Scientist: Climate change will contribute to more frequent floods in Venice

Last week, the high tide (so-called acqua alta) flooding the city reached an exceptionally high level in Venice, 187 cm above average sea level; the second highest in the city’s history. St. Square The brand was flooded to a height of 154 cm. The historic center of the city was under water.

– This is not the first flood of this scale. Since the city was built, it has been flooded many times. The flood of November 4, 1966, when the water level was 194 cm, is particularly memorable in the modern history of Venice – reminds Dr. Marek Kasprzak from the Department of Geomorphology of the University of Wrocław in an interview with PAP.

Floods in Venice are usually caused by several factors acting at the same time. The expert calculates the following: syzygian tide (the maximum sea state when the Sun, Earth and Moon line up in one line), storm and intense inflow of water from swollen rivers. The picture is completed by the simultaneous damming of sea waters by the Sirocco wind. The unfavorable situation of the city is deepening due to the decline of its area. It is estimated that since 1897, Venice has decreased by 23 cm. This is the result of, among others, drying the area occupied for development.

– It is expected that as a result of current, rapid climate changes, the flood risk in Venice will increase – emphasizes the expert. In his opinion, this is influenced by both the projected increase in the level of the world ocean, which, according to the forecasts included in the IPCC (Intergovernmental Panel on Climate Change) report, may amount to as much as 52-98 cm in 2100 compared to the years 1986-2005, as well as the more frequent occurrence of extreme weather conditions.

– Without preventive measures, the future of the city looks bleak – says Dr. Kasprzak.

Can Venice be saved?

Dr. Kasprzak thinks so. – The protection of Venice is ineffective not because of the lack of potential technical solutions, but rather because of administrative, financial and social problems – he adds.

Other cities or countries located very low to the sea have dealt with the problem of flooding. – The fact that movable barriers blocking the inflow of swollen sea waters into bays, estuaries or estuarine sections of rivers are effective is proven by the existing structures on the coast of the Netherlands, the Thames Barrier in London and the St. Petersburg Dam protecting the Neva Bay, the scientist enumerates.

He adds that theoretically it is also possible to raise the entire city. This type of work was carried out in the 1850s and 1860s in Chicago, raising the existing buildings by approximately 2–3 m above the level of Lake Michigan. Dr. Kasprzak says that the salvation for Venice should be the MOSE system of mobile flood barriers. “Moses”. The project, started in 2003, has not yet been completed, and the completed structures not only have not achieved their full planned effectiveness, but also lose their functionality and require renovations.

– Protecting Venice from floods is possible and, due to its great cultural value, it should be a priority for the Italian government, and perhaps even for the international community, says the scientist.

As he reminds us, the phenomenon of extraordinary swell of the sea in the Venetian Lagoon, resulting in the flooding of Venice or the nearby city of Chioggia, is so frequent that there is a special phrase describing it “acqua alta”.

Venice has been flooded due to cyclic tides since the beginning of its existence, which is due to its specific location – it was located on islands located inside the Venetian Lagoon. It is a bay separated from the open sea by barrier islands forming an elongated embankment (lido) above the water.

The sediments filling the lagoon have evolved into more or less permanent islands – the old part of Venice is located on them. Their height above the average sea level usually does not exceed 1 m. Only some fragments of the islands rise to 2–3 m above sea level. In their natural state, they were occupied by salt marshes and dunes and separated by natural channels carrying tidal water.