Fluvial: Wikis

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Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used.[1][2]

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Fluvial processes

Fluvial processes comprise the motion of sediment and erosion of or deposition (geology) on the river bed.

Erosion by moving water happens in two ways. First, the movement of water across the bed has an effect (This is called hydraulic action). Second, the sediment being transported in the river wears away the bed (Abrasion) and the fragments themselves are ground down becoming smaller and more rounded (Attrition).

The sediment is transported as either bedload (The coarser fragments which move close to the bed) and the suspended load (Finer fragments carried in the water). There is also a component carried as dissolved material.

For each grain size there is a specific velocity at which the grains start to move, called Entrainment velocity. However the grains will continue to be transported even if the velocity falls below the entrainment velocity due to the reduced (or removed) friction between the grains and the river bed. Eventually the velocity will fall low enough for the grains to be deposited. This is shown by the Hjulstrøm curve. A river is continually picking up and dropping solid particles of rock and soil from its bed throughout its length. Where the river flow is fast, more particles are picked up than dropped. Where the river flow is slow, more particles are dropped than picked up. Areas where more particles are dropped are called alluvial or flood plains, and the dropped particles are called alluvium.

Even small streams make alluvial deposits, but it is in the flood plains and deltas of large rivers that large, geologically-significant alluvial deposits are found.

The amount of matter carried by a large river is enormous. The names of many rivers derive from the color that the transported matter gives the water. For example, the Huang He in China is literally translated "Yellow River", and the Mississippi River in the United States is also called Big Muddy. It has been estimated that the Mississippi River annually carries 406 million tons of sediment to the sea,[3] the Huang He 796 million tons, and the Po River in Italy 67 million tons.[4]

See also

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Fluvial processes

This is also related to multistory deposits

Fluvial Channel Patterns

Fluvial landforms

References

  1. ^ K.K.E. Neuendorf, J.P. Mehl, Jr., and J.A. Jackson, eds., 2005, Glossary of Geology. American Geological Institute, Alexandria, Virginia. 800 pp.
  2. ^ Wilson, W.E. & Moore, J.E. 2003. Glossary of Hydrology, American Geological Institute, Springer, 248pp.
  3. ^ Mathur, Anuradha; Dilip da Cunha (2001). Mississippi Floods: Designing a Shifting Landscape. New Haven, CT: Yale University Press. ISBN 0-300-08430-7
  4. ^ Dill, William A. (1990). Inland fisheries of Europe. Rome, Italy: UN Food and Agriculture Organization. ISBN 92-5-102999-7. http://www.fao.org/docrep/009/t0377e/t0377e00.htm

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