WERF SELECT Model

Watch a brief video overview of the WERF SELECT model.

(Click here to watch it in a larger-screen format.)

A wide array of different BMPs and LID practices are available for application on a developing watershed or for retrofit in developed areas. BMP choices are often based principally on minimizing the capital cost of installation of the BMPs.

SELECT is a simple planning level tool that enables a stormwater manager to examine the effectiveness of alternative scenarios for controlling stormwater pollution and the whole life cost associated with each scenario. Thus, the manager can make more informed decisions on which practices to permit with some confidence that they will meet imposed TMDL limits and also can have some confidence that the capital and O&M costs involved in implementing BMPs are known.

SELECT is encoded within an Excel spreadsheet, which means that it is intuitive and easy to use for most individuals. The control panel has several functional areas that guide users in setting defaults, inputting user information, and executing the model.

SELECT uses a long-term record of hourly rainfall to drive the model; this hourly rainfall is translated into runoff using a runoff coefficient that is related to the effective imperviousness of the catchment. This runoff is introduced to the BMP. If there is capacity in the BMP, the runoff is captured; if the BMP is full, the runoff is discharged untreated to the receiving waters. The model calculates total outflow as the sum of what is treated and what is not.  SELECT output data includes annual pollutant loads discharged to the receiving water, pollutant load frequency curves with uncertainty estimates, and an estimate of the whole life cost of the BMPs applied in the watershed. BMPs that can be simulated in SELECT include:
  • Extended detention
  • Bioretention
  • Wetland basin 
  • Swale
  • Permeable pavement
  • Filter
  • Generic (user-defined) 

 Water quality parameters that can be simulated include:

  • Total Suspended Solids
  • Total nitrogen
  • Total phosphorus
  • Total zinc
  • Total copper
  • Fecal coliform

To download the SELECT tool from our website go to the “Search Research Publications and Tools” tab and use Keyword = SELECT or type in Project Number = SWC1R06c.

A SELECT User Support Website is available to assist users. The website includes video tutorials that provide an introduction to the tool, an overview of the model's main features, step-by-step instructions for performing common model user tasks, and answers to frequently asked questions.

To receive updates to SELECT and other related news, please send an email to tconnor@werf.org.