About WinSLAMM


The primary purpose of the WinSLAMM model is to identify sources of urban stormwater pollutants and to evaluate the efficiency of control practices. WinSLAMM is based on actual field data, rather than theoretical equations that have not been verified for their applicability to urban runoff. Uncertainties are represented using Monte-Carlo simulations. WinSLAMM uses long-term rainfall records, rather than design storms. Soil compaction effects are incorporated. The model does a complete mass balance and routing of water volume and particulate mass, considering the combined effects of all controls. Hydraulic and particle size routing occurs for each device individually, and serial effects of multiple devices are being expanded for these parameters in the new model 10 version. The effects of the sedimentation controls are calculated using modified Puls hydraulic routing with surface overflow rate particulate routing. Costs and runoff flow-duration probability curves can be calculated based on site-control measures being considered.


Dr. Robert Pitt and John Voorhees, PV and Associates, Inc.

Contact information

Dr. Robert Pitt, 205-348-2684,


Long-term rainfall records available from NOAA (many cities are already built into the model). Land use descriptions available from development plans. Design parameters for specific stormwater control measures (developed by user)


Volume and particulate pollutant reductions based on control measures. Costs and flow-duration probability curves.


Design engineers, municipal and other site plan reviewers.

Scales of Relevance

Single lot to large-scale residential, commercial, and/or industrial development to sections of cities and watersheds.


WinSLAMM currently is used in the state of Wisconsin to evaluate stormwater management options. It also is being used to model the effectiveness of retrofitting stormwater control practices into areas with combined sewer overflows at many locations.


The model development is self-supported by the authors. However, additional support to expand various capabilities has been received from others, including the U.S. Environmental Protection Agency, the Wisconsin Department of Natural Resources, the U.S. Geological Survey, the Stormwater Management Authority of Jefferson County, AL; the Tennessee Valley Authority, Economic Development group; Contech Stormwater Solutions; and Hydro-International.