Rivers in SC and NC are still feeling the effects of Hurricane Florence
Months after the drenching storm pummeled the Carolinas, rivers are still showing effects from Hurricane Florence.
The storm, which hit as a Category 1 near Wrightsville Beach, N.C., on Sept. 14, was remarkable in part for how much water it carried. The cyclone unleashed 11 trillion gallons of precipitation that took weeks to flow through rivers in North and South Carolina, inundating several communities as it went.
It was eight months later that Cara Schildtknecht, the Waccamaw Riverkeeper, finally saw water levels in her river return to normal.
The Waccamaw, a 140-mile black water river, flows from Lake Waccamaw through the seat of Horry County and empties into Winyah Bay, near Georgetown. Earlier in 2019, the river was well below what the National Weather Service would call “flood stage.” Still, there were small signs that a flood had rolled through: boat landings and other low-lying areas continued to flood at high tides and swampy areas stayed more saturated than usual.
“Even in March and April, we had some (anglers) saying the fisheries still aren’t back to what they had been,” Schildtknecht said.
Water level gauges from the U.S. Geological Survey show that at Longs, near the state line, the Waccamaw mostly returned to its 30-year average level before the end of last year.
But farther down the river, higher water levels have persisted. In Bucksport, which saw catastrophic flooding last year in part because it sits at the confluence of two waterways, the Waccamaw stayed above the expected average except for a few brief periods between the flood and this spring.
The lingering water on the Waccamaw is even more remarkable given that the watershed has not seen excessive rainfall since the storm. According to data from the National Weather Service, the river’s path saw average or below-average rainfall from Oct. 1 to late May.
Farther north on the state line, a particularly wet winter meant that the Lumber River was for months swamping some rural infrastructure, like the bridge at Matthews Bluff, south of Lumberton.
“Every time it would start to drop a little bit, the rain would come back,” said Lumber Riverkeeper Jefferson Currie.
Hurricanes and other flooding events don’t just threaten homes and infrastructure when they make rivers swell. Drenching storms also threaten to change the chemistry of the waterways and imperil the animals that live there.
The Neuse River in North Carolina has long had an issue with nutrient pollution because of the many swine and poultry farms located in the basin. While more nutrients may sound positive, additional phosphorus and nitrogen from animal waste can actually wreak havoc by encouraging the runaway growth of toxic algae, said Lower Neuse Riverkeeper Katy Hunt.
That algae saps the water of its oxygen, leading to an environment that weakens or suffocates fish. By May, dead menhaden fish, a filter-feeder at the low end of the food chain, were turning up in the Neuse, Hunt said. She said there had also been reports of spring fish kills in the Pungo River, which is part of the nearby Pamlico watershed.
“We’re seeing it in both river basins, and the concerning thing is that it’s not hot yet,” said Hunt, who is based in New Bern. “We typically don’t start to see massive fish kills like this until July, August, when it’s been hot for a while.”
Similar problems have happened in the Waccamaw. Oxygen readings briefly dipped to zero in early October, just after the flooding peaked near Conway, about 30 minutes north of Myrtle Beach.
Susan Libes, a water chemist at Coastal Carolina University, said that’s happened before, but not for the length of time it persisted last autumn. She thinks the situation was so severe that bacteria in the water, faced with no oxygen but a huge amount of organic material that wouldn’t usually be available, started releasing sulfur gasses.
The chemical reaction is similar to what happens in sewer pipes when raw sewage moves too slowly and bacteria depletes the oxygen in the effluent. The resulting gases are so strong they can eat through metal, in some cases.
“There were some biochemical processes going on that were quite extraordinary,” Libes said, though she was unable to actually test the water at the time to confirm her theory.
The gases have a strong smell and are harmful to plant life, as well as humans. Libes, who lives on the Waccamaw north of Conway, said she remembers the stench from last year.
“It was so bad that my eyes were watering inside my house,” she said.