Study shows Wilmington’s nuisance flooding is getting worse

Flooding issues continue to plague certain areas

WILMINGTON, N.C. (WECT) - It’s a somewhat common scene in Wilmington and the Cape Fear region — a beautiful sunny day without a cloud in the sky — yet, water across the road. It’s known as many things, sunny day flooding, nuisance flooding; but, according to new research, it’s getting worse, and Wilmington was at the top of the list for the increase in nuisance flooding events.

While most people attribute these instances to events like king tides or full moons, a new report shows that humans might have a bigger role in exacerbating these events than previously thought.

Dr. Thomas Wahl is a researcher and assistant professor at the University of Central Florida. He, along with others, recently published a research article that shows just how big of an impact things like dredging is having on tidal events.

Of course, these types of changes to ecosystems are not the only cause of these flooding events — sea-level rise is the biggest culprit.

“We know that the main reason for these nuisance flooding events to happen more frequently is sea-level rise — without a question. Sea level is rising and that leads to higher high tides,” Wahl said.

Our study was basically trying to understand whether there are other components — other things

“Research has shown that with a certain amount of sea-level rise going forward into the future that these nuisance flooding events, and the cumulative impact of these nuisance flooding events, may be as large or even larger than the impacts that we see from very rare but very extreme hurricane surge,” Wahl said.

And according to that research, the City of Wilmington saw the most extreme tidal changes out of all of the locations surveyed.

“Wilmington (NC) provides an extreme (but illustrative) example of a secular change in tides at an estuarine station; the tidal range has increased at a rate of 542 mm/century since 1935 due, in large part, to channel deepening,” according to the study.

While tidal changes can be attributed to sea-level rise, there are also human aspects to the problem that bears some responsibility — in Wilmington’s case, that’s due to dredging and channel deepening.

“Wilmington, for example, experienced the strongest effects from changes in tides on NF (both number of NF days and duration) among all tide gauges considered here. The tide gauge is located upstream in the Cape Fear River, 47 km from the mouth of the estuary. The tidal range has increased by approximately 0.38 m since 1936 (0.57 m since 1887), mainly due to extensive dredging, channel deepening, and associated reduction of hydraulic drag,” according to the research.

So, what can be done to help mitigate the problem? It’s not easy and possibly improbable for many locations but restoring wetlands could help.

“If we were to put back wetlands that were there 100 years ago that we took out, these wetlands we know were very good at taking out some of the energy from storm surges and wake that might impact the area; so this is one way of reversing at least some of these impacts,” Wahl said.

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