Venice mayor Luigi Brugnaro blamed climate change for the city’s devastation after flood levels reached the second highest level since records started in 1923, reports the BBC. ‘The situation is dramatic. We ask the government to help us’, he said on Twitter. High tides peaked at 1.87 metres last Tuesday night, just below the highest recorded tide of 1.94 in 1966. High tide levels hit the city again on Wednesday morning, reaching 1.60 metres.
According to the authorities, more than 85% of the city was flooded, affecting businesses and tourist sites. Flood waters have caused irreparable damage to St Marks’ Basilica and affected other historical buildings in the city, including luxury Gritti Palace hotel, a city landmark. Two people are reported dead in the area, one of them electrocuted as he tried to start a pump, and another one also at his home.
Acqua alta (high water) is a term used in Italy’s Veneto region for the exceptional high tides that occur in the northern Adriatic Sea: it can last 3 to 4 hours during the peak of the high tide. The peaks reach their maximum in the Venetian Lagoon, flooding Venice, affecting as well other parts of the northern Adriatic. The acqua alta phenomenon occurs mainly in winter time, when a combination of astronomical tide, strong south wind (sirocco) and a seiche (a standing wave in an enclosed body of water, in this case the Adriatic) can cause a larger inflow of water into the Venetian Lagoon.
A multi-billion-euro project to protect the city from high tides using a flood barrier, known as Mose, has been ongoing for years, but has experienced all sorts of problems, from corruption, to cost overruns and delays. It is expected to be completed and running by 2021.
Flooding in Venice is quite common, and Venetians are used to coping with acqua alta; a tide up to 90 cm above sea level leaves Venice virtually unaffected, while a 140 cm tide affects more than one-third of the city. This is considered an exceptional tide, and statistically occurs once every 5 years. However, out of the top 10 tides, five have occurred in the past 20 years and the most recent one was only last year, said BBC meteorologist Nikki Berry.
Two factors that also contribute to Venice flooding are subsidence (due to natural causes and human activity) and sea level rise, linked to climate change. Together, these two factors have caused Venice to sink 23 cm in the last century, according to the High Water Information Centre from the Municipality of Venice.
Although a single event cannot be blamed on climate change, the increased frequency of exceptional tides is a huge concern. As Nikki Berry points out, in our changing climate, sea levels are rising and a city like Venice, which is already sinking, is particularly susceptible to such changes.