Continuous Modeling of Bioinfiltration Storm-Water Control Measures Using Green and Ampt

Abstract

Continuous simulation of storm-water control measures (SCM) requires consideration of the variable environmental and site factors that affect infiltration. This article reviews the theory of the Green and Ampt infiltration model and presents a unit process approach to how it can be applied to a bioinfiltration SCM. The paper discusses how to vary the soil moisture parameters using the soil water characteristic curve, how to modify the Green and Ampt equation for different basin cross-sections, and how to model or bound the infiltration rate when soil media layers are added. Both the standard Green and Ampt parameters and alternative moisture conditions were compared with data from a bioinfiltration SCM; these results confirm that the standard parameter tables often used to select Green and Ampt parameters represent conservative, wet conditions, and that a single value for the parameters will not be able to reproduce the range of infiltration rates observed in the field. When using variable soil moisture conditions, the Green and Ampt model adequately reproduces the infiltration rates observed at the bioinfiltration site.