Resilient Economies Strategies for Sinking Cities and Flood Risks 2025

Research, case studies and expert perspectives highlight several enablers to addressing subsidence, including regulation and policy, infrastructure and investment, community and stakeholder engagement, and technology, data and research. Regulation and policy Regulation and policy provide the strategic foundation for addressing land subsidence, translating vision into actionable standards, incentives and compliance mechanisms. Evidence- based policy, developed through multistakeholder consensus, is essential to driving effectiveness. Policy alone, however, is not sufficient. Success depends on the alignment of legal frameworks with infrastructure readiness and institutional coordination, particularly in rapidly urbanizing or resource-constrained places. Integrated policy and infrastructure interventions, such as Tokyo’s Building Water Act, demonstrate how such solutions can halt severe subsidence.142 Although there are currently no international standards specific to land subsidence, several existing guidelines and technical standards address aspects of subsidence management within broader themes of engineering practices, groundwater management and disaster risk reduction. Harnessing and harmonizing such guides can support subsidence risk management at local, national and international levels. International frameworks such as the Sendai Framework for Disaster Risk Reduction 2015-2030 and UN- Habitat’s New Urban Agenda encourage countries to integrate land-use planning, water management and geophysical risk monitoring into their national strategies.143,144 Standard bodies focusing on geotechnical monitoring and measurements of soil also provide direction (e.g. ISO 14688).145 Infrastructure and investments Resilient infrastructure and strategic investment are central to preventing, mitigating and adapting to sinking cities and building resilience. Interventions range from protective measures, such as sea levees and aquifer replenishment, to nature-based solutions. Adopting context-specific infrastructure solutions informed by local geological and climate conditions is crucial, as a one-size-fits-all approach can be counterproductive. For instance, a sea wall that is beneficial in one location may cause long- term land erosion elsewhere. Thus, understanding the intended impacts of proposed solutions is critical for managing subsidence-related risks and costs. The focus must shift from reactive repairs to anticipatory investments that protect critical assets (e.g. water systems, utilities, buildings) against subsidence and climate risks. Improving water systems is particularly important, including the following actions: –Reduce aquifer dependence: Implement policies and incentives to transition from over-extraction of groundwater to alternative water sources. –Expand surface water supply: Invest in infrastructure to diversify and expand surface water resources. –Adopt circular water use: Integrate nature- based solutions, such as green roofs, rain gardens and infiltration parks, to enhance water absorption and enable rainwater harvesting and greywater reuse. –Promote conservation and education: Strengthen public understanding of the links between human behaviour, land and water use, and their economic and social consequences. Investment is fundamental to these strategies. While governments often lead large-scale projects, such as Tokyo’s $2.8 billion G-Cans flood project, the limited commercial viability of many interventions calls for innovative funding models. The private sector can play a pivotal role through public-private partnerships, green bonds and land value capture mechanisms. Cities such as Tokyo, Shanghai and Rotterdam demonstrate the power of integrated approaches over time. Tokyo halted decades of subsidence by expanding its piped water supply and regulating groundwater use, while Rotterdam’s water square exemplified multifunctional infrastructure. With regards to commercial incentives, the private sector can fully or co-finance resilience structures, benefitting from development rights or future revenue linked to property valuation. To ensure long-term impact, cities must make use of diverse financial instruments aligned with policy objectives.3.2 What are the key enablers of positive change? Focus must shift from reactive repairs to anticipatory investments that protect critical assets against subsidence and climate risks. Resilient Economies: Strategies for Sinking Cities and Flood Risks 34