Key Facts
• June 26: Intense rain due to an active cold front impacted Japan nationwide.
• 22 locations recorded the highest June rainfall in observation history.
• Heavy rain and thunderstorms began in the evening, especially in Kanto and Tohoku regions.
• Gifu Prefecture’s Jizo Bridge was severely bent due to sudden water level rise.
• Urban flooding reported in Kansai, causing potential accidents and damage.
• Kashiwa City, Chiba Prefecture, implemented real-time water level monitoring systems.
• Air hammer phenomenon in sewers caused manhole covers to be displaced.
• Sewer capacity: 50 mm/hour, but recent rains reached 100–150 mm/hour.
• Residents can access manhole sensor data for evacuation decisions.
• June 27: Thunderstorm warnings issued for Hokkaido and mountainous areas in Kanto.
Summary
On June 26, Japan experienced record-breaking rainfall at 22 locations due to an active cold front and tropical airflows, leading to severe thunderstorms and flooding. Urban areas like Kansai faced sudden inundation, while infrastructure such as Gifu’s Jizo Bridge suffered damage. Kashiwa City in Chiba Prefecture introduced advanced water level monitoring systems to mitigate risks, including the air hammer phenomenon in sewers. With rainfall exceeding sewer capacity, these systems aim to enhance evacuation readiness. Thunderstorm alerts remain in effect for Hokkaido and Kanto’s mountainous regions on June 27.
