Major coastal cities in US face billions in flood losses

A year ago, Superstorm Sandy slammed into New York and New Jersey. By the time it was over, Sandy was the second-costliest storm in U.S. history.

But by 2050, officials predict a storm like Sandy could cost more than four times as much as sea levels rise and more areas become vulnerable to flooding.

According to a recent study, if the 136 largest coastal cities do not invest in better flood protection global losses will top $1 trillion annually by 2050.

Among those 136, three U.S. cities — New Orleans, New York and Miami — could account for 31 percent of all global losses.

U.S. cities are wealthy: Ports, buildings and homes are built in the floodplain — usually with protections against a 100-year flood.

A 100-year flood is not a flood that occurs once every 100 years, but instead is a flood that has a 1 percent chance of occurring in a single year. This means there is about a one in four chance a home could flood during the course of an average 30-year mortgage.

The study found that with protection investments of $50 to $60 billion annually, the economic loss from floods could drop from $1 trillion to $50 billion in 2050. Researchers say the study is meant not to provide exact loss estimates, but instead demonstrate the enormous economic value in upgrading flood defenses.

“The real challenge for all the cities is to do this before they get a storm,” says World Bank economist Stephane Hallegatte.

Animations by Dave Mayers

NOTE: The above images and animated GIF are from an animation that was originally posted here on Oct. 29, 2013.

Correction: A previous version of the table had mislabeled the column that measures the protection level in years (in 2005) as average annual losses (in millions) and vice versa.