An irregular channel cross section option defines a channel using the channel slope and the station, elevation, and Manning's n at each input coordinate point. The number of coordinates allowed is unlimited, but using more coordinates will take longer to compute the results. All coordinates and n values may be copied from Microsoft Excel and pasted into the table. After all data have been entered, plot and view the channel cross section looking downstream.
Manning's n is defined as shown in the figure below. An n value is assigned for each segment of the cross section beginning at the left (looking downstream) coordinate (below). If the n value is the same throughout the cross section, copy the n value by dragging the value from the first cell.