Long-term performance of bioretention systems in storm runoff management under climate change and life-cycle condition

Abstract

Bioretention system (BS), a low impact development (LID) practice, is a natural and decentralized design implemented into the built environment for managing storm runoff widely. However, high uncertainties regarding the efficiency of BS over their life cycle may result in overestimates of the actual performance. Uncertainty of climate change may also limit the effectiveness of BSs. To provide BS that efficiently controls surface runoff, this study proposes a modeling method (General circulation models) for simulating the performances of BSs over its life cycle under a single climate change scenario (RCP 8.5). A case study in Guangzhou shows extreme storms are becoming more frequent but with shorter duration under a high-emissions scenario. The long-term efficiencies of BSs in reducing peak flow and runoff volume were examined during the simulated period in the Stormwater Management Model. Performance improved as the implementation area increased, but the marginal increase shrank. The overall efficiency of the BS fell as its structure aged and climate change worsened. BSs are effective for small rainfall events, with peak flow and runoff volume reduced by more than 75 % by BSs covering more than 5% of the catchment area, given rainfall in the 0–25 % percentile range. But many extreme storms may not be effectively mitigated (reduction of less than 25 %), even with very large BS areas. Performance will be even more limited in the presence of highly impervious catchment. The modeling method and results of this study, which prescribe a holistic and dynamic consideration in evaluation of BS, can help improve decision support systems for LID planning.