Technical data

Chapter 3 Performing Hydrologic Studies
50
To calculate the peak discharge using the TR-55 Tabular Hydrograph
Method (continued)
Steps
Use
to look up
5 Select the rainfall distribution type from the
Rainfall Distribution list.
6 Specify the subarea name.
7 Specify the area of subarea #1.
Type a value for the subarea’s area in the edit
box, or, if you created a watershed with the
Terrain Model Explorer, select the polyline
representing the subarea from your drawing by
clicking Area and selecting the polyline. You can
also draw a new polyline representing the limits
of the subarea for selection.
Calculate the Peak Runoff
by Using the TR-55
Tabular Method
8 Specify the time of concentration value for
subarea #1.
Type in a value for the time of concentration, or
click Tc to display the Time of Concentration
Calculator.
Use this calculator to specify the sheet flow,
shallow flow, and channel flow parameters, and
compile the time of concentration data for
subarea #1.
Calculate the Watershed
Time of Concentration
9 Specify the time of travel value for subarea #1.
Type in a value for the time of travel, or click Tt to
display the Time of Travel Calculator.
Calculate the time it takes for runoff from one
subarea to travel through another subarea to the
composite watershed outflow point.
Calculate the Watershed
Time of Travel
10 Specify the downstream subareas for subarea #1.