The structure design of integrated urban drainage systems: A view of robust optimization

Rapid urbanization puts a lot of pressure on urban water pollution from point and non-point sources, calling for the practical, specific, and integrated management of urban drainage systems (UDS). The structural design of an integrated UDS is essential for highly complex and uncertain urban water management. In this study, we developed a multi-objective robust optimization model to explore the optimal structures of UDS considering system uncertainty. We applied this model to City B, northern China, to illustrate its effectiveness. The results show that the model can produce optimal designs with a more robust performance in terms of structural uncertainty. When the uncertainty degree ranges from 5% to 20%, a considerable extra cost (increased by 1.10-2.68 times) is required to improve the robustness of UDS. With the increase in structural uncertainty, the fraction of the cost invested in the stormwater subsystem increased from 10.2% to 27.2%. The findings showed that stormwater management is efficient in coping with system uncertainty. The research results promote an understanding of robust urban drainage systems.