An Evaluation of Stormwater Best Management Practice: Relationships Between Design and Efficiency

Water quality continues to be threatened by human development activities such as stormwater runoff from urbanization. This study tackles the question of how stormwater best management practice (BMP) system design affects pollutant removal efficiency, through the examination of 12 case study sites (across five states) that use three common BMP system types (detention, retention, and wetland channel). Water quality information was obtained from the International Stormwater Database and site grab samples. Development conditions were recorded by orthophotos and assessed using Geographic Information System (GIS) and Autocad Civil 3D data. Total suspended solids (TSS) measurements were used as the indicator of the BMP performance. The study relates TSS removal efficiency with a series of form-based design variables, which landscape architects can control by design. Mixed findings are reported from this study that none of the form-based variables present significant correlation with the TSS removal efficiency. However, site-contextual variables, especially the percent of impervious cover area, play an important role in BMP performance. The study also reveals that for some BMP sites, deviation from the original design intents jeopardizes system efficiency