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Table Of Contents
Chapter 5 Working with Hydrology Commands
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3 Click Output. The data is displayed in a text editor, such as Notepad.
4 Click OK to return to the TR-55 Tabular Hydrograph Method dialog box.
Calculating Runoff With the TR-20 Method
The SCS TR-20 Unit Hydrograph Method is one of the most sophisticated
hydrologic analysis methods, allowing you to use variable length storm events.
This method uses a dimensionless (or unit) hydrograph and a rainfall
distribution curve to calculate peak discharge.
A dimensionless hydrograph represents the discharge of water that would occur
during a storm that lasts 24 hours and creates a uniform 1 inch of depth of
runoff. In this runoff calculation method, the dimensionless hydrograph is used
to represent the average capacity of a watershed to discharge runoff. The unit
hydrograph provided in the TR-20 Method was derived from a large number of
natural unit hydrographs from watersheds varying widely in size and
geographic location. If a natural unit hydrograph is available for the region