The process is slow enough to ignore day to day, yet fast enough to radically redraw coastlines within a human lifetime. New research on subsidence, the gradual sinking of land, suggests that some of the world’s biggest cities are on a path where retreat, not defence, may become the only realistic option.
What scientists are seeing beneath our feet
A team of researchers, writing in the journal Nature Sustainability, analysed 48 major coastal cities showing clear signs of subsidence. Together, these cities represent around one fifth of the world’s urban population.
Subsidence itself is not new. Land has always risen and fallen due to tectonic movements and natural compaction. What has changed is the speed. Urban growth, groundwater pumping, oil and gas extraction, and massive construction projects now amplify natural processes.
In several megacities, land is sinking faster than local sea level is rising, turning a long-term climate threat into a near-term urban emergency.
Using satellite radar data spanning decades, the researchers measured how quickly city districts are dropping. The numbers sound small at first glance – just a few millimetres per year – but stretched over decades they add up to several decimetres, enough to erase defences and redraw flood maps.
Six cities on the front line
Among the 48 cities studied, several stand out for both the speed of their subsidence and the sheer number of people exposed.
- Jakarta, Indonesia – sinking by up to 26 mm per year
- Ahmedabad, India – up to 23 mm per year
- Istanbul, Turkey – up to 19 mm per year
- Houston, Texas, USA – up to 17 mm per year
- Lagos, Nigeria – up to 17 mm per year
- Manila, Philippines – up to 17 mm per year
Those annual rates are comparable to stacking a coin every year under your house. Eventually, entire neighbourhoods end up below sea level during high tides or storms.
Jakarta: the capital that decided to move
Jakarta has become the emblem of subsiding cities. Built on soft coastal sediments, criss-crossed by rivers and heavily dependent on groundwater, the Indonesian capital has been sinking for decades.
Some districts have dropped several metres. Floods that used to be occasional now arrive with almost every heavy rain. Sea walls have been repeatedly raised, only to be overtaken again by the combination of subsiding land and rising waters.
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Indonesia has taken a radical step: planning a new capital roughly 1,000 kilometres away on the island of Borneo.
The move is framed as a way to ease congestion and spread development, but the unspoken driver is the simple arithmetic of elevation. Parts of Jakarta are becoming too low, too risky and too expensive to defend indefinitely.
Ahmedabad and Istanbul: growth on unstable ground
Ahmedabad, one of India’s fastest-growing cities, sits on alluvial soils that compact when water is pumped out. Rapid, often unplanned urbanisation has triggered a surge in groundwater extraction to supply homes, factories and farms.
The result is uneven sinking. Some districts drop faster than others. Roads crack, pipelines warp and drainage systems lose their slope, trapping water where it used to flow away.
Istanbul faces a different mix of pressures, but a similar trend. The city’s relentless expansion, new transport links and massive infrastructure projects place extra weight on already complex geology. The sinking rates remain lower than in Jakarta but are accelerating in several corridors of development.
Houston, Lagos and Manila: resource pressure and coastal risk
Houston exemplifies a North American version of the problem. Decades of oil and gas extraction, combined with groundwater pumping for industry and suburbs, have led to measurable subsidence across parts of the metropolitan area.
Lagos, by contrast, is expanding along low-lying coastal flats. Sand mining for construction, together with uncontrolled development on wetlands, weakens natural defences and destabilises the ground. The city’s population has exploded, multiplying the number of people exposed to future flooding.
Manila faces a cocktail of risks. Heavy groundwater use, soft deltaic sediments and frequent typhoons mean that every extra centimetre of relative sea-level rise has real human consequences. Many informal settlements cling to marginal land that will be first to go under.
Across these cities, subsidence turns a predictable climate trend into a sharper, more localised shock.
Europe and France: not spared, just slower
The study also looked at cities in Europe, including France. The rates of sinking are generally lower than in parts of Asia or Africa, thanks to stricter controls on groundwater extraction and different urban histories.
Yet the combination of modest subsidence with rising seas still creates problems. Low-lying districts in cities such as Venice, Rotterdam or parts of the French Atlantic coast are already struggling with more frequent flooding and saltwater intrusion.
Engineers can buy time with sea walls, pumps and flood barriers. These measures shift risk but do not stop the underlying land from slowly dropping.
Why disappearance feels inevitable in some places
Researchers are cautious with the word “inevitable”, but the underlying maths is stark. A city district that is sinking at 10–20 mm per year while sea level is rising by 3–4 mm per year faces relative water level increases of well over 1 metre within a few generations.
| Process | Typical rate | Main drivers |
|---|---|---|
| Global sea-level rise | 3–4 mm per year | Warming oceans, melting ice |
| Urban subsidence | Up to 20–30 mm per year in hotspots | Groundwater pumping, construction, resource extraction |
| Relative water rise for residents | Often 10–30 mm per year | Sea-level rise + land sinking combined |
At these speeds, raising sea walls every decade quickly becomes impractical. Poorer residents tend to live in the most exposed zones, making large-scale relocation socially and politically painful.
Without a dramatic change in how cities build, pump and plan, large parts of some megacities will likely be abandoned to the water this century.
What can slow the sinking?
Subsidence is not entirely unstoppable. In some regions, reducing groundwater extraction has already cut sinking rates. Tokyo and parts of Shanghai, for instance, saw improved stability after tighter regulation in past decades.
Researchers and planners point to a combination of measures:
- Limiting groundwater pumping and switching to surface water where possible
- Protecting wetlands and natural buffers that help stabilise soils
- Designing lighter buildings and infrastructure on vulnerable ground
- Redirecting urban growth away from the lowest-lying districts
- Preparing phased relocation plans for the most at-risk communities
These approaches demand long time horizons and upfront investment, something many fast-growing cities struggle to provide. Yet each year of delay locks in more people and assets on slowly sinking land.
Key terms that shape the debate
Two technical ideas often appear in this discussion. The first is subsidence itself: the downward movement of land, caused either by natural compaction and tectonics or by human activities such as pumping water, oil or gas from underground layers.
The second is relative sea-level rise. This is what residents feel on their doorsteps. It combines global sea-level rise with any vertical motion of the land. A city with low global sea-level rise but high subsidence can face greater flooding risk than a stable city in a faster-warming region.
Scenarios for the next fifty years
Urban risk modellers run simulations using different futures. In a “business-as-usual” scenario, where groundwater use and construction patterns continue unchanged, several coastal megacities see tens of millions of residents living in zones that are regularly flooded by 2070.
In a more managed scenario, strict limits on groundwater extraction and a shift in urban planning towards higher ground slow the pace of exposure. Flooding still increases, but defence lines hold for longer and retreat can be planned rather than forced by crisis.
For families in low-lying neighbourhoods, these scenarios translate into very concrete questions: Will insurance still be available? Will homes retain any value? Will their children grow up behind ever-higher walls, or in a different part of the country altogether?
The cumulative pressures on coastal life
Subsidence by itself is already a challenge. Combined with sea-level rise, more intense storms, heavier rainfall and rapid urbanisation, it turns into a layered risk.
For example, heavier rainstorms can overwhelm drainage systems that were designed with old ground levels in mind. As land sinks, those drains lose gradient, so water simply pools. At the same time, higher tides push salty water further inland, affecting drinking supplies and agriculture.
The threat to sinking cities is not a single dramatic event, but the slow narrowing of safe, dry, affordable places to live.
That cumulative squeeze is why researchers now talk openly about the likely disappearance of parts of major cities. Not because they vanish overnight, but because at some point, people decide that staying no longer makes sense.
