From Bangkok to Miami, rising seas are only half the story. The ground underneath these cities is dropping just as fast.

Coastal flooding that once arrived once a decade is now an annual event in several major cities, and the reason isn’t only rising seas. In many of these places, the ground itself is dropping, sometimes faster than the water is climbing. Researchers have already mapped the subsidence rates, and the conclusions are no longer up for debate: several global cities are on track to lose significant ground, literally, by 2030.

The complicating factor is that this isn’t a single-cause crisis. Decades of groundwater extraction have compressed the soil beneath many of these cities, and once that compression happens, it cannot be reversed. In some places, the land is sinking faster than the tide is rising, turning a slow-moving climate story into an urgent one.

Bangkok and Jakarta Are Losing the Ground Beneath Them

Bangkok sits roughly five feet above sea level and is sinking by nearly an inch a year, partly because of the dense clay soil beneath it. Researchers have identified it as one of the cities most likely to face severe short-term impact from warming, with coastal districts and even the capital’s main international airport at risk of partial submersion within years.

Jakarta has already made its decision. North Jakarta has dropped more than eight feet in the past decade, and nearly half the city now sits below sea level. Rather than wait, Indonesia is spending an estimated $35 billion relocating its capital to Nusantara, a new city on Borneo expected to be finished by the mid-2040s. It’s a rare case of a government abandoning the fight instead of engineering around it.

Venice and Miami Show Two Different Paths Forward

Venice has spent generations sinking, but its response, a system of movable underwater floodgates, has become a working model for managed defense. The barriers now activate dozens of times a year, and that frequency is rising alongside the Adriatic Sea, which local monitoring groups say is delivering higher tides more often than ever recorded.

Miami’s challenge runs in the opposite direction: the porous limestone underneath the city lets water rise through streets even on cloudless days. A 2024 study in the journal Nature found Miami carries the highest flood exposure among dozens of American coastal cities studied, with tens of thousands of properties potentially affected by 2050. Insurers have begun pulling out of the state altogether.

New Orleans and Ho Chi Minh City Sit on Sinking Deltas

Parts of New Orleans already sit 15 feet below sea level, a vulnerability made brutally clear during Hurricane Katrina in 2005. The city has continued sinking since, even with a rebuilt levee system that was designed around older flood models rather than today’s accelerated projections.

Ho Chi Minh City faces a similar squeeze. Roughly 45% of the city sits under a meter above sea level, and rapid development combined with groundwater pumping has already caused half a meter of sinking in 25 years. Vanishing wetlands mean each storm now hits with less natural protection than the last.

Why Sinking Matters More Than the Sea Itself

The pattern connecting all of these cities is easy to miss: flood models typically account for sea level rise but not for how quickly the land underneath is dropping. A 2024 Nature study found most U.S. coastal cities analyzed are sinking faster than two millimeters annually, meaning some communities have far less runway than official projections suggest.

What separates the cities likely to survive from those likely to lose ground isn’t the rate of sinking. It’s whether there’s enough money and political will to fight it. Venice, the Netherlands and Jakarta have all made expensive, deliberate choices. Cities like Kolkata, Alexandria and Banjarmasin have far fewer resources to do the same, and far less time to decide.

By 2030, that gap won’t be theoretical. It will show up in flood maps, insurance premiums, and the slow departure of anyone who has somewhere else to go.

Source: The Amazing Times