Theoretical Background
Theoretical background
Upper course
The source of the river is normally found in an area of high ground. The river usually flows through a steep V-shaped valley. Most of the erosion that occurs in the upper course is vertical and as the river bed is eroded lower the valley becomes steeper. The river is narrow with a shallow channel. As discharge is calculated by measuring the cross sectional area of the channel multiplied by the velocity, the discharge is small. The river is mainly slow flowing as most of its energy is used overcoming the friction of the large angular bedload. The bedload is large and angular as it hasn’t been subjected too much erosion. Any changes to the direction of the river are a result of interlocking spurs as the water wants to follow the path of least resistance. The main feature seen in the upper course is the waterfall.
Waterfall
This forms when a layer of harder rock lies over a layer of softer rock. The softer rock erodes quicker and a step forms. Hydraulic action and abrasion deepens the step and a waterfall forms. The erosion makes a plunge pool and the hard rock hangs over the plunge pool. When the hard rock becomes unstable it falls and the waterfall moves backwards. This process repeated can lead to a gorge forming.
Middle course
The middle course usually has a gentle gradient and is in a sloping valley. The river is wider and has a deeper channel as more lateral erosion has occurred. The velocity is greater than that of the upper course as there is a greater volume of water in the river (because of tributaries flowing into the river and surface run off) and less energy is used overcoming the lesser friction of the smoother less angular bedload. There is more transportation of material, and more suspended sediment. The bedload is smaller and more rounded as it has been subjected to more erosion (namely attrition or corrosion). The main feature seen is the meander.
Meander
These are bends that form when the slope of a river
Upper course
The source of the river is normally found in an area of high ground. The river usually flows through a steep V-shaped valley. Most of the erosion that occurs in the upper course is vertical and as the river bed is eroded lower the valley becomes steeper. The river is narrow with a shallow channel. As discharge is calculated by measuring the cross sectional area of the channel multiplied by the velocity, the discharge is small. The river is mainly slow flowing as most of its energy is used overcoming the friction of the large angular bedload. The bedload is large and angular as it hasn’t been subjected too much erosion. Any changes to the direction of the river are a result of interlocking spurs as the water wants to follow the path of least resistance. The main feature seen in the upper course is the waterfall.
Waterfall
This forms when a layer of harder rock lies over a layer of softer rock. The softer rock erodes quicker and a step forms. Hydraulic action and abrasion deepens the step and a waterfall forms. The erosion makes a plunge pool and the hard rock hangs over the plunge pool. When the hard rock becomes unstable it falls and the waterfall moves backwards. This process repeated can lead to a gorge forming.
Middle course
The middle course usually has a gentle gradient and is in a sloping valley. The river is wider and has a deeper channel as more lateral erosion has occurred. The velocity is greater than that of the upper course as there is a greater volume of water in the river (because of tributaries flowing into the river and surface run off) and less energy is used overcoming the lesser friction of the smoother less angular bedload. There is more transportation of material, and more suspended sediment. The bedload is smaller and more rounded as it has been subjected to more erosion (namely attrition or corrosion). The main feature seen is the meander.
Meander
These are bends that form when the slope of a river