Injection was used successfully in Long Beach, California in the late s to halt subsidence caused by oil and gas extraction as well as groundwater usage. After the land surface dropped nearly 30 feet, injection stabilized the subsidence and a slight rebound in land surface elevation a little over 30cm was even seen in some spots. Early research indicated that a similar amount of uplift could be achieved in Venice, which could make a big difference for a city on the edge.
The precision of those predictions was limited, however, by the lack of detailed knowledge about the layers of sediment beneath the city. A new paper, published in Water Resources Research , adds that information and uses it to show that the idea really could work in Venice. Without boreholes around the city to provide observations of the stratigraphy, researchers have relied on data gathered by seismic surveys. Like the familiar sonar systems used by submarines, seismic surveys require a much more powerful signal to be generated so its return can be analyzed as it bounces off sediment in the subsurface.
And, attempts to use potent air and water guns as seismic signal sources caused problems by kicking up large amounts of sediment. The Italian National Research Council acquired a large amount of old, raw seismic data from an Italian oil company, and the researchers were able to use it to construct a high-quality, three-dimensional model of the stratigraphy below Venice.
This allowed them to confirm the presence of a continuous layer of impermeable clay below which injected water could increase pore pressure, rather than simply bubble up to the surface. It also allowed them to determine the thickness and extent of the various layers proposed to be used for the injection. The group simulated the effects of 12 injection wells in a ring around the city. The results showed that, after 10 years of continuous seawater injection a total of almost million cubic meters of water , the city could be lifted centimeters.
That would greatly cut down on the frequency with which the MOSE floodgate system would have to be activated each year. That, in turn, decreases operational and maintenance costs, and reduces the ecological impact of the system. In addition, the uplift around the city would benefit the slowly-drowning salt marshes in the lagoon. Periodically, a section of a canal is blocked off and drained so that necessary repairs can take place.
If this work is not carried out, the canals will fill with sediment brought in by the tide and materials eroded from the buildings. Venetians have had to find inventive ways to bring modernity to the medieval city.
A late-night stroll around the calle of Venice is illuminated by electricty. But how does the electrical current pass safely around a city of water? By following the path of its inhabitants. In order to criss-cross rivers, the cables run within bridges, passing between islands unnoticed.
The same is true of phone lines, as well as water and gas pipelines. This prevents the buildings from sinking into the marshland, which is a volatile environment. The length of the tree trunks is around 25m. This means that they reach the more solid sedimentary clay, which is below the marshland called Caranto.
Reaching this layer of earth gave the foundations strength and stability. This is when narrow holes are dug in the ground and filled with concrete. They act like the roots of trees to securely anchor a building to the ground. On top of the wooden poles, 2 layers of thick wooden planks were added, and then a layer of stone blocks.
The salty mud that surrounds the tree trunks has preserved the wood and prevented it from rotting. The constant flow of saltwater around wood causes it to petrify. This is a process where the pores within the wood are replaced by minerals, and as a result, the wood becomes as hard as stone.
Who would choose to build a city on a remote group of muddy islands? Venice was built on the water to protect it from armies that invaded northern Italy. The area to the north of Venice on mainland Italy was very susceptible to attack. Traveling through this region was the easiest way for invading forces to reach the fertile lands of northern Italy called the Po Valley. This region is protected from Europe by the Alps, apart from a small opening to the East.
If invading armies wanted to reach the fertile Po Valley, the easiest option was to go through Veneto. As a result of many invasions over hundreds of years, many Roman people were forced from their land. This created a refugee crisis in this region. These displaced populations found the Venitian Lagoon and decided to settle there due to its natural defenses. The lagoon acted like a giant moat!
The church is an example of Byzantine architecture. It was built in to replace two earlier and smaller shrines. The building has a lavish interior, with walls covered in golden mosaics and a roof that features 5 domes. The building is named after St Mark, whose remains are contained within. This is a truly remarkable building, as because of this, it can be jam-packed if you wish to visit.
So expect to queue if you want to see the incredible interior. However, it is still worth visiting as its interior is finely detailed and features many important art works. This is a style that takes its cues from Byzantine and Islamic styles.
This blend of Eastern and Western architecture perfectly represents how Venice was an important trading center in the past. The building was initially built as a meeting place for members of the government.
But in , the building was converted into a museum and remains this way today, allowing visitors to view its richly decorated interior. The building features a giant dome, which has become an iconic part of the Venetian skyline.
As such, the building is one of the most visited churches in the city. Originally built to connect the regions of San Marco and San Polo, the bridge now serves an additional function by enabling electricity cables and other services to cross the water without being visible to the public.
Venice is said to be sinking at a rate of between 1 and 2mm per year.
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