Japan braces for dual typhoons as 1 in 5 face flooding risk, study reveals

Japan needs to improve flood defences and early-warning systems to give residents more time to evacuate when danger threatens, experts say

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A house in central Japan’s Noto peninsula risks being washed away by a swollen river following last month’s heavy rain. Photo: Kyodo News via AP

Published: 10:00am, 2 Oct 2024Updated: 10:03am, 2 Oct 2024

Two typhoons are bearing down on Japan even as the search continues for 10 people missing after record rainfall and widespread destruction on the north coast, with climate experts warning that extreme weather events are becoming increasingly commonplace.

The trend is particularly concerning given that 20 per cent of the Japanese population – about 26 million people – live in low-lying coastal areas or near major rivers at risk of flooding.

A study published on Tuesday by the Asahi newspaper revealed that the number of residents living in flood-prone areas has surged by about 900,000 over the past two decades, even as Japan’s overall population declined by nearly 1.6 million during the same period.

Flooded streets are seen after a river burst its banks in Wajima, Japan’s Ishikawa prefecture, following heavy rain last month. Photo: Kyodo

Experts attribute the worsening weather patterns to global warming, but they also highlight that much of the resulting damage stems from the inadequate management of Japan’s rural areas. Tragically, at least some of storm-related deaths can be traced back to a public failure to heed warnings.

“Over the last decade, Japan has experienced an increase in incidents of severe rainfall, in particular during the summer typhoon season,” said Yoshihiro Iijima, a climatology professor at Tokyo Metropolitan University.

This puts low-lying coastal regions at risk of flooding, especially when storms compromise barrages and other coastal defences. The threat is heightened when weather systems coincide with high tides or “king tides” associated with new or full moons.

“It is not only low-lying land that is at risk as heavy rainfall in inland basins can cause flooding in river systems and the surrounding flat areas that are often where people live,” Iijima told This Week in Asia. “Yet another issue is landslides caused by heavy rain that destabilises hillsides.”

Japan has experienced increased rainfall in recent years, driven by rising ocean surface temperatures that enhance evaporation. Parts of the Pacific Ocean have seen temperature increases of up to 5 degrees Celsius (9 degrees Fahrenheit) in just a decade, with the Sea of Japan among the hardest hit.