Landscape design and the role of created, restored, and natural riparian wetlands in controlling nonpoint source pollution

Abstract

General design principles, landscape locations, and case studies of natural and constructed riverine wetlands for the control of nonpoint source (NPS) water pollution are presented. General design principles of wetland construction for NPS pollution control emphasize self-design and minimum maintenance systems, with an emphasis on function over form and biological form over rigid designs. These wetlands can be located as instream wetlands or as floodplain riparian wetlands, can be located as several wetlands in upstream reaches or fewer in downstream reaches of a watershed, and can be designed as terraced wetlands in steep terrain. Case studies of a natural riparian wetland in southern Illinois, an instream wetland in a downstream location in a northern Ohio watershed, and several constructed riparian wetlands in northeastern Illinois demonstrate a wide range of sediment and phosphorus retention, with greater efficiencies generally present in the constructed wetlands (63–96% retention of phosphorus) than in natural wetlands (4–10% retention of phosphorus). By itself, this could be misleading since the natural wetlands have much higher loading rates and actually retain an amount of nutrients comparable to constructed wetlands (1–4 g P m −2 year −1).