create at least 10 minutes of travel time
over its length . Example sections of four
basic channel and swale types are shown
on Figure 330-31 . Design charts for trapezoidal
sections with 2 :1 side slopes are
shown as Figures 330-32 through 330-34.
Bottom widths should not be wider than 1
800 mm (6 ft) to prevent braiding at low
flows . Other shapes, side slopes and bottom
widths can be designed using a computer
model to solve Manning's Equation .