Asian cities urged to bolster defence against rising seas

Building in flood-prone areas and "ill-conceived" land reclamation projects should be stopped, he said, adding that some cities should consider moving key assets to safer places.

"Sponge city" schemes in China which incorporate sustainable drainage systems into infrastructure - like water-absorbing asphalt and green spaces to prevent water from pooling - could also work across the region, he added.

The highest-risk cities globally are Guangzhou and Dongguan in China's Pearl River Delta Economic Zone, which generates 20% of the country's GDP and 3.8% of global wealth, the report said.

"It is a massive global manufacturing hub," said Clisby, adding that both cities should look at relocating key assets and investing in large-scale engineering projects.

Across China, $348 billion of GDP and nearly 8 million people are located in areas at high and extreme risk of sea level rise, the report noted.

While China and Japan have the resources to put in place measures to mitigate flood risks, Clisby said, Vietnam, India and Indonesia have more limited resources and institutional capacity to meet the challenges posed by rising seas.

Indonesia is already planning to move its capital to the island of Borneo, as Jakarta - on the north coast of Java island - is slowly sinking and suffers regular flooding.

"They are starting to think about a decade time-scale to readjust their risk exposure, and things like that will be more common in the next decade," said Clisby.