Selection of cost-effective Green Stormwater Infrastructure (GSI) applicable in highly impervious urban catchments

Urban areas such as roads, and parking lots, present different sets of problem, vehicular Nonpoint source (NPS) loadings derived from vehicular use are very high, while the roof have low NPS pollutant loadings. Therefore, this study was conducted to monitor the actual stormwater runoff characteristics of various landuse types and the treatment efficiency of the constructed GSI systems applied. The data used to calculate the pollutant concentrations were gathered from a total of 172 storm events during the five year monitoring period on a paved road, parking lot and roof landuse site. Based on the results, the road and parking lot landuses have characteristics of large amount of stormwater runoff, high peak flow and runoff of high pollutant concentration due to the vehicular activities. Applicable facilities include pretreatment facilities, such as infiltration trench, subsurface flow (SSF) and hybrid constructed wetland and tree box filter which have SA/CA ratios within 1∼2% were appropriate for facilities effective for reducing pollutants including infiltration and filtration functions. Meanwhile, the roof landuse contains low pollutants in comparison to other land uses, so, bioretention, rain garden, and free water surface (FWS) constructed wetland which have SA/CA ratio within 5% were appropriate to enable processing and recycling of large amount of stormwater runoff that have infiltration and retention function. Therefore, costeffective GSI design must not only depend on treated runoff quantity but also quality of the treated runoff for landuse.