AQA AS Geography Rivers: Erosion, Transportation and Deposition

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Preview of AQA AS Geography Rivers: Erosion, Transportation and Deposition

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Erosion
The energy of a river flowing downhill causes erosion.
The bed and bands of a river can be eroded ­ making the river longer, deeper and wider.
Headward Erosion Vertical Erosion Lateral Erosion
Makes the river longer. Makes the river deeper. Makes the river wider.
Happens near a river's Happens in the upper Happens in the middle
source as throughflow stages of a river. and lower stages of the
and surface runoff river.
cause erosion at the
point the water enters
the river channel.
There are 4 ways in which river erosion happens:
Hydraulic Action The force of water that hits river banks, and then pushes water
into cracks.
Air becomes compressed, pressure increased and the riverbank
may, in time collapse.
Abrasion (corrasion) When a river picks up material and then rubs it against its bed
and banks.
Erosion occurs by the process of abrasion, and is most effective
during times of flood.
It is the main method of both vertical and horizontal erosion.
Attrition Boulders collide with one another as they move down the river,
and can break into smaller pieces.
Over time rocks become more rounded in appearance.
Corrosion (solution) Occurs where rocks dissolve in water by a chemical process and
are carried away

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Transportation
Transportation is the process of eroded material being carried in a river.
The velocity of a river provides the energy needed for it to transport eroded material.
The eroded material carried in a river is called its load.
It can be carried in 4 ways:
Solution Substances that can dissolve are carried
along in the water
Suspension Very small particles of clay and silt are
carried in suspension.
The larger the amount of turbulence and
velocity the more particles that can be
picked up.…read more

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Deposition
Deposition happens when the river loses energy.
When it slows down, it loses energy and drops some of its load.
The speed and energy of a river can be reduced in many ways:
Reduced rainfall Causes lower discharge
The river slows down and has less energy
Increased evaporation Causes lower discharge
Friction In shallow areas and areas close to the
banks, friction is at its greatest.…read more

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