SWMM-based methodology for block-scale LID-BMPs planning based on site-scale multi-objective optimization: a case study in Tianjin

Low impact development type of best management practices (LID-BMPs) aims to mitigate urban stormwater runoff and lessen pollutant loads in an economical and eco-friendly way and has become a global concern in modern urban stormwater management. A new methodology based on stormwater management model (SWMM) for block-scale LID-BMPs planning was developed. This method integrated LID-BMP chain layout optimization in site-scale parcels with scenario analysis in the entire block-scale urban area. Non-dominated sorting genetic algorithm (NSGA-II) was successfully coupled to SWMM through Python to complete the site-scale optimization process. Different LID scenarios of the research area were designed on the basis of the optimized LID-BMP chain layout. A multi-index evaluation that considered runoff quantity indices, pollutant loads, and construction costs simultaneously helped select the cost-effective scenario as the final planning scheme. A case study in Tianjin, China, was conducted to demonstrate the proposed methodology. Results showed that more than 75% control rate of total runoff volume, 22%–46% peak flow reduction efficiency, and more than 32% pollutant removal rate were achieved. The robustness analysis indicated that the selected final planning scheme was considerably robust with varied weight values.