Fundamentals of Fluvial Geomorphology and Channel Processes
Figure 2.6 Typical Plan and Cross Sectional View of Pools and Crossings
calculated by dividing the cross section area by the channel width. The hydraulic radius (r),
which is important in hydraulic computations is defined as the cross sectional area divided by
the wetted perimeter. In wide channels with w/d greater than about 20 the hydraulic radius
and the mean depth are approximately equal. The conveyance, or capacity of a channel is
related to the area and hydraulic radius and is defined as AR2/3.
Channel Bars. Channel bars are depositional features that occur within the channel.
The size and location of bars are related to the sediment transport capacity and local geometry
of the reach. The enlargement of a bar generally results in caving of the opposite banks in
order to maintain conveyance of the discharge. The primary types of bars are point bars,
middle bars, and alternate bars.
Point bars form on the inside (convex) bank of bends in a meandering stream. A
typical point bar is shown in Figure 2.3. The size and shape of the point bar are determined
by the characteristics of the flow. The development of a point bar is partially due to the flow