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A '''streambed''' or '''stream bed''' is the bottom of a [[stream]] or [[river]] ([[bathymetry]]) and is confined within a [[Stream channel|channel]], or the banks (sides) of the waterway.<sup>[1]</sup> Usually, the bed is kept clear of terrestrial [[vegetation]] and instead supports different types of aquatic vegetation ([[aquatic plant]]), depending on the type of streambed material and water velocity. Streambeds 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 banks and canyons made by the stream are usually harder. Soft sand and debris often fill the bed. Dry, buried stream beds can actually be underground water pockets <ref name=":1">{{Cite web |title=Below sandy, dry riverbeds: A medicine against drought |url=https://www.un-ihe.org/below-sandy-dry-riverbeds-medicine-against-drought |access-date=2023-06-08 |website=www.un-ihe.org |language=English}}</ref>. During times of rain, sandy streambeds can soak up at retain water, even during dry seasons, keeping the water table close enough to the surface to be obtainable by local people.<ref name=":1" />
A '''streambed''' or '''stream bed''' is the bottom of a [[stream]] or [[river]] ([[bathymetry]]) and is confined within a [[Stream channel|channel]], or the banks (sides) of the waterway.<sup>[1]</sup> Usually, the bed is kept clear of terrestrial [[vegetation]] and instead supports different types of aquatic vegetation ([[aquatic plant]]), depending on the type of streambed material and water velocity. Streambeds 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 banks and canyons made by the stream are usually harder. Soft sand and debris often fill the bed. Dry, buried stream beds can actually be underground water pockets <ref name=":1">{{Cite web |title=Below sandy, dry riverbeds: A medicine against drought |url=https://www.un-ihe.org/below-sandy-dry-riverbeds-medicine-against-drought |access-date=2023-06-08 |website=www.un-ihe.org |language=English}}</ref>. During times of rain, sandy streambeds can soak up at retain water, even during dry seasons, keeping the water table close enough to the surface to be obtainable by local people.<ref name=":1" />


The nature of any streambed is always a function of the flow dynamics and the local geologic materials. The climate of an area will determine the amount of [[precipitation]] a stream receives and therefore the amount of water flowing over the streambed. A streambed is usually a mix of particle sizes which depends on the water velocity and the materials introduced from upstream and from the watershed. Particles can be from very fine silts and clays to large cobbles and boulders ([[grain size]]). In general, sands move most easily, and particles become more difficult to move as they increase in size. Silts and clays, although smaller than sands, can stick together, making them harder to move along the streambed<ref name=":0">{{Cite book |last=Allan |first=David |title=Stream Ecology: Structure and Function of Running Waters |publisher=Springer |year=2009 |isbn=9781402055829 |edition=2nd |location=Dordrecht, The Netherlands |pages={{!}}pages=36-41 |language=en}}</ref>.
The nature of any streambed is always a function of the flow dynamics and the local geologic materials. The climate of an area will determine the amount of [[precipitation]] a stream receives and therefore the amount of water flowing over the streambed. A streambed is usually a mix of particle sizes which depends on the water velocity and the materials introduced from upstream and from the watershed. Particle sizes can range from very fine silts and clays to large cobbles and boulders ([[grain size]]). In general, sands move most easily, and particles become more difficult to move as they increase in size. Silts and clays, although smaller than sands, can stick together, making them harder to move along the streambed<ref name=":0">{{Cite book |last=Allan |first=David |title=Stream Ecology: Structure and Function of Running Waters |publisher=Springer |year=2009 |isbn=9781402055829 |edition=2nd |location=Dordrecht, The Netherlands |pages={{!}}pages=36-41 |language=en}}</ref>.


The streambed is very complex in terms of erosion and deposition. Different sized particles get sorted to different parts of a streambed as water velocity changes and [[sediment]] is transported, eroded and deposited on the bed<ref>{{Cite journal |last1=Garcia |first1=Marcelo |last2=Parker |first2=Gary |year=1991 |title=Entrainment of Bed Sediment into Suspension |journal=Journal of Hydraulic Engineering |language=en |volume=117 |issue=4 |pages=414–435 |doi=10.1061/(asce)0733-9429(1991)117:4(414)}}</ref> as the water flows downstream. Deposition usually occurs on the inside of curves, where water velocity slows, and erosion occurs on the outside of stream curves, where velocity is higher.<ref name=":0" /> FIND OR CREATE DIAGRAM. In streams with a low to moderate grade, deeper, slow water pools [[Stream pool|(stream pools]]) and faster shallow water [[Riffle|riffles]] often form as the stream meanders downhill.<ref name=":0" /> Pools can also form as water rushes over or around obstructions in the waterway.<ref name=":0" />
The streambed is very complex in terms of erosion and deposition. Different sized particles get sorted to different parts of a streambed as water velocity changes and [[sediment]] is transported, eroded and deposited on the bed<ref>{{Cite journal |last1=Garcia |first1=Marcelo |last2=Parker |first2=Gary |year=1991 |title=Entrainment of Bed Sediment into Suspension |journal=Journal of Hydraulic Engineering |language=en |volume=117 |issue=4 |pages=414–435 |doi=10.1061/(asce)0733-9429(1991)117:4(414)}}</ref> as the water flows downstream. Deposition usually occurs on the inside of curves, where water velocity slows, and erosion occurs on the outside of stream curves, where velocity is higher.<ref name=":0" /> FIND OR CREATE DIAGRAM. In streams with a low to moderate grade, deeper, slower water pools [[Stream pool|(stream pools]]) and faster shallow water [[Riffle|riffles]] often form as the stream meanders downhill.<ref name=":0" /> Pools can also form as water rushes over or around obstructions in the waterway.<ref name=":0" />


The intensity and frequency of both drought and rain events are expected to increase with climate change<ref>{{Cite journal |last=Blöschl |first=Günter |last2=Hall |first2=Julia |last3=Viglione |first3=Alberto |last4=Perdigão |first4=Rui A. P. |last5=Parajka |first5=Juraj |last6=Merz |first6=Bruno |last7=Lun |first7=David |last8=Arheimer |first8=Berit |last9=Aronica |first9=Giuseppe T. |last10=Bilibashi |first10=Ardian |last11=Boháč |first11=Miloň |last12=Bonacci |first12=Ognjen |last13=Borga |first13=Marco |last14=Čanjevac |first14=Ivan |last15=Castellarin |first15=Attilio |date=2019 |title=Changing climate both increases and decreases European river floods |url=https://www.nature.com/articles/s41586-019-1495-6 |journal=Nature |language=en |volume=573 |issue=7772 |pages=108–111 |doi=10.1038/s41586-019-1495-6 |issn=1476-4687}}</ref> <ref>{{Cite journal |last=Marsooli |first=Reza |last2=Lin |first2=Ning |last3=Emanuel |first3=Kerry |last4=Feng |first4=Kairui |date=2019-08-22 |title=Climate change exacerbates hurricane flood hazards along US Atlantic and Gulf Coasts in spatially varying patterns |url=https://www.nature.com/articles/s41467-019-11755-z |journal=Nature Communications |language=en |volume=10 |issue=1 |pages=3785 |doi=10.1038/s41467-019-11755-z |issn=2041-1723 |pmc=PMC6706450 |pmid=31439853}}</ref>. Where natural conditions of either [[grassland]] or [[forest]] ameliorate peak flows, streambeds should remain more stable and exhibit minimal scour. They should retain rich organic matter and, therefore continue to support a rich biota. ([[River ecosystem|river ecosystem)]] The majority of sediment washed out in higher flows 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 over time.<ref name="Phillips&Jerolmack2016">{{cite journal |last1=Phillips |first1=Colin B. |last2=Jerolmack |first2=Douglas J. |year=2016 |title=Self-organization of river channels as a critical filter on climate signals |journal=Science |volume=352 |issue=6286 |pages=694–697 |bibcode=2016Sci...352..694P |doi=10.1126/science.aad3348 |pmid=27151865 |doi-access=free}}</ref> Where conditions produce unnatural levels of [[surface runoff]], such as occurs in urban and suburban areas with high levels of [[Impervious surface]], watershed erosion increases and can lead to thinner soils upslope. Streambeds can exhibit a greater amount of scour, often down to bedrock, and banks may be undercut causing [[bank erosion]]. This increased bank erosion widens the stream and can lead to an increased sediment load downstream.<ref>{{Cite web |last=US EPA |first=ORD |date=2015-12-23 |title=Urbanization - Stormwater Runoff |url=https://www.epa.gov/caddis-vol2/urbanization-stormwater-runoff |access-date=2023-06-08 |website=www.epa.gov |language=en}}</ref>
The intensity and frequency of both drought and rain events are expected to increase with climate change<ref>{{Cite journal |last=Blöschl |first=Günter |last2=Hall |first2=Julia |last3=Viglione |first3=Alberto |last4=Perdigão |first4=Rui A. P. |last5=Parajka |first5=Juraj |last6=Merz |first6=Bruno |last7=Lun |first7=David |last8=Arheimer |first8=Berit |last9=Aronica |first9=Giuseppe T. |last10=Bilibashi |first10=Ardian |last11=Boháč |first11=Miloň |last12=Bonacci |first12=Ognjen |last13=Borga |first13=Marco |last14=Čanjevac |first14=Ivan |last15=Castellarin |first15=Attilio |date=2019 |title=Changing climate both increases and decreases European river floods |url=https://www.nature.com/articles/s41586-019-1495-6 |journal=Nature |language=en |volume=573 |issue=7772 |pages=108–111 |doi=10.1038/s41586-019-1495-6 |issn=1476-4687}}</ref> <ref>{{Cite journal |last=Marsooli |first=Reza |last2=Lin |first2=Ning |last3=Emanuel |first3=Kerry |last4=Feng |first4=Kairui |date=2019-08-22 |title=Climate change exacerbates hurricane flood hazards along US Atlantic and Gulf Coasts in spatially varying patterns |url=https://www.nature.com/articles/s41467-019-11755-z |journal=Nature Communications |language=en |volume=10 |issue=1 |pages=3785 |doi=10.1038/s41467-019-11755-z |issn=2041-1723 |pmc=PMC6706450 |pmid=31439853}}</ref>. Where natural conditions of either [[grassland]] or [[forest]] ameliorate peak flows, streambeds should remain more stable and exhibit minimal scour. They should retain rich organic matter and, therefore continue to support a rich biota. ([[River ecosystem|river ecosystem)]] The majority of sediment washed out in higher flows 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 over time.<ref name="Phillips&Jerolmack2016">{{cite journal |last1=Phillips |first1=Colin B. |last2=Jerolmack |first2=Douglas J. |year=2016 |title=Self-organization of river channels as a critical filter on climate signals |journal=Science |volume=352 |issue=6286 |pages=694–697 |bibcode=2016Sci...352..694P |doi=10.1126/science.aad3348 |pmid=27151865 |doi-access=free}}</ref> Where conditions produce unnatural levels of [[surface runoff]], such as occurs in urban and suburban areas with high levels of [[Impervious surface]], watershed erosion increases and can lead to thinner soils upslope. Streambeds can exhibit a greater amount of scour, often down to bedrock, and banks may be undercut causing [[bank erosion]]. This increased bank erosion widens the stream and can lead to an increased sediment load downstream.<ref>{{Cite web |last=US EPA |first=ORD |date=2015-12-23 |title=Urbanization - Stormwater Runoff |url=https://www.epa.gov/caddis-vol2/urbanization-stormwater-runoff |access-date=2023-06-08 |website=www.epa.gov |language=en}}</ref>


=== References ===
=== References ===

Revision as of 18:57, 8 June 2023

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A streambed or stream bed is the bottom of a stream or river (bathymetry) and is confined within a channel, or the banks (sides) of the waterway.[1] Usually, the bed is kept clear of terrestrial vegetation and instead supports different types of aquatic vegetation (aquatic plant), depending on the type of streambed material and water velocity. Streambeds 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 banks and canyons made by the stream are usually harder. Soft sand and debris often fill the bed. Dry, buried stream beds can actually be underground water pockets [1]. During times of rain, sandy streambeds can soak up at retain water, even during dry seasons, keeping the water table close enough to the surface to be obtainable by local people.[1]

The nature of any streambed is always a function of the flow dynamics and the local geologic materials. The climate of an area will determine the amount of precipitation a stream receives and therefore the amount of water flowing over the streambed. A streambed is usually a mix of particle sizes which depends on the water velocity and the materials introduced from upstream and from the watershed. Particle sizes can range from very fine silts and clays to large cobbles and boulders (grain size). In general, sands move most easily, and particles become more difficult to move as they increase in size. Silts and clays, although smaller than sands, can stick together, making them harder to move along the streambed[2].

The streambed is very complex in terms of erosion and deposition. Different sized particles get sorted to different parts of a streambed as water velocity changes and sediment is transported, eroded and deposited on the bed[3] as the water flows downstream. Deposition usually occurs on the inside of curves, where water velocity slows, and erosion occurs on the outside of stream curves, where velocity is higher.[2] FIND OR CREATE DIAGRAM. In streams with a low to moderate grade, deeper, slower water pools (stream pools) and faster shallow water riffles often form as the stream meanders downhill.[2] Pools can also form as water rushes over or around obstructions in the waterway.[2]

The intensity and frequency of both drought and rain events are expected to increase with climate change[4] [5]. Where natural conditions of either grassland or forest ameliorate peak flows, streambeds should remain more stable and exhibit minimal scour. They should retain rich organic matter and, therefore continue to support a rich biota. (river ecosystem) The majority of sediment washed out in higher flows 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 over time.[6] Where conditions produce unnatural levels of surface runoff, such as occurs in urban and suburban areas with high levels of Impervious surface, watershed erosion increases and can lead to thinner soils upslope. Streambeds can exhibit a greater amount of scour, often down to bedrock, and banks may be undercut causing bank erosion. This increased bank erosion widens the stream and can lead to an increased sediment load downstream.[7]

References

  1. ^ a b "Below sandy, dry riverbeds: A medicine against drought". www.un-ihe.org. Retrieved 2023-06-08.
  2. ^ a b c d Allan, David (2009). Stream Ecology: Structure and Function of Running Waters (2nd ed.). Dordrecht, The Netherlands: Springer. pp. |pages=36-41. ISBN 9781402055829.
  3. ^ 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).
  4. ^ Blöschl, Günter; Hall, Julia; Viglione, Alberto; Perdigão, Rui A. P.; Parajka, Juraj; Merz, Bruno; Lun, David; Arheimer, Berit; Aronica, Giuseppe T.; Bilibashi, Ardian; Boháč, Miloň; Bonacci, Ognjen; Borga, Marco; Čanjevac, Ivan; Castellarin, Attilio (2019). "Changing climate both increases and decreases European river floods". Nature. 573 (7772): 108–111. doi:10.1038/s41586-019-1495-6. ISSN 1476-4687.
  5. ^ Marsooli, Reza; Lin, Ning; Emanuel, Kerry; Feng, Kairui (2019-08-22). "Climate change exacerbates hurricane flood hazards along US Atlantic and Gulf Coasts in spatially varying patterns". Nature Communications. 10 (1): 3785. doi:10.1038/s41467-019-11755-z. ISSN 2041-1723. PMC 6706450. PMID 31439853.{{cite journal}}: CS1 maint: PMC format (link)
  6. ^ 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.
  7. ^ US EPA, ORD (2015-12-23). "Urbanization - Stormwater Runoff". www.epa.gov. Retrieved 2023-06-08.
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