Sand Transport on the Continental Shelf

Dyer, KR; Soulsby, R.L.

doi:10.1146/annurev.fl.20.010188.001455

Cited by 140 publications

(64 citation statements)

References 43 publications

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“…In particular, it is typical of the models used to describe the erosion of marine sands [Dyer and Soulsby, 1988]. Additionally, we note that by varying the quantity in equation (6), we may approximate various alternative forms of deposition: for example, = 1 recovers the case of continuous deposition from a well-mixed suspension,Q d =ŵ sĈ , which is commonly used in studies of coarse particle transport in marine environments [see, e.g., Schuttelaars and de Swart, 1999].…”

Section: Appendix B: Alternative Erosion Formulationsmentioning

confidence: 99%

Cross‐shore sediment transport and the equilibrium morphology of mudflats under tidal currents

Pritchard

Hogg

2003

J. Geophys. Res.

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[1] We describe a mathematical model of suspended sediment transport under cross-shore tidal currents on an intertidal mudflat. We employ a Lagrangian formulation to obtain periodic solutions for the sediment transport over idealized bathymetries and use these to investigate the process of settling lag. In deep water away from the shoreline the concentration of suspended sediment tends to a constant value, and we may invert the relation between bathymetry and offshore concentration to estimate how the gradient of a flat in a state of equilibrium varies with the sediment properties and supply. These analytical estimates are compared successfully with the numerical experiments of previous studies. We discuss the robustness of our modeling framework and demonstrate its application to different descriptions of sediment transport and tidal regimes.

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Section: Appendix B: Alternative Erosion Formulationsmentioning

confidence: 99%

Cross‐shore sediment transport and the equilibrium morphology of mudflats under tidal currents

Pritchard

Hogg

2003

J. Geophys. Res.

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“…The largest contributions to stress often occur through ejecting or sweeping motions (Soulsby, 1983). Typically, ejections are associated with entrainment of mass (sediment particles) into suspension, while sweeps are effective at transporting bedload (Cao, 1997;Dyer and Soulsby, 1988;Heathershaw, 1979;Keylock, 2007;Soulsby, 1983;Yuan et al, 2009). While ejections and sweeps reportedly occur in relatively equal proportions near the bed, the former type dominates higher in the water column (Cellino and Lemmin, 2004).…”

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confidence: 99%

Wave-induced coherent turbulence structures and sediment resuspension in the nearshore of a prototype-scale sandy barrier beach

Kassem

Thompson

Amos

et al. 2015

Continental Shelf Research

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Abstract:The suspension of sediments by oscillatory flows is a complex case of fluid-particle interaction. The aim of this study is to provide insight into the spatial (time) and scale (frequency) relationships between wave-generated boundary layer turbulence and eventdriven sediment transport beneath irregular shoaling and breaking waves in the nearshore of a prototype sandy barrier beach, using data collected through the Barrier Dynamics Experiment II (BARDEX II). Statistical, quadrant and spectral analyses reveal the anisotropic and intermittent nature of Reynolds' stresses (momentum exchange) in the wave boundary layer, in all three orthogonal planes of motion. The fractional contribution of coherent turbulence structures appears to be dictated by the structural form of eddies beneath plunging and spilling breakers, which in turn define the net sediment mobilisation towards or away from the barrier, and hence ensuing erosion and accretion trends. A standing transverse wave is also observed in the flume, contributing to the substantial skewness of spanwise turbulence. Observed low frequency suspensions are closely linked to the mean flow (wave) properties. Wavelet analysis reveals that the entrainment and maintenance of sediment in suspension through a cluster of bursting sequence is associated with the passage of intermittent slowly-evolving large structures, which can modulate the frequency of smaller motions. Outside the boundary layer, small scale, higher frequency turbulence drives the suspension. The extent to which these spatially varied perturbation clusters persist is associated with suspension events in the high frequency scales, decaying as the turbulent motion ceases to supply momentum, with an observed hysteresis effect. The suspension of sediment in turbulent flows is a complex case of fluid-particle interaction, governed by shear stresses (momentum exchanges) at the bed and within the benthic boundary layer (BBL). Defining the physical processes which dictate the resuspension of sediments in coastal and estuarine settings is fundamental for accurate predictions of bed morphology evolution (Van Rijn et al., 2007), and has profound implications for the biogeochemical processes that shape their local ecology (Thompson et al., 2011). It is also a prerequisite to quantifying erosion and deposition trends, and hence guiding engineering applications such as beach nourishment, defence schemes against erosion and flooding, maintenance of marine infrastructure and waterways, and aggregate dredging. There is a genuine need for better, robust models of suspended sediment transport in the coastal zone (Aagaard and Jensen, 2013). In a vision paper on future research needs in coastal dynamics, Van Rijn et al. (2013) highlighted the pressing need for research to support such models, focusing in particular on sand transport in the shoreface (non-breaking waves), surf and swash zones; employing field and controlled laboratory experiments.The mobilisation of sediments in the nearshore and shoreface is dominated b...

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“…Previous studies suggested that the ejections were associated with entrainment of sediment particles into the water column, while sweeps were effective at transporting bedload (Heathershaw, 1979;Soulsby, 1983;Dyer and Soulsby, 1988;Cao, 1997;Keylock, 2007;Yuan et al, 2009). To distinguish between different processes, in this study the term "resuspension" is used for particles initially laying on the bed and at some point lifted into the water column, in contrast to particles permanently in suspension (i.e., washload).…”

Section: Turbulent Burstingmentioning

confidence: 99%

The influence of turbulent bursting on sediment resuspension under unidirectional currents

et al. 2017

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Abstract. Laboratory experiments were conducted in an open channel flume with a flat sandy bed to examine the role of turbulence on sediment resuspension. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components and acoustic backscatter as a proxy to suspended sediment concentration. Estimates of sediment transport assume that there is a mean critical velocity that needs to be exceeded before sediment transport is initiated. This approach does not consider the turbulent flow field that may initiate sediment resuspension through event-based processes such as the "bursting" phenomenon. In this paper, laboratory measurements were used to examine the sediment resuspension processes below and above the mean critical velocity. The results within a range above and below the measured mean critical velocity suggested that (1) the contribution of turbulent bursting events remained identical in both experimental conditions, (2) ejection and sweep events contributed more to the total sediment flux than up-acceleration and down-deceleration events, and (3) wavelet transform revealed a correlation between the momentum and sediment flux in both test conditions. Such similarities in conditions above and below the measured mean critical velocity highlight the need to re-evaluate the accuracy of a single time-averaged mean critical velocity for the initiation of sediment entrainment.

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Sand Transport on the Continental Shelf

Cited by 140 publications

References 43 publications

Cross‐shore sediment transport and the equilibrium morphology of mudflats under tidal currents

Cross‐shore sediment transport and the equilibrium morphology of mudflats under tidal currents

Wave-induced coherent turbulence structures and sediment resuspension in the nearshore of a prototype-scale sandy barrier beach

The influence of turbulent bursting on sediment resuspension under unidirectional currents

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