Water quality continues to be threatened by human development activities such as stormwater runoff from urbanization. This study addresses the question of how stormwater Best Management Practice (BMP) system design choices affect pollutant removal efficiency, through the examination of 12 case study sites (across five states) that use three common BMP system design types (detention, retention, and wetland channel). Water quality information was obtained from the International Stormwater

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... and site composite grab samples. Development conditions were inventoried by orthophotos and assessed using Geographic Information System (GIS) and AutoCAD data. This study relates Total Suspended Solid (TSS) load removal efficiency with a series of form-based design variables, which landscape architects can control through their scope of services. System design characteristics of age, size, form, and material selection, along with site-specific precipitation regimens and extent-of-development, were compared with use of TSS removal efficiency in order to determine possible design relationships. Primary removal efficiency methods of individual design types were then evaluated to prioritize conclusions for practical applications. Mixed findings from this study report that one material-based and two form-based design variables hold significant correlation with the TSS removal efficiency. However, site-contextual variables, especially the Natural Resource Conservation Service (NRCS) hydrologic weighted curve value, play an important role in BMP performance and may supersede possible design impacts. The study also reveals that for some BMP sites, a deviation from original design intent may jeopardize system removal efficiency.