Channel Routing Hydrograph - Convex Method

Channel routing is used to analyze the effects of a channel on a hydrograph's peak flow and travel time. You may choose from either the Convex or Modified Att-Kin methods to route a hydrograph downstream.

The Convex method is derived from inflow-outflow hydrograph relationships. The following equation is used:

    O_i+1 = CI_i + (1 - C)O_i

where:   O_i+1   = Outflow discharge at (i+1)th time step (cfs or cms)
          C       = Routing Coefficient
            I_i       = Inflow discharge at (i)th time step (cfs or cms)
            O_i      = Outflow at (i)th time step (cfs or cms)

The routing coefficient C can be computed using an empirical equation by SCS.

    C = V / (V + 1.7)       for English units
    C = V / (V + 0.518)    for Metric units

where:   V = Flow velocity (ft/s or m/s)

Please refer to the National Engineering Handbook Section 4 for the detail of the Convex method.

Select Convex Method from Watershed > Hydrograph Routing > Channel Routing menu. Specify the inflow hydrograph and enter the routing coefficient C or channel flow velocity to let the program to calculate the coefficient. The routing interval is as same as the time increment of the inflow hydrograph.

After entering all information, click on Routed Hydrograph button to generate the routing hydrograph. A dialog is opened with the tabular and graphic hydrograph data, from there you can draw the hydrograph on screen and save it to a file.

Routed Hydrograph Dialog

Pulldown Menu Location: Watershed > Hydrograph > Channel Routing > Convex Method
Keyboard Command: chanrout
Prerequisite: None