Development of a Vegetative Based LID Suitability Index for Coastal Counties of South Carolina.

Development of a Vegetative Based LID Suitability Index for Coastal Counties of South Carolina

Dhanuska Wijesinghe¹, Daniel R. Hitchcock^2*, David L. White³, Dara M. Park¹

¹Department of Agriculture and Environmental Sciences, Clemson University, Clemson, SC, 29634

²Baruch Institute of Coastal Ecology and Forest Science, Box, 596, Georgetown, SC, 29442

³Clemson University Campus Computing and Internet Technology, Clemson University, Clemson, SC, 29634

*Contact: dhitchc@clemson.edu

Low-impact design (LID) attempts to maintain natural hydrologic conditions in urban development. Vegetative based LID practices (stormwater wetlands and bioretention cells) have become popular as a stormwater control measure (SCM) in Coastal South Carolina (SC). A suitability index was developed to identify appropriate sites for wetland (retention-based) versus bioretention (infiltration-based) systems in South Carolina’s four most populated coastal counties (Georgetown, Horry, Charleston, and Beaufort). The index utilized a GIS based model that integrates seven key landscape features (land cover, water table depth, hydrologic soil group, drainage class, slope, percent impervious and parcel data) based on the siting criteria from the Coastal SC LID Manual and South Carolina Department of Health Environmental Control (DHEC) BMP Manual. The index allows the user to make an informed decision on LID practice and placement location within a site under development based on science and not just by visual inspection. The suitability index is available as an online GIS tool (http://bit.ly/clemson-cri ) as well as an online story map (http://bit.ly/clemson-cri-story-map). The model demonstrated that a larger percentage of land is suitable for bioretention systems over wetland based systems. This was prominent in the Charleston city area where there are seasonally high water tables, low relief, and well drained soils. In comparison, a larger percentage of Myrtle Beach city area was suitable for wetland based systems due to presence of shallow water tables, low relief, and poorly drained soils. The Suitability Index can serve as an informational and educational tool for planners, developers, engineers, land managers, regulators, among others. However, the index will need significant ground-truthing and checks for accuracy before it can fully be implemented as a decision-making tool.

Key Words: Low-impact Design, Wetlands, Bioretentions