Urban flood management in a changing climate: Global and Japanese insights from Technical Deep Dive on Urban Flood Management
Floods are among the most frequent and costly natural disasters worldwide, particularly in urban areas, and their impacts are exacerbated by rapid urbanization and climate change. Between 1980 and 2016, floods caused over US$1.6 trillion in damages and more than 225,000 deaths globally. Among World Bank client countries, floods are one of the most frequent hazards and are closely linked to climate change impacts. Without effective mitigation strategies, these losses could increase tenfold by 2050.
To help address the rising threat of floods to urban areas, the World Bank Tokyo Development Learning Center (TDLC), in collaboration with the Tokyo Disaster Risk Management (DRM) Hub and the Global Facility for Disaster Reduction and Recovery (GFDRR), hosted a Technical Deep Dive (TDD) on Urban Flood Management from March 3 to 7, 2025. This intensive program convened 44 participants from 11 countries to exchange knowledge, explore innovative approaches, and collaborate on strategies for managing urban flood risks. The TDD provided a platform for urban flood management experts worldwide by exploring how to integrate gray and green infrastructure, enhance urban resilience, and mitigate the impacts of extreme weather events.
The participants benefitted from a mix of expert presentations covering both global and local best practices, interactive discussions, and site visits that provided participants with firsthand insights into Japan's flood management techniques. During the peer learning sessions, participants shared the various challenges they face in managing urban flood impacts in their cities and projects, including rapid and uncontrolled urbanization, insufficient financing, the effects of climate change, weak coordination among stakeholders, and a lack of infrastructure connectivity. To explore solutions to these issues, the TDD introduced best practices from Japan and other countries, providing participants with insights into effective flood management strategies.
Japan's integrated approach to urban flood resilience
Japan has long been at the forefront of flood management, continually refining its approaches in response to evolving climate and urbanization challenges. Approaches have involved from sole reliance on engineered solutions into having a comprehensive strategy that incorporates nature-based solutions (NbS), community-driven initiatives, and risk-informed urban planning. Japan's "River Basin Disaster Resilience and Sustainability by All" approach, led by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), serves as a model for other nations striving to enhance disaster preparedness.
In Tokyo, participants visited the Storm Surge Management Center, where they learned about flood prevention measures along the city's coastal areas. The visit included a tour of the floodgate monitoring room and drainage pumping station, showcasing Tokyo's robust flood management infrastructure.
In Kyoto the TDD showcased examples of sustainable flood management integrating urban planning with flood control measures. Kyoto's enhanced urban resilience is attributed to a city-wide strategy that incorporates both gray and green infrastructure. On the policy side, the city has adopted the "Rain Resilient City Development" initiative, which combines hard measures-such as detention basins and underground reservoirs-with soft measures such as disaster awareness programs and information dissemination to minimize flood damage. Specific investments include (1) rain gardens - which are urban gardens that absorb rainwater and help reduce drainage burdens, (2) detention basins such as Nanasegawa Basin, which play a crucial role in flood mitigation.
Additionally, the TDD presented cases from other Japanese cities such as those from Shizuoka City and Kitakyushu City. Shizuoka showcased its strategic infrastructure investments, including enhanced river embankments and drainage systems, to strengthen resilience against extreme weather. Kitakyushu highlighted the interplay between solid waste management and urban flood risks, demonstrating how effective waste management prevents drainage blockages and mitigates flooding. These cases underscored the importance of integrated urban planning and multi-sectoral coordination in building flood-resilient cities.
A holistic approach to flood resilience: Key lessons and action plans
Through expert discussions and site visits, the key message delivered during the TD was the importance of a multi-dimensional approach for effective urban flood management. Flood management should account for holistic governance and stakeholder collaboration, as flood resilience cannot be achieved by government efforts alone. Japan's approach emphasizes the coordination of national and local governments, the private sector, and communities, ensuring that disaster resilience strategies are integrated across different levels of society.
The TDD also sought to demonstrate the value of integrating gray and green infrastructure, where nature-based solutions (NbS) complement engineered flood control measures. This approach not only reduces flood risks but also enhances environmental sustainability and social well-being. Additionally, ensuring long-term urban flood resilience requires sustainable operations and maintenance (O&M) of infrastructure, supported by institutionalized strategies and secure financing mechanisms.
Building on these insights, participants developed action plans to convert learnings from Japan into actionable next steps in their home countries and projects. Common themes in the action plans included emphasis on enhancing resilience through a combination of gray and green infrastructure, need for multi sectoral coordination among governments, private sectors, and communities to implement effective flood strategies, and flood risk mapping and data-driven urban planning as essential tools for supporting strategic decision-making. As climate change accelerates, integrating flood management with urban planning and water resource management will be the key to increasing the resilience of cities.
Participant voices
"One of my key takeaways is the need to integrate different approaches-both "gray" infrastructure projects, such as construction and engineering works, and "green" initiatives, which focus on community engagement and behavioral change. A comprehensive, integrated approach is essential to create lasting solutions that improve people's lives and change habits at a societal level."
Edgard Usuy, Secretary of Planning for the State Government of Santa Catarina, Brazil
"In Japan, local governments at various levels are effectively taking ownership and leadership in engaging communities in planning as well as implementation. That is something very important for South Sudan."
Droma Kat, Urban Specialist, World Bank