Modeling Infiltration in Green Stormwater Infrastructure: Effect of Geometric Shape

Abstract

Geometric shape can play an important role in modeling and designing green stormwater infrastructure (GSI) systems because of its influence on system infiltration processes. The effects of GSI system geometry were assessed by evaluating the area available for infiltration and pressure head dependency of infiltration. Two common GSI types with different geometries, a bioinfiltration rain garden and an infiltration trench, were continuously simulated using the storage unit (SU) object and low impact development (LID) module in the USEPA Storm Water Management Model (SWMM). The models were calibrated and validated using three years of observed data. The results suggest that the stored water depth in GSI systems has a substantial effect on infiltration in narrow, vertical-walled infiltration trenches, while soil moisture conditions play a relatively more important role for infiltration in shallow rain gardens with gradually sloping walls. As such, when modeling the effect of water depth and soil moisture, the SU object was found to simulate the infiltration trench better than the LID module, while the LID module worked better for the rain garden.