Energy Outlook

By: Jacob Kim

As Tokyo faces more extreme weather patterns due to climate change, the city is expanding its underground flood control system, known as the Metropolitan Outer Area Underground Discharge Channel or the “cathedral.” This massive network of tunnels and reservoirs, designed to prevent flooding, is being upgraded to handle unprecedented levels of rainfall expected in the future. The increase in rainfall is linked to rising temperatures, as explained by Professor Seita Emori from the University of Tokyo, who warns that as global temperatures rise, the amount of water vapor in the atmosphere increases, leading to heavier rainfall.

The “cathedral” is located in Kasukabe, just north of Tokyo, and spans 6.3 kilometers of tunnels with 59 massive pillars, each weighing 500 tonnes and standing 18 meters tall. The system has already prevented billions of yen in flood damage since it became operational in 2006. During Typhoon Shanshan in August 2024, the system successfully diverted and stored rainwater, preventing floods in vulnerable areas. Now, as climate risks escalate, Tokyo is expanding the system, including a new regulating reservoir near Nogata Station, to further increase its capacity.

This project, which took 13 years and 230 billion yen ($1.63 billion) to build, is not only essential for flood protection but also serves as a tourist attraction due to its striking architectural features. The misty, cool chambers, illuminated by natural light filtering through small openings, evoke an ancient temple-like atmosphere, earning it names like “the shrine” and “the temple.” The system’s upgrades are part of Tokyo’s broader strategy to adapt to the realities of climate change, ensuring the city remains protected from increasingly severe storms and floods.

Tokyo’s approach serves as a model for other cities facing similar challenges, emphasizing the importance of investing in climate resilience infrastructure. The expansion of the “cathedral” demonstrates the urgent need for large-scale solutions to protect urban areas from the impacts of global warming, highlighting Tokyo’s commitment to safeguarding its future through innovative engineering.

Sources

https://www.reuters.com/investigates/special-report/climate-change-japan-rain/