Storm Water Best Management Practices Decision Support Tool

Storm Water Runoff Calculator

This page presents a stand alone computer program for calculating the amount of storm water runoff and the peak runoff rate. The program is based on the method presented in NRCS Technical Report TR-55. The program can be used to generate estimates for equipment selection or cost estimation purposes.

The Calculator is based upon the US Department of Agriculture's Urban Hydrology for Small Watersheds TR-55, June 1986. It is recommended that users read this 2.5M .pdf file before using the Calculator.

Also of interest is the Runoff Curve Numbers for Urban Areas, a table from the TR-55, which provides the basis for the Calculator.

The Storm Water Runoff Calculator is a separate application. When clicking on this link, you will be given the choice of running the program from it's current location, or saving the program to disk. As the program is quite small, it is more convenient to run the program unless you want to keep a copy on your computer. If the program asks if you want to install and run "Runoff2.exe" from this web site, click on "Yes".