Compare the cross profile of the upper and lower courses of a typical riverWatch
Compare the cross profile of the upper and lower courses of a typical river and explain why this occurs. [6 marks]
In the upper course of a river the cross-profile valley is narrow and steep-sided due to vertical erosion by the river combined with weathering and mass movement of valley slopes. In addition, the river is narrow and shallow because the river is less powerful and discharge is relatively low. The lower course of a river has an almost flat valley floo. Much of the valley floor is sediment deposited by the river due to a lower velocity in the lower course accounting for its flatness. In the lower course the river is wide and deep as river tributaries join the river and with more power and energy it is able to erode the channel making it wider and deeper.