A wave of sea-level rise threatens to submerge some coastal cities and destroy their waterfronts.
But why are they worried?
It’s a question economists have been asking for years.
As sea levels rise, coastal cities are forced to build seawalls, to keep their streets from rising and to protect homes from flooding.
Now, experts say the seas are rising too fast.
In the US, more than 1.4 million homes and businesses are underwater and hundreds of millions more are vulnerable to flooding, according to a recent report by the US Federal Emergency Management Agency.
Why are coastal cities so vulnerable?
It may be that coastal cities were built too low, according, according a new study by the National Academy of Sciences, which says cities should consider building higher to keep up with the sea-rise.
But what exactly does it mean to “build high enough to keep the seas out”?
A rising sea has implications for the US and global economy.
“It’s important to understand what that means,” said Peter W. Weisbrot, a professor of engineering and public policy at the University of Florida, who co-authored the new study with his co-authors.
The study is titled, “Building the most expensive coastal buildings: How coastal cities can avoid catastrophic coastal flooding.”
The report estimates that the total cost of protecting against sea-levels rise will top $2 trillion over the next 50 years.
A rise in the sea could submerge an area of up to 15 feet or more in just 30 years.
In other words, if you live on a small island in the Atlantic, a city’s floodplain would likely stretch out to 30 miles.
Weisbroth and his coauthor, James B. Smith, are studying how cities and states have handled their flood-protection needs.
They say the US needs to build an infrastructure that could withstand the sea rise, while also making sure that cities aren’t inundated in the event of major storms.
The authors say coastal cities need to build more than 30 feet (9 meters) of sea walls and shorelines to protect them from storms, but many states aren’t doing enough to prepare.
In coastal cities, storm surge is much higher than in inland cities, which are less prone to storms.
And storms are more likely to occur in areas that have more built-up infrastructure.
So far, the US has managed to reduce storm surge by a quarter, according the report.
However, the authors say the nation still has more work to do.
For the study, Weisbart and Smith analyzed data from more than 100 coastal cities across the US.
They compared how coastal cities responded to rising sea levels and how their infrastructure was designed to accommodate the extra water.
Overall, the study found that cities were well prepared to withstand rising sea-water, but some didn’t even have the capacity to build new floodplains to keep it out.
To help mitigate the consequences of rising sea, the researchers say the governments of the US have set aside $30 billion for coastal development.
Cities in Florida, Hawaii and California have already started spending the money.
If states and cities are willing to spend the money, the cost of building the sea walls, shorelines and other infrastructure will fall dramatically, the report says.
And cities will be able to pay for these improvements if they can also buy back flood insurance policies, which is another way to pay off the government.
The report recommends that states and the federal government do more to address coastal vulnerability, particularly when it comes to coastal development, such as flood protection.
It also suggests building more flood barriers and storm surge mitigation structures in coastal cities.
Read more on this story at Bloomberg Businessweek