Study of Land Use Impacts and Options for Innovative Stormwater Management in a Rapidly Changing Watershed: Richland Creek, Wake County, North Carolina

Abstract

The Blue Ridge Corridor (BRC) in northwest Raleigh, NC is currently being redeveloped through a partnership between the Blue Ridge Corridor Alliance (BCRA) and the City of Raleigh. However, the scope of this development is unprecedented within the region and larger watershed of Richland Creek. Rapid urbanization can degrade water quality and functionality of these ecosystems. Our team’s goal is to provide a baseline for water quality and quantity in the watershed, assess land cover changes, develop a stormwater case study, and create a green stormwater framework that would provide guidance and opportunity for ecologically minded development. We analyzed and modeled recent and projected future land use and land cover change. Development in the Richland Creek Watershed has increased by 9.22% in the past 22 years, and an additional 24% of the watershed will become urbanized in the next 20 years, largely at the expense of forested land. Accelerating urban land pressures will require well-designed development to maintain water quality and ecosystem health. The results of our water quality and quantity assessment reveal signatures of increased urban land covers in Richland and Crabtree Creeks. Although rainfall has been constant, stream flow has increased, a change that can be attributed to runoff from increased impervious surface. Additionally, we see increased total hardness attributable to the weathering of asphalt, and increased turbidity attributable to the rapid transport of urban runoff. Improved monitoring of Richland and Crabtree Creek will help assessment of the watershed under increasing development. We modeled replacement of impervious surface cover (ISC) with pervious surfaces to determine how runoff could be reduced in current and future development. Decreasing ISC for three points of interest (POI) had varying effects, but overall decreased peak flows in all storm events. Development should focus on areas where a change in land cover does not greatly impact peak flows and avoid hydrologically sensitive areas. We identified relevant examples of green stormwater infrastructure that could be implemented in the corridor, outlined their benefits, and identified possible funding programs for their construction and maintenance. A public StoryMap was a step in the final synthesis of the project, which was to create a framework for ecologically minded development in the BRC. Our ArcGIS online StoryMap provides context of the project, overview of methods, results, and recommendations. Environmental and economic success of the Blue Ridge Corridor development will be more likely if engaged stakeholders possess a shared understanding of the development and how green infrastructure and low-impact design can reduce environmental costs and maximize environmental benefits throughout the project. This framework is achievable through the implementation of the following recommendations: (1) Maximize the use of green stormwater infrastructure throughout the BRC; (2) Regular monitoring of Richland Creek through placement of USGS gage; and, (3) Inform and engage stakeholders through creation of a publicly available StoryMap. These three steps address the findings, limitations, and next steps identified in the project. Incorporation of the framework into the BRC development plans is critical to the ecosystem health and resilience of the Richland Creek watershed.