Real-time Regulation of Detention Ponds via Feedback Control: Balancing Flood Mitigation and Water Quality

Floods in urban areas are becoming more intense due to unplanned urbanization and more frequent due to climate change. One of the most effective strategies to alleviate the effects of flooding is the use of flood control reservoirs such as detention ponds, which attenuate flood waves by storing water and slowing the release after the storm. Detention ponds can also improve water quality by allowing the settlement of pollutants inside the reservoir. The operation of most detention ponds occurs passively, where the outflows are governed by fixed hydraulic structures such as fully open orifices and weirs. The operation of detention ponds can be enhanced with active controls: orifices can be retrofitted with controlled valves, and spillways can have controllable gates such that their control schedule can be defined in real-time with a model predictive control (MPC) approach. In this paper, we develop a distributed quasi-2D hydrologic-hydrodynamic coupled with a reservoir flood routing model and an optimization approach (MPC) to identify the opening or closing of valves and movable gates working as spillways. We adapt the optimization problem to switch from a flood-related cost function to a heuristic function that aims to increase the detention time when no inflow hydrographs are predicted within a prediction horizon. The numerical case studies show the potential results of applying the methods herein developed in a real-world watershed in Sao Paulo, Brazil. We test the performance of MPC compared to static (i.e., fixed hydraulic device opening) alternatives with valves either fully or partially opened. The results indicate that the control algorithm presented in this paper can achieve greater flood and proxy water quality performance compared to passive scenarios.