2.0

Using the TR-55 Graphical Method to Calculate the Peak Runoff Flow
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Specifying a Frequency Adjustment Factor
You can use the Frequency Factor Editor dialog box to select a frequency
adjustment factor.
To specify a frequency adjustment factor
1 Click the Adjustment Factor box into which you want to place the adjustment
factor. The Rational Method dialog box is displayed.
2 Click Factor.
The Frequency Factor Editor dialog box is displayed.
3 In the Frequency column, enter the frequencies (in years).
Select a text box and enter the value.
4 In the corresponding Factor column, enter an adjustment factor for each year.
Select a text box and enter the value.
5 Select the Use frequency factor check box.
6 Click OK to return to the Rational Method dialog box.
An adjustment factor is placed in the Adjustment Factor text box you selected
in step 1. Autodesk Civil Design automatically calculates the correct adjustment
factor based on the Rainfall Frequency you selected in the Rational Method
dialog box and the frequency factors you entered in the Frequency Factor Editor
dialog box.
Using the TR-55 Graphical Method to Calculate
the Peak Runoff Flow
The Autodesk Civil Design Graphical Peak Discharge and Tabular Hydrograph
Methods are based on Technical Release 55 (TR-55), Urban Hydrology for Small
Watersheds. The Soil Conservation Service (SCS), now called the National
Resources Conservation Service (NRCS), first published the TR-55 in 1975, and
updated it to its current form in 1986. TR-55 was originally developed to be a