Venice has been slowly sinking, a process known as subsidence. This has been exacerbated by the extraction of groundwater from wells, although this practice has now been stopped.
Rain
A more or less intense rainy period that increases the amount of water in the lagoon basin and in the rivers that flow into it.
Sirocco Winds
These are warm winds from the southeast, which can push seawater into the Venetian Lagoon, raising the water level.
The most important factor, however, is the sirocco. Because even with heavy rainfall on the mainland and correspondingly an increased water inflow, hardly any water accumulates in the lagoon without a southerly wind.
So that you are well prepared for Venice, you can find here my personal packing list for the lagoon city, with everything that should not be missing in your luggage.
Impact of Acqua Alta in Venice
Venice, often referred to as “The Floating City,” is renowned for its intricate canal system, historic architecture, and rich cultural heritage. However, the recurring phenomenon of acqua alta, or high water, has posed significant challenges to this UNESCO World Heritage site. The impact of these flooding events on Venice is multifaceted, affecting its buildings, economy, and the daily lives of its residents.
Architectural and Cultural Heritage Damage
One of the most immediate and visible impacts of flooding in Venice is the damage it inflicts on the city’s historic buildings and artworks. The flooding in Venice, even if temporary, can have lasting effects on the structural integrity of buildings. The foundations, primarily made of wooden piles, are susceptible to rot when exposed to water for prolonged periods. Moreover, the bricks and mortar, which many Venetian structures are composed of, can deteriorate rapidly when in contact with saltwater. This erosion not only weakens the buildings but also threatens the invaluable artworks, frescoes, and mosaics housed within them. Over time, the repeated exposure to acqua alta can lead to irreversible damage to Venice’s architectural treasures.
Economic Implications
Venice’s economy is heavily reliant on tourism. Each year, millions of tourists flock to the city to traverse its canals, visit its historic sites, and partake in its cultural festivities. However, severe flooding events can deter visitors, leading to a significant drop in tourism revenue. Hotels, restaurants, shops, and other businesses that cater to tourists often face temporary closures or reduced patronage during and after significant flood events. The economic consequrnces of these disruptions can be profound, especially for local business owners and workers who depend on the steady influx of tourists.
Challenges for Residents
For the residents of Venice, acqua alta is not just an occasional inconvenience; it’s a disruptive force that affects their daily lives. Navigating the city becomes a challenge as many streets and squares get submerged. While temporary wooden walkways are set up to aid pedestrian movement, they are not always sufficient, especially during extreme flooding. Residents often have to resort to wearing rubber boots or waders to move around. Additionally, ground-floor apartments and shops are at risk of water intrusion, leading to property damage and the potential loss of personal belongings. The repeated need for cleanup and repairs can be both financially and emotionally taxing for the local populace.
Good to know
Not all parts of the city are equally susceptible to flooding, as the following table of the Comune di Venezia shows, because the ground of the alleys and squares has adapted to seismic and tectonic movements over the centuries, so that it is anything but flat.
Moreover, the actual depth of water in the streets is much less than the “flood level” suggests. (See the “extreme case” below, where 135 cm of high water meant 40 cm of water in Piazza San Marco).
| Height of the flood | Percentage of Venice flooded |
| Up to 80 cm (2.6 feet) | 0% (normal tide) |
| 100 cm (3.3 feet) | 4% |
| 110 cm (3.6 feet) | 12% |
| 120 cm (3.9 feet) | 35% |
| 130 cm (4.3 feet) | 70% |
| 140 cm (4.6 feet) | 90% |
An extreme case
In October 2019, the flood reached 135 cm. Piazza San Marco was inundated by at least 40 cm of water, which was called the worst Acqua alta of the decade. In recent years, however, the Acqua alta has reached 150 cm or more several times at the beginning of winter, flooding most of the city.
The worst flood in the history of Venice was in 1966, when the flood reached 194 centimeters. The second worst event was in November 2019, when the water reached 187 centimeters.
Fortunately, the city has made changes over the years to mitigate the effects of Acqua Alta. For example, substations have since been moved out of harm’s way, and ground-floor wiring in many apartments is now mounted high enough on the walls to prevent short circuits in most cases. Thanks to these changes, massive power outages did not occur during the 2019 flood – in 1966, the city was without power for days.
What you can expect with the high tide in Venice
Most of the time, the Acqua Alta is only a mild nuisance: You may have to dodge a pond or two in Piazza San Marco or dodge water splashing onto a fondamenta, a sidewalk next to a canal.
However, if you hear a siren, be prepared for more severe flooding, especially in the lower-lying areas of the historic center. A siren means that an unusually high tide in Venice will peak in three to four hours.
Depending on the height of the high tide in Venice and where you are in the city, you can expect flooding several hours before and after the high tide peaks. These floods can range from a few inches to a major inundation.
The Venice Tide Center states that its three-hour forecasts are 95% reliable, with an accuracy of plus or minus 10 centimeters.
The city provides elevated wooden walkways in flood-prone areas; you can see a map of these walkways at most ACTV vaporetto stops.
Depending on the level reached, not all areas of Venice will be flooded: in fact, this depends on the height above sea level of the area in question and its distance from the Bocche di Porto, the lagoon opening.
In order to tackle the flooding problem, in addition to the pedestrian bridges in the most frequented areas of the city, the MOSE project was launched in 2003: a series of mobile bulkheads built along the openings of the Venetian Lagoon facing the open sea, which are designed to close during exceptional flood events to protect the lagoon from the high tide in Venice.
How to prepare for the flood in Venice
If you plan to be in Venice during the fall and winter months, you should pack rubber boots – especially for visits near the full or new moon, when the Acqua Alta is most likely.
Alternatively, you can pack several plastic trash bags and string or rubber bands to hold them in place. Garbage bags aren’t elegant, but they can keep your shoes and legs dry.
Another option is to buy rubber boots in Venice or temporary plastic rain boots from souvenir stands and street vendors. However, if you have very large feet, it might be difficult to find suitable boots – and you definitely need to protect yourself before the water rises.
Good to know
You can find rubber or plastic rain boots at Ratti, where you’ll find a wide selection of rubber boots for men and women in many sizes. The long-established hardware and housewares store is just a few minutes’ walk from Piazza San Marco.
If you’re visiting Venice from fall to spring, you shouldn’t book ground-floor accommodation. (This is probably not a problem in hotels, as rooms are usually on upper floors, but AirBnB apartments at street level can be risky.)
If high water occurs in Venice, avoid frolicking in the water. High water is an expensive nuisance for locals, and those who splash in the streets, kick up water, or strip and swim in front of the Basilica di San Marco will not make friends in Venice. Locals consider such pranks disrespectful.
While it is unlikely that the Acqua alta will be more than a mild nuisance during your stay, and it poses no danger to people: Even during Venice’s record flood of 1966, when the entire city was inundated, no one drowned.
More YouTube Videos about the flooding in Venice of 1966
Floods in Venice – Related Links
Official website of the Venice Tide Center including high tide forecast
The graph on this Italian language page of the Comune di Venezia shows the expected tides for the next days.
Acqua Alta: floodplains
This map does not cover the whole city center, but it shows the all important parts of the city. The areas colored blue (especially the dark blue ones) are most at risk of flooding in Acqua Alta.
hi!tide Venice App (Android and iOS)
Download the free – and official – Venice tide forecast app for your smartphone.
Newspaper article: The floating city
These dramatic photos show the flooding on November 11, 2012, when Venice had its sixth highest water level in 150 years.