Generation of optimal (de)centralized layouts for urban drainage systems: A graph-theory-based combinatorial multi-objective optimization framework

The suitability and effectiveness of decentralized paradigms in the field of underground conveyance drainage infrastructures for coping with the current and upcoming sustainability and resilience demands has been documented in recent research. However, a generic and holistic framework that can be quickly put in practice is lacking. To this end, this study proposes a scheme for creating and optimizing decentralization scenarios in terms of sewer layout configurations for both flat and steep terrains with the aid of a combinatorial graph-theory-based optimization. Additionally, a novel and generalized formula is derived to determine the degree of centralization coupled with three layout objective functions, thereby eliminating several feasible layout solutions. The results indicate that cherry picking an appropriate sewer structure (topological layout) at the planning stage can largely influence the design construction costs (reduction up to 49% for steep terrain and 25% for flat terrain), as well as the resilience response of the final network. Therefore, as a general rule of thumb, breaking down the centralized network into a decentralized one can reduce construction cost and improve resilience.