River efficiency coursework

A key influencing factor is the long river profile, illustrated in the diagram to the right. The long profile is a graph of a river that marks the change in altitude from the upper course to its lower course. All along its course, the river uses energy to carry out erosion, transport and deposition of sediment.

The river is less efficient. In the middle and lower course the channel becomes larger and smoother (less rough), this makes the river more efficient. The wetted perimeter is proportionately smaller than the amount of discharge in the channel. Therefore there is less friction to reduce velocity.

In more traditional text books the river in its three sections, has been characterised as having a dominant role or function. Namely in the upper course, the river is eroding bedrock. In the middle course the river is thought to be transporting this eroded material and in the lower course, the river's transported bedload is deposited.

The ability of the river to transport bedload depends on a number of factors, primarily its energy, but of course discharge and average velocity are closely related. Hydrologists use the term channel efficiency to describe the river's ability to transport bedload and discharge. Hydraulic radius is a measure of channel efficiency.