Time of Concentration - Rational Method

This command calculates the time of concentration (Tc) by the Rational method. The Tc is the time required for water to flow from the most distant point in the watershed to the measurement point.

The Rational method calculation based on the runoff coefficient, length of flow and average slope. These values are set in the dialog shown. The formula is:
    Tc = (1.8(1.1 - c)L^1/2) / S^0.33
Where:   c   = Runoff coefficient
             L   = flow length (ft or m)
             S   = average land slope (%)

Time of Concentration Dialog

Pulldown Menu Location: Watershed -> Time of Concentration > Rational Method
Keyboard Command: flowtc3
Prerequisite: None