Pocket Wetland Impacts on Stormwater Runoff and Water Quality

Impervious surface areas within an urban catchment can generate higher runoff volumes and degrade water quality in local streams. Pocket wetlands are an end-of-pipe stormwater management system that detain runoff and improve stormwater quality before entering the channel. These wetlands are used as a ‘polishing’ feature in stormwater management systems. The working hypothesis is that a pocket wetland will attenuate flow and improve water quality, which can be modeled with an areal decay model. Stormwater runoff and water quality was monitored upstream, downstream and at the inlet of a wetland in the Churchville subwatershed in Brampton, ON, April – October 2014. Results indicate the wetland provided short-term storage for the remediation of water quality through rainfall events, which were then estimated using an areal decay model. This study provides evidence on the performance of pocket wetlands for stormwater management and design.