More than 3 million Americans could soon be facing rising sea-level pressure in their cities, a study released Tuesday found.
The findings, based on a study of flood risk in New York, Florida, Illinois, Georgia and Pennsylvania, are the first to quantify the effects of rising sea level on vulnerable communities.
While rising sea water is expected to raise flood risk for the United States, it could also raise it for some places in other countries, according to the study by University of North Carolina and Duke University.
It found that for coastal communities in Florida, a city of nearly 100,000 people in a state with about 7.4 million people, rising sea waters could bring significant flooding.
Flooding is already occurring in parts of New York City, and a flood of up to 12 feet in a city like New York would be deadly, the study found.
Other studies have shown that the number of fatalities from flooding in the U.S. has increased dramatically in the last century.
The study is the first large-scale analysis of the flood risk posed by sea-levels in different parts of the country.
The researchers found that flooding was most likely to occur in coastal cities and that there was a “potential for significant impacts on urban infrastructure.”
While the risk of flooding in coastal areas may be more manageable than it is for inland areas, the researchers say it is still important to be aware of the risk.
The report also found that the city of New Orleans, a coastal city with nearly 80,000 residents, is most at risk from flooding because of its reliance on heavy industries like shipping and agriculture.
Other coastal cities like the Florida Keys, where there are about 2.5 million people and about 1,000 coastal miles, are more vulnerable, but their numbers may be even more vulnerable because of their high density of housing.
The authors did not find any other cities that have experienced increases in flood risk since the study was conducted.
“While there is some concern that the risks associated with sea-rise will increase over time, we have to be cautious about making predictions about future flooding,” said study co-author Chris Mather, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado.
“We do not have reliable data on the size of coastal cities, and we do not know if the projected changes in sea level will cause greater flooding.”
The researchers also noted that while many coastal cities have had higher population density, those cities tend to have higher land areas, which could be less vulnerable to flooding.
They also found cities like New Orleans that are closer to the coast, which has fewer high-rise buildings, are also more vulnerable.
“In general, it is important to look at the number and types of building type, as well as the land areas and the population density,” Mather said.
“These are the areas that are more likely to be vulnerable.
We have not found an increase in coastal risk associated with a coastal location.”
The study was published in the Proceedings of the National Academy of Sciences.
For the study, researchers compared flood risks in coastal communities that were exposed to high sea-water for decades and those that were not, based off a dataset from the National Oceanic and Atmospheric Administration.
Flood risk was measured based on data from a variety of sources, including weather stations, weather models and the National Flood Insurance Program.
“The most reliable data we have on coastal flood risk is from NOAA,” Middletons co-authors, John Wiens and Michael Gebhardt, said in a statement.
“Our results show that coastal cities with high concentrations of commercial and residential structures are at greater risk of inundation from rising sea.”
Middlets co-authored the study with a colleague, Robert Higgs.
Their work was funded by the National Science Foundation and the United Kingdom’s National Environment Research Council.