Why Does Venice Flood, and What is Being Done About It?
Why Does Venice Flood, and What is Being Done About It?
Throughout November 2019, Venice has been inundated with the city’s worst floods in half a century. Photographs and videos spread across the world showing the city’s iconic St Mark’s Square underwater, with a 2-meter-high surge threatening irreparable damage to historic sites such as Saint Mark’s Basilica. While the city has been battling rising water levels since the 5th century, the recent floods, set against the context of climate change, have spurred debate about how coastal cities are vulnerable to rising sea levels, and how the damage can be mitigated against.
Venice has become accustomed to periodic flooding, described in local folklore as “acqua alta” (high water). While the city can experience flooding almost 60 times per year in the autumn and winter months, recent decades have seen a notable increase in the severity and regularity of floods. The afore-mentioned St Mark’s Basilica, for example, has flooded six times in 1,200 years. Four of those floods have been in the last 20 years.
There are several factors that make Venice particularly prone to flooding. As detailed by Reuters, sea levels around the coastal city have been rising for decades as a result of climate change, with a 20-centimeter rise estimated over the last century. While the water level has been rising, the city itself has been sinking by approximately one millimeter per year due to the soft, moving terrain on which it is built. The fragile base on which the city is built has been compromised further in recent decades, with the city pumping groundwater for drinking and industrial use up until the 1970s.
Venice’s geographical location has also contributed to the city’s flooding. Located on a marshy, shallow lagoon on the edge of the Adriatic Sea, the Venetian islands have been subjected to tidal variations of 50cm in sea levels throughout the year. A series of barrier islands known as “barene” have protected the inner islands from flooding since the 12th century, with Venetians blocking rivers and strengthening the barrier islands to enhance the city’s protection.
When the 1960s heralded the excavation of the Canale dei Petroli, permitting oil tankers to reach the mainland port near Venice, the centuries-old protections were compromised and the lagoon eroded. As a result, Scirocco winds blowing from the southeast can now drive water into the lagoon, which combines with high tides to increase the risk of serious flooding.
The changing attitude of Venetians to their built environment has also indirectly increased the risk of flooding. For centuries, when new buildings were built in the city, they were built on top of the pillars and foundations of old buildings, which steadily raised the city. In a recent interview with Rolling Stone, Venice restoration expert Pierpaolo Campostrini described how flooding risks were lessened by building the city higher at the sacrifice of 13th and 15th-century palazzos.
They were not sentimental about the past. They did not worry about preserving old buildings. They just built new ones on top of the old ones. And the city kept rising. But of course, we can’t do that anymore. Now, there are cultural constraints. We don’t want to lose the beautiful Renaissance architecture we have here. Knocking it down and building on top of it is not an option. We have to find another way to save it.
-Pierpaolo Campostrini, Venetian restoration expert speaking to Rolling Stone magazine
The latest flooding, which covered 85% of the city, has drawn attention to the question of how Venice can save itself from heightening floods. The most apparent solution in MOSE; an unfinished scheme of 78 storm gates that began construction in 2003. Anchored by four vast retractable gates at the inlets of the Lido, Malamocco, and Chioggia, the scheme has been designed to seal the entire lagoon from high tides in fifteen minutes. The multi-billion-euro project has however been plagued with cost overruns, corruption scandals, and delays. Even if completed, questions have been raised over how effective MOSE will be, with worries that almost daily use of the barriers will increase pollution and alter sewage flows.
While the MOSE project may turn into an impressive example of humankind holding back the power of nature through brute force, a long-term approach to protecting Venice from flooding may be to work with nature, rather than against it. Re-naturalizing barrier islands to slow the tide, and ceasing industrial activity that requires the dredging and deepening of the lagoon, have already been suggested as ways to restore the centuries-old balance between the city and natural surroundings. The city could also look to other regions for inspiration, including pioneering Dutch methods in water management, prioritizing the ethos of “living with water.”
While coastal cities around the world will face the looming issues of sea-level rise, Venice’s precarious situation is as much about local political incompetence as it is about global environmental changes. The future offers no respite, with dire flooding projections suggesting that in 50 years the city will experience annual floods on the scale that are currently making headlines around the world. Therefore, city officials must reach beyond a fault-ridden barrier scheme and take urgent steps that merge short-term mitigation with a long-term redress of the symbiotic relationship between the city and lagoon, land and water, urban and natural.