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4.2.1
Hydrology Studio
SCS Hydrographs
As described in the Quick Start Tutorials, runoff hydrographs are added to your model
by clicking one of the Runoff Hydrograph buttons on the Ribbon Toolbar at the Main
Window. In this case, click the [SCS] button. After the icon has been added, simply
click on its icon or row, depending on which tab you are working from, to populate its
input window. Simply fill-in-the-blanks and click [Compute].
Required Data
The following is a description of each of the required input items.
Name
Enter any descriptive name for this hydrograph. It will appear on the printed reports
as well as the Basin Model.
Runoff Area
Enter the sub-basin area. No size limit.
Curve Number, CN
Enter the SCS Curve Number for this area. A table of CNs is available here. For a
composite CN, press the [%] button. Up to six sub-basin areas and corresponding
CNs can be entered for a composite CN.
Time of Concentration, Tc
Tc is the time it takes for runoff to travel from the most remote upstream point in the
drainage area to the downstream point in question. Select one of the four Tc options
from the drop-down list box.
User - Check this option to override the computed Tc and enter Tc manually.
Lag - The TR-20 default method.
Kirpich - This method is normally used for natural basins with well defined routes for
overland flow along bare earth or mowed grass roadside channels. It is similar to the
Lag method but will typically give shorter times compared to the Lag method. Use this
method when the subarea is dominated by channel flow.
TR55 - Compute Tc by using the built-in TR55 worksheet. See Tc by TR55.
If you chose Lag, Kirpich or TR55, click the ellipsis [...] button to open the
corresponding input screen. There, Tc will be computed and automatically inserted
into the Tc input box.
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