Major coastal cities in US face billions in flood losses

by @alexandranewman October 29, 2013 5:30AM ET

Is your city prepared for a catastrophic storm? New Orleans is now leading the pack in preparedness

Natural Disasters

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.

Costliest U.S. Storms

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.

Flood losses could top one trillion dollars in 2050

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.

Three U.S. cities could account for 31 percent of all 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.

During a 30-year mortgage, a home in a 100-year floodplain has a 1-in-4 chance of being flooded.

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.

Flood losses could climb to $50 trillion

“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.

Protections in U.S. cities
City Average annual loss (in millions) Protection level in years (in 2005)
Miami 2,099 100
New York-Newark 1,960 100
New Orleans 1,583 100
Tampa-St Petersburg 763 50
Boston 741 50
Philadelphia 279 50
Virginia Beach 278 140
Baltimore 238 50
Los Angeles-Long Beach Santa Ana 188 50
San Francisco - Oakland 149 50
Houston 119 50
Providence 118 50
Seattle 85 50
Washington, D C 74 50
San Diego 12 50
Portland 3 50
San Jose 2 50
Notes: To compare the U.S. cities to others around the world, visit this table.
Source: "Future flood losses in major coastal cities," Nature Climate Change.