River Processes

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River Processes
Erosion
Involves the breaking and wearing away of rock and soil along the river bed and
banks
Also involves the breaking down of rock particles being carried downstream by the
river
Main types
Hydraulic action the force of the river against the banks causes air to be trapped in
cracks and crevices . The pressure weakens the banks and gradually wears it away
Abrasion rocks carried along by the river wear down the bed and banks
Attrition rocks being carried by the river smash together and break into smaller,
smoother and rounder particles
Solution soluble particles are dissolved in water
Transport
Solution minerals are dissolved in the water and carried along in solution
Suspension fine, light material is carried along in the water
Saltation small pebbles are bounced along the river bed
Traction large boulders and rocks are rolled along the river bed
Rivers need energy to transport materials, and levels of energy change as the river moves
from source to mouth
When energy levels are high, large rocks and boulders can be transported.
Energy levels are usually higher near a rivers source , when its course is steep and
its valley narrow. Energy levels rise much higher in times of flood
When energy levels are low, only small particles can be transported. Energy
levels are lowest when velocity drops as a river enters a lake or sea (mouth)
Deposition
When a river loses energy, it will drop or deposit some of the material it is
carrying
Deposition may take place when a river enters an area of shallow water or when
the volume of water decreases e.g. after a flood or in times of drought
It is common towards the end of a river's journey at the mouth
Deposition can form deltas e.g. the Nile Delta

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