Evaluation of Stormwater Mitigation Performance with LID Infrastructures, In-Sewer Space, and Real-Time Control Strategies

Because low-impact development (LID) infrastructures are effective in capturing and utilizing urban stormwater runoff, real-time control (RTC) strategies can be viewed as soft infrastructures, offering an additional suite of opportunities to improve the stormwater drainage system performance. However, there is a paucity of analyses that disentangle the contributing sources of performance enhancement in these joint hard-soft stormwater infrastructures. This study evaluated the stormwater system performance with integrated LID infrastructures, in-sewer storage capacity, and RTC strategies. Our results showed that LID infrastructures play a major role in mitigating the flow peaks and high volumes, whereas adding RTC to the storage unit and in-sewer flow control mostly improves the performance under relatively small rainfall events, e.g., those with a 3-year return period. The critical contribution of RTC is realized by utilizing storage units as much as possible during the rainfall event. A downstream storage unit that is too close to the outfall may not be suitable for RTC application together with in-sewer capacity utilization. In the present case, the combination of a midstream storage unit and upstream control site at branch pipes worked better than those at other locations. The results suggest that the integration of LID and RTC on a simulation-system level can enhance the reduction of the peak runoff and total discharged volume only if the storage site and control locations are selected carefully.