Evaluating Controller Performance and Placement on System-level Urban Flooding Reduction and Water Quality Improvement

Increases in urbanization and climate change are forcing urban drainage engineers to more effectively leverage stormwater storage facilities to minimize flooding and water quality impacts. This process becomes increasingly challenging due to the operations of storage coordination across the system-level watershed. This study presents a system-level real-time control simulation for assessing watershed-scale performance. The objective of this work is to make a trade-off between the flooding mitigation at flooded nodes and water quality stress reduction at storage ponds. An open-source tool called PySWMM was used to conduct control rule simulation and water quantity and quality modeling. For testing this tool, four rule-based control scenarios were performed: baseline control, the downstream individual control, system-level control with 11 same controllers, and system-level control with 11 different controllers. Meanwhile, three indicators, including peak depth shaving efficiency, pollutant removal efficiency, and flooded-hour reduction, were used to evaluate the controller performance in system-level operation coordination. A real-world and watershed-scale urban drainage system, called Network A, was selected as the case study. Our results indicate that the most downstream controller performs best in alleviating downstream flooding while the system-level controller has better performance in obtaining global benefits with a higher Peak Depth Shaving Efficiency (up to 7.30% ), Pollutant Removal Efficiency (up to 66.59%), and Flooded-hour Reduction (up to 71.01%). A quantitative controller placement analysis based on Controller Placement Index (CPI) was then conducted to determine which controllers have positive or negative effects on system-level outcomes. The CPI values suggest that upstream ponds with lower storage capacity should be regulated, while those downstream ponds with larger storage volumes ought to be uncontrolled, to maximize the global benefits. This paper provides a basis for improving the design of a system-level and watershed-scale controlled urban drainage systems.