June 17, 2019

The Colorado Water Science Center in cooperation with Colorado DOT recently released two storm runoff modeling tools (TR55 and Rational Method) in StreamStats. The StreamStats application can be used to delineate drainage basins for user-selected sites on gaged or ungaged streams and return basin characteristics for use in the storm runoff models.

The TR55 is based on the runoff curve number method (Soil Conservation Service, 1986). It is used within the StreamStats interface to calculate storm runoff volume, peak discharge, and a corresponding hydrograph. The TR55 tool is applicable for small drainage basins in urban areas and utilizes input from three StreamStats-generated basin characteristics (precipitation, drainage area, and runoff-curve number).

The Rational Method (Kuichling, 1889) is a simple equation for estimating a design discharge from a small watershed and is used within the StreamStats interface to calculate peak discharge. Like TR55, the Rational Method was developed for small drainage basins in urban areas and utilizes input from three StreamStats-generated basin characteristics (precipitation intensity, drainage area, and soil runoff coefficient).