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| {{short description|Processes associated with rivers and streams}}
| | #REDIRECT [[Fluvial sediment processes]] |
| [[File:Matanuska River 8727.JPG|right|thumb|Deep, eroding [[glaciofluvial deposit]]s alongside the [[Matanuska River]], [[Alaska]]]] | |
| In [[geography]] and [[geology]], '''fluvial processes''' are associated with [[river]]s and [[stream]]s and the [[Deposition (geology)|deposits]] and [[landform]]s created by them. When the stream or rivers are associated with [[glacier]]s, [[ice sheet]]s, or [[ice cap]]s, the term '''glaciofluvial''' or [[Fluvioglacial landform|fluvioglacial]] is used.<ref>{{cite book |url=https://store.americangeosciences.org/glossary-of-geology-fifth-edition-revised.html |editor-first1=Klaus K.E. |editor-last1=Neuendorf |editor-first2=James P. |editor-last2=Mehl James P..Jreditor-first3=Julia A. |editor-last3=Jackson |year=2011 |title=Glossary of Geology |publisher=American Geological Institute |location=Alexandria, Virginia |pages=800 |edition=5th revised |isbn=978-3642066214 |oclc=751527782}}</ref><ref>[https://books.google.com/books?id=if-PaNVS7cAC&pg=PA84&dq=fluvioglacial+definition&lr=&ei=KaQrSpnHMIncygTF_fScBw Wilson, W.E. & Moore, J.E. 2003. Glossary of Hydrology, American Geological Institute, Springer, 248pp.]</ref>
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| ==Fluvial processes==
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| [[File:ISS013-E-46370.jpg|thumb|The White River is so named due to the clay it picks up in the Badlands of South Dakota. Here it flows into the Missouri River and colors it with clay.]]
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| Fluvial processes include the [[sediment transport|motion of sediment]] and [[erosion]] or [[deposition (geology)|deposition]] on the [[river bed]].<ref>{{cite book|last=Charlton|first=Ro|title=Fundamentals of fluvial geomorphology|url=https://archive.org/details/fundamentalsfluv00char|url-access=limited|year=2008|publisher=Rutledge|location=London|isbn=978-0-415-33454-9|page=[https://archive.org/details/fundamentalsfluv00char/page/n274 234]}}</ref><ref>{{cite book|last=Wohl|first=Ellen|title=Rivers in the Landscape: Science and Management|year=2014|publisher=Wiley-Blackwell|isbn=978-1118414897|page=330}}</ref>
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| The movement of water across the [[stream bed]] exerts a [[shear stress]] directly onto the bed. If the [[Cohesion (geology)|cohesive]] strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow. In addition, if the river carries significant quantities of [[sediment]], this material can act as tools to enhance wear of the bed ([[abrasion (geology)|abrasion]]). At the same time the fragments themselves are ground down, becoming smaller and more rounded ([[Attrition (erosion)|attrition]]).
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| Sediment in rivers is transported as either [[bedload]] (the coarser fragments which move close to the bed) or [[suspended load]] (finer fragments carried in the water). There is also a component carried as dissolved material.
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| For each grain size there is a specific [[flow 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 [[Hjulström curve]].
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| 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]].
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| Even small streams make alluvial deposits, but it is in [[floodplain]]s and [[River delta|deltas]] of large rivers that large, geologically-significant alluvial deposits are found.
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| The amount of matter carried by a large river is enormous. It has been estimated that the [[Mississippi River]] annually carries 406 million tons of sediment to the sea,<ref>Mathur, Anuradha; Dilip da Cunha (2001). Mississippi Floods: Designing a Shifting Landscape. New Haven, CT: Yale University Press. {{ISBN|0-300-08430-7}}</ref> the [[Yellow River]] 796 million tons, and the [[Po River]] in [[Italy]] 67 million tons.<ref>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 {{Webarchive|url=https://web.archive.org/web/20180301093624/http://www.fao.org/docrep/009/t0377e/t0377e00.htm |date=2018-03-01 }}</ref> The names of many rivers derive from the color that the transported matter gives the water. For example, the [[Yellow River|Yellow River (Huang He)]] in [[China]] is named after the hue of the sediment it carries,<ref>{{Cite book |last1=MOSTERN |first1=RUTH |url=https://www.jstor.org/stable/j.ctv1vbd1d8 |title=The Yellow River: A Natural and Unnatural History |last2=HORNE |first2=RYAN M. |date=2021 |publisher=Yale University Press |isbn=978-0-300-23833-4 |pages=33 |doi=10.2307/j.ctv1vbd1d8.7|jstor=j.ctv1vbd1d8 }}</ref> and the [[White Nile]] is named for the clay it carries.
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| ==See also==
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| * [[Body of water]]
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| ===Fluvial processes===
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| {{div col}}
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| *{{annotated link|Bradshaw model}}
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| *{{annotated link|Corrosion}} (solution)
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| *{{annotated link|Erosion}}
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| **{{annotated link|Downcutting}}
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| *{{annotated link|Saltation (geology)}}
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| *{{annotated link|Suspension (chemistry)}}
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| {{end div col}}
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| ===Fluvial channel patterns===
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| {{div col}}
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| *{{annotated link|Anastomosis}}
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| *{{annotated link|Braided river}}
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| *{{annotated link|Channel pattern}}
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| *{{annotated link|Meander|Meandering river}}
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| {{end div col}}
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| ===Fluvial landforms===
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| {{Div col}}
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| *{{annotated link|Channel (geography)}}
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| *{{annotated link|Confluence}}
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| *{{annotated link|Cut bank}}
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| *{{annotated link|Crevasse splay}}
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| *{{annotated link|Drainage basin}} (watershed)
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| *{{annotated link|Esker}}
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| *{{annotated link|Floodplain}}
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| *[[Fluvial landforms of streams]]
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| *{{annotated link|Fluvial terrace}}
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| *{{annotated link|Canyon}} (Gorge)
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| *{{annotated link|Gully}}
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| *{{annotated link|Island}}
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| *{{section link|Levee|Natural levees}}
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| *{{annotated link|Meander}}
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| *{{annotated link|Oxbow lake}}
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| *{{annotated link|Pendant bar}}
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| *{{annotated link|Plunge pool}}
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| *{{annotated link|Point bar}}
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| *{{annotated link|Riffle}}
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| *{{annotated link|River}}
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| *{{annotated link|River delta}}
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| *{{annotated link|River island}}
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| *{{annotated link|River valley|aka=vale}}
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| *{{annotated link|Shoal|aka=bar}}
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| *{{annotated link|Spring (hydrology)}}
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| *{{annotated link|Stream}}
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| *{{annotated link|Stream pool}}
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| *{{annotated link|Waterfall}}
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| *{{annotated link|Yazoo stream}}
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| {{div col end}}
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| ===Related terms===
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| *[[wiktionary:lacustrine|lacustrine]] – of or relating to a [[lake]]
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| *[[wiktionary:maritime|maritime]] – of or relating to a [[sea]]
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| *[[wiktionary:oceanic|oceanic]] – of or relating to an [[ocean]]
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| *[[wiktionary:palustrine|palustrine]] – of or relating to a [[marsh]]
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| ==References==
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| {{reflist}}
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| {{Sediment transport}}
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| [[Category:Hydrology]]
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| [[Category:Fluvial landforms| ]]
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| [[Category:Sedimentology]]
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| [[Category:Geomorphology]]
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