Optimal Positioning of RTC Actuators for Autonomous Control of Sewer Networks

The enlargement of impervious areas, combined with the increase in the frequency of extreme precipitations due to climate change, pose increasing challenges for the management and operation of urban drainage systems (UDS). Local Real-Time Control (RTC) systems represent a potentially cost-effective alternative to concrete-based solutions (e.g. storage tanks) for enhancing the performance and resilience of UDS. Existing methods to locate Flow Control Devices (FCDs) commanded by RTC focus on identifying in-sewer storage capacity, without considering the hydraulic interactions occurring between the FCDs, their impact on the operation of existing UDS assets, and temporal variation of rainfall-runoff volumes within the catchment. In this study, a novel simulation-optimisation framework is developed to determine the optimal positioning of FCDs controlled by RTC in sewer networks. Optimal FCD locations are identified by a genetic algorithm (GA) solver coupled with hydraulic modelling software. The method is tested in two case study catchments with different characteristics, positioning FCDs commanded by a local and decentralised RTC system called CENTAUR. Results demonstrate how the proposed methodology provides a more robust evaluation of potential FCD placement schemes compared to storage-based design methods, facilitating the design and implementation of effective RTC systems in sewer networks. In the case studies evaluated, the local RTC was capable of efficiently reducing/preventing CSO spills discharged during high-frequency storm events, while mitigating CSO spills discharged during more severe storms. The simulation-optimisation framework is then further developed to optimise the spatial allocation of FCDs combined with simplified Sustainable Drainage Systems (SuDS), for CSO spill volume reduction. Optimal FCD-SuDS configurations are selected in two case study catchments to mitigate CSO spills over synthetic storm events. Implementation schemes are then validated over continuous rainfall series. Results show how the proposed method can successfully maximise the combined benefits of the two technologies when increasing the water storage capacity of UDS, highlighting the unexplored potential of FCD-SuDS intervention schemes as a flexible and decentralised solution for stormwater management.