Bioretention performance: a review of field studies

ABSTRACT Over the past decade, there have been multiple studies into how bioretention systems perform in field, rather than laboratory, conditions, and into the quality of stormwater coming off urban catchments, yet in Australia standards, guidelines and software models have remained relatively static. A review of 15 field studies of bioretention systems, collectively covering 513 storm events, found a weighted average volumetric loss of 51% despite many of the systems having impermeable liners or were on clayey soils. The loss of water is about 17 times higher than is predicted by MUSIC when configured in accordance with standard guidelines. Some of the studies found increased pollutant concentrations in the effluent, with volumetric loss being the primary mechanism for pollutant load reduction. This research shows that bioretention systems perform more like sponges than filters and can have a potentially large impact on urban hydrology by reducing the volume and frequency of runoff, and helping attenuate minor flood events. Ultimately, this could lead to a better integration of the quality and quantity aspects of urban stormwater management.