By Katelyn Sheets

North Carolina’s piedmont region is growing fast – according to the U.S. Geological Survey, “urban land use in the region is projected to nearly triple by 2060.”^[1] As development continues, metropolitan regions in the piedmont must adapt to reduce the impact of development on local streams. There are a variety of practices that can be implemented by cities to ameliorate the flooding effects of urban development, including protecting riparian zones, setting up rain gardens, and installing permeable pavers. Each of these methods aims to increase groundwater absorption of runoff to prevent small streams from being overwhelmed.

North Carolina’s piedmont, the relatively flat center region of the state nestled between the coast and the mountains, has grown rapidly in recent years. Much of North Carolina’s growth in the early 2000s occurred in the piedmont’s urban centers, including the Metropolitan Statistical Areas (MSAs) of Raleigh-Durham-Cary and Charlotte-Gastonia-Salisbury.^[2] As a result of this growth, North Carolina’s piedmont has experienced damage to its stream systems. Increased urbanization and development has decreased stream basins’ ability to properly absorb storm runoff, leading to increased risk of flooding.^[3] If you’ve ever waded through a foot of water to reach your car in the parking deck of Raleigh’s Crabtree Valley Mall, which sits adjacent to Crabtree Creek, you may be familiar with this phenomenon.

Riparian zones are defined by the National Park Service as “lands that occur along the edges of rivers, streams, lakes, and other water bodies.”^[4] The vegetation that grows in riparian zones is critical to preventing flooding, as it slows the flow of runoff and allows more water to seep into the soil rather than directly into the stream.^[5] Beyond their benefits for flood prevention, riparian zones improve water quality by filtering runoff through vegetation and are a critical habitat for wetland wildlife.^[6] Luckily, North Carolina has already implemented a Riparian Buffer Protection Program administered by the North Carolina Department of Environmental Quality (NCDEQ).^[7] Cities in the Piedmont should continue to devote resources to ensuring compliance with these riparian buffer regulations and cooperate with NCDEQ procedures.

Rain gardens, small concave impressions filled with soil and vegetation, are another way to reduce flooding in urban areas.^[8] Rain gardens, like the vegetation in riparian zones, slow the flow of stormwater into local streams. They create areas where runoff can be absorbed into groundwater as opposed to accumulating in the streets and flowing directly into streams. While research on implementation in the U.S. is limited, research out of Kyoto, Japan supports the efficacy of rain gardens for flood prevention.^[9] The use of rain gardens in Nakagyo Ward of Kyoto decreased the number of flooding nodes and “reduced stormwater hazards.”^[10] Rain gardens would be relatively easy to integrate into existing Piedmont urban landscaping plans with minimal impact on city residents. Alternatively, cities could provide funding in the form of subsidies or rebates for residents who construct rain gardens on their properties. An additional benefit of rain gardens is that they can be constructed with native flora, supporting local ecosystems and species.

As an alternative to traditional concrete paths and driveways, cities could support the installation of permeable pavers. Permeable pavers are pavers designed with more space in between them to allow for increased groundwater absorption compared to traditional pavers.^[11] Like rain gardens, the installation of permeable pavers will have minimal impact on city residents, as residents will still be able to drive, park, or walk on them.^[12] City governments can install permeable pavers on state-owned property throughout the city as well as provide incentives for residents to install them on their properties. One barrier to implementation, however, is cost. Local governments can apply for a variety of federal grants and programs to fund permeable paver installation, such as the Watershed and Flood Prevention Operations (WFPO) Program through the National Resources Conservation Service or the Water Infrastructure Finance and Innovation Act (WIFIA) program through the Environmental Protection Agency.^[13], [14]

Multiple piedmont cities have already expressed support for sustainable development practices. Durham, for instance, has outlined each of the above strategies in its Urban Open Space Plan.^[15] Charlotte’s Mayor, Vi Lyles, has made sustainable development a priority in her work. According to her, “sustainable cities showcase smart choices.”^[16] Mayor Lyles was recently reelected to her fourth term, indicating strong political support for her sustainable development push.^[17] As urban regions in the piedmont continue to grow, local governments must take notes from cities like Durham and Charlotte, leaders in piedmont sustainable development, and take proactive measures to decrease flood risk.

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^[1] Urban growth in the southeastern U.S. potentially threatens health of small streams. U.S. Geological Survey. (2019, November 12). https://www.usgs.gov/news/national-news-release/urban-growth-southeastern-us-potentially-threatens-health-small-streams

^[2] Trelease, A. (2006). Piedmont Urban Crescent. NCpedia. https://www.ncpedia.org/piedmont-urban-crescent 

^[3] Putnam, A. (1972). Effect of urban development on floods in the Piedmont Province of North Carolina. Open-File Report. https://doi.org/10.3133/ofr72304 

^[4] U.S. Department of the Interior. (n.d.). Riparian zones – It’s all about the water. National Parks Service. https://www.nps.gov/articles/000/nrca_glca_2021_riparian.htm#:~:text=Riparian%20zones%2C%20or%20areas%2C%20are,by%20the%20presence%20of%20water.

^[5] Importance of protecting riparian areas. Tinkers Creek Watershed Partners. (2016, September 9). https://www.tinkerscreek.org/importance-protecting-riparian-areas/#:~:text=These%20areas%20also%20provide%20water,and%20volume%20of%20flood%20waters.

^[6] Importance of protecting riparian areas. Tinkers Creek Watershed Partners. (2016, September 9). https://www.tinkerscreek.org/importance-protecting-riparian-areas/#:~:text=These%20areas%20also%20provide%20water,and%20volume%20of%20flood%20waters.

^[7] North Carolina Department of Environmental Quality. (n.d.). Riparian Buffer Protection Program. NC DEQ. https://www.deq.nc.gov/about/divisions/water-resources/water-quality-permitting/401-buffer-permitting/riparian-buffer-protection-program

^[8] Rain gardens. City of Durham. (n.d.). https://www.durhamnc.gov/787/Rain-Gardens 

^[9] Zhang, L., Ye, Z., & Shibata, S. (2020). Assessment of rain garden effects for the management of Urban Storm Runoff in Japan. Sustainability, 12(23), 9982. https://doi.org/10.3390/su12239982 

^[10] Zhang, L., Ye, Z., & Shibata, S. (2020). Assessment of rain garden effects for the management of Urban Storm Runoff in Japan. Sustainability, 12(23), 9982. https://doi.org/10.3390/su12239982 

^[11] Permeable Pavers Archives. Unilock. (n.d.). https://unilock.com/permeable-pavers/ 

^[12] Pervious Pavers. Alliance for the Chesapeake Bay. (n.d.). https://stormwater.allianceforthebay.org/take-action/installations/pervious-pavers

^[13] Watershed and flood prevention operations (WFPO) program. Natural Resources Conservation Service. (2022, September 24). https://www.nrcs.usda.gov/programs-initiatives/watershed-and-flood-prevention-operations-wfpo-program

^[14] Environmental Protection Agency. (2022, June 13). EPA Announces $6.5 Billion in New Funding Available for Water Infrastructure Projects. EPA. https://www.epa.gov/newsreleases/epa-announces-65-billion-new-funding-available-water-infrastructure-projects

^[15] Urban open space plan. Durham City-County Planning Department. (2017, March). https://www.durhamnc.gov/DocumentCenter/View/13869/UOSP_013017 

^[16] Fromm, J. (2022, September 10). Sustainable Cities will have a competitive advantage: Charlotte mayor & Hitachi Experts Weigh in. Forbes. https://www.forbes.com/sites/jefffromm/2022/09/06/sustainable-cities-will-have-a-competitive-advantage–charlotte-mayor–hitachi-experts-weigh-in/?sh=787d9367e704

^[17] Duncan, C. (2023, November 7). VI Lyles wins fourth term as Charlotte mayor. Spectrum Local News. https://spectrumlocalnews.com/nc/charlotte/news/2023/11/07/charlotte-mayor-council-election-results