Hyperconcentrated Sand‐Water Mixture Flows over Erodible Bed

Winterwerp, Johan C.; Bakker, W.H.; Mastbergen, Dick R.; Rossum, Henk van

doi:10.1061/(asce)0733-9429(1992)118:11(1508)

Cited by 100 publications

(105 citation statements)

References 7 publications

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“…8; Paull et al, 2011). Experiments have shown how up-slope migrating cyclic steps can be produced by flows with high sediment volume concentrations of up to~40 vol.% (Winterwerp et al, 1992). Dredging has shown how sustained dense flows of sand can be generated by breaching, whereby flow starts at a local steeping at the base of slope, and then 'eats' its way back upslope (Mastbergen and van den Berg, 2003).…”

Section: Monterey Canyon Offshore Californiamentioning

confidence: 99%

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Talling

Paull

Piper

2013

Earth-Science Reviews

211

184

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Subaqueous sediment density flows are one of the volumetrically most important processes for moving sediment across our planet, and form the largest sediment accumulations on Earth (submarine fans). They are also arguably the most sparely monitored major sediment transport processes on our planet. Significant advances have been made in documenting their timing and triggers, especially within submarine canyons and delta-fronts, and freshwater lakes and reservoirs, but the sediment concentration of flows that run out beyond the continental slope has never been measured directly. This limited amount of monitoring data contrasts sharply with other major types of sediment flow, such as river systems, and ensure that understanding submarine sediment density flows remains a major challenge for Earth science. The available monitoring data define a series of flow types whose character and deposits differ significantly. Large (N 100 km 3 ) failures on the continental slope can generate fast-moving (up to 19 m/s) flows that reach the deep ocean, and deposit thick layers of sand across submarine fans. Even small volume (0.008 km 3 ) canyon head failures can sometimes generate channelised flows that travel at N 5 m/s for several hundred kilometres. A single event off SE Taiwan shows that river floods can generate powerful flows that reach the deep ocean, in this case triggered by failure of recently deposited sediment in the canyon head. Direct monitoring evidence of powerful oceanic flows produced by plunging hyperpycnal flood water is lacking, although this process has produced shorter and weaker oceanic flows. Numerous flows can occur each year on river-fed delta fronts, where they can generate up-slope migrating crescentic bedforms. These flows tend to occur during the flood season, but are not necessarily associated with individual flood discharge peaks, suggesting that they are often triggered by delta-front slope failures. Powerful flows occur several times each year in canyons fed by sand from the shelf, associated with strong wave action. These flows can also generate up-slope migrating crescentic bedforms that most likely originate due to retrogressive breaching associated with a dense near-bed layer of sediment. Expanded dilute flows that are supercritical and fully turbulent are also triggered by wave action in canyons. Sediment density flows in lakes and reservoirs generated by plunging river flood water have been monitored in much greater detail. They are typically very dilute (b 0.01 vol.% sediment) and travel at b 50 cm/s, and are prone to generating interflows within the density stratified freshwater. A key objective for future work is to develop measurement techniques for seeing through overlying dilute clouds of sediment, to determine whether dense near-bed layers are present. There is also a need to combine monitoring of flows with detailed analyses of flow deposits, in order to understand how flows are recorded in the rock record. Finally, a source-to-sink approach is needed because the character of subm...

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Section: Monterey Canyon Offshore Californiamentioning

confidence: 99%

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Talling

Paull

Piper

2013

Earth-Science Reviews

211

184

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“…Fukuoka et al (1982), on the other, hand, describe a wide range of bedforms in supercritical flow, one of them identifiable as cyclic steps. Winterwerp et al (1992) provided unambiguous documentation of cyclic steps in the field, and also developed a shallowwater analysis for the flow and suspended sediment transport over a specified field of steps that illustrated the role of the hydraulic jumps. Parker (1996) documented these steps in experiments on the formation of alluvial fans as well as other contexts, and christened the morphology with the name ''cyclic steps.'…”

Section: Cyclic Steps In Alluviummentioning

confidence: 99%

Cyclic steps: A phenomenon of supercritical shallow flow from the high mountains to the bottom of the ocean

Kostic

Sequeiros

Spinewine

et al. 2010

Journal of Hydro-environment Research

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“…Under the right conditions of Froude-supercritical flow, multiple knickpoints can form under quasi-equilibrium conditions (Winterwerp et al, 1992;Taki et al, 2005;Yokokawa et al, 2011). These knickpoints take the form of cyclic steps, that is, trains of upstream-migrating bedforms, each bounded by hydraulic jumps and can form under conditions of constant stationary base level, with new steps forming at the downstream end of the reach as previously formed steps migrate out of the reach.…”

Section: Introductionmentioning

confidence: 99%

Multiple knickpoints in an alluvial river generated by a single instantaneous drop in base level: experimental investigation

Cantelli

Muto

2014

Earth Surf. Dynam.

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Abstract. Knickpoints often form in bedrock rivers in response to base-level lowering. These knickpoints can migrate upstream without dissipating. In the case of alluvial rivers, an impulsive lowering of base level due to, for example, a fault associated with an earthquake or dam removal commonly produces smooth, upstreamprogressing degradation; the knickpoint associated with suddenly lowered base level quickly dissipates. Here, however, we use experiments to demonstrate that under conditions of Froude-supercritical flow over an alluvial bed, an instantaneous drop in base level can lead to the formation of upstream-migrating knickpoints that do not dissipate. The base-level fall can generate a single knickpoint, or multiple knickpoints. Multiple knickpoints take the form of cyclic steps, that is, trains of upstream-migrating bedforms, each bounded by a hydraulic jump upstream and downstream. In our experiments, trains of knickpoints were transient, eventually migrating out of the alluvial reach as the bed evolved to a new equilibrium state regulated with lowered base level. Thus the allogenic perturbation of base-level fall can trigger the autogenic generation of multiple knickpoints which are sustained until the alluvial reach recovers a graded state.

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Hyperconcentrated Sand‐Water Mixture Flows over Erodible Bed

Cited by 100 publications

References 7 publications

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

How are subaqueous sediment density flows triggered, what is their internal structure and how does it evolve? Direct observations from monitoring of active flows

Cyclic steps: A phenomenon of supercritical shallow flow from the high mountains to the bottom of the ocean

Multiple knickpoints in an alluvial river generated by a single instantaneous drop in base level: experimental investigation

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