Catchment-Scale and Local-Scale Based Evaluation of LID Effectiveness on Urban Drainage System Performance

Recent studies have demonstrated the effectiveness of low impact development (LID) in preventing urban flooding in urban catchments. Majority of the past research focuses on the overall effects of LID on urban flood reduction in various configurations. However, how urban drainage system (UDS) performance changes at spatial scale under LID effectiveness within urban catchment is rarely explored. This study evaluates performance of UDS under different spatial placement strategies of LID to understand how urban flood dynamics of drainage system changes at catchment and local-scales. A practical UDS in China was chosen as a case study and divided into three sections (upstream, center, and downstream), with a combination of four LID practices installed on one of these sections or the entire catchment under six different rainfall scenarios and five different setting scales. An evaluation of individual LID practices demonstrated bioretention cell takes first place, followed by rain garden and green roof, and permeable pavement ranked at last place based on their overall performances. Results also confirmed the significant impact of the placement location of LID on UDS performance. Uniform placement strategy proves to be the best among four strategies because of the maximum potential for flood mitigation and improvement of UDS performance. Other investigated spatial placement strategies have approximately similar performances but are relatively poorer compared to the uniform strategy. Furthermore, the placement of LID facilities nearer to the flooded locations maximizes the benefits in terms of flood reduction and also reduces probability of transferring hydraulic load to other parts of UDS.