River erosion, transport and deposition Cambridge IGCSE Geography (9–1) revision
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In plain words
A river is a conveyor belt. It picks material up, carries it and puts it down again. Which of the three it is doing at any spot depends on how much energy it has.
7 things to know
- Erosion is the wearing away of the bed and banks. There are four processes.
- Hydraulic action: the force of the water breaks material from the bed and banks. Abrasion: the load carried by the river scrapes against the bed and banks and wears them away.
- Attrition: stones in the load knock against each other and become smaller and rounder. Solution: some rocks, such as limestone, are dissolved by the water.
- Transportation is the carrying of the load. Traction: large boulders are rolled along the bed. Saltation: small stones bounce along the bed.
- Suspension: fine particles are carried along within the water, making it look muddy. Solution: dissolved material is carried invisibly.
- Deposition happens when a river loses energy and drops its load: where it slows down, on the inside of bends, where it meets the sea, or when its discharge falls. The heaviest material is dropped first.
- A river erodes downwards (vertical erosion) in its upper course, and sideways (lateral erosion) lower down.
Worked example
Explain why the stones in a river are large and angular near the source, and small and rounded near the mouth.
- Near the source the stones have only just fallen into the river and have travelled a short distance.
- As they are carried downstream they knock against each other. This is attrition.
- Each knock breaks off sharp edges, so they become smaller and rounder the further they travel.
Tips and tricks
- Abrasion wears away the river's bed and banks. Attrition wears away the load itself. They are the pair most often confused.
- Name the process and then say how it works. The name alone usually earns one mark of two.
It lands in your notebook with its questions as flashcards.
River erosion, transport and deposition: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which process is the force of the water breaking material from the banks?
Water is forced into cracks and loosens material.
Which process makes the stones in a river smaller and rounder?
The stones knock against each other.
How are large boulders transported?
They are rolled along the bed.
How is fine silt transported?
It is carried within the water.
When does a river deposit its load?
Slower water can carry less.
What is saltation?
The stones are lifted and dropped again and again.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 10 marks. Write your answers on paper, then check them.
River erosion, transport and deposition
Cambridge IGCSE Geography (9–1) 0976 · 10 marks · papermunch.org
Name ______________________________ Date ______________
Describe two processes of river erosion.[4]
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Hydraulic action: the force of the moving water breaks material away from the bed and banks. Abrasion: stones carried by the river scrape and wear away the bed and banks.
Describe two ways in which a river transports its load.[4]
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Traction: large stones are rolled along the bed. Suspension: fine particles of silt and clay are carried within the water. (Also: saltation, solution.)
Explain why a river deposits material on the inside of a bend.[2]
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The water flows more slowly on the inside of a bend. It has less energy, so it can no longer carry its load.
Answers: River erosion, transport and deposition
- 1. Hydraulic action: the force of the moving water breaks material away from the bed and banks. Abrasion: stones carried by the river scrape and wear away the bed and banks.
- 2. Traction: large stones are rolled along the bed. Suspension: fine particles of silt and clay are carried within the water. (Also: saltation, solution.)
- 3. The water flows more slowly on the inside of a bend. It has less energy, so it can no longer carry its load.