Modeling a BioInfiltration Best Management Practice: Fid-Bau Portal

Modeling a BioInfiltration Best Management Practice

Heasom, W. / Traver, R. G.

A Bioinfiltration best management practice (BMP) was constructed within a parking area serving a dormitory and parking complex on the west campus of Villanova University in 2001 Figure 1). It was retrofitted into an existing mounded turf traffic island serving as a traffic lane divider. The BMP was constructed by excavating six feet below the existing grade; backfilling with a sand-soil mixture; grading a bowl-shaped depression for a temporary pond; and planting with salt tolerant grasses and shrubs native to the Atlantic shore. The drainage area for the BMP is 1.5 acres of which one-half is impervious. The BMP has performed well for the five years it has been in service and has infiltrated approximately 80% of the precipitation delivered to the watershed. The modeling approach developed for this site is based on HEC-HMS. Green and Ampt is used to represent the losses on the pervious areas. The infiltrating basin is modeled using stage-storage routing with diversion elements representing two physical components of the infiltration: the rapid infiltration that occurs during precipitation generated inflow and the recession infiltration that occurs continuously over the wetted area of the pond. Ongoing calibration has brought the modeled results into close alignment with the flows observed during continuous monitoring and has revealed a definite and consistent seasonal pattern to the infiltration effects. Research initiatives following on this work emphasize a better understanding of how the observed and modeled infiltrations relates to the properties of the soil; the unsaturated flow conditions; and the groundwater. It is expected that the finding will be useful in continuing to develop design criteria.