Sediment transport and shear stress partitioning in a vegetated flow

Bouteiller, Caroline Le; Venditti, Jeremy G.

doi:10.1002/2014wr015825

Cited by 70 publications

(78 citation statements)

References 65 publications

(128 reference statements)

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“…The total resistance experienced by the overlying flow (

τ_{t o t a l}

) is often partitioned into two components: (1) a bed stress component

(|, τ_{b e d})

that is due to the stress imposed by sediment grains at the bed; and (2) a form drag component

(|, τ_{d r a g})

that is due to drag forces either by mobile bed forms [e.g., Van Rijn , ] or by immobile roughness (e.g., coral structures or aquatic vegetation, Le Bouteiller and Venditti , ].

τ_{t o t a l} = τ_{b e d} + τ_{d r a g}

…”

Section: Background: Flow Structure and Sediment Transport Within Roumentioning

confidence: 99%

“…[]). While the overlying flow may experience increased hydraulic resistance as a result of this roughness, the flow that actually interacts with the underlying bed can be substantially attenuated, which in turn reduces the bed shear stresses [e.g., Le Bouteiller and Venditti , ]. In aquatic canopies, this flow attenuation can promote sediment deposition, especially when canopy densities are high [e.g., Gacia et al ., ; James et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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Sediment transport in the presence of large reef bottom roughness

Pomeroy

Lowe

Ghisalberti

et al. 2017

J. Geophys. Res. Oceans

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The presence of large bottom roughness, such as that formed by benthic organisms on coral reef flats, has important implications for the size, concentration, and transport of suspended sediment in coastal environments. A 3 week field study was conducted in approximately 1.5 m water depth on the reef flat at Ningaloo Reef, Western Australia, to quantify the cross‐reef hydrodynamics and suspended sediment dynamics over the large bottom roughness (∼20–40 cm) at the site. A logarithmic mean current profile consistently developed above the height of the roughness; however, the flow was substantially reduced below the height of the roughness (canopy region). Shear velocities inferred from the logarithmic profile and Reynolds stresses measured at the top of the roughness, which are traditionally used in predictive sediment transport formulations, were similar but much larger than that required to suspend the relatively coarse sediment present at the bed. Importantly, these stresses did not represent the stresses imparted on the sediment measured in suspension and are therefore not relevant to the description of suspended sediment transport in systems with large bottom roughness. Estimates of the bed shear stresses that accounted for the reduced near‐bed flow in the presence of large roughness vastly improved the relationship between the predicted and observed grain sizes that were in suspension. Thus, the impact of roughness, not only on the overlying flow but also on bed stresses, must be accounted for to accurately estimate suspended sediment transport in regions with large bottom roughness, a common feature of many shallow coastal ecosystems.

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“…The total resistance experienced by the overlying flow (

τ_{t o t a l}

) is often partitioned into two components: (1) a bed stress component

(|, τ_{b e d})

that is due to the stress imposed by sediment grains at the bed; and (2) a form drag component

(|, τ_{d r a g})

that is due to drag forces either by mobile bed forms [e.g., Van Rijn , ] or by immobile roughness (e.g., coral structures or aquatic vegetation, Le Bouteiller and Venditti , ].

τ_{t o t a l} = τ_{b e d} + τ_{d r a g}

…”

Section: Background: Flow Structure and Sediment Transport Within Roumentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sediment transport in the presence of large reef bottom roughness

Pomeroy

Lowe

Ghisalberti

et al. 2017

J. Geophys. Res. Oceans

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“…Recent studies involving 2-D depth-averaged models (Chen et al, 2007;Le Bouteiller and Venditti, 2015) have quantified the effect of vegetation through parameterization as "form drag" as opposed to "skin friction". To account for 3-D vertical structures, estuary-scale models have implemented both mean and turbulent flow impacts of vegetation (Temmerman et al, 2005;Kombiadou et al, 2014;Lapetina and Sheng, 2014).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity analysis of a coupled hydrodynamic-vegetation model using the effectively subsampled quadratures method (ESQM v5.2)

et al. 2017

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Abstract. Coastal hydrodynamics can be greatly affected by the presence of submerged aquatic vegetation. The effect of vegetation has been incorporated into the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system. The vegetation implementation includes the plant-induced three-dimensional drag, in-canopy waveinduced streaming, and the production of turbulent kinetic energy by the presence of vegetation. In this study, we evaluate the sensitivity of the flow and wave dynamics to vegetation parameters using Sobol' indices and a least squares polynomial approach referred to as the Effective Quadratures method. This method reduces the number of simulations needed for evaluating Sobol' indices and provides a robust, practical, and efficient approach for the parameter sensitivity analysis. The evaluation of Sobol' indices shows that kinetic energy, turbulent kinetic energy, and water level changes are affected by plant stem density, height, and, to a lesser degree, diameter. Wave dissipation is mostly dependent on the variation in plant stem density. Performing sensitivity analyses for the vegetation module in COAWST provides guidance to optimize efforts and reduce exploration of parameter space for future observational and modeling work.

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“…3, parts B). By analogy with measurements made in a water flume (Wiberg and Nelson, 1992;Le Bouteiller and Venditti, 2015), it can be considered that the flow and turbulence in the sastrugi region are the result of interaction between flow separation and wake formation, which can lead to a local Reynolds shear stress peak corresponding to flow separation. Above the region of influence of the wake, named outer region, the flow has adjusted to increased roughness and exhibited a logarithmic profile, as shown by the relative continuous time series of C DN10 and u * (Fig.…”

Section: Discussionmentioning

confidence: 99%

Brief communication: Two well-marked cases of aerodynamic adjustment of sastrugi

et al. 2016

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Abstract. In polar regions, sastrugi are a direct manifestation of drifting snow and form the main surface roughness elements. In turn, sastrugi alter the generation of atmospheric turbulence and thus modify the wind field and the aeolian snow mass fluxes. Little attention has been paid to these feedback processes, mainly because of experimental difficulties. As a result, most polar atmospheric models currently ignore sastrugi over snow-covered regions. This paper aims at quantifying the potential influence of sastrugi on the local wind field and on snow erosion over a sastrugi-covered snowfield in coastal Adélie Land, East Antarctica. We focus on two erosion events during which sastrugi responses to shifts in wind direction have been interpreted from temporal variations in drag and aeolian snow mass flux measurements during austral winter 2013. Using this data set, it is shown that (i) neutral stability, 10 m drag coefficient (C DN10 ) values are in the range of 1.3-1.5 × 10 −3 when the wind is well aligned with the sastrugi, (ii) as the wind shifts by only 20-30 • away from the streamlined direction, C DN10 increases (by 30-120 %) and the aeolian snow mass flux decreases (by 30-80 %), thereby reflecting the growing contribution of the sastrugi form drag to the total surface drag and its inhibiting effect on snow erosion, (iii) the timescale of sastrugi aerodynamic adjustment can be as short as 3 h for friction velocities greater than 1 m s −1 and during strong drifting snow conditions and (iv) knowing C DN10 is not sufficient to estimate the snow erosion flux that results from drag partitioning at the surface because C DN10 includes the contribution of the sastrugi form drag.

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Sediment transport and shear stress partitioning in a vegetated flow

Cited by 70 publications

References 65 publications

Sediment transport in the presence of large reef bottom roughness

Sediment transport in the presence of large reef bottom roughness

Sensitivity analysis of a coupled hydrodynamic-vegetation model using the effectively subsampled quadratures method (ESQM v5.2)

Brief communication: Two well-marked cases of aerodynamic adjustment of sastrugi

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