With the CN values for the drainage area defined, we can continue to the Pervious
TC Calculator. Press the Pervious TC Tab and enter the information shown. Make the
change to the entry by clicking on the row. The data will be relocated to the input
fields at the top of the form. revised the input and press the Update button. Again,
since we are not using the impervious calculators press the Impervious TC tab and
zero out each row by clicking on the row to transfer the data to the input fields.
Then press the Delete button.
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Select the Compute tab, select from the drop down, the 10 yr event. Press the Compute
button. The program will compute the peak runoff, volume and time to peak for the
design event specified on the opening page of the dialog. Note that later on, the
program will ignore the design event and use a design event specified at the time
of computation!
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Repeat the process to create the second drainage area by going back to the DATA
tab and using the current record as the template. Press the New Basin
button and the OK to accept the default label that is assigned to the basin.
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Modify the CN number for the Pervious CN Tab. Dont forget to press the Update button.
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Modify the KFactor for the Pervious TC Tab by selecting the drop down on the second
row of the dialog. Select Smooth Surfaces for a factor of 0.011.
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Recompute the hydrograph for a 10 yr event to make sure that the data entered is
sufficient to derive an answer.
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