Resilient Economies Strategies for Sinking Cities and Flood Risks 2025

Examples of cities with areas experiencing subsidence FIGURE 2 Mexico City, Mexico43 350–450mm/year Jakarta, Indonesia44 10–280mm/year Semarang, Indonesia45 60–120mm/yearBangkok, Thailand47,48 9–30mm/yearHo Chi Minh City, Viet Nam49,50 40–70mm/year Shanghai, China51,52 5–13mm/yearVenice, Italy53 1–70mm/year New Orleans, US46 5–50mm/yearNew York City, US54,55 1–2mm/yearBeijing, China56,57 15–138.5mm/yearTehran, Iran58 50–250mm/yearPeshawar, Pakistan60 28–59mm/year Lagos, Nigeria61 2–87mm/yearChicago, US62 2–3mm/year San Diego, US63 1–2mm/yearHeze, China59 5–16mm/yearCharlotte, US64 1–2mm/yearHouston, Texas, US65 5–20mm/yearOtura, Spain66 1–10mm/yearSan Joaquin Valley, US68 150–300mm/year Phoenix, Arizona, US69 1.8–18.3mm/yearChittagong, Bangladesh70,71 10–20mm/year Ahmedabad, India72 15–35mm/year Yangon, Myanmar73 10–110mm/yearTianjin, China74 5–50mm/year Rafsanjan Plain, Iran67 300mm/year Lower limitUpper limit RangeEstimated subsidence rate (mm/year)* *Multiple sources. The data was gathered from different sources and may vary based on measurement methodologies and time. This highlights the need to collect and update data. Note: Land subsidence rates can vary spatially within cities, across regions and globally. Thus, reported rates do not indicate uniform sinking risks for an entire city; rather, they highlight that specific areas within a city are experiencing land subsidence, and it varies. Source: World Economic Forum. Land subsidence, the gradual or sudden sinking of the ground, results from a complex interplay of natural geological processes and, increasingly, unsustainable human activities. While factors such as local geology, seasonal groundwater fluctuations and seismic activity contribute to subsidence, mounting evidence indicates that human actions are now the dominant accelerant globally. Excessive groundwater extraction is the leading anthropogenic driver of urban land subsidence. Over- extraction for domestic, industrial and agricultural use leads to aquifer-system compaction, peat oxidation, uneven soil compression and, in some cases, the formation of sinkholes. This also includes the drainage of land for development purposes, often a factor in coastal and delta-built cities (low-lying landforms with rivers and connection to a larger body of water). Recent studies analysing hundreds of subsidence-prone areas found that approximately 77% of cases were linked to human activity, with around 60% directly attributed to groundwater withdrawal.75 Another study of 200 locations encountering subsidence revealed that 55% of cases resulted from underground water extraction.76 As urban populations expand and water demand rises, groundwater aquifers are depleted beyond their natural replenishment rates, resulting in irreversible soil compaction. The consequences, such as infrastructure damage, increased flood risk and heightened vulnerability to sea-level rise and extreme weather, often remain hidden until critical thresholds are crossed. Once the ground compacts or collapses, recovery can be difficult and costly. Urbanization is also a driver of land subsidence, particularly when combined with vulnerable geological conditions and rising water demand. The interplay between urban growth, geological factors and historical development practices complicates the challenge.77,78 The pressure (weight) 1.2 Why do cities sink? Resilient Economies: Strategies for Sinking Cities and Flood Risks 13