Design and Performance Simulation of Road Bioretention Media for Sponge Cities

Road bioretention is one of the promising low impact development (LID) best management practices (BMPs) for the construction of sponge cities. Design of the media used in the soil layer of a bioretention facility is critical to its performance regarding infiltration, filtration, and storage of a high volume of runoff from impervious areas. In this study, a coarse aggregate void filling (CAVF) method was adopted for the design of bioretention soil media. The key hydrological parameter of the bioretention media, the average matrix suction at its wetting front, was estimated through finite-element simulation of the rainfall infiltration process. Using the obtained parameter, a bioretention structure was designed, then modeled in the Storm Water Management Model (SWMM) software to analyze its potential hydrologic benefits in terms of reduction in both peak flow and total volume of surface runoff into storm drains in a rainfall event. It was found that the permeability of bioretention soil media is the key factor that affects outflow reduction ratio, peak flow reduction rate, and peak time of the system. The bioretention media composition design method adopted in this study seems promising for use in the material and structural design of road bioretention facilities for sponge cities.