What happens to water quality after two decades of hurricanes

UNC-Chapel Hill study describes the long-term impacts of hurricanes

The Lasting Effect of Hurricanes
June 7, 2018

As another hurricane season begins, there’s new research showing how decades of tropical storms have had a long lasting effect on North Carolina in ways you may not think about. Everyone knows about the damaged homes and businesses, the washed-out roads and flooded farm fields. But a new study by researchers at North Carolina State University and the University of North Carolina at Chapel Hill finds that more than two decades of hurricanes have had a lasting, negative effect on North Carolina’s coastal ecology. Those effects include massive fish kills and unsafe water quality.

17 Hurricanes over Two Decades

From 1996 through 2017, North Carolina was battered by hurricanes Fran (1996), Bertha (1996), Bonnie (1998), Floyd (1999), Dennis (1999), Isobel (2003), Frances (2004), Ophelia (2005), Ernesto (2006), Earl (2010), Arthur (2014), Joaquin (2015), Hermine (2016), Matthew (2016), Harvey (2017), Irma (2017), and Maria (2017). The study looked at what happened to the Pamlico Sound after a hurricane passed over the area. It’s the second largest estuary in the United States. The Neuse River flows into Pamlico Sound. The findings, published in the journal “Biogeochemistry” include:

• An increase in algae blooms, which can cause fish kills. Algae blooms can also make water quality unsafe for humans, and force state officials to close fisheries

• More fish and shellfish kills and the localized death of fish populations

• “Dead Zones”, which are areas with excessive nutrient pollution that depletes oxygen needed for organisms to live.

Stormwater runoff leads to problems downriver

Those effects are all due to the large amounts of rainwater dumped by the storm into the Neuse River and eventually the Pamlico Sound.

“Hurricanes lead to large discharges of nutrients and organic matter into watersheds and then into coastal waters,” explains Hans Pearl, Kenan Professor of Marine and Environmental Sciences at the University of North Carolina Institute of Marine Sciences in Morehead City. “All of that matter changes of the biochemistry of coastal ecosystems.”

Researchers studied satellite images from before and after the storms as well as water quality tests. The data revealed how flooding and erosion sent huge inputs of nutrients and organic matter into the estuary. The data also showed that after major storms, including Hurricane Matthew, the discharges were so large that dead zones extended for miles, forcing state officials to close fisheries.

Factoring in climate change

The scientists point out that because of climate change, the long-term trend is for storms to become larger and more severe. “As extreme weather events become more frequent, North Carolina must learn to manage the flow of organic matter and nutrients into estuaries and coastal waters, said Christopher Osburn, Ph.D., professor of Marine, Earth, and Atmospheric Sciences at North Carolina State University.

—Frank Graff 

Frank Graff is a producer/reporter with UNC-TV, focusing on Sci Tech Now North Carolina, a weekly science series that airs Tuesdays on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!