Spatial layout optimization of green infrastructure based on life-cycle multi-objective optimization algorithm and SWMM model

Rapid urbanization and more frequent urban floods instigated by climate change make traditional gray infrastructure become less effective and efficient. Green infrastructure (GI) have proved to be effective measures to address urban floods. Whether the GI layout can yield significant benefits and low investment cost requires further exploration. Besides, the type, size, and location of GI needs to be optimized to achieve better performance. A life-cycle evaluation framework coupled with a multi-objective optimization algorithm (NSGA-II) and SWMM was proposed for GI layout optimization. The framework took investment cost, economic-environmentalsocial monetization benefit, and runoff control capacity into consideration. Tongzhou District in Beijing was selected for empirical analysis. Simulation results reveled that GIs performed good in runoff control and the optimal layout under 10-year return period was recommended. The total cost and benefit of the recommended layout is 6.34x109 RMB and 8.36x106 RMB/Design rainfall, respectively, which outperforms than other scenarios. Permeable pavement accounted for the highest proportion in the optimized layout scenario. For actual construction, decision-makers should select appropriate measures according to local conditions (e.g., precipitation, land use type, cost of GIs) and choose the optimal layout scheme according to their preference. Results displayed can provide a reproducible and dependable planning scheme for future Sponge City construction in China.