Abstract
Bioretention is widely used in urban sustainable stormwater management.
However, limited numerical research has been conducted on its
performance in cold regions, particularly for winter snowmelt, spring
runoff and summer large storms (> 50 mm) for urban flood
mitigation. In this study, HYDRUS 1D was used to explore these knowledge
gaps. The model was comprehensively calibrated and validated against
2-year hydrologic and water quality data of four bioretention columns
with different designs under lab-simulated cold region conditions. The
Morris method was used to measure the sensitivity and interaction of the
calibrated hydraulic parameters. The model revealed that the effective
hydraulic conductivity ( KS) values of the soil
media were similar for winter snowmelt and spring runoff when the soil
temperature was around -0.5 °C. Preferential flow is likely to occur in
soil media during winter or spring of cold regions. The summer modeling
showed that the bioretention could substantially reduce peak flow,
ponding depth and duration for large storm events (even for 1:100 local
storm with 83.4 mm in 4 hours). The water quality modeling confirmed
experimental results that the bioretention effectively removed phosphate
and ammonium but had leaching issues for chloride and nitrate. Finally,
optimization and recommendations of bioretention columns were provided.