Describe How, and Explain Why, Channel Characteristics Change Downstream. (15 Marks) Essay

385 WordsDec 15, 20132 Pages
Describe how, and explain why, channel characteristics change downstream. (15 marks) Channel characteristics are changed when the river flows downstream by many factors such as cross-profile of a river, wetted perimeter, erosion, hydraulic radius, roughness and efficiency. Channel characteristics change as the river flows from upstream to downstream. In the upper course the river tends to be more narrower, steep and uneven due to the deposition of large boulders it also has a larger wetted perimeter. The bank of the river channel becomes worn away as a result of vertical erosion, due to the processes of hydraulic action which is the forces of flowing water against the river bed and banks caused by the volume of flowing water compared to kinetic energy and attrition which is the material being carried in the river colliding which then breaks the loads down into smaller pieces. Also the velocity of the water in its upper course of the river is slower as more energy is needed in overcoming friction on the uneven channel. however as the river travels more downstream less vertical and more lateral erosion begins to take place, the process of erosion which takes place her is attrition which is the carrying an breaking of the load and also abrasion which is when the material collides and wears away the bed rock, resulting the the river channel becoming more smoother, an also during the mid course you are more likely to come across flood plains. The channel characteristics also change when going downstream as the roughness decreases meaning that features such as potholes cannot be formed as the bed load is too small due to erosion wearing it away and breaking it down in to more smaller and rounder particles. Also as result of traveling downstream the mid-course and lower course tend to be more efficient and also has a smaller wetted perimeter. The velocity of the
Open Document