2.0

Table Of Contents
Time of Concentration and Time of Travel
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To specify the specify the sheet flow
1 In the Sheet Flow Time Calculator dialog box, type a description for the sheet
flow segment in the Description box.
2 In the Mannings n box, type the Mannings n roughness coefficient for the
sheet flow surface.
You can also click Select to display the Sheet Flow  Mannings n dialog box and
select a coefficient from a list of typical sheet flow roughness values.
NOTE
These sheet flow Mannings n values are significantly higher than typical
channel roughness values. These n values are for very shallow depths of
about 0.1 foot. The Sheet Flow  Mannings n dialog box contains the
setting values from SCS TR-55 manual, Table 3-1. These values are stored
in the c:\Program Files\Land Desktop R2\land\prot\hdsheet.cof folder.
3 In the Flow Length box, type either the sheet flow length, or click Select to
specify the length by selecting an object or points in the drawing.
4 In the Two-yr 24-hr Rainfall box, type the two-year, 24-hour rainfall depth.
You can also click Select to select the rainfall depth from the Define Rainfall-
Frequency dialog box.
NOTE
The two-year rainfall depth is always used, regardless of the storm
frequency being analyzed.
5 In the Land Slope box, type the slope of the sheet flow segment. You can also
click Select to calculate the slope by selecting contour lines in the drawing.
When you specify all four values in the dialog box, the sheet flow time is
displayed in the Sheet Flow Time field. When you click OK to return to the
Time of Concentration calculator, this value is inserted into the Sheet box.
TIP
To display the sheet flow data in a text editor, click Output. From here, you
can print the data to a file or printer.
6 Click OK.