Council Receives Low Impact Development Report

The Raleigh City Council today received a report from the City of Raleigh Stormwater Management Advisory Commission on how low-impact post-construction practices can help protect Raleigh’s streams and lakes from further deterioration. According to the report, the overall quality of surface water in Raleigh and downstream in the Neuse River continues to decline.

Conventional site-development designs usually focus on efficient site drainage by the use of impervious surfaces to collect, concentrate, and discharge runoff from a site as quickly as possible. Stormwater detention ponds are often used as the main treatment method. According to the North Carolina Division of Water Quality, this method increases stormwater drainage volume and concentrates the pollutants delivered to local waterways.

Low-impact development focuses on handling stormwater runoff as close to the site of the precipitation as possible, in a manner that mimics how nature manages precipitation, without compromising a site’s development potential. When water from small rainfalls is held on-site and infiltrated into the ground or evaporated, pollutants that otherwise would be carried off-site with runoff stay on-site and the impact on local waterways is reduced naturally.

Features commonly incorporated into low-impact development designs can include:

• Conservation of natural vegetation and replacement of removed vegetation;
• Construction of less impervious surface, disconnecting impervious surfaces from piped collection systems, and using pervious pavements where practical;
• Harvesting and storing rainwater in cisterns and ponds and using it for irrigation purposes in place of potable water;
• Slowing and filtering runoff through rain gardens, bio-retention cells, trees, planter boxes, wetlands, green roofs, decentralizing runoff controls; and,
• Slowing, filtering, and conveying runoff through vegetated filter strips and swales instead of paved gutters, ditches, and underground storm drains.

The City Council referred the report to the City Public Works Committee for additional review.

The Stormwater Management Advisory Commission serves as the official citizen advisory board to the Raleigh City Council on issues related to stormwater & drainage management policy. It consists of ten members, all of whom reside within the Raleigh City limits. Members are appointed by Council to overlapping two-year terms.