Cost-Effectiveness Analysis of Green–Gray Stormwater Control Measures for Non-Point Source Pollution

The control of non-point source pollution (NPS) is an essential target in urban stormwater control. Green stormwater control measures (SCMs) have remarkable efficiency for pollution control, but suffer from high maintenance, operation costs and poor performance in high-intensity rainfall events. Taking the Guilin Road subwatershed in Rizhao, China, as a case study, a scheme for coupling gray and green stormwater control measures is proposed, and the gray SCMs are introduced to compensate for the shortcomings of green SCMs. The System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN) model was employed to investigate the cost-effectiveness of three scenarios (green SCMs only, gray SCMs only, and coupled green–gray SCMs). The results show that the optimal solutions for the three scenarios cost USD 1.23, 0.79, and 0.80 million, respectively. The NPS control ability of the coupled green–gray scenario is found to be better than that of the other two scenarios under rainfall events above moderate rain. This study demonstrates that coupled green–gray stormwater control management can not only effectively control costs, but can also provide better pollution control in high-intensity rainfall events, making it an optimal scheme for effective prevention and control of urban non-point source pollution.