Performance of two bioswales on urban runoff management

One of the most challenging environmental issues facing urban landscape management is surface runoff and its associated pollutants. Traditional management strategies focus on the rapid draining and removal of runoff to protect public safety, but the unintended consequence is the depletion of excess surface water that could be used for recharging groundwater, irrigating urban landscapes, or sustaining wildlife habitats. To combat this issue, there is a need for green infrastructure, which uses natural and engineered systems that mimic processes in nature, to control stormwater runoff. This paper assesses the effectiveness of bioswales as an urban runoff management strategy. To determine the temporal impact of bioswales on surface runoff, pollutant levels, and tree growth, the authors collected data for low, medium, and high pollutant loadings in two bioswales in Davis, California. The treatment bioswale contained engineered soil mix and the control bioswale had undisturbed native soil. Results showed that the treatment bioswale eliminated more than 99.4% of the surface runoff and reduced pollutant levels by an average of 99.3% across all three experiments. Tree growth characteristics were largely the same for both sites. The results demonstrate bioswales are an effective green infrastructure strategy for urban runoff management. Based on this research, urban landscape managers can employ bioswales to reduce surface runoff, remove runoff pollutants, and support tree growth in an urban landscape.