Large Submarine Sand Waves

Jordan, G. F.

doi:10.1126/science.136.3519.839

Cited by 92 publications

(8 citation statements)

References 7 publications

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“…Similar disagreements were observed by other researchers (e.g. Jordan 1962;Stride 1970;Flemming 1978 andStow 2002). Flemming (1978) further noted that this deviation is always encountered in areas where the flow systems form part of a larger and deeper water body.…”

Section: Morphometricssupporting

confidence: 86%

Bedform evolution and dynamics of a geostrophic current-swept shelf, northern KwaZulu-Natal, South Africa

et al. 2021

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When compared to tide-dominated shelves, shelves swept by geostrophic flows are relatively understudied, yet geostrophic currents have the potential to construct substantial current-generated shelf bedforms. This paper examines the evolution of a series of bedforms encountered along the narrow Agulhas Current-swept northern KwaZulu-Natal shelf. Their evolution is placed in the context of progressive current impingement and variation in flows associated with the postglacial transgression and culminating in the present-day highstand. Ultra-high resolution seismic reflection, multibeam, side-scan sonar and single beam data sets reveal several bedform scales and morphologies; wave ripples and shoreface-connected ridges are associated only with the inner shelf, and 2D and 3D very large dunes are more cosmopolitan and span the entire shelf sector. The inner shelf is marked by rock outcrop (aeolianite), surrounded by sandy sediment, grading seaward into sediment starved bedforms associated with bioclastic gravels. Where sufficient sediment exists in local depocenters, very large dunes form discontinuous fields along the outer shelf. The seismic stratigraphy of the outer shelf reflects the effects of postglacial flooding by rising sea levels and increasing current impingement by the Agulhas Current. The Holocene wave ravinement surface is overlain by flat-lying strata (early dune development and dune amalgamation with first current exposure), in turn covered by hummocky, sub-horizontal aggrading beds (amalgamation), overlain by inclined cross-bedded packages (lee faces of the bedforms formed during migration and full current interaction). Morphometric analyses show that for both the inner and outer shelf, no relationships exist between water depth, wavelength and spacing. Height to spacing (H/L) relationships are weak but nevertheless show a broadly positive trend. Bedform heights are lower on the inner shelf compared to the outer shelf, but bedform spacing is greater on the inner shelf, with a 40% overlap in H/L indices observed between the two areas. The departures in overlap can be linked to the competing offshore Agulhas Current and the inshore wave-dominated processes. Bedforms of the inner shelf plot below the global H/L mean and can be related to the more infrequent incursions of the Agulhas Current core. At the time of survey, the Agulhas Current was likely situated well offshore, resulting in reduced current activity in the survey area resulting in rounding of the dune crests, degradation of the dune crests and trough infilling. On the outer shelf, the H/L values plot above the mean global trend, suggesting vertical accretion due to the faster currents. Crest rounding and downlapping of the upstream lee faces onto the downstream stoss faces indicate dune degradation, which is related to a seaward location of the Agulhas Current at the time of survey.

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Section: Morphometricssupporting

confidence: 86%

Bedform evolution and dynamics of a geostrophic current-swept shelf, northern KwaZulu-Natal, South Africa

et al. 2021

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“…Whetten and others (1969) mapped the lower river, noting that 45 percent of the channel between Bonneville Dam and the Willamette River confluence was covered in sand waves, with abundance increasing to 80 percent for the segment between the Willamette and Cowlitz River confluences, and 86 percent for the segment between the Cowlitz River and the ocean. Hauschild and others (1966) reported dunes in the Columbia River channel averaging 1.5 m high, and 30-90 m in length; dimensions slightly smaller than those described by Jordan (1962) near Longview, which had amplitudes averaging about 2 m, lengths of about 500 m, and average spacing of about 100 m. Smaller bedforms, primarily current ripples, are commonly superimposed on these large sand waves. Hauschild and others (1966) reported that the dunes in deeper parts of the channel evolved from long and low to short and high as discharge increased.…”

Section: Sediment Movement and Transfersmentioning

confidence: 92%

“…Large sand waves and other channel bedforms along the estuary have been described by Hickson and Rodolf (1951), Jordan (1962), Hauschild and others (1966), Whetten and others (1969) and Sherwood and Creager (1990). Whetten and others (1969) mapped the lower river, noting that 45 percent of the channel between Bonneville Dam and the Willamette River confluence was covered in sand waves, with abundance increasing to 80 percent for the segment between the Willamette and Cowlitz River confluences, and 86 percent for the segment between the Cowlitz River and the ocean.…”

Section: Sediment Movement and Transfersmentioning

confidence: 99%

Columbia River Estuary ecosystem classification—Concept and application

Simenstad¹,

Burke²,

O'Connor³

et al. 2011

Open-File Report

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. Tables Executive SummaryThis document describes the concept, organization, and application of a hierarchical ecosystem classification that integrates saline and tidal freshwater reaches of estuaries in order to characterize the ecosystems of large flood plain rivers that are strongly influenced by riverine and estuarine hydrology. We illustrate the classification by applying it to the Columbia River estuary (Oregon-Washington, USA), a system that extends about 233 river kilometers (rkm) inland from the Pacific Ocean. More than three-quarters of this length is tidal freshwater. The Columbia River Estuary Ecosystem Classification ("Classification") is based on six hierarchical levels, progressing from the coarsest, regional scale to the finest, localized scale: (1) Ecosystem Province; (2) Ecoregion; (3) Hydrogeomorphic Reach; (4) Ecosystem Complex; (5) Geomorphic Catena; and (6) Primary Cover Class. We define and map Levels 1-3 for the entire Columbia River estuary with existing geospatial datasets, and provide examples of Levels 4-6 for one hydrogeomorphic reach. In particular, three levels of the Classification capture the scales and categories of ecosystem structure and processes that are most tractable to estuarine research, monitoring, and management. These three levels are the (1) eight hydrogeomorphic reaches that embody the formative geologic and tectonic processes that created the existing estuarine landscape and encompass the influence of the resulting physiography on interactions between fluvial and tidal hydrology and geomorphology across 230 kilometers (km) of estuary, (2) more than 15 ecosystem complexes composed of broad landforms created predominantly by geologic processes during the Holocene, and (3) more than 25 geomorphic catenae embedded within ecosystem complexes that represent distinct geomorphic landforms, structures, ecosystems, and habitats, and components of the estuarine landscape most likely to change over short time periods. 2 IntroductionWe describe the rationale, conceptual basis, and application of a hierarchical ecosystem classification for large-river, flood-plain estuaries, and provide examples from the application of this controlling factor approach for the Columbia River estuary (Oregon-Washington, USA). A number of estuarine, delta and river-flood plain classifications based on ...

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“…In comparison with artificial structures, sand waves have special topographic features [12][13][14][15][16][17][18]. Water width between adjacent sand waves with significant random fluctuation is much larger than sand wave width, and sand wave height is comparable with water depth.…”

mentioning

confidence: 99%

“…We consider the one-dimensional theoretical system to test the physical mechanism of band structure and wave localization of surface water waves over uneven sand wave bottoms. Detailed geophysical application requires determining the sand wave parameters based on the geophysically topographic features, which is out of scope of this study and has been reported elsewhere [12][13][14][15][16][17][18][19]. The system shown in Fig.…”

mentioning

confidence: 99%

Band gaps and localization of surface water waves over large-scale sand waves with random fluctuations

Shao

Zhong

et al. 2012

Phys. Rev. E

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Band structure and wave localization are investigated for sea surface water waves over large-scale sand wave topography. Sand wave height, sand wave width, water depth, and water width between adjacent sand waves have significant impact on band gaps. Random fluctuations of sand wave height, sand wave width, and water depth induce water wave localization. However, random water width produces a perfect transmission tunnel of water waves at a certain frequency so that localization does not occur no matter how large a disorder level is applied. Together with theoretical results, the field experimental observations in the Taiwan Bank suggest band gap and wave localization as the physical mechanism of sea surface water wave propagating over natural large-scale sand waves.

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Large Submarine Sand Waves

Cited by 92 publications

References 7 publications

Bedform evolution and dynamics of a geostrophic current-swept shelf, northern KwaZulu-Natal, South Africa

Bedform evolution and dynamics of a geostrophic current-swept shelf, northern KwaZulu-Natal, South Africa

Columbia River Estuary ecosystem classification—Concept and application

Band gaps and localization of surface water waves over large-scale sand waves with random fluctuations

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