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Table Of Contents
Time of Concentration and Time of Travel
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For more information on the Tt equations and other limitations of TR-55, see
the SCS TR-55 manual, Chapter 3, Time of Concentration and Travel Time.
To calculate the watershed time of travel
1 From the Hydrology menu, choose Runoff ä Time of Travel (Tt) to display the
Time of Travel Calculator dialog box.
2 In the Description box, type a description for this segment. Select a description
field and enter the description.
3 In the Shallow box, type the shallow flow time. You can enter this value
directly, or click Select to calculate the shallow flow time from the Shallow Flow
Time Calculator dialog box.
4 In the Channel box, type the channel flow time. You can enter this value
directly, or click Select to calculate the channel flow time from the Channel
Flow Time Calculator dialog box.
Autodesk Civil Design calculates the sum of the shallow and channel travel time
segments and displays this value as the Total Tt.
5 Click Save to save the current values as the new defaults for the Time of Travel
Calculator. This stores the calculated data so that when you access the Time of
Travel Calculator from the TR-55 Tabular Hydrograph Method dialog box, you
can load the defaults you saved by clicking Default.
The Default button is available only when the Time of Travel Calculator is
activated from another calculator (in which case defaults are not automatically
loaded).
6 You can also output or clear the information from the dialog box by using the
following guidelines:
If you want to} Then click}
output the total time of concentration
to a text file
Output.
clear all the boxes in the dialog box Clear.
7 Click OK.