Resilient Economies Strategies for Sinking Cities and Flood Risks 2025

Population ~30 millionArea ~6,340km22.2 Shanghai’s evolution: integrating policy and sponge city Context In China, Shanghai has grappled with localized land subsidence since the 1920s, with some hotspots sinking by more than 2.6m between 1921 and 1965, primarily due to urban expansion and groundwater extraction.106,107 The economic consequences have been significant. Between 1950 and 2001, Shanghai’s total losses from subsidence reached an estimated CNY 290 billion, with direct damages accounting for CNY 18.9 billion. The challenge extends beyond Shanghai; over 50 cities in China, including Tianjin, Taiyuan, Xi’an, Wuxi and Cangzhou, have areas of more than two metres of subsidence.108 Today, Shanghai also faces a compounded risk landscape, as land subsidence can converge with global sea-level rise and intensifying weather patterns. These intersecting threats place immense pressure on flood defences and critical infrastructure, necessitating continuous advanced prevention, mitigation and adaptation strategies.109,110 Solutions Shanghai’s response to land subsidence has been defined by a blend of policy innovation, infrastructure investment and nature-based solutions over the decades. While not all solutions are centred on combating land subsidence, they help to minimize sinking by rebalancing the urban water system. –Early interventions: Initial measures included regulating deep wells, pioneering artificial groundwater recharge (e.g. the “winter recharge and summer withdrawal” policy), establishing monitoring networks and relocating factories to suburban areas.111 These efforts temporarily reduced subsidence, but rapid urban development in the 1990s led to renewed challenges, driven by groundwater pumping to dry out sites for large construction projects, the increased weight of new high-rises and continued reliance on groundwater.112,113 –Regulatory transformation: In 2013, Shanghai enacted the Regulation of Prevention and Control of Land Subsidence of Shanghai Municipality, recognized for its alignment with strategic environmental assessment principles.114 It is viewed as a science-based framework integrating groundwater management, robust monitoring and risk-based zoning. Key features include: –Land and water management: Shanghai set a strict annual subsidence cap of 6mm, enforced by multiple city departments. It also shifted water reliance to surface sources and continued artificial groundwater recharge. Resilient Economies: Strategies for Sinking Cities and Flood Risks 21