Soil & Water

Urbanization and land use change is occurring at unprecedented rates in the southeastern United States. Balancing economic expansion and its impacts, while preserving the land’s attraction and environmental health, is a challenge relevant to everyone. Home and landowners, developers, design professionals and natural resource managers can improve environmental quality using Low Impact Development (LID) techniques and solutions.

The North Carolina Arboretum has over 22 LID examples funded through North Carolina State University and the French Broad River Training Center. The Center provided design guidance, construction oversite and water quality monitoring for a variety of rain gardens (bioretention), stormwater wetlands, vegetated conveyances, rain pockets, green roofs, permeable paving and water harvesting.

LID is an integral part of site design; it includes different treatments that remedy polluted stormwater. This technique minimizes development’s hydrologic impacts to receiving waters by preserving natural areas and capturing, slowing and cooling the majority of storm events to approach replicating the predevelopment hydrology. LID usually has several interconnected practices that treat stormwater runoff differently than conventional stormwater management that conveys and disposes of runoff as quickly as ordinances allow or mandate. Most ordinances over the past several decades have encouraged design professionals to concentrate on water quantity, minimize flooding and protect the public by routing larger storms (10 or 25 year) through the site at predevelopment flow rates. While important, the collective impacts of this approach have impaired the biological integrity of receiving streams and other surface water because they significantly alter site hydrology and do not mandate pollutant reductions in stormwater. These impairments are closely correlated with untreated impervious areas. The Center for Watershed Protection has suggested that stream impacts occur when the watershed reaches ten percent of impervious cover and become further impaired at twenty-five percent (Schuler, 2000). Mimicking predevelopment hydrology is one way to mitigate impacts from land use change, including development

At The North Carolina Arboretum, active and passive education interprets attractive LID techniques and practices that reduce pollutant loading and mitigate peak flow of small storm events. Workshops and tours extend scientifically based information regarding the design, implementation, interpretation and maintenance of the many LID practices. Workshops and field tours for design professionals convey design, construction sequencing, pollution removal efficiency, and discuss maintenance guidelines and techniques. Environmental design practitioners learn to integrate concepts and techniques into practice to meet water quality goals, some of which are mandated. Recent regulations specify performance standards for removing pollutants and treating the smaller storm events, such as the National Pollutant Discharge Elimination System (NPDES) Phase II stormwater regulations. This has created a greater demand for LID techniques, education, and interpretation.

References

Schueler, Thomas R. and Holland, H., 2000. The Practice of Watershed Protection. Center for Watershed Protection.

Society for Ecological Restoration International Science and Policy Working Group, 2004. The SER International Primer on Ecological Restoration.