In an era of accelerating climate change, cities are increasingly vulnerable to two interrelated threats: extreme heat and urban flooding. While each city faces its own hazards, there are lessons in resilience that Tokyo and Los Angeles offer for municipalities worldwide. This article explores how urban planning, infrastructure investments, and community-based policy can help protect citizens — especially the most vulnerable — from heat stress and flood risk.
Why Heat and Flood Risks Matter
Extreme heat is among the deadliest climate hazards in many metropolitan regions. Urban “heat islands” amplify risk by increasing ambient temperatures in built-up zones, especially where vegetation is scarce and pavement is abundant. Flooding, likewise, becomes more frequent and unpredictable due to heavier storms and overwhelmed drainage systems.
Together, heat waves and floods impose economic, health, and social burdens. Heat worsens chronic health conditions; floods disrupt housing, infrastructure, and essential services. Cities that fail to adapt face higher costs in emergency response, healthcare, and post-disaster recovery.
Tokyo: Engineering Resilience and Policy Responses
Tokyo faces hot summers, aging population, and increased rainfall intensity. It has adopted multiple strategies for heat adaptation and flood control.
Flood Protection: G-Cans and Underground Infrastructure
One of Tokyo’s signature infrastructure projects is the Metropolitan Area Outer Underground Discharge Channel (also called G-Cans). It is an underground floodwater management system with tunnels and chambers that relieve overflow during heavy rain events.
This system has prevented billions of dollars in potential flood damage by diverting sudden stormwater surges.
As of recent upgrades, Tokyo is expanding this type of underground capacity to respond to more intense, “guerrilla-downpour” storms.
Heat Adaptation: Subsidies & Social Measures
Tokyo is also experimenting with policy approaches to reduce heat risk among vulnerable populations. For example, the city introduced a temporary exemption on fixed water-bill charges during summer months to encourage proper use of air conditioning, particularly among older residents.
Research shows that in Tokyo wards, older adults are disproportionately affected by heat-related deaths.
Furthermore, the Tokyo Metropolitan Government published a formal Climate Change Adaptation Plan, which includes nature-based strategies, smart agriculture, and urban greening to mitigate rising temperatures.
Los Angeles: Heat Action Plans & Flood Management
Los Angeles confronts both rising heat and flood risk — despite its dry-climate reputation, sudden cloudbursts and stormwater runoff pose a challenge in built-up areas with limited green space.
Heat Action Planning
Los Angeles County has developed a Heat Action Plan (CHAP) focused on making outdoor spaces cooler (e.g. more shade), improving buildings for passive cooling, and strengthening emergency communications and response.
One strategy is to reduce the “urban heat island” effect through cool roofs, cool pavements, and increased urban greening.
The Resilient Los Angeles strategy includes both flood-control planning and heat-adaptation measures integrated into city resilience goals.
Flood Risk & Planning
Los Angeles maintains a formal Floodplain Management Plan, which governs how new development should consider flood risk, drainage infrastructure, and emergency responses.
Coordination between housing, emergency management, and infrastructure authorities is part of the city’s disaster preparedness efforts.
There are also nature-based solutions in LA, such as constructed wetlands and urban forest projects that serve multiple roles: flood mitigation, cooling through shade, biodiversity, and recreational benefits.
What Can Your City Learn?
Drawing on Tokyo and Los Angeles as case studies, here are general recommendations any city could consider to strengthen heat and flood resilience:
- Invest in dual-function infrastructure: underground storage or drainage tunnels that can buffer floodwaters *and* reduce surface runoff stress during storms;
- Implement Heat Action Plans: set targets for reducing urban heat island effect via greening, cool surfaces, shade structures, and retrofitting buildings;
- Support vulnerable populations: subsidies, adjusted utility policies, or social assistance to encourage safe cooling (e.g. helping low-income or elderly households access air conditioning or cooling centers);
- Use nature-based design: wetlands, parks, permeable surfaces to manage both stormwater and ambient temperature;
- Coordinate emergency preparedness across agencies: integrate flood and heat risk into housing, urban planning, and public health strategies;
- Monitor & update climate adaptation plans regularly: ensure that adaptation strategies stay aligned with evolving climate models and demographic shifts.
Costs and Financing
Massive infrastructure projects like Tokyo’s underground flood channel or Los Angeles’ stormwater retrofits can cost in the order of hundreds of millions to billions of dollars. For example, expansions to Tokyo’s flood-control “cathedral” system have involved multiyear budgets in the billions of yen (which translates into on-order of billions of USD).
Similarly, adaptation plans in Los Angeles are backed by city- or county-level budgets, bonds, or grants, sometimes integrating state-level climate resilience funds.
Conclusion
As climate change intensifies, cities cannot treat heat waves and flooding as separate problems. Integrated planning, combining engineering, nature-based design, and equitable social policy, is essential. Cities like Tokyo and Los Angeles show that resilience is achievable — but it requires vision, sustained investment, and coordination across multiple sectors.
By learning from such examples, your city can develop its own tailored strategy to protect residents from future climate-driven extremes.
Sources: Tokyo Metropolitan Government, Los Angeles County Sustainability Office, peer-reviewed and official adaptation-plan documents (see inline citations).
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