Technical information

144 | Chapter 10 Hydrology and Hydraulics
An error message is displayed at the bottom of the dialog box whenever you
make an error entering data.
The civil engineering tools include the following hydrology calculators:
■ Time of travel
■ Time of concentration
■ Runoff (Rational, TR-55, and TR-20)
You can use the calculators in two different ways: independently or nested.
If you use the calculators independently, you use only one dialog box at a
time. If you use them in a nested fashion, you can access certain calculators
from within other dialog boxes. For example, while calculating time of
concentration (T
c
), you may want to calculate the sheet flow component of
T
c
. A separate calculator is displayed to perform these calculations and trans-
fer the results to the other dialog box. Each calculator has its own command
to run the calculator and save the values to a file.
The hydrology calculators all use a similar data-entry methodology. The fol-
lowing illustration shows a time of concentration calculator. To solve for the
total T
c
, you enter values for Sheet, Shallow, and Channel flow in the boxes,
or click Select to display separate calculators for these components.
As an additional feature, you can enter values as mathematical equations.
For example, if the first sheet flow component is the sum of two
sub-components, 10 and 5 minutes, you can type 10+5, and 15 is displayed.