Friction with the river bed and banks can reduce the velocity of the river leading to deposition. 

Find out more about river deposition.

In the upper course, the channel is very narrow and very shallow. By the middle course, the channel becomes wider and deeper usually over 1 m. By the lower course, the channel becomes wider still and the channel is much deeper.

Find out more about the cross profile of a river.

Rapids are fast flowing, turbulent sections of the river where the bed has a relatively steep gradient. They are found in the upper course of the river.

Find out more about the landforms of erosion in the upper course of a river.

The transportation of dissolved chemicals. This varies along the river depending on the presence of soluble rocks.

Find out more about how rivers transport material.

Waterfalls and gorges are typically found in the upper course of the river.

Find out more about the landforms of erosion in the upper course of a river.