As a stormwater engineer and researcher, I’m always watching the weather closely, a habit I’ve long shared with my dad. So, when an unnamed storm (Potential Tropical Cyclone 8) dumped 20 inches of rain on Carolina Beach in September, I called him to talk about it. He lives in the town where I grew up, a small mountain community near the Tennessee border. As we chatted, he said, “man, if we got that kind of rain here, things would be really bad.”
His words replayed in my mind the next week as I watched the online stream gauge of Asheville’s French Broad River rise to its highest point ever recorded, surpassing the previous record from 1916. He was absolutely right. Twenty inches of rain would have been really bad, but circumstances went straight to catastrophic when many places, my hometown included, saw 30 inches of rain over the course of Hurricane Helene.
The close timing of the two storms is an eerie reminder of the growing risks associated with large storm events. The 2020 North Carolina Climate Science Report highlights that as we observe the atmospheric water vapor content increasing, we should anticipate storms to get more intense and occur more frequently.
This certainly has implications for how our communities can be preparing for future natural disasters, including how we might protect infrastructure that’s in place to treat smaller storms.
Stormwater control measures are practices, such as ponds and rain gardens, designed to remove pollutants and minimize nuisance flooding during small to medium sized storm events. In the Cape Fear region, most stormwater control measures are designed to capture and treat 1.5 inches of rain. Now, imagine if your neighborhood pond was, instead, large enough to treat 20 or 30 inches! It is logistically and economically unfeasible to build stormwater control measures that large.
However, it is important that the practices be able to survive those large storms, so that they can continue to function after those events subside.
While destruction is sometimes unavoidable, such as during hurricanes Helene and Florence, our group recently conducted a study identifying key attributes that increase the resiliency of stormwater control measures to extreme weather events. In addition to several important design elements, we found that well-maintained stormwater control measures are typically more resilient to extreme events than those stormwater control measures that are not actively maintained.
Often the assumption is that stormwater control measures can be maintained with standard landscaping practices. However, stormwater control measures are water quality treatment devices, and specialized training is required to maintain their proper function. Stormwater control measures that receive this specialized maintenance are more likely to operate properly and have a higher likelihood of surviving extreme storms.
North Carolina State University’s Engineering Research Group offers an Extension workshop and certification on stormwater control measure inspection and maintenance activities. We encourage anyone interested in stormwater control measure maintenance to attend, from regulators and professional landscapers to homeowners and property managers. Information on upcoming workshops can be found at https://stormwater.bae.ncsu.edu.
Amber Ellis is an Extension Associate for North Carolina State University’s Stormwater Engineering Research Group in the Biological and Agricultural Engineering Department, with an office at the New Hanover County Arboretum, 6206 Oleander Drive, Wilmington, N.C. You can reach Ellis at adellis3@ncsu.edu.