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Flow and sediment suspension events over low-angle dunes: Fraser Estuary, Canada
The morphodynamics of large sand‐bedded rivers and estuaries are ultimately controlled by the way bed material is moved and the development of large, subaqueous sand dunes that control hydraulic flow resistance. It is widely thought that the primary mechanism for moving sandy bed material in these c...
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| Published in: | Journal of geophysical research. Earth surface 2013-09, Vol.118 (3), p.1693-1709 |
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| Main Authors: | , , , , , |
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| cites | cdi_FETCH-LOGICAL-c4088-41918558c01433c4f4a98525b27ab49e5bd142f57f1db85aadcf7bcefd62179c3 |
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| container_title | Journal of geophysical research. Earth surface |
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| creator | Bradley, R.W. Venditti, J. G. Kostaschuk, R. A. Church, M. Hendershot, M. Allison, M. A. |
| description | The morphodynamics of large sand‐bedded rivers and estuaries are ultimately controlled by the way bed material is moved and the development of large, subaqueous sand dunes that control hydraulic flow resistance. It is widely thought that the primary mechanism for moving sandy bed material in these channels is large‐scale coherent flow structures that cause suspension events whose properties vary with flow, especially in tidally influenced environments. Here, we examine mean flow and sediment suspension events over low‐angle dunes (lee face angle |
| doi_str_mv | 10.1002/jgrf.20118 |
| format | article |
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Key Points
Suspension events dominate sediment transport over low‐angle dunes
Upwelling and downwelling in the flow contribute to sediment suspension events
Approximately 70% of suspended sediment is carried within suspension events</description><identifier>ISSN: 2169-9003</identifier><identifier>EISSN: 2169-9011</identifier><identifier>DOI: 10.1002/jgrf.20118</identifier><language>eng</language><publisher>Washington: Blackwell Publishing Ltd</publisher><subject>Brackish ; Channels ; Dunes ; Estuaries ; Flow resistance ; Flow separation ; Freshwater ; Geomorphology ; River beds ; Saline water ; Saline-freshwater interfaces ; Salt water ; Salts ; Sand ; sand-bedded rivers ; Sediment transport ; Sedimentary structures ; Sediments ; Suspended sediments ; suspension ; Tides ; Unsteady flow ; Upwelling ; variable flow ; Water column ; Wedges</subject><ispartof>Journal of geophysical research. Earth surface, 2013-09, Vol.118 (3), p.1693-1709</ispartof><rights>2013. American Geophysical Union. All Rights Reserved.</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c4088-41918558c01433c4f4a98525b27ab49e5bd142f57f1db85aadcf7bcefd62179c3</citedby><cites>FETCH-LOGICAL-c4088-41918558c01433c4f4a98525b27ab49e5bd142f57f1db85aadcf7bcefd62179c3</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktopdf>$$Uhttps://onlinelibrary.wiley.com/doi/pdf/10.1002%2Fjgrf.20118$$EPDF$$P50$$Gwiley$$H</linktopdf><linktohtml>$$Uhttps://onlinelibrary.wiley.com/doi/full/10.1002%2Fjgrf.20118$$EHTML$$P50$$Gwiley$$H</linktohtml><link.rule.ids>314,780,784,11513,27923,27924,46467,46891</link.rule.ids></links><search><creatorcontrib>Bradley, R.W.</creatorcontrib><creatorcontrib>Venditti, J. G.</creatorcontrib><creatorcontrib>Kostaschuk, R. A.</creatorcontrib><creatorcontrib>Church, M.</creatorcontrib><creatorcontrib>Hendershot, M.</creatorcontrib><creatorcontrib>Allison, M. A.</creatorcontrib><title>Flow and sediment suspension events over low-angle dunes: Fraser Estuary, Canada</title><title>Journal of geophysical research. Earth surface</title><addtitle>J. Geophys. Res. Earth Surf</addtitle><description>The morphodynamics of large sand‐bedded rivers and estuaries are ultimately controlled by the way bed material is moved and the development of large, subaqueous sand dunes that control hydraulic flow resistance. It is widely thought that the primary mechanism for moving sandy bed material in these channels is large‐scale coherent flow structures that cause suspension events whose properties vary with flow, especially in tidally influenced environments. Here, we examine mean flow and sediment suspension events over low‐angle dunes (lee face angle <30°) in the unsteady flow of the Fraser Estuary, Canada. At high tide, flow nearly ceased and a salt wedge entered the channel, forcing salt water under the downstream‐moving fresh water. The salt wedge persisted in the channel until late in the falling tide, causing stratification in the water column and instabilities along the saline‐fresh water interface. At low tide, mean velocities peaked and forced the saline water out of the channel. Flow over the low‐angle dunes displayed topographically induced patterns previously observed over high‐angle dunes, but permanent flow separation was not observed. Large‐scale sediment suspension events dominated sediment flux during low tide and became larger scale, yet less frequent, as the tide began to rise. The suspension events appeared to form over the lower stoss of the dunes and grew up over the bed forms and, less commonly, emerged downstream of the crest. Suspension events move ~69% of the total sediment in the flow above low‐angle dunes when they are present.
Key Points
Suspension events dominate sediment transport over low‐angle dunes
Upwelling and downwelling in the flow contribute to sediment suspension events
Approximately 70% of suspended sediment is carried within suspension events</description><subject>Brackish</subject><subject>Channels</subject><subject>Dunes</subject><subject>Estuaries</subject><subject>Flow resistance</subject><subject>Flow separation</subject><subject>Freshwater</subject><subject>Geomorphology</subject><subject>River beds</subject><subject>Saline water</subject><subject>Saline-freshwater interfaces</subject><subject>Salt water</subject><subject>Salts</subject><subject>Sand</subject><subject>sand-bedded rivers</subject><subject>Sediment transport</subject><subject>Sedimentary structures</subject><subject>Sediments</subject><subject>Suspended sediments</subject><subject>suspension</subject><subject>Tides</subject><subject>Unsteady flow</subject><subject>Upwelling</subject><subject>variable flow</subject><subject>Water column</subject><subject>Wedges</subject><issn>2169-9003</issn><issn>2169-9011</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2013</creationdate><recordtype>article</recordtype><recordid>eNp9kMtOwzAQRSMEEhV0wxdYYoMQKR4_GocdqtoCgvIQCHaWkzgoJXWKp6H07zEUWLBgNjO-OnfkuVG0B7QHlLLj6bMve4wCqI2ow6Cfxml4bP7OlG9HXcQpDaWCBKwT3YzqZkmMKwjaoppZtyDY4tw6rBpH7FsQkDRv1pPAxcY915YUrbN4QkbeYNCHuGiNXx2RgXGmMLvRVmlqtN3vvhM9jIb3g7P48np8Pji9jHNBlYoFpKCkVDkFwXkuSmFSJZnMWGIykVqZFSBYKZMSikxJY4q8TLLclkWfQZLmfCc6WO-d--a1tbjQswpzW9fG2aZFDSIVXEoKMqD7f9Bp03oXfqehz5WAhHEWqMM1lfsG0dtSz301C5dpoPozX_2Zr_7KN8CwhpdVbVf_kPpifDf68cRrT4UL-_7rMf5F9xOeSP04GWt2eyUu1NNED_gHZWWK9A</recordid><startdate>201309</startdate><enddate>201309</enddate><creator>Bradley, R.W.</creator><creator>Venditti, J. G.</creator><creator>Kostaschuk, R. A.</creator><creator>Church, M.</creator><creator>Hendershot, M.</creator><creator>Allison, M. A.</creator><general>Blackwell Publishing Ltd</general><scope>BSCLL</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7ST</scope><scope>7TG</scope><scope>7UA</scope><scope>8FD</scope><scope>C1K</scope><scope>F1W</scope><scope>FR3</scope><scope>H8D</scope><scope>H96</scope><scope>KL.</scope><scope>KR7</scope><scope>L.G</scope><scope>L7M</scope><scope>SOI</scope></search><sort><creationdate>201309</creationdate><title>Flow and sediment suspension events over low-angle dunes: Fraser Estuary, Canada</title><author>Bradley, R.W. ; Venditti, J. G. ; Kostaschuk, R. A. ; Church, M. ; Hendershot, M. ; Allison, M. A.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c4088-41918558c01433c4f4a98525b27ab49e5bd142f57f1db85aadcf7bcefd62179c3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2013</creationdate><topic>Brackish</topic><topic>Channels</topic><topic>Dunes</topic><topic>Estuaries</topic><topic>Flow resistance</topic><topic>Flow separation</topic><topic>Freshwater</topic><topic>Geomorphology</topic><topic>River beds</topic><topic>Saline water</topic><topic>Saline-freshwater interfaces</topic><topic>Salt water</topic><topic>Salts</topic><topic>Sand</topic><topic>sand-bedded rivers</topic><topic>Sediment transport</topic><topic>Sedimentary structures</topic><topic>Sediments</topic><topic>Suspended sediments</topic><topic>suspension</topic><topic>Tides</topic><topic>Unsteady flow</topic><topic>Upwelling</topic><topic>variable flow</topic><topic>Water column</topic><topic>Wedges</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Bradley, R.W.</creatorcontrib><creatorcontrib>Venditti, J. G.</creatorcontrib><creatorcontrib>Kostaschuk, R. A.</creatorcontrib><creatorcontrib>Church, M.</creatorcontrib><creatorcontrib>Hendershot, M.</creatorcontrib><creatorcontrib>Allison, M. 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Earth surface</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Bradley, R.W.</au><au>Venditti, J. G.</au><au>Kostaschuk, R. A.</au><au>Church, M.</au><au>Hendershot, M.</au><au>Allison, M. A.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Flow and sediment suspension events over low-angle dunes: Fraser Estuary, Canada</atitle><jtitle>Journal of geophysical research. Earth surface</jtitle><addtitle>J. Geophys. Res. Earth Surf</addtitle><date>2013-09</date><risdate>2013</risdate><volume>118</volume><issue>3</issue><spage>1693</spage><epage>1709</epage><pages>1693-1709</pages><issn>2169-9003</issn><eissn>2169-9011</eissn><abstract>The morphodynamics of large sand‐bedded rivers and estuaries are ultimately controlled by the way bed material is moved and the development of large, subaqueous sand dunes that control hydraulic flow resistance. It is widely thought that the primary mechanism for moving sandy bed material in these channels is large‐scale coherent flow structures that cause suspension events whose properties vary with flow, especially in tidally influenced environments. Here, we examine mean flow and sediment suspension events over low‐angle dunes (lee face angle <30°) in the unsteady flow of the Fraser Estuary, Canada. At high tide, flow nearly ceased and a salt wedge entered the channel, forcing salt water under the downstream‐moving fresh water. The salt wedge persisted in the channel until late in the falling tide, causing stratification in the water column and instabilities along the saline‐fresh water interface. At low tide, mean velocities peaked and forced the saline water out of the channel. Flow over the low‐angle dunes displayed topographically induced patterns previously observed over high‐angle dunes, but permanent flow separation was not observed. Large‐scale sediment suspension events dominated sediment flux during low tide and became larger scale, yet less frequent, as the tide began to rise. The suspension events appeared to form over the lower stoss of the dunes and grew up over the bed forms and, less commonly, emerged downstream of the crest. Suspension events move ~69% of the total sediment in the flow above low‐angle dunes when they are present.
Key Points
Suspension events dominate sediment transport over low‐angle dunes
Upwelling and downwelling in the flow contribute to sediment suspension events
Approximately 70% of suspended sediment is carried within suspension events</abstract><cop>Washington</cop><pub>Blackwell Publishing Ltd</pub><doi>10.1002/jgrf.20118</doi><tpages>17</tpages><oa>free_for_read</oa></addata></record> |
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| identifier | ISSN: 2169-9003 |
| ispartof | Journal of geophysical research. Earth surface, 2013-09, Vol.118 (3), p.1693-1709 |
| issn | 2169-9003 2169-9011 |
| language | eng |
| recordid | cdi_proquest_miscellaneous_1494355015 |
| source | Wiley Online Library AGU 2016; Wiley-Blackwell Read & Publish Collection |
| subjects | Brackish Channels Dunes Estuaries Flow resistance Flow separation Freshwater Geomorphology River beds Saline water Saline-freshwater interfaces Salt water Salts Sand sand-bedded rivers Sediment transport Sedimentary structures Sediments Suspended sediments suspension Tides Unsteady flow Upwelling variable flow Water column Wedges |
| title | Flow and sediment suspension events over low-angle dunes: Fraser Estuary, Canada |
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