Venice today is an amusement park. It has some of the most beautiful buildings in Europe and is a World Heritage Site, but waves of tourists also come for its other big tourist attraction: the canals. The city has become so romanticized that it almost subsists on tourism, and a tragedy like the COVID-19 pandemic was an absolute disaster. This symbiosis with tourism is a love/hate relationship, but most importantly, it can be something that destroys the city itself.

This is because Venice is built on a forest of millions of tree trunks that have been kept in perfect condition for hundreds of years. A forest we are endangering.

Escape to the islands. Today’s Venice was built on an archipelago consisting of 118 islands connected to each other by 455 bridges. It’s an impressive network and walking its streets is truly special. Although it may not seem like the best place to establish a city, we can say that the first settlers had no choice. The city was founded in the 5th century in this area, which provided special protection against attacks by Germanic peoples.

At first it was just a lagoon with access to the Adriatic Sea and inhabited by fishermen, but it was a residential area with ideal characteristics to resist attacks and was the place where people who fled from the surrounding cities due to these attacks settled. Of the barbarians. Everyone needed to be housed, so they began to expand the city and, as usual, began to take over the sea.

stakes. When we build a building, we lay its foundation on the ground. They are vital because they are the things that support construction, but the problem with Venice was that there was no land to build on, there was mud. Since it was not possible to empty all these and of course not lay a brick foundation, starting from the 9th century, they started to cut down millions of trees in the surrounding area, build piles and lay the foundations of the city.

These are wooden pillars that are driven into unstable (clay) soil and rise several meters high to reach a layer durable enough to hold these piles. The entire pile was under water, and buildings began to be built at the shallowest end. In fact, if we were to visit Venice, the only trees we would see would be those of the masts to which the boats are tied.

Wait, there’s wood in the water? Now the question is… doesn’t it rot? In nature, living trees and wood get along well and can be semi-submersible. However, when the tree dies, it begins to rot if it comes into contact with water. This is because organisms (xylophages) come and start eating it. However, if we completely submerge the wood in water, these xylophages cannot start doing their job.

Because organisms that eat wood need oxygen, and yes, there is oxygen in the water, but it is not enough for these organisms, so the wood remains intact. This is more than a theory, because in some accidents that took place in Venice, it was discovered that the piles remained almost intact after certain years.

X-ray of Venice. Image from Science Channel

good wood. As we mentioned, the wood to build the foundations of the city was extracted from nearby oak and oak forests. It is a type of tree that has natural resistance to xylophages and also has very good properties to serve as a foundation and carry large weights. The salt water also gradually hardened the tree trunks, making them more like rocks than trees.

Venice understood the importance of wood to its survival. They used it not only to eat land in the lagoon, but also to build the fleet of important naval forces. Ships were vital for the city to both defend itself and conduct trade, so a program was established to control the timing of logging and reforestation, and the use of quality trees (used in buildings and trees) was prohibited. make firewood. In fact, not only is there wood under the city, there is also a large amount of wood in the structures of the main buildings.

high water

Settlement. Going back to the piles, one thing that happens with every building is that it has a settling period. This is something that happens in every city and causes the building to slowly sink due to its weight. Let’s say it settles into the ground and is something that affects many areas regardless of the quality of the soil, but in others it is a more serious problem. For example, we see that major cities in China sank due to the great weight of the bed, and a festival was held in Venice.

Since the base is still clayey and soft, this settlement occurs no matter how hard the piles are driven into a harder layer. And the result is buildings with displacements of a few centimeters. In fact, what is curious is that many of them did not collapse (even though, as we said, accidents have occurred throughout history).

high water and defenses. The city is a marvel of engineering, but it gets flooded from time to time. This is known as acqua alta and is basically the high tide that occurs between autumn and spring. When the water exceeds a certain level, a large part of the city is flooded, one of the most common spots being St. Mark’s Square. It is a favorite activity for tourists who take photos and walk along the elevated walkways, but it is a serious problem for the city.

These investigations are estimated to cost the city around five and a half million euros a year due to hours not worked (as shops cannot open), but this also affects assets. That’s why the MOSE system was launched in 2020. These are huge defenses (dams) arranged at the main junctions between the Adriatic and the lagoon and raised when necessary to prevent floods from affecting the city too much. These are defense systems that cost around 7 billion euros and, according to those responsible, they have been working adequately since they were installed.

Climate change and travels. This settlement of the city causes the city to sink 2 to 4 centimeters every century, but this is something that can be accelerated. There are two main problems here: Climate change and tourism. The melting of the poles is a situation that threatens all coastal cities, but it could be a disaster in a sensitive city like Venice. Moreover, tourism is something that disturbs the city bed.

Venice is sinking not because of the arrival of millions of tourists every year, but because of the activities of cruise ships and other vessels. The streets are canals and boats have been using them for years, but now there are all kinds of boats (police boats, typical tourist gondolas, private boats and even delivery boats). In addition to these vehicles, passenger ships, while the masses passing a few meters away from the city leave impressive images, they also stir up the seabed and disturb the soft clay soil that is the foundations of the city. So much so that they forbade them to come within a certain distance.

Venice you are not special. All this makes Venice a special city, but just like this Italian wonder, stilts are used all over the world. There are a few towns built on stilts in some areas, but these are generally prominent, so they are quite degraded by xylophage attacks. However, two other cities that exemplify the use of piles are Amsterdam and Mexico City. Additionally, buildings such as the London Bridge, Saint Isaac’s Cathedral in Saint Petersburg or the Brooklyn Bridges in New York, Notre Dame in Paris or Toledo in Madrid are also built on wooden piles.

Pictures | Science Channel, Paolo da Reggio, Slice Science, Didier Descouens

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