Study on bioretention for stormwater management in cold climate, Part I: Hydraulics

Simulated storm events were applied to four large bioretention columns to approximate 1.6 years of equivalent volume in Edmonton, Alberta's typical climate. Summer, winter, and spring runoff were simulated in temperature-controlled laboratories with a range of 20 degrees C to +20 degrees C. During summer less porous bioretention media (i.e. loam soil) effectively weakened peak flows by >83% for 1:2 year events while more porous bioretention media (i.e. sandy loam soil) maintained hydraulic conductivities >9.1 cm/h. Winter operation consisted of all columns being subjected to 20 degrees C and then 1 degrees C repeatedly. Events were applied at an air temperature of 1 degrees C and, although frozen initially, more porous media experienced faster water breakthrough and ponding disappearance in winter indicating that hydraulic performance during intermittent warming periods in winter may be achievable. All columns' hydraulic performance rebounded quickly in the subsequent summer. All columns successfully managed 1:2 year events in terms of infiltration rate, ponding depth and duration. Preliminary results also showed that both media have the potential to manage less frequent (1:5 and 1:10 year) events.