Environment-Economic Benefit Analysis of LID Practices Based on SWMM from a Local Level: A Case Study in Chengdu

Among all the practices, the runoff control effect of permeable pavement is the best when arranged separately, but with the increase of rainfall intensity, the effect of Low Impact Development (LID) began to decrease, so it is particularly important to take combined practices. This study comprehensively evaluates the performance of LID practices from the perspective of the environment and economy. Seven different scenarios are set in this study, the runoff control rate and node surcharge hours control rate are calculated through the SWMM simulation results, to obtain the environmental benefit parameters. The hesitant fuzzy evaluation method is used to evaluate the construction cost, maintenance cost, runoff control rate, and node overload hours control rate, and the results are used as the environmental and economic benefit weight. Finally, the comprehensive benefit P is calculated. The results show that the comprehensive benefit index of 30% permeable pavement is the highest under a single measure, and the comprehensive benefit index of 5% green roof and 25% permeable pavement is the highest under combined measures. Taking Chengdu as an example, this study verifies the flooding mitigation effect of different combinations of LID practices and provides effective information for decision-makers who implement LID practices for flood control and disaster reduction in communities.