Urban Storm Water Drainage System Optimization Using a Sustainability Index and LID/BMPs

Urban stormwater drainage systems (USDSs) play an essential role in protecting cities from excessive rainfalls and urban floods. To quantify the performance of the USDSs, a new sustainability index is proposed based on reliability, resiliency, and vulnerability indices. These performance indices evaluate different aspects of a USDS with a comprehensive view of the system's level of service. Using the proposed sustainability index, two USDS design/rehabilitation optimization models are introduced and compared to see which one offers a more sustainable solution and lower implementation cost. The first model (Case I) applies Best Management Practices (BMPs) to an existing USDS to improve sustainability with minimum costs. The second model rehabilitates the channel sizes along with using BMPs. A part of the Tehran Stormwater Drainage System (TSDS) is chosen as the study area to evaluate the proposed methodology. Optimization models are developed by linking the NSGA-II optimization algorithm with the EPA SWMM model. The best solutions are extracted from both cases' Pareto fronts and compared using the Nash bargaining method. Results showed that designing/rehabilitating USDSs by optimizing the BMPs size and channel size would result in a higher sustainability index and lower costs.