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  • Writer's pictureScarlett Lee

The flooding of Venice and its response


Flooding, Flooded San Marco Square, Flooding of Venice, night view of San Marco square, night view of Venice, rising sea level, climate change,
Flooded San Marco Square reflects the lightings of surrounding buildings

Venice is very much vulnerable to flooding. As a man-made island built on water, the creation of Venice has already brought some change to the environment from the beginning, and this man-made impact is still shown at how the city responds against flooding. It is true that the water context where Venice is sitting on makes the city prone to flooding and there were a few high tides so called acqua alta before 2000, but severe flooding has been recently much more frequent due to climate change.

 


Flooding, Flooded San Marco Square, Flooding of Venice, night view of San Marco square, night view of Venice, rising sea level, climate change
Flooded San Marco Square reflects the lightings of surrounding buildings

While living in Venice during the flood-prone period, I have seen and experienced the city’s vulnerability to flooding and how the city is protected by flood-prevention system called Mose. Mose is a flood barrier being built between three inlets in order to stop the influx of high tides from the Adriatic Sea. When high tides are expected, Mose is lifted and it prevents Venice being severely flooded. During my stay in Venice between September and November 2023, Mose has been operating when the sea level above 120cm is expected, so any areas below 120cm sea level were flooded including San Marco square that sits a lowest point from sea level and some vaporettos’ operation were rerouted or suspended. From around the middle of October in Venice, high tides were very much frequent usually above 100cm, so it was very common that streets were flooded and an access to a ground floor level of some buildings was restricted.



Mose is installed between three inlets in order to protect Venice from the influx of high tides from the Adriatic Sea. (Credit: Marco Zorzanello, National Geographic)


Flooding of Venice, Mose, flood prevention gate, Lido inlet, flood barriers
The structure of Mose is built at Lido inlet. The flood barriers are lifted when a high tide is expected.


Flooded Venice, flooding of Venice, flooding, rising sea level, climate change
The area below 120cm sea level is flooded during high tides as Mose does not operate below 120cm sea level

Some might wonder why Mose only activates when sea level is above 120cm rendering the areas below the level still flooded. The reason is, if the flooding prevention gate is lifted too frequently, it would bring a detrimental impact on ecosystem. Venetian marshes, that play an important role in eating up carbon dioxide, flourish by sediments carried by high tides. If Mose operates too often, tidal sediments would not flow to nourish marshes, endangering the ecosystem (Viviano, 2022). For this reason, Mose has been operating when high tide above 120cm is expected in order to minimise a harmful impact on the ecosystem while protecting Venice from heavy flooding.

 


Venetian marshes play an important role in eating up carbon dioxide but they are in the risk of being destroyed in case of the frequent operation of Mose, which is more likely to happen due to rising sea level
Venetian marshes play an important role in eating up carbon dioxide but they are in the risk of being destroyed in case of the frequent operation of Mose, which is more likely to happen due to rising sea level

However, the reality is, the frequency of high tide above 120cm has been consistently increasing due to climate change. For example, during 25-30 October 2023, high tides above 120cm were persistent resulting that Mose system consistently worked about a weeklong. As a result, the lagoon had stagnant water without any fresh water naturally coming in and out, and odd smells of the stagnant water was pervasive. Since the construction and operation of Mose, several big changes were occurred. The speed of the influx of the Venetian lagoon has been very drastically fast since Mose has been built based on the argument of a local person whom I talked to. In order to build the Mose system, a little island was built at the Lido inlet and the waterway has become narrower. Therefore, the speed of water coming in and out has become much faster.



High tides more than 120cm sea level were expected about a weeklong during 25-30 October 2023 (Credit: Official webpage of Città di Venezia, https://www.comune.venezia.it/content/centro-previsioni-e-segnalazioni-maree)


An artificial island is created at the Lido inlet to build Mose. As a result, the speed of water flow has become more fast as the waterway has become narrower (Credit: Google Earth)


Any damage to the ecosystem by the Mose system was not immediately seen yet, but the construction of Mose has already made a big change to the environment and the frequent activation of Mose would eventually led a detrimental impact to the environment. Considering the consistently increasing sea level due to climate change, it is anticipated that the frequency of the operation of Mose will be increasing to protect the flood-prone city, and it is more likely that it would have an adverse effect on the ecosystem. Furthermore, the activation of the mechanical system is very much costly with about 200,000€ for each time. Although there is no doubt that Mose protects Venice from severe flooding for now, it is inevitable to ask a question if the system is a sustainable solution in the long run.


 

When I met a local person from Lido, I asked whether any flood protection measurement was made to protect the island because I got an impression that the three islands facing Adriatic Sea including Lido were just used as barriers to protect Venice. He said that seawalls called Murazzi and submerged barriers were built to protect Lido from flooding. The construction of Murazzi was decided in 1751 while submerged barriers were relatively recently built in late 20th century. A destructive storm occurred in 1966 showed that Murazzi is not enough to protect the island from a strong wave and stop sand beach being eroded (Hawkins, et al., 2007). Therefore, a submerged barrier and sand nourishment were created along the shoreline of Lido and Pellestrina to reduce a power of wave energy. Since this action, a long array of beaches was created along the shoreline of the islands, changing the landscape significantly.

 


Murazzi is built in Lido to reduce the power of sea wave, flooding of Venice
Murazzi is built in Lido to reduce the power of sea wave


To protect Lido from flooding, Murazzi is built with regular intervals and a submerged barrier and sand nourishment were created along the shoreline. As a result, a long array of beach is created at Lido (Credit: Google Earth)


It is undoubtable that Mose has protected Venice from severe flooding and to be honest, it was a relief not experiencing a severe flooding while I was staying in Venice. At the same time, I have been sceptical that Mose can be a sustainable solution to flooding because a consistently rising sea level will result in more frequent operation of Mose, ending up destroying Venetian ecosystem and exhausting a budget for its operation. Humans have consistently made changes to the natural environment to exploit and get benefits from it, and this tradition continues even now, and Venice is one of the examples. The plan of building the city on water was audacious from the beginning and the city has been consistently changing and developing to meet the demand of people. Mose clearly shows the human-oriented response to address the natural and man-made disaster - flooding. As explained before, the mechanical system cannot be a sustainable solution in the long run considering its impact to the ecosystem. Isn’t there a sustainable and alternative solution to create a symbiotic relationship between humans and the natural environment?


 

Reference

 

Viviano, F., 2002. Saving Venice from flooding may destroy the ecosystem that sustains it. National Geographic

 

Hawkins, S. J., Burcharth, H. F., Zanuttigh, B. and Lamberti, A., 2007. Environmental Design Guidelines for Low Crested Coastal Structures. United Kingdom: Elsevier Science & Technology.



*All images are taken by Scarlett Lee unless stated otherwise. The images of Scarlett Lee cannot be used or distributed without permission.

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