Time of Concentration - Kirpich Method

This command calculates the time of concentration (Tc) by the Kirpich method, which is developed for small drainage basins in Tennessee and Pennsylvania, with basin areas from 1 to 112 acres. The formula is:
    Tc = KL^0.77 / Sⁿ
where:    L   = basin length (ft)
             S   = basin slope (ft/ft)
             K   = 0.0078 for Tennessee, 0.0013 for Pennsylvania
             n   = 0.385 for Tennessee, 0.5 for Pennsylvania

The estimated Tc is multiplied by 0.4 if the overland flow path is concrete or asphalt, or by 0.2 if the channel is concrete-lined.

Select Kirpich Method from Watershed > Time of Concentration menu. In the dialog, choose a location of either Pennsylvania or Tennessee, and specify the basin conditions. The flow path data can be obtained from picking a 3D polyline and the program calculates the length and slope of the flow automatically. Click on Calculate button to see the result.

Peak Flow Dialog
Pulldown Menu Location: Watershed -> Time of Concentration > Kirpich Method
Keyboard Command: flowtc4
Prerequisite: None