Venice can be partially saved, and in the short term it already is being saved, thanks to a massive flood-barrier system that went operational in 2020. But the deeper answer depends on what you mean by “saved.” Protecting the city from catastrophic flooding for the next few decades looks achievable. Protecting it through the end of this century and beyond, as sea levels climb and the ground continues to settle, is a far more uncertain proposition that no single piece of engineering can guarantee.
Why Venice Keeps Sinking
Venice sits on a bed of soft sediments deposited over thousands of years. These layers of sand, silt, and clay compact under their own weight over time, a process that has been going on since long before anyone built a city on top of them. The Holocene deposits closer to the surface are especially compressible, and their natural consolidation contributes to ongoing subsidence across the wider Venice coastland.
Nature’s pace was slow enough that Venice could handle it for centuries. What sped things up dramatically was industrial-era groundwater pumping. Starting in the early twentieth century, factories on the mainland, especially around the industrial port of Marghera, drew enormous quantities of water from the aquifer system beneath the lagoon. That pumping compacted the clay layers sandwiched between the aquifers, pulling the ground down. Modeling of the period from 1930 to 1973 estimated that Venice sank about 15 centimeters due to this groundwater withdrawal alone, with most of the blame falling on the heavy industrial pumping at Marghera rather than on wells within the historic city itself.1Water Resources Research. Mathematical simulation of the subsidence of Venice: 2. Results Italian authorities eventually restricted groundwater extraction, and the most acute phase of human-caused sinking slowed considerably. But the damage was done: the city had lost elevation it could not recover, and natural geological compaction never stopped.2Tectonophysics. Using high resolution data to reveal depth-dependent mechanisms that drive land subsidence: The Venice coast, Italy
Centuries of human intervention also reshaped the lagoon itself. Major rivers that once fed sediment into the lagoon were diverted starting in the medieval period to prevent silting up of navigation channels. That decision solved one problem but created another: without fresh sediment input, the lagoon’s salt marshes and shallow flats began eroding rather than building up, altering the entire morphological setting of the southern basin over the past millennium.3Geophysical Research Letters. Morphostratigraphic framework of the Venice Lagoon (Italy) by very shallow water VHRS surveys: Evidence of radical changes triggered by human‐induced river diversions Venice’s vulnerability today is not just about the city going down or the sea coming up. It is also about the lagoon losing the natural buffers that once absorbed storm energy.
The Rising Sea
Subsidence makes Venice lower. Climate-driven sea-level rise makes the water higher. Together, they accelerate what researchers call “relative sea-level rise,” which is the gap between the land and the water surface that actually determines how often the city floods. Projections for Venice by 2100 range from roughly 32 to 62 centimeters under a low-emissions scenario to 58 to 110 centimeters under a high-emissions scenario.4Natural Hazards and Earth System Sciences. Sea-level rise in Venice: historic and future trends A worst-case scenario tied to rapid ice-sheet melting could push that figure to around 180 centimeters, though researchers consider that plausible but unlikely.
These are not abstract numbers. Every centimeter of relative sea-level rise translates into more frequent flooding episodes. Venice’s historic center has already experienced a striking acceleration: 18 of the 28 extreme flood events that inundated more than 60 percent of the city have occurred in just the last 23 years.5Scientific Reports. Long-term adaptation pathways for Venice and its lagoon under sea-level rise The seasonal pattern is well understood: the largest and most frequent floods hit between November and March, driven primarily by strong sirocco winds that push Adriatic water northward into the shallow lagoon.6Natural Hazards and Earth System Sciences. Extreme floods of Venice: characteristics, dynamics, past and future evolution
The catastrophic flood of November 2019 illustrated how multiple factors can stack up. A deep low-pressure system generated powerful southeasterly winds along the length of the Adriatic. A fast-moving secondary depression generated a meteotsunami. The peak storm surge arrived in sync with astronomical high tide. Wind gusts averaged 28 meters per second over the lagoon, and the monthly mean sea level in the Adriatic was already abnormally high due to persistent large-scale atmospheric patterns.7Progress in Oceanography. Local and large-scale controls of the exceptional Venice floods of November 2019 The result was widespread damage to the city. That event became a painful demonstration of what happens when engineering solutions are not yet in place.
How MOSE Has Changed the Picture
MOSE (Modulo Sperimentale Elettromeccanico) is a system of 78 mobile steel gates installed across the three inlets that connect the Venice Lagoon to the Adriatic Sea. Under normal conditions the gates rest flat on the seabed, allowing ships and tidal water to pass freely. When a dangerous storm surge is forecast, compressed air is pumped into the hollow gates, raising them to block incoming water. The system became operational in 2020 after decades of planning, construction, cost overruns, and a corruption scandal that delayed completion.
The results so far have been encouraging. During a severe storm in November 2022, MOSE held back a water-level difference of roughly 1.2 to 1.3 meters between the open sea and the lagoon side at the various inlets. Without the barriers, water levels inside the lagoon would have been the highest ever recorded.8Coastal Engineering. Prototype data analysis of the dynamics of the Venice gate-barriers during an extreme storm event Instead, the city stayed dry. Modeling studies looking at near-term conditions confirm that MOSE will be able to defend Venice from high water for the foreseeable future, as long as sea-level rise stays within moderate bounds.9Journal for Nature Conservation. The impact of operating the mobile barriers in Venice (MOSE) under climate change
The system’s physical behavior during heavy weather has also been carefully monitored. During that 2022 storm, offshore waves reached nearly 3 meters with mean periods of about 6.5 seconds. The gates oscillated modestly, with typical angular movements around one degree, and physical displacements on the order of 15 to 30 centimeters. These are well within the design limits, suggesting the structure can handle severe Adriatic storms without mechanical failure.10Coastal Engineering. Prototype data analysis of the dynamics of the Venice gate-barriers during an extreme storm event
Where MOSE Runs Into Trouble
MOSE was designed for the sea-level conditions of the late twentieth century. The concern is not whether it works now but whether it will keep working as relative sea levels climb. One critical constraint involves wind. Even when MOSE blocks the surge coming through the inlets, strong winds blowing across the lagoon’s surface can still pile water up inside it, a phenomenon called wind setup. Analysis shows that once relative sea-level rise reaches about 40 centimeters above present levels, this wind-driven flooding inside the closed lagoon will begin to overwhelm the system’s ability to protect all urban settlements.11Coastal Engineering. How long the Mo.S.E. barriers will be effective in protecting all urban settlements within the Venice Lagoon? The wind setup constraint Under even the most optimistic climate scenario, Venice is likely to reach that 40-centimeter threshold sometime this century.
There is also the question of how often the barriers will need to close. As sea levels creep upward, the number of tidal events exceeding the closure threshold increases steeply. Researchers modeling partial-closure strategies found that even with selective use of individual inlets, roughly a third to 38 percent of events still require full closure of all three inlets at a relative rise of 40 centimeters, climbing to 50 percent of events at a 50-centimeter rise.12Natural Hazards and Earth System Sciences. Exploring the partial use of the Mo.S.E. system as effective adaptation to rising flood frequency of Venice Each closure disrupts port operations and navigation. And crucially, frequent closures choke off the exchange of water between the lagoon and the open sea, with serious consequences for the lagoon ecosystem.13Regional Environmental Change. Boon and burden: economic performance and future perspectives of the Venice flood protection system The lagoon depends on tidal flushing to maintain oxygen levels, flush pollutants, and support the fisheries and habitat that surround Venice. A lagoon sealed off for large portions of the autumn and winter could become a very different and much less healthy body of water.
A Lagoon Under Pressure From More Than Tides
Flooding gets the headlines, but the lagoon’s ecological health has been deteriorating for reasons that MOSE cannot address. Salt marshes, which act as natural wave buffers and sediment traps, have been disappearing across back-barrier lagoons worldwide, and Venice is no exception. The causes include wave-driven lateral erosion, relative sea-level rise, and a chronic shortage of fresh mineral sediment caused by those centuries-old river diversions.14Water Resources Research. Hydrodynamic Feedbacks of Salt‐Marsh Loss in the Shallow Microtidal Back‐Barrier Lagoon of Venice (Italy) As marshes shrink, the lagoon’s open water area grows, which in turn allows larger waves to form and erode more marsh in a self-reinforcing cycle.
Commercial shipping compounds this erosion. Large vessels navigating the deep channels dredged through the lagoon generate powerful wakes. Measurements at channel margins recorded average depression-wave heights of about half a meter, with one extreme event from a 280-meter cargo ship producing a drawdown of nearly 2.5 meters.15Scientific Reports. The effects of ship wakes in the Venice Lagoon and implications for the sustainability of shipping in coastal waters That energy dissipates as it moves outward, but within several hundred meters of the channel it drives intense sediment resuspension, with concentrations in the water column reaching 1,000 milligrams per liter. The Malamocco-Marghera industrial canal, dug in 1970, shows particularly stark damage. More than 3,000 commercial vessels per year navigate through it, collectively resuspending an estimated 1.2 million metric tons of sediment annually and contributing to significant erosion of the central lagoon’s shallow flats.16Scientific Reports. Assessing the human footprint on the sea-floor of coastal systems: the case of the Venice Lagoon, Italy Cruise ships, before restrictions were tightened in 2021, also scoured the seabed during docking maneuvers, carving pits up to 120 meters long and 3.5 meters deep near the cruise terminal.
What Saltwater Does to the Buildings Themselves
Even if every flood were somehow prevented, Venice’s buildings face a quieter form of destruction from the saltwater that permeates the lagoon environment. The tidal range in the Venice Lagoon averages more than 60 centimeters and can exceed 1.7 meters in extreme cases. This cycle of wetting and drying drives saltwater into the brickwork of Venice’s buildings, where dissolved salts crystallize as the masonry dries. Laboratory testing on historical Venetian bricks has shown that moisture alone reduces the compressive strength of bricks, and the combination of moisture and salt reduces it further. Paradoxically, salts without moisture can actually strengthen brick, but that dry condition rarely persists in a city that sits in a tidal lagoon.17Engineering Failure Analysis. Experimental investigation on bricks from historical Venetian buildings subjected to moisture and salt crystallization Walk through Venice at low tide and you can see the damage with your own eyes: crumbling lower walls, salt bloom on facades, and exposed brick that looks like it has been chewed.
Below the waterline, Venice’s wooden pile foundations face their own version of slow decay. Most of the city’s historic buildings rest on timber pilings driven into the lagoon mud. When those piles stay fully submerged in oxygen-poor sediment, they can last for centuries. But investigation of the foundation piles at the Church of Santa Maria Maggiore found that the state of preservation varied dramatically depending on burial depth. Piles closer to the sediment surface, where more oxygen was available, showed much quicker decay from soft-rot fungi and bacteria than deeply buried piles.18Construction and Building Materials. Assessing the wood compressive strength in pile foundations in relation to diagnostic analysis: The example of the Church of Santa Maria Maggiore, Venice As the lagoon bottom erodes and water chemistry changes, more of these piles become exposed to conditions that accelerate rot. Flood barriers keep water out of living rooms, but they do not protect foundations from the biological processes occurring in the mud beneath them.
Could Venice Literally Be Raised?
One of the more audacious proposals for defending Venice involves pumping seawater deep underground to physically lift the city. The idea, developed by Italian researchers in the 2000s, calls for injecting seawater into a brackish aquifer 600 to 800 meters beneath the lagoon. Modeling studies suggest this could raise Venice uniformly by about 25 to 30 centimeters over a ten-year injection period.19Water Resources Research. Can Venice be raised by pumping water underground? A pilot project to help decide Later models using refined hydrogeological data confirmed the feasibility of that range.20Water Resources Research. A new hydrogeologic model to predict anthropogenic uplift of Venice
The obvious concern is whether pumping fluid into the ground beneath a city full of medieval and Renaissance buildings might cause uneven ground movement that cracks walls and collapses foundations. Analysis of this risk found that even under pessimistic assumptions about the aquifer’s geological variability, the maximum ground-surface tilt produced by injection would be several times smaller than the tilt caused by the industrial-era groundwater pumping Venice already survived, and about twenty times smaller than the tilt values the city currently experiences from other causes.21Water Resources Research. Anthropogenic Venice uplift by seawater pumping into a heterogeneous aquifer system On paper, this approach could buy Venice an extra generation of protection by offsetting projected sea-level rise for a few decades. In practice, it has never moved beyond the modeling stage. The political, regulatory, and financial obstacles are substantial, and the idea of deliberately manipulating the subsurface beneath a UNESCO World Heritage Site makes decision-makers understandably cautious.
A City Losing Its Residents
The technical debates about barriers and injection wells take place against a backdrop of demographic collapse. Venice’s resident population has fallen from about 170,000 in the early 1950s to fewer than 50,000 in 2024.22Scientific Reports. Long-term adaptation pathways for Venice and its lagoon under sea-level rise The reasons are intertwined with the flood problem but not reducible to it. Housing costs driven up by tourism, the inconvenience of living in a car-free island city, limited job opportunities outside the service sector, and repeated disruption from high water have all pushed residents to the mainland. Meanwhile, more than 22 million tourists visit each year, generating an estimated two to three billion euros in turnover.
This imbalance creates a paradox. Tourism funds the economy that pays for Venice’s preservation, but the tourism industry also resists measures that might reduce visitor numbers or restrict access. Cruise-ship traffic, for instance, was a major source of lagoon erosion before partial restrictions were imposed. And the conversion of apartments into short-term vacation rentals steadily removes housing from the residential market, accelerating the population decline that makes Venice feel less like a living city and more like an open-air museum. Saving Venice from the sea means little if there is no functioning community left to inhabit it.
What the Next Decades Actually Look Like
The honest assessment is layered. For the next 20 to 30 years, MOSE gives Venice a real and proven line of defense against storm surges. The barriers work, they have been tested in severe conditions, and they can protect the city as long as the relative sea-level rise stays below roughly 40 centimeters. Beyond that threshold, MOSE alone will not be enough. Researchers studying long-term adaptation pathways increasingly frame the problem as requiring multiple strategies deployed in sequence: MOSE for the near term; potentially seawater injection or local ground-raising for the mid-term; and possibly more radical interventions, including raising entire sections of the city or restructuring the lagoon inlets, if high-end sea-level projections materialize.23Scientific Reports. Long-term adaptation pathways for Venice and its lagoon under sea-level rise
None of these interventions addresses the slow corrosion of building materials, the loss of lagoon habitat, or the erosion of the social fabric that gives Venice its reason to exist. The barriers are a magnificent piece of engineering that bought the city time. Whether that time gets used wisely depends on decisions about emissions, urban policy, shipping regulation, and housing that have almost nothing to do with flood gates. Venice can be saved from sinking in the sense that it does not have to drown. Whether it can be saved as a living, ecologically healthy, inhabited city is a question that engineering alone cannot answer.