Multi-objective siting-sizing for smart real-time coordinated flood management in mixed urban-natural watersheds

Population growth and urbanization have increasingly driven the expansion of urban areas into floodplains. To address this issue, detention basins provide a well-established approach for reducing flood risk while decreasing the need for costly upgrades to downstream stormwater conveyance infrastructure. The integration of Offline Real-Time Control (ORTC) can further enhance the effectiveness of detention storage by enabling more adaptive and responsive flood control management. This study presents a two-layer approach for minimizing peak flow. First, the layout of distributed detention dams is optimized at the non-urban scale by considering three objectives: minimizing the downstream peak flow, minimizing the runoff volume reaching the urban area, and minimizing the implementation cost. Second, pre-event optimized operation is fine-tuned at a finer scale to improve the performance of flood mitigation measures. The cost-effectiveness of each alternative is then evaluated over its lifetime, and the most promising management strategy is selected. The findings show that optimizing the location and dimensions of distributed detention dams can reduce peak flows by up to 83%. Incorporating ORTC further improves performance, achieving an additional peak flow reduction. The results indicate that ORTC can suppress flood peaks while avoiding the cost escalation typically associated with higher-capacity infrastructure designs. This study demonstrates that coordinated ORTC operation can serve as a practical and cost-effective strategy for meaningful flood risk reduction by using available storage capacity more efficiently.