A procedure to design road bioretention soil media based on runoff reduction and pollutant removal performance

Abstract

Gradation design of urban road bioretention soil media is critical for the construction and performance of sponge cities, but current design methods are simplistic with reliance on local experiences. This study proposes an experiment-modeling based design procedure that effectively balances runoff reduction and pollutant removal performance based on both material properties analysis and project site performance simulation. A coarse aggregate void filling (CAVF) method is adopted for soil medium design and a stormwater treatment performance evaluation system is proposed for road bioretention containing the designed soil media. The proposed procedure was illustrated in a case study of a real project scenario. A hydrological model was built in the Storm Water Management Model (SWMM) software to evaluate the runoff reduction and pollutant removal performance. Results show that soil medium permeability is a key factor affecting the quantity and quality of runoff. Soil media with higher permeability improve the runoff reduction performance but decrease the pollution removal efficiency of the bioretention. Compared to the existing soil media design methods that are highly empirical or simplistic, the proposed design procedure relies on objective evaluation indices and quantitative analysis steps, and so may be applied to various design scenarios in stormwater management practices with improved reliability.