The rivers energy is focused on the river bed (vertical erosion).
As it gets deeper the valley sides are worn away through weathering.
This leaves steep valley sides, creating the V-shape.
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Interlocking Spurs- upper course
'Pairs' of highland left either side of the valley.
These are created as the river winds around areas of harder rock to find the easiest route.
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Waterfall Diagram- upper course
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Waterfalls- upper course
A waterfall will form where hard rock overlays softer rock.
The river will erode the softer rock quicker, creating a 'step' in the river bed.
The water will then fall vertically from the hard rock to the soft rock below.
The hard rock is under cut, meaning it loses support and overhangs the drop.
Splash back causes hydraulic action to erode the rocks behind the fall of the water.
Hydraulic action and abrasion cause a plunge pool to form where water and load swirl around, eroding the rock futher.
The overhanging hard rock collapses into the plunge pool.
As the undercutting continues, a new overhang is created and the process repeats.
The waterfall retreats upstream leaving behind a gorge.
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Gorges- upper course
As the waterfall retreats upstream, it leaves a steep sided valley downstream called a gorge.
Every time the overhanging rock breaks off, the gorge retreats and grows longer.
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Meanders Diagram- middle course
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Meanders- middle course
The current is faster on the outside of the bend because the river channel is deeper (there's less friction to slow the water)
Therefore, more erosion takes place on the outside of the bend, forming river cliffs.
The current is slower on the inside of the bend because the river channel is shallower (there's more friction to slow the water down)
So eroded material is deposited on the inside of the bend, forming slip-off slopes.
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Ox-bow Lakes- middle course
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Ox-bow Lakes- middle course
Erosion causes the outside bends to get closer until there's only a small bit of land left between the bends (called the neck).
The river breaks through this land, usually during a flood, and the river flows along the shortest course.
Deposition eventually cuts off the meander forming an ox-bow lake.
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Flood Plains- lower course
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Flood Plains- lower course
The flood plain is the wide valley floor on either side of a river which occasionally gets flooded.
When a river floods onto the flood plain, the water slows down and deposits the eroded material that it's transporting. This builds up the flood plain (makes it higher).
Meanders migrate (move) across the flood plain, making it wider.
The deposition that happens on the slip-off slopes of meanders also builds up the flood plain.
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Levees- lower course
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Levees- lower course
Natural embankmets (raised areas) along the edges of a river channel.
During a flood, eroded material is deposited over the whole flood plain
The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down.
Over time, the deposited material builds up, creating levees along the edges of the channel, e.g. along the Yellow River in China
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