City loved by UK tourists could sink like Atlantis by 2100 without huge change

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But ultimately, climate experts fear the only permanent solution is to relocate the city to safer ground, necessary if sea-level rises over 5-metres - which is projected to occur after 2300 - but at a staggering cost of 100 billion Euros (£87 billion).

The Conversation article by Robert James Nicholls - Professor of Climate Adaptation at the University of East Anglia - Marjolijn Haasnoot, Professor of Climate Adaptation, Utrecht University; and Piero Lionello - Professor of Atmospheric Physics and Oceanography, University of Salento - reveals the alarming results of their study into Venice's future.

The historic city is built atop 120 small islands crisscrossed by 177 canals and nearly 400 bridges and its current flood defences include a trio of movable barriers at the lagoon's edge that can seal the area from high tides.

The team wrote in The Conversation: "Each option becomes relevant at different points as sea levels rise. The city’s flood defences have already been upgraded substantially, at a cost of €6 billion (£5.2 billion).

"This involves a series of huge steel gates attached to the seafloor, known as the Mose barriers. When raised, these barriers effectively seal off the Venetian Lagoon from the wider Mediterranean Sea.

"The Mose barriers mean the flood risks are currently manageable, but the frequency of their use is rising.

"In the first five years of use (between 2020 and 2025) the system was closed for 108 high waters, while in the first two months of 2026 it was activated 30 times."

And as sea levels continue to climb, it would need to be closed more and more often – potentially for weeks at a time each year.

They warned: "This creates a series of problems. Frequent closures would disrupt shipping and tourism, alter the lagoon’s ecology, and would require major new systems for sewage treatment and huge pumps to maintain lagoon water levels.

"A system designed for occasional protection risks becoming a semi-permanent barrier – something it was never intended to be.

"With additional measures, such as raising the city by injecting sea water into the rocks deep underground, reversing the subsidence to some degree, these barriers could remain effective for some time – perhaps even after a metre of sea-level rise.

"But even under relatively low levels of warming, the sea is projected to keep rising for centuries, eventually pushing beyond what the barriers can handle."

The authors estimate that dykes or closing the lagoon may be necessary in the case of a 0.5m sea rise, which may occur before 2100.

A fully enclosed lagoon – protected by a much larger “super levee” and supported by continuous pumping – could protect the city from up to 10m of sea level rise, but at severe cost to the living lagoon.

But they warned relocating the city might be necessary beyond 4.5 metres of sea level rise, which is projected to occur after 2300.

The team added: "The financial costs of these choices are substantial. We used the costs of Mose and other previous engineering projects (adjusted for inflation to 2024 prices) to estimate the cost of each adaptation strategy."

Co–author Professor Robert Nicholls, from the University of East Anglia, said in the journal Scientific Reports: "This analysis shows that there is no optimal adaptation strategy for Venice.

"Any approach taken must balance multiple factors including the wellbeing and safety of Venice's residents, economic prosperity, the future of the lagoon's ecosystems, heritage preservation, and the region's traditions and culture.

"This study shows that all low–lying populated coastal areas should recognise the challenge of long–term sea–level rise and start considering adaptation implications now."