Rising seas and coastal risks

Floodplain Mapping Program.

Shay’s work zeroes in on one storm: Isabel, which made landfall in North Carolina in 2003 as a Category 2 hurricane. Using data on coastal topography and bathymetry compiled for the floodplain mapping modeling effort, Shay models the storm at current sea levels and at sea levels ranging from .5 to 2 meters higher.

Although his simulations show more pronounced storm surge and flooding during the hypothetical Hurricane Isabels, Shay stressed that the results depict a possible future, not a certainty.

“There are a lot of unknowns and uncertainties,” he said. “A warming ocean will cause some sea level rise just because of thermal expansion, but we don’t know how fast the ocean will warm or how fast the Greenland ice will melt or whether the West Antarctic ice sheet will melt. All those things have a range of possible outcomes and we want to understand as many of the possible outcomes as we can.”

Rising seas and changing risks

RENCI Senior Scientist Brian Blanton develops simulations using the same ADCIRC and SWAN models, but focuses on understanding the risks coastal communities will face from hurricanes and extratropical storms if sea levels rise.

 

“We are looking at the changes in risk associated with these storms—particularly risks from waves and surge — while making various assumptions about the future climate, such as increases in sea level, increasing rates of sea level rise and increased storm intensity,” said Blanton.

The work, funded by the North Carolina’s Floodplain Mapping Program, uses the same datasets as the floodplain modeling project and data from Applied Research Associates on probable hurricanes that could head toward North Carolina over the next 100 years. Blanton then uses that data to generate probable hurricane and severe storm events under different conditions that could be affected by climate change, such as higher sea levels, increased storm intensities and changes in the frequencies of storms.

The work will harness the power of a RENCI supercomputer to run about 2,000 individual storm simulations in six different climate scenarios, according to Blanton. Each simulation set will be crunched into statistical analyses that will help to clarify how coastal risks change under each climate scenario.

The end product, he said, will be a scientific evaluation of the risk of living on the coast—whether economic risk, risk to infrastructure or risk to lives — under changed conditions, which planners, emergency managers, scientists and policymakers will then be able to compare to their current understanding of coastal risks.

“With an understanding of not only the flood hazard data and the risk data but also of the uncertainty that goes along with that data — because the uncertainty can be quite high when your talking about a 100-year future climate — we hope to be able to inform the discussion on policy at the state, regional and maybe down at the county level as to what possible future risks may be,” said Blanton.