The Tokyo-Yokohama conurbation in Japan is the world’s riskiest metropolitan area, according to a report by Swiss Re.

With a population of about 30 million, the combined metropolis is home to the most people exposed to five natural disasters: earthquake, storm, storm surge, tsunami and river flood.

Manila in the Philippines ranks second, followed by the Pearl River Delta in China, Osaka-Kobe in Japan and Jakarta in Indonesia.

The report says floods threaten more people than any other natural catastrophe, with most major cities built along coastlines or waterways.

“Across the 616 cities assessed, river flooding poses a threat to more than 379 million residents.

“More than 283 million inhabitants could potentially be affected by earthquakes and 157 million people are at risk from strong winds.

“In many cases, urban populations must be prepared to cope with more than one hazard.”

Australia and New Zealand are exposed to natural disasters but have smaller cities, so do not feature in the top 10, the report says.

Swiss Re analysed the loss potential of 616 major metropolitan areas – home to about 1.7 billion people and accounting for about 50% of global GDP.

Completing the top 10 at-risk cities are Nagoya (Japan), Kolkata (India), Shanghai (China), Los Angeles (US) and Tehran (Iran).

By 2050 6.3 billion people will live in cities, according to the United Nations.

“Strengthening the resilience of these communities is therefore becoming a matter of urgency,” Swiss Re says.