Lessons Learned from Measuring and Monitoring Water Quantity Performance of Green Stormwater Infrastructure in Complex Urban Environments

Urban highways are important vessels for the transport of people and goods through cities, but they create large impervious areas that contribute to the generation of urban runoff. Green stormwater infrastructure has become an increasingly important tool to mitigate stormwater challenges associated with highways, especially in cities trying to prevent combined sewer overflow events while facing increasing storm volumes and intensities. The Villanova Center for Resilient Water Systems is working with Temple University, AECOM, and PennDOT to study rain gardens in urban environments and develop recommendations on designing, maintaining, and monitoring green stormwater infrastructure systems along Interstate-95 through Philadelphia, PA. The water quantity performance of ten rain gardens collecting runoff from highway decks and varying in size, shape, soil media, inflow conditions, and vegetation have been studied in this partnership via the collection and analysis of hydrologic data. Attempting to measure water quantity results and monitor site performance in complex urban settings presents a myriad of unique challenges due to intense and turbulent inflow, spatial limitations, proximity to the public, and other factors. This study discusses various aspects of measuring and monitoring flow from an elevated highway, through a bioinfiltration basin, into an outlet structure. It reviews lessons learned on calming turbulent inflow, selecting instrumentation for resilience in urban settings, sampling and analysis methods for obtaining high quality data, and the use of modeling software to represent bioinfiltration systems. Because of their complex and dynamic nature, urban green stormwater infiltration systems require creative approaches in their implementation and monitoring.