Modeling Dynamic Performance of Urban Infiltration Trench Systems: Methodology and a Case Study in Philadelphia

Abstract Infiltration trenches are popular green stormwater infrastructure (GSI) systems in dense urban areas primarily due to their small footprints that cope with the limited available space and subsurface utility conditions. To investigate the dynamic, seasonal performance of urban infiltration trench systems, more than three years of continuous rainfall and water level data from an infiltration trench in Philadelphia, Pennsylvania, were analyzed. The recession rates in the infiltration trench showed a seasonality (higher recession rates in warmer months and lower recession rates in colder months) and a head-dependency (higher recession rates in higher water levels). To incorporate this dynamic performance into a simple modeling approach that can be used in practical applications, both event-based and continuous simulation models were developed using storage units in SWMM, and calibrated/validated against observed data. The most important conclusions for dynamic modeling of infiltration trench systems were the introduction of monthly adjustment factors for saturated hydraulic conductivity (Ksat) and a head-dependent component for infiltration to the surrounding in-situ soil in the model, both of which were determined by calibration. Benefits of the presented dynamic modeling approach were demonstrated by comparing the dynamic and static modeling results, indicating the capability of the dynamic approach to promote sustainable and resilient design of infiltration trench systems.