Experiments on the Sediment Transport Along Pool‐Riffle Unit

Hassan, Marwan A.; Chartrand, Shawn M.; Radić, Valentina; Ferrer‐Boix, Carles; Buckrell, Emma; McDowell, Conor

doi:10.1029/2022wr032796

Cited by 10 publications

(8 citation statements)

References 89 publications

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“…Sediment finer than 0.5 mm was excluded to avoid material moving in suspension. The same mixture of sediment was used by Chartrand et al (2018) and Hassan et al (2022). The upstream 8 m long section consisted of a fixed and immobile flat bed made of particles with grain size equal to the D 90 of the parent material (D 90 being the diameter such that 90% of the parent material is finer).…”

Section: Experimental Design Methodology and Datamentioning

confidence: 99%

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Influence of Sediment Supply Timing on Bedload Transport and Bed Surface Texture During a Single Experimental Hydrograph in Gravel Bed Rivers

Hassan,

Li,

Viparelli

et al. 2023

Water Resources Research

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Channel stability and sediment transport in gravel bed streams depend on temporally and spatially variable fluid forces, bed surface structures, armoring, and sediment supply/storage. Of particular interest here is the influence of sediment supply timing on bedload transport rate and grain size distribution, bed surface composition and channel morphology. We conducted flume experiments in a sediment feed flume with poorly sorted sediment. A symmetrical, identical stepped hydrograph was used with five different sediment feeding schemes: no feed, constant feed, rising‐limb only feed, falling‐limb only feed, and variable feed. The same sediment mass of 800 kg was fed during each experiment. Sediment transport rates ranged over five orders of magnitude regardless of feeding scheme. Clockwise hysteresis was observed for bedload transport rate and bedload grain size, that is, the transport rate was larger and coarser during the rising limb. Counterclockwise hysteresis was observed for the grain size distribution of the bed surface, that is, the bed surface was finest during the rising limb. In all experiments sediment yield during the rising was higher than during the falling limb, indicating that the rising limb is more capable to transport the supplied sediment. Our study provides insight on how timing of sediment supply influences sediment transport and bed surface during a single hydrograph, essential information for artificial sediment supply projects to restore and habilitate gravel bed streams.

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Section: Experimental Design Methodology and Datamentioning

confidence: 99%

“…(2018) and Hassan et al. (2022). The upstream 8 m long section consisted of a fixed and immobile flat bed made of particles with grain size equal to the D 90 of the parent material ( D 90 being the diameter such that 90% of the parent material is finer).…”

Section: Introductionmentioning

confidence: 95%

Influence of Sediment Supply Timing on Bedload Transport and Bed Surface Texture During a Single Experimental Hydrograph in Gravel Bed Rivers

Hassan,

Li,

Viparelli

et al. 2023

Water Resources Research

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“…The flume 19 , 33 is 18 m long with the bed inclined at a 1.5% slope. The width is variable, ranging from 0.38 to 0.80 m (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…To characterize the impact of the interactions between particles of various sizes in the proposed conceptual model, we conducted flume experiments with poorly sorted natural sediments (0.5–32 mm). The flume had a varying width (0.38–0.80 m) to force pool-riffle development 19 , in order to more closely recreate natural river conditions. Moreover, our experiment is unique in that a time series of sediment transport rates were measured for individual size classes from a video based light table at a 1 s temporal resolution (see Figs.…”

Section: Introductionmentioning

confidence: 99%

Interaction of various-sized particles in river flow

Fan

Zhong

Nie

et al. 2023

Sci Rep

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Sediment transport is essential to the source-sink systems; however, the interaction between two complex multiscale nonlinear systems, turbulence of the river flow and wide size sediment, has heretofore restricted our understanding of sediment motion. We have conducted flume experiments deploying a video-based technique that records sediment transport rate of each particle size at 1 s resolution. The observations reveal detailed interactions between flow and particles of sizes ranging from 0.5 to 32 mm, such that small suspended particles (< ~ 5 mm) keep swirling in the wake vortices of the keystones (larger than 20 mm) until large to very-large-scale coherent structures destroy the wake vortices and bring the small particles downstream. Keystones destabilize consequently as the surrounding small and intermediate particles move, and in turn, a group of sheltered particles is entrained following the dislodging of the keystones. This heuristic model highlights the interactions of turbulence and different-sized particles.

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“…The persistence of this pool-riffle pattern is selfsustaining with respect to both flowing water and changes in bed terrain. This phenomenon can be attributed to the interplay of spatial patterns in flow velocity and bed-load transport, as discussed by Hassan et al (2022), as well as the downstream control exerted by riffles in non-vegetated sections. As water enters the deeper pool (located at the trailing edge of the patch), its velocity decreases, subsequently reducing the initiation of sediment transport.…”

Section: The Influence Of Bedformsmentioning

confidence: 96%

Drag Coefficient of Emergent Vegetation in a Shallow Nonuniform Flow Over a Mobile Sand Bed

Zhang,

Cheng,

Hassan

et al. 2024

Water Resources Research

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Widely distributed in natural rivers and coasts, vegetation interacts with fluid flows and sediments in a variable and complicated manner. Such interactions make it difficult to predict associated drag forces during sediment transport. This paper investigates the drag coefficient for an emergent vegetated patch area under nonuniform flow and mobile bed conditions, based on an analytical model solving the momentum equation following our previous work (Zhang et al., 2020, https://doi.org/10.1029/2020WR027613). Emergent vegetation was modeled with rigid cylinders arranged in staggered arrays of different vegetation coverage ∅. Laboratory flume tests were conducted to measure variations in both the water and bed surfaces along a vegetated patch on a sand bed. Based on the experimental and theoretical analyses, a dimensionless drag model integrating both terms of flow properties and bed effects is proposed to predict the drag coefficient Cd over a mobile bed. The calculated values of Cd exhibit two different trends, that is, nonmonotonically or monotonically increasing along the streamwise direction, due to the combined effect of water surface gradient and bed slope. The morphodynamic response of the mobile bed to nonuniform flow manifests as an evolution in the bed slope within the vegetated patch. Ongoing scouring directs the flow's energy toward overcoming the rising Cd and bed slope, leading to a relatively stable stage with a low sediment transport rate. This study advances the existing understanding of the drag coefficient's role over a mobile bed within nonuniform flows. It also enhances the applicability of vegetation drag models in riverine restoration.

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Experiments on the Sediment Transport Along Pool‐Riffle Unit

Cited by 10 publications

References 89 publications

Influence of Sediment Supply Timing on Bedload Transport and Bed Surface Texture During a Single Experimental Hydrograph in Gravel Bed Rivers

Influence of Sediment Supply Timing on Bedload Transport and Bed Surface Texture During a Single Experimental Hydrograph in Gravel Bed Rivers

Interaction of various-sized particles in river flow

Drag Coefficient of Emergent Vegetation in a Shallow Nonuniform Flow Over a Mobile Sand Bed

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