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River landforms - Coggle Diagram
River landforms
Levees
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When river floods over its banks, velocity is reduced
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Course (heavier) sediment is deposited first, traps smaller sediment
With more and more flooding, deposited sediment raises the river banks - reduces flooding
Waterfalls
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Weaker rock is eroded faster, creates steep gradient between hard and soft rock
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More soft rock is eroded so plunge pool gets bigger by mainly hydraulic action and abrasion) causing overhand of hard rock. Back wall of waterfall also erodes.
Meanders
Fast flowing water swings around the outside bend of a meander, erodes bank and forms river cliff (water is deep)
On inside bend, velocity is low, sediment is deposited, forming slip-off slope
Riffles
Shallow areas associated with straighter sections of rivers in-between meanders. Have rocky beds and turbulent flow due to friction
Pools
Deeper areas associated with meanders bends. Finer sediment and less turbulent flow die to smoother river bed.
Floodplains
Area on each side of a river, prone to flooding
When river floods, water containing large quantities of alluvium (river silt) pours out onto the flat valley floor
The water soaks away, leaving the deposited sediment behind
Over 100's of years, repeated flooding cause thick alluvial deposit that is fertile and often used for farming
Oxbow lakes
Meander bends become large, ends of the meander bend become closer and meander neck narrows.
River floods, river cuts through the neck of river to take shorter route and creates new channel.
Old bend is cut of from main channel and eventually forms oxbow lake until continued deposition of sediment carries on.
V-shaped valleys
Near source of river, water is shallow and there is a lot fo friction between the water and the river bed
Rocks beneath river are eroded, leads to steeper gradient - makes water descend quickly giving it energy to erode river bed further
Gorges
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The softer rock is eroded, eventually the hard rock overhand becomes to heavy and drops into plunge pool