Tokyo has revised its flood guidelines for underground spaces to counter increasingly abnormal weather. As a result, the update introduces AI-driven risk assessments and mandates preventive measures in high-risk zones. Tokyo’s metropolitan government announced the changes in late September 2025. This marks the first comprehensive overhaul of the flood guidelines in 17 years. Importantly, the revised rules address vulnerabilities in subway stations, underground malls, and private building basements. Officials say the update reflects growing concern over intense rainfall events.
Under the new regime, the city will now use artificial intelligence to analyze historical damage data, weather trends, and terrain conditions. Consequently, the system will map flood risk and identify the best evacuation routes for underground facilities. The plan targets the “highest risk” areas, including transit hubs and subterranean retail zones.
Earlier this year, city officials began drafting the changes. They cited mounting evidence that recent torrential rains have overwhelmed infrastructure not built for such extremes. The previous guidelines, introduced in 2008, did not account for shifting precipitation patterns.
Furthermore, Tokyo’s mayor and the city’s disaster management bureau led the initiative. They collaborated with academic experts in hydrology, climate science, and AI modeling. In addition, private-sector stakeholders—such as mall and commercial building owners—provided important feedback.
The revisions arrive amid rising climate volatility in Japan. In recent years, Tokyo and nearby prefectures have faced record rainfall, sudden downpours, and flood-related damage to infrastructure. As a result, these events have disrupted services, caused property losses, and raised public safety concerns. Officials believe underground parts of the city are now especially exposed.
According to public records, Tokyo has experienced several underground floods over the past decade. These affected subway tunnels and the lower floors of buildings. Notably, while flooding incidents have remained sporadic, their intensity has increased. The risk is higher because underground spaces lack natural drainage and depend on pump systems.
Moreover, an expert in urban disaster management commented that the updated guidelines were long overdue. She explained that integrating AI should improve prediction accuracy and emergency response. However, she warned that the system’s success will depend on accurate data, ongoing maintenance, and inter-agency coordination.
A Tokyo government official said the new rules will roll out in phases. To start, the focus will be on busy subway stations and underground shopping areas. Planned steps include drills, inspections, and upgrades to emergency systems. On the policy front, this shift reflects a major change in Tokyo’s disaster response strategy. Rather than waiting to react, the city now prioritizes proactive adaptation. This approach could set a precedent for other major cities in Japan.
Looking ahead, Tokyo plans to monitor system performance closely. Officials will periodically review the flood guidelines to update thresholds and refine AI algorithms. Eventually, the system may extend to cover surface-level infrastructure as well. By acting now, Tokyo aims to reduce casualties, minimize property damage, and avoid future disruption. As weather patterns continue to evolve, the new protocol may serve as a model for climate resilience across urban Japan.
