UNC computer model tracks storm surge, flooding during hurricane season

Jul. 27, 2013 @ 04:25 PM

As Tropical Storm Dorian eases west toward the Virgin Islands and Puerto Rico from the middle of the Atlantic Ocean, UNC-Chapel Hill scientists are eyeing the storm as a research opportunity.

Rick Luettich, director of both the UNC-Chapel Hill Institute of Marine Sciences in Morehead City and the Coastal Hazards Center on UNC-Chapel Hill’s campus, has spent more than 20 years trying to perfect a computer modeling system that produces high-resolution forecasts of storm surge, near-shore waves and flooding.

When tropical storms or hurricanes threaten to hit the East and Gulf coasts, the ADCIRC Surge Guidance System can help local emergency responders predict what neighborhoods will take the toughest hits and help the U.S. Coast Guard determine where to target its emergency personnel and supplies.

Luettich describes the North Carolina coastline as “intriguing” because of its delicate barrier island system and the fact it’s very vulnerable to the might of hurricanes and nor’easters, strong winter storms that form off the coast.

“Not long after getting here, I was motivated by a real desire to understand and to be able to predict how water moves in coastal North Carolina and how water moves in other systems,” Luettich said.

UNC’s Institute of Marine Sciences is located along Bogue Sound, and each summer, about 24 interns explore the marshes and estuaries and pitch in with research, such as studying the effects of coastal circulation on early life stages of fish, oysters and crabs.

“That’s one of the beauties of being here on the coast,” Luettich said. “I can go out and collect data to verify if the information is accurate.”

Back in 1990, when Luettich started work on the first crude model of ADCIRC, nothing else like it existed. Studies at the time focused on water movement farther off the coast, not the “brown water” areas that would be dramatically affected by storms, he said.

The U.S. Army Corps of Engineers started to recognize its value, that the analyzed data filled the gap linking coastal circulation to storm surge and the flooding of lowland areas.

After that, FEMA jumped on board and now uses ADCIRC as the primary tool to determine its flood insurance program rates. The National Weather Service, National Hurricane Center and local and regional emergency management divisions use the data to make evacuation decisions, position supplies and personnel and for search and rescue, according to the Coastal Hazards Center at UNC.

Staff members working on ADCIRC hope to take lessons learned from past hurricanes and incorporate them into future system models. ADCIRC tracked Hurricane Sandy in 2012 as it swiped the Outer Banks. They targeted Hurricane Irene in August 2011, when the eye of the storm passed 20 miles east of the marine sciences institute and knocked out its power. They even conducted preliminary research in New Orleans, focusing on the threat of storm surge and how it would affect the levee system, before Hurricane Katrina hit in 2005.

The levee system itself failed during Katrina, Luettich said, but they tried to piece together data they could use after the catastrophic event, even if many of their sensors and equipment were wiped out along the Gulf.

“After Katrina went through, we were at the right place at the right time with the right tools,” he said.

Tracking Tropical Storm Chantal this July was the trial run for what has been pegged as a potentially active hurricane season.

ADCIRC also was recognized this summer at the International Supercomputing Conference in Leipzig, Germany. The system’s computing power is not actually housed at the Institute of Marine Sciences, where it would be too vulnerable if a storm hit and wiped out power and communications.

ADCIRC is housed at the Renaissance Computing Institute, also known as RENCI, at UNC-Chapel Hill’s main campus.

Brian Blanton, RENCI’s senior research scientist, has worked with Luettich for 15 years on different versions of the ADCIRC system.

A lot of computing power is needed to break down a model to the tiniest beach dune, Blanton said. The goal is to put together a “true data-sharing facility,” where data being crunched on different ADCIRC forecast systems can be presented as one big information database, he said.

Louisiana State University, the University of Texas, University of Notre Dame and the College of Staten Island, which was affected by Hurricane Sandy, have all contributed to the data grid.

Placing everyone’s data into one system will allow for quicker and more efficient data dissemination, according to the Coastal Hazards Center.

As the ADCIRC team continues to pay attention to tropical storm No. 4, Dorian, they are prepared to ramp up their forecasts if it edges closer to the East coast.

“If it ends up in an area we have a good grid for, we’ll be running it and we’ll be ready for it,” Blanton said.

For information and to view the ADCIRC forecasts, visit nc-cera.renci.org.