A framework for optimization and assessment of long-term urban stormwater management scenarios under climate change and performance challenges.

In the context of global warming and the increase in extreme rainfall events, the introduction of grey-green integrated infrastructure offers new possibilities for urban flood management. However, within these integrated systems, green infrastructure is more vulnerable to climate fluctuations and has a shorter lifespan, posing challenges to maximizing the overall benefits. Consequently, this study conducted a multi-stage optimization at a representative site in Guangzhou, China, to explore the most effective configuration of grey and green infrastructure under climate change, and to assess the short-term and long-term benefits of these optimized layouts. While multi-stage optimized layouts have slightly higher life cycle costs compared to directly optimized layouts with the same level of centralization, they demonstrate superior hydrological performance in simulations. In the short term, these layouts exhibit greater robustness under various design rainfall scenarios, with up to a 56.79 % improvement in runoff reduction compared to traditional direct optimization layouts. Over the long term, multi-stage optimized layouts continue to show better performance, but with an average maximum improvement of 9.47 % in runoff reduction. As global warming intensifies, leading to more frequent and severe rainfall events, urban stormwater management planning and design must embrace a more sustainable and forward-looking approach.