Multi-Scale Retention to Improve Urban Stormwater Drainage Capacity Based on a Multi-Objective Optimization Strategy

With global climate changing, numerous cities have a rise in the frequency of heavy rainfall events. Concurrently, the rapid urbanization is increasing the impermeable surfaces, heightening the vulnerability to cope with flooding of urban stormwater drainage systems. This work compared the different retention strategies to mitigate flooding risks by simulating various scenarios using StormDesk 2.0. Additionally, it conducts multi-objective optimization of retention volume reduction, overflow volume reduction, and cost constraints through NSGA-II to obtain adaptation schemes across diverse scenarios. The findings demonstrate that, compared with the maximum area and overflow reduction ratio schemes, the drainage capacity can increase 15% under the adaptation scheme. Furthermore, the investment of the adaptation scheme is the most economical, at 10.59% of the maximum area scheme, and the overflow reduction surpasses that of the maximum area scheme by 45.8%. The most economical unit control cost in the adaptation scheme was USD 64.2/m 3 , while the full cost reached USD 277,337.9, highlighting its superior cost-benefit. The above results can provide a paradigmatic reference for enhancing stormwater drainage capacity in urban built-up areas.