Miami, New Orleans, Tokyo and New York have been named as some of the world cities which could face trillions of dollars of flood damage in the future.
Experts have produced data analysing which global cities are most at risk from extreme rainfall, both in terms of population and also the huge financial cost.
And the alarming figures show that by 2070, Miami will have assets worth $3.5 trillion (£2.16 trillion) exposed to a '1-in-100 year' flood event, with Guangzhou, China, and New York the second and third cities with the most assets at risk.
As many as 150m people in the world's major cities - close to four times the current 40m - will have to rely on flood defences for protection by 2070.
Analysts for the OECD (Organisation for Economic and Co-operation Development) ranked major cities in terms of population and 'assets' to a 1-in-100 year flood event now and in the future.
Their gloomy forecast predicts that property and infrastructure at risk worth $3 trillion (£1.85 trillion) today (five per cent of current world GDP), will become $35 trillion (£21.6 trillion) by the 2070s.
More than 136 key port cities worldwide were analysed for the data to reveal the likely impact of climate change.
Nine of the ten cities with the highest population at risk will in Asia.
London was ranked 41st in a list for population exposed in 2070. It was placed 27th for property and infrastructure exposed to flooding.
After Miami, Guangzhou had an estimated $3.3 trillion (£2.04m) assets at risk from flooding, while greater New York had $2.1 trillion (£1.29 trillion) at risk.
Around half of those exposed to coastal flooding caused by storm surge and high wind damage worldwide are contained in just 10 cities split between developed and developing countries.
Analysts say cities in 'deltaic locations' have a higher coastal flooding risk due to their tendency to be at 'lower elevations and experience significant subsidence'.
The figures emerged as the U.S. and Caribbean continues to count the cost from Superstorm Sandy, which swept in during late October.
Estimates blame Sandy for at least $62m (£38m) damage in the U.S. where it killed 125 people, and $315m (£195m) in the Caribbean, where 71 more lost their lives.