Resilient Economies Strategies for Sinking Cities and Flood Risks 2025

Key factors driving sinking cities FIGURE 4 Groundwater pumping and drainage of organic soil Overuse for domestic, industrial and agricultural needs, leading to aquifer compaction and soil sinking.81 Draining wetlands or peatlands causes soil shrinkage and compaction, often linked to groundwater extraction.82 Underground mining and hydrocarbon extraction Removal of minerals, oil or gas, destabilizing subsurface layers. The spatial extent of subsidence depends on exploitation depth, rock mass geo-mechanical conditions and post-mining void reclamation.84 Hydrocarbon extraction results in reservoir compaction. As fluids are extracted, the pressure within the reservoir decreases, causing the surrounding geological layers to compress.85 Hydro-compaction Soil compaction due to wetting of previously dry, loose or low-density soil. Natural geological compaction and conditions Gradual settling of soils and sediments due to natural processes.88Urbanization and load pressure (in relation to soil conditions and history) Dense development and expansion of built areas and assets, increasing pressure on vulnerable soils; depending on geology.83 Geothermal extraction Removal of geothermal fluids leads to subsurface volume loss and thermal contraction of rocks can further worsen subsidence.86 Thawing permafrost Melting of frozen ground can contribute to ground instability and subsidence. Thawing permafrost is primarily driven by climate change, global warming.87 Climate change Extreme drought and heat can increase soil erosion risks and higher groundwater demands. Sea-level rise can increase ecosystem loss and flood risks, causing soil erosion. Extreme weather increases risk of wildfires, rainfall, storms, increasing flood and wind risks, leading to soil erosion and subsidence. 15 Resilient Economies: Strategies for Sinking Cities and Flood Risks