You are here:
Comparison of WinSLAMM Modeled Results with Monitored Biofiltration Data
Citation:
Pitt, R., J. Voorhees, D. Bambic, D. O'Bannon, AND M. Simon. Comparison of WinSLAMM Modeled Results with Monitored Biofiltration Data. Presented at World Environmental & Water Resources Congress 2013, Cincinnati, OH, May 19 - 23, 2013.
Impact/Purpose:
To compare WinSLAMM modeled results with monitored biofiltration data.
Description:
The US EPA’s Green Infrastructure Demonstration project in Kansas City incorporates both small scale individual biofiltration device monitoring, along with large scale watershed monitoring. The test watershed (100 acres) is saturated with green infrastructure components (including curb-cut biofilters with extra subsurface storage, rain gardens, cascading biofilters, and porous concrete sidewalks). An adjacent 87 acre control watershed is also being monitored. These monitoring results at the small and large scales will be used to verify the WinSLAMM stormwater quality model to enable evaluations of specific design options of these stormwater controls and for analyses of green infrastructure alternatives at other areas of the city. WinSLAMM is a unique model in that it evaluates stormwater controls based on unit operation processes and actual design values, and incorporates complete hydraulic, particulate, and pollutant routing between and within the stormwater controls in an area. The biofiltration control in WinSLAMM uses full modified Puls routing calculations associated with pond storage along with a variety of "discharge" and soil treatment options. The inflow hydrograph is separated into small time intervals for the routing calculations. As water enters the device, all flow is routed to the below ground section as long as the engineered media infiltration rate is greater than the inflowing water rate. The above ground storage begins to fill once the inflow rate exceeds the engineered media infiltration rate. If the inflow rate is high enough and the excess volume exceeds the available storage, the water will begin to be discharged through the above ground surface outlets. As water enters the below ground section of the device, it discharges through the native media (with Monte Carlo options to incorporate measured variability in the infiltration rates) and, as the bottom section fills, through the underdrain (if used). All water that flows through the underdrain is assumed to be filtered by the engineered media and varies by type of media for different runoff particle size fractions. WinSLAMM was initially used to evaluate the biofilter designs for the test area and was calibrated using the early test and control watershed flow and rainfall data. Now that the green infrastructure elements have all been constructed and are being monitored, the model will be verified at both small and large scales.
