Rivers: Explaining how Transportation, Erosion and Deposition can Change with Distance Downstream Flashcards
Describe and explain how the processes of erosion, transportation and deposition can change with distance downstream: (6 marks)
In the upper course erosion is the main process, especially vertical erosion due to gravitational potential energy, so that steep v-shaped valleys are created. Load is mainly transported by traction as large boulders are rolled along the river bad whilst saltation means that smaller particles bounce along the river bed.
Moving to the middle course, the change from gravitational potential energy to kinetic energy means that the river can transport more load. Much of this load is transported by saltation and suspension, which is where smaller particles are carried by the river water. In addition, the river will begin to erode laterally rather than vertically creating meanders. Larger material will be deposited on the inside of meanders where the river has less energy.
In the lower course the river has a high discharge and lots of kinetic energy due to the water given to the main river from its tributaries. This means the river carries lots of dissolved load through the process of solution. Deposition becomes the main process when the river spills onto the surrounding floodplain consequently it loses energy and fine clays and alluvium are deposited.
