Fluvial Landforms (AQA GCSE Geography): Revision Note
Exam code: 8035
Erosion Landforms
River landscape characteristics
The changes in river channel characteristics, lead to changes in the river landscape
The upland and lowland areas of rivers have distinctive landforms
Upland:
Waterfalls
Gorges
V-shaped valleys
Interlocking spurs
These are landforms created through erosion
Waterfalls and gorges
Waterfalls form where there is a drop in the river bed from one level to another
This drop is often due to changes in the hardness of the rock, where hard rock overlies soft rock
Hydraulic action and abrasion are the main erosional processes:
The soft rock erodes more quickly, undercutting the hard rock and creating a plunge pool
This leads to the development of an overhang of hard rock which eventually over time, collapses
The overhang falls into the plunge pool increasing abrasion and making the plunge pool deeper
The process then begins again and the waterfall retreats upstream leaving a steep sided gorge
V-shaped valleys
Vertical erosion is dominant in the upper course of the river
This cuts down into the river bed and deepens the river channel
Weathering and mass movement leads to material from the valley sides collapsing into the river forming a steep v-shaped valley
Interlocking spurs
In the upper course of the river the channel starts to meander
Erosion happens on the outside of the bend
In the upland areas this forms interlocking spurs
Worked Example
Study Figure 1, a photograph showing some features of a river in the Lake District
Explain how the landforms shown in Figure 1 are created by physical processes
[6 marks]
Answer:
Waterfalls and gorges such as the one shown in Figure 18 are often formed where a river flows over hard rock that lies over an area of softer rock.[U] In Figure 18, the soft rock is eroded more rapidly than the hard rock due to the sheer force of the water hitting the rocks through hydraulic action and also by rocks scraping the banks and bed due to abrasion. [Ap] This leads to undercutting of the hard rock, which forms an overhang. [U] Eventually, because the overhang is unsupported, it breaks up and falls into the plunge pool, which forms at the bottom of the waterfall. [U] The material increases the amount of abrasion and deepens the plunge pool. [U] This process is repeated again and again, meaning that the waterfall retreats upstream, leaving behind the steep sided gorge as shown in Figure 18. [Ap]
Marking guidance
This is a 'Level of response' answer.
Each point made in the answer does not equal a mark.
The command is 'explain your answer' which means the answer needs to
Mark allocation
3 marks for understanding [U]
3 marks for application [Ap]
Common errors
The following errors mean that answers cannot achieve a Level 3 (top marks):
Identification of only one landform (maximum 4 marks, Level 2). The question asks for an explanation of 'landforms'.
References to landforms, such as interlocking spurs, not shown in the photograph, receive no credit.
Alternative content
The answer above is just one example of a response to this question. Other information which could be used in the answer includes:
Formation of rapids.
Examiner Tips and Tricks
Reading the question carefully is essential. It is very easy to misread it and assume the question only requires an explanation of one landform when it needs you to write about at least two landforms.
Landforms of erosion and deposition
Some landforms are created through a combination of erosion and deposition including:
Meanders
Ox-bow lakes
Meanders
In lowland areas lateral erosion is dominant
Meanders increase in size
The fastest water flow (thalweg) is on the outside of the river bends, leading to erosion:
The erosion undercuts the riverbank forming a river cliff
The riverbank collapses and the edge of the meander moves further out
The slowest flow is on the inside of the river bends, leading to deposition:
The deposits form a slip-off slope
Deposition on one side and erosion on the other leads to the meander migrating across the valley
Oxbow lakes
With distance downstream the size of the meanders increase
The erosion on outside bends can eventually lead to the formation of a meander neck
At a time of the flood, the river may cut through the neck of the meander forming a straighter course for the water
The flow of water at entry and exit from the meander will be slower, leading to deposition
The meander becomes cut off from the main river channel, forming an oxbow lake
Oxbow lake formation
Examiner Tips and Tricks
Remember when describing the formation of oxbow lakes it is important to state that the river will break through the neck of the meander during a flood. At other times the river does not have enough power to break through.
Worked Example
Explain the formation of an ox-bow lake.
[4 marks]
Answer:
A meander is a winding curve [K] in a river where water flows fastest on the outer bend of the river [K] where there is less friction leading to erosion forming a river cliff [U] the flow on the inside of the bend is slower leading to deposition forming a slip off slope. [U] The neck of the meander narrows and then during flood conditions the river breaks through with the river taking the shortest route. [K] Deposition then occurs at the edges of the new straight section and cuts of the old meander forming an ox-bow lake. [U]
Marking guidance
This is a 'Level of response' answer.
Each point made in the answer does not equal a mark.
The command word is 'explain' which means the answer needs to outline how and why physical and human factors increase the risk of flooding.
Mark allocation
3 marks for knowledge [K]
3 marks for understanding [U]
Common errors
The following errors mean that answers cannot achieve a Level 2 (top marks):
Not correctly outlining the sequence.
No reference to the processes.
Examiner Tips and Tricks
It is important when describing the formation of landforms that you correctly outline the sequence. To revise this try writing out as a flow chart or numbered steps. Putting the information into a different format will help you remember it.
Depositional landforms
Floodplains and levees
Floodplains are flat expanses of land on either side of the river
The migration of meanders leads to the formation of the floodplain
High discharge may cause the river to overflow the banks
More of the water is in contact with the land surface as the water spreads across the floodplain
Increased friction reduces velocity and material is deposited across the floodplain gradually increasing the floodplain height
The heaviest material is deposited first nearest to the river channel forming natural embankments called levees
Estuaries
An estuary is where the river meets the sea
Large deposits of sediment form mudflats and salt marshes
These are the result of the interaction between the river and tides
Incoming tides bring in sediment which mixes with the sediment being carried by the river
When the incoming tide of salt water meets the freshwater of the river, the river velocity decreases and deposition occurs
The deposited sediment builds up in layers to form mudflats which rise above the water surface, particularly at low tide
Eventually the vegetation starts to grow on the mudflats and form salt marshes
Worked Example
Explain how river levées are formed.
[4 marks]
Answer:
Levées are found in the lower course of the river and are long, raised embankments adjacent to the river. [K] When the river floods, friction reduces the velocity and leads to deposition [U] The largest material is deposited first and the finer material further away. [K] After many floods, the larger sediment builds up to form embankments which are higher than the surrounding floodplain. [U]
Marking guidance
This is a 'Level of response' answer.
Each point made in the answer does not equal a mark.
The command word is 'explain' which means the answer needs to outline how and why levées form.
Mark allocation
2 marks for knowledge [K]
2 marks for understanding [U]
Examiner Tips and Tricks
In revision, many students focus on the formation of waterfalls and meanders/oxbow lakes. It is important to revise landforms from all sections of the river course, including levées and floodplains.
Case study: River Tees
The River Tees is located in north-east England
It is 85 miles from source to mouth
It flows eastwards from the source in the Pennines to the mouth where it flows into the North Sea
Landforms of erosion
High Force waterfall is the highest waterfall in England
High Force formed where dolerite, a hard igneous rock (known locally as 'whinstone') lays over a softer sedimentary rock, limestone
The water erodes the limestone more quickly, undercutting the hard dolerite
Eventually the dolerite falls because it is unsupported and the process starts again
The retreat of the waterfall upstream as a result of this process has left behind a steep sided gorge
Landforms of erosion and deposition
In the middle and lower sections of the River Tees the river flows over flat, low-lying land
Meanders form such as in the area to the south-east of Darlington
Landforms of deposition
In the middle and lower sections floodplains and levées also form as a result of repeated flooding of the areas
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