Rivers

geography

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  • Created by: Emma
  • Created on: 29-04-10 17:52

Hjulstrom curve

  • the top part of the curve are the particles that are eroded and transported.
  • the middle of the curve is the particles that are transported and already eroded.
  • the bottom part of the curve are particles are deposited,
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Upper Stage

Upper stage valleys are steep V shapes. vertical erosion creates narrow valley floors and steeply sloped sides.

EROSION

mainly vertical and by abrasion. Erosion occurs when there are high energy conditions and discharge are high after heavy rain or ice melt. the rough channel causes turbulence and the large angular bedload is dragged along the river bed causing intense downwards erosion.

TRANSPORTATION

Mainly large particles such as boulders carried by traction or saltation during high energy conditions.

DEPOSITION

little deposition-

mainly largest particles deposited in the river as energy levels drop

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Middle Stage

Middle stage valleys are wider caused by lateral erosion. deposition creates a flood plain on the valley floor.

EROSION

Mainly lateral and by abrasion, Attrition of larger particles in this stage means that sediment particle size decreases from source to mouth.

TRANSPIRATION

More materail carried in suspension as particle size decreases. some larger particles are moved by saltation.

DEPOSITION

Sand and gravel are deposited across the flood plain as the river floods ad friction reduces the river's energy.

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lower Stage

Lower stage valleys are wide with gently sloping sides. There's a much wider flood plain cause by deposition.

EROSION

althought the velocity and discharge are highest in this stage, there's less erosion because the turbulence is lower and sediment particle size is reduced. some lateral erosion occurs during the formation of meanders.

TRANSPORTATION

Mainly smaller particles such as silt and clay carried by suspension or substances carried in solution.

DEPOSITION

Smaller particles such as sand silt and clay are deposited on the flood plain when the river floods and in the river mouth as the sea absorbs river energy.

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