Sinking cities are among the most serious urban risks of the 21st century. Around two billion people live in areas affected by land subsidence—the sinking of the ground caused largely by groundwater extraction and soil compaction. Global economic exposure is vast, estimated at $8.2 trillion, or about 12% of global GDP, according to the United Nations.
Few cities illustrate this problem more starkly than Tokyo in the mid-20th century. But stay with us—this story has a rare happy ending.
During Japan’s postwar industrial boom, factories and a fast-growing population relied heavily on groundwater. By the 1960s, parts of Tokyo were sinking by as much as 24 centimeters (about 9.5 inches) per year—among the fastest rates ever recorded in a major city.
Parts of Tokyo subsided a staggering 15 feet in the twentieth century. In some districts, groundwater levels had fallen nearly 60 meters below sea level. The consequences were dramatic: floodwaters spread farther and lingered longer, and major typhoons exposed how vulnerable the city had become.
Tokyo’s response was unusually decisive. Instead of treating flooding and subsidence separately, policymakers went after the root cause: groundwater overuse. National laws passed in the 1950s and 1960s strictly limited industrial and building-related groundwater pumping, regulated well construction, and enforced reporting and penalties.
At the same time, Tokyo invested heavily in surface water infrastructure, expanding dams, treatment plants, and distribution networks to replace groundwater as the city’s primary water source. Today, hundreds of facilities supply water across the city. Even building owners are now required to include rainwater or reclaimed water systems in their environmental plans to reduce groundwater demand.
Complementing hard infrastructure, Tokyo mandated rooftop greenery and permeable surfaces on large developments, improving rainwater infiltration and supporting groundwater recharge. Continuous monitoring using wells and satellite data ensured problems were detected early.
The results were extraordinary. Tokyo became the first major city affected by subsidence to stabilize. By the early 1970s, subsidence rates had slowed sharply. Today, even in the hardest-hit areas, sinking has largely stabilized at around 1 centimeter per year or less. The city’s cumulative sinking has effectively plateaued, even as Tokyo continued to grow into one of the world’s largest and most complex urban economies.
Tokyo’s experience proves that strong regulation, long-term infrastructure investment, and coordinated governance can halt—and even reverse—severe land subsidence, offering a clear roadmap for megacities facing risks beneath their streets.