Scientists warn that no adaptation measure can sustain Venice as rising sea levels threaten to swallow the city.
Venice may be forced to relocate in the future as scientists scramble to save it from the growing threat of flooding.
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A new study, published in the journal Scientific Reports, has assessed existing and potential adaptation strategies for the Italian city against sea-level rise projections from the UN’s Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report.
Venice, a UNESCO World Heritage Site within the Venetian Lagoon, has experienced increasing flooding over the past 150 years. Last summer, powerful thunderstorms swept through the region, overwhelming drainage systems and turning streets into fast-flowing rivers.
In 2019, severe flooding caused two deaths and hundreds of millions of euros worth of damage, including to the tourist hotspot of St Mark’s Basilica. Glass barriers and a €3.3 million restoration plan were unveiled back in 2023 to protect the 900-year-old church, which remains at the mercy of the tides.
Scientists have now outlined three possible adaptation strategies for Venice, warning that rapid action is “essential”. The study’s author says Venice exemplifies the challenges that many low-lying coastal areas will face due to sea-level rise over the coming centuries, including the Maldives and the Netherlands.
Will Venice be relocated?
The authors predict that dikes may be necessary beyond 0.5 metres of sea-level rise – which may occur by 2100, even if emissions are kept low – at an estimated cost of €500 million to €4.5 billion.
These are engineered embankments, which are usually made from earth, sand or rock, that are built along coastlines or rivers to act as a barrier against potential flooding.
Closing the lagoon with a “super levee” (a wide reinforced embankment) could also be viable beyond 0.5 metres of sea-level rise, and could protect the city against sea level rise of up to 10 metres. However, the initial cost for this could exceed €30 billion.
As a last resort, the study says that relocating the city, its residents and historic landmarks may be necessary beyond 4.5 metres of sea-level rise – which is projected to occur after 2300 – at a cost of up to €100 billion.
The authors warn that the construction of large-scale interventions such as permanent barriers can take between 30 and 50 years, meaning early planning is essential.
‘No optimal strategy for Venice’
“Our analysis shows that there is no optimal strategy for Venice,” says Professor Robert Nicholls of the Tyndall Centre for Climate Change Research at the University of East Anglia.
“Any approach taken must balance multiple factors, including the well-being and safety of Venice’s residents, economic prosperity, the future of the lagoon’s ecosystems, heritage preservation and the region’s traditions and culture.”
Nicholls says that all low-lying populated coastal areas should recognise the challenge of long-term sea-level rise and “start considering adaptation implications now.”
“Given the high cultural value of Venice, these costs are clearly incomplete and no adaptation measure can sustain the Venice that we see today in the long term,” he adds.
Why are sea levels rising in Venice?
Venice is already at risk during high spring tides due to its position in a shallow coastal lagoon.
According to Royal Museums Greenwich, seasonal sirocco winds can also cause ‘storm surges’, driving water across the Adriatic Sea into the lagoon and towards the city. When high tides and storm surges collide, flooding can be extreme.
Global warming is also accelerating sea level rise across the world, due to a combination of glacier melt and thermal expansion of seawater as it warms.
To make things worse, Venice’s city ground level is currently sinking by around 1mm a year due to natural land displacements. This has been worsened by human activity, such as pumping groundwater from beneath the lagoon. However, this is now banned.
