A stream bed or streambed is the bottom of a stream or river (bathymetry) or the physical confine of the normal water flow (channel). The lateral confines or channel margins are known as the stream banks or river banks, during all but flood stage. Under certain conditions a river can branch from one stream bed to multiple stream beds.[1] A flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is the part of the channel up to the normal water line, and the banks are that part above the normal water line. However, because water flow varies, this differentiation is subject to local interpretation. Usually, the bed is kept clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages and therefore might support vegetation some or much of the time.
A woman digs in a dry stream bed in Kenya to find water during a drought.
The nature of any stream bed is always a function of the flow dynamics and the local geologic materials, influenced by that flow. With small streams in mesophytic regions, the nature of the stream bed is strongly responsive to conditions of precipitationrunoff. Where natural conditions of either grassland or forest ameliorate peak flows, stream beds are stable, possibly rich, with organic matter and exhibit minimal scour. These streams support a rich biota. Where conditions produce unnatural levels of runoff, such as occurs below roads, the stream beds will exhibit a greater amount of scour, often down to bedrock and banks may be undercut. This process greatly increases watershed erosion and results in thinner soils, upslope from the stream bed, as the channel adjusts to the increase in flow. The stream bed is very complex in terms of erosion. Sediment is transported, eroded and deposited on the stream bed.[2] The majority of sediment washed out in floods is "near-threshold" sediment that has been deposited during normal flow and only needs a slightly higher flow to become mobile again. This shows that the stream bed is left mostly unchanged in size and shape.[3]
Beds are usually what would be left once a stream is no longer in existence; the beds are usually well preserved even if they get buried, because the walls and canyons made by the stream usually have hard walls, usually soft sand and debris fill the bed. Dry stream beds are also subject to becoming underground water pockets (buried stream beds only) and flooding by heavy rains and water rising from the ground and may sometimes be part of the rejuvenation of the stream.
^Jerolmack, Douglas J.; Mohrig, David (2007). "Conditions for branching in depositional rivers". Geology. 35 (5): 463–466. Bibcode:2007Geo....35..463J. doi:10.1130/G23308A.1.
^Garcia, Marcelo; Parker, Gary (1991). "Entrainment of Bed Sediment into Suspension". Journal of Hydraulic Engineering. 117 (4): 414–435. doi:10.1061/(asce)0733-9429(1991)117:4(414).
^Phillips, Colin B.; Jerolmack, Douglas J. (2016). "Self-organization of river channels as a critical filter on climate signals". Science. 352 (6286): 694–697. Bibcode:2016Sci...352..694P. doi:10.1126/science.aad3348. PMID 27151865.
External links
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May 15, 2023
stream, riverbed, redirects, here, other, uses, riverbed, disambiguation, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sou. Riverbed redirects here For other uses see Riverbed disambiguation This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Stream bed news newspapers books scholar JSTOR February 2017 Learn how and when to remove this template message A stream bed or streambed is the bottom of a stream or river bathymetry or the physical confine of the normal water flow channel The lateral confines or channel margins are known as the stream banks or river banks during all but flood stage Under certain conditions a river can branch from one stream bed to multiple stream beds 1 A flood occurs when a stream overflows its banks and flows onto its flood plain As a general rule the bed is the part of the channel up to the normal water line and the banks are that part above the normal water line However because water flow varies this differentiation is subject to local interpretation Usually the bed is kept clear of terrestrial vegetation whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages and therefore might support vegetation some or much of the time A stream bed armored with rocksThe old bed of the Mississippi River near Kaskaskia Illinois left behind after the river shifted A woman digs in a dry stream bed in Kenya to find water during a drought The nature of any stream bed is always a function of the flow dynamics and the local geologic materials influenced by that flow With small streams in mesophytic regions the nature of the stream bed is strongly responsive to conditions of precipitation runoff Where natural conditions of either grassland or forest ameliorate peak flows stream beds are stable possibly rich with organic matter and exhibit minimal scour These streams support a rich biota Where conditions produce unnatural levels of runoff such as occurs below roads the stream beds will exhibit a greater amount of scour often down to bedrock and banks may be undercut This process greatly increases watershed erosion and results in thinner soils upslope from the stream bed as the channel adjusts to the increase in flow The stream bed is very complex in terms of erosion Sediment is transported eroded and deposited on the stream bed 2 The majority of sediment washed out in floods is near threshold sediment that has been deposited during normal flow and only needs a slightly higher flow to become mobile again This shows that the stream bed is left mostly unchanged in size and shape 3 Beds are usually what would be left once a stream is no longer in existence the beds are usually well preserved even if they get buried because the walls and canyons made by the stream usually have hard walls usually soft sand and debris fill the bed Dry stream beds are also subject to becoming underground water pockets buried stream beds only and flooding by heavy rains and water rising from the ground and may sometimes be part of the rejuvenation of the stream See also EditArmor hydrology Benthic zone Hyporheic zone ThalwegReferences Edit Jerolmack Douglas J Mohrig David 2007 Conditions for branching in depositional rivers Geology 35 5 463 466 Bibcode 2007Geo 35 463J doi 10 1130 G23308A 1 Garcia Marcelo Parker Gary 1991 Entrainment of Bed Sediment into Suspension Journal of Hydraulic Engineering 117 4 414 435 doi 10 1061 asce 0733 9429 1991 117 4 414 Phillips Colin B Jerolmack Douglas J 2016 Self organization of river channels as a critical filter on climate signals Science 352 6286 694 697 Bibcode 2016Sci 352 694P doi 10 1126 science aad3348 PMID 27151865 External links Edit Media related to Stream beds at Wikimedia Commons Retrieved from https en wikipedia org w index php title Stream bed amp oldid 1121428747, wikipedia, wiki, book, books, library,
