As the Earth’s climate changes, the worst inundations from hurricanes and tropical storms could become far more common in low-lying coastal areas, a new study suggests. Researchers from Princeton University and the Massachusetts Institute of Technology found that regions such as the New York City metropolitan area that currently experience a disastrous flood every century could instead become submerged every one or two decades.
The researchers report in the journal ‘Nature Climate Change’ that projected increases in sea level and storm intensity brought on by climate change would make devastating storm surges – the deadly and destructive mass of water pushed inland by large storms – more frequent. Using various global climate models, the team developed a simulation tool that can predict the severity of future flooding an area can expect.
The researchers used New York City as a test case and found that with fiercer storms and a 3-foot rise in sea level due to climate change, “100-year floods” – a depth of roughly 5.7 feet above tide level that occurs roughly once a century – could more likely occur every three to 20 years. What today are New York City’s “500-year floods” – or waters that reach more than 9 feet deep – could, with climate change, occur every 25 to 240 years, the researchers wrote.
The research is not only the first to examine the future intensity of storm surges, but also to offer a tool for estimating an area’s vulnerability, said co-author Michael Oppenheimer, the Albert G. Milbank Professor of Geosciences and International Affairs at Princeton.
“Coastal managers in cities like New York make daily decisions about costly infrastructure that would be affected by such storms. They need a reliable indicator of the risk,” he said.
“Our modeling approach is designed as a key step in this direction,” Oppenheimer said. “As the world warms, risks will increase across a variety of fronts, and the threat to coastal infrastructure in the face of an already-rising sea level and potentially stronger hurricanes could be one of the most costly unless we are able to anticipate and reduce vulnerability.”
Lead author Ning Lin, a postdoctoral fellow at MIT, said that knowing the frequency of storm surges may help urban and coastal planners design seawalls and other protective structures. Lin, who received her Ph.D. from Princeton in 2010, began the project at Princeton then continued it at MIT; the current report is based on her work at MIT.
“When you design your buildings or dams or structures on the coast, you have to know how high your seawall has to be,” said Lin, noting that Manhattan’s seawalls now stand a mere 5 feet high. “You have to decide whether to build a seawall to prevent being flooded every 20 years.”
Lin and Oppenheimer worked with study co-authors Kerry Emanuel, an MIT atmospheric science professor, and Erik Vanmarcke, a Princeton professor of civil and environmental engineering. Lin, Vanmarcke and Emanuel also co-wrote a 2010 report on the project published in the ‘Journal of Geophysical Research’ that was based on Lin’s work at Princeton.
Carol Friedland, an assistant professor of construction management and industrial engineering at Louisiana State University, sees the latest results as a useful tool to inform coastal design – particularly, she notes, as most buildings are designed with a 60- to 120-year “usable lifespan”.
“The physical damage and economic loss that result from storm surge can be devastating to individuals, businesses, infrastructure and communities,” Friedland said. “For current coastal community planning and design projects, it is essential that the effects of climate change be included in storm-surge predictions.”
The researchers ran a total of 45,000 storm simulations for the New York City region under two scenarios: current climate conditions from 1981 to 2000 based on observed data and four global climate models; and projected climate conditions for the years 2081 to 2100 based on the four climate models, as well as future carbon dioxide output as predicted by the Intergovernmental Panel on Climate Change (IPCC). Oppenheimer is a longtime participant in the IPCC.
