River Processes

The various process found along the courses of a river.

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Waterfalls (Fluvial Erosion)
A band of hard rock (whinstone) meets softer rock (limestone). Softer rock erodes more forming a step. Water speed increases, more erosive power. Undercut hard rock collapses, abrasion creating a plunge pool. A gorge forms with waterfall retreat.
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Rapids (Fluvial Erosion)
Relatively steep sections of the river with turbulent flow with several sections of hard rock. Similar formation to waterfalls.
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Potholes (Fluvial Erosion)
Small cylindrical hollows in the riverbed. Abrasion scrapes out holes as turbulent eddy currents swirl a river's bedload around in a circular motion.
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Braiding (Fluvial Deposition)
Occurs when a river carries lots of eroded sdiment. If the sediment becomes too heavy or river velocity drops, sediment is dropped. The river divides into winding channels to pass the sediment buildup and eventually reform as one channel.
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Flood Plains (Fluvial Deposition)
A river overflows and floods the flat land around it. Increase in the wetted perimeter/reduction in hydraulic radius causes increase in friction. Reduction in velocity of river. Fine silt is deposited on the flood plain.
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Levees (Fluvial Deposition)
Natural raised embankments either side of a river channel. During floods, material is deposited across flood plain (decreased velocity). Heavier material (sand, gravel) is dropped first nearer to river. Over time, material builds up on river bank.
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Deltas (Fluvial Deposition)
River reaches sea, velocity decreases. River deposits load, load builds up. Alluvium rises out of water and blocks channel path (eyots). River is forced to braid into distributaries to reach the sea. Three types of delta.
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Arcuate Delta (Deltas Continued)
Looks like a fan shape, arching out to sea from the river.
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Cuspate Delta (Deltas Continued)
Land around the mouth of the river justs out like an arrow into the sea.
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Bird's Foot Delta (Deltas Continued)
The river splits on the way to the sea, each part of the river juts into the sea like a bird's foot.
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Meanders (Fluvial Erosion and & Deposition)
Alternating pools (deep) and riffles (shallow) equally spread along river. Pools - more efficient/erosive. Riffles - Energy lost, friction. Max flow on one side of river. Turbulence at pools increased - helicoidal flow. Sediment on sides. Bends.
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Other cards in this set

Card 2

Front

Relatively steep sections of the river with turbulent flow with several sections of hard rock. Similar formation to waterfalls.

Back

Rapids (Fluvial Erosion)

Card 3

Front

Small cylindrical hollows in the riverbed. Abrasion scrapes out holes as turbulent eddy currents swirl a river's bedload around in a circular motion.

Back

Preview of the back of card 3

Card 4

Front

Occurs when a river carries lots of eroded sdiment. If the sediment becomes too heavy or river velocity drops, sediment is dropped. The river divides into winding channels to pass the sediment buildup and eventually reform as one channel.

Back

Preview of the back of card 4

Card 5

Front

A river overflows and floods the flat land around it. Increase in the wetted perimeter/reduction in hydraulic radius causes increase in friction. Reduction in velocity of river. Fine silt is deposited on the flood plain.

Back

Preview of the back of card 5
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