Bed level motions and sheet flow processes in the swash zone: Observations with a new conductivity-based concentration measuring technique (CCM + )

Zanden, Joep van der; Alsina, José M.; Caceres, Ivàn; Buijsrogge, R.H.; Ribberink, Jan S.

doi:10.1016/j.coastaleng.2015.08.009

Cited by 31 publications

(54 citation statements)

References 41 publications

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“…These have yielded insights into swash zone sediment processes and morphology, but, as for field experiments, estimates of swash sediment transport are either inferred from bed elevation measurements or are limited to suspended sediment flux based on co-located velocity and suspended sediment concentration measurements. More recently, van der Zanden et al (2015) and Puleo et al (in press) obtained measurements of intra-swash sediment concentrations and velocities within the sheet-flow layer of swash in large-scale wave flume experiments. The studies used conductivity-based instrumentation for the concentration measurements; for the sheet-flow velocities, Puleo et al (in press) used an acoustic velocity profiler while van der Zanden et al (2015) cross-correlated concentration measurements from a pair of concentration probes horizontally separated by 15 mm.…”

Section: Introductionmentioning

confidence: 99%

“…More recently, van der Zanden et al (2015) and Puleo et al (in press) obtained measurements of intra-swash sediment concentrations and velocities within the sheet-flow layer of swash in large-scale wave flume experiments. The studies used conductivity-based instrumentation for the concentration measurements; for the sheet-flow velocities, Puleo et al (in press) used an acoustic velocity profiler while van der Zanden et al (2015) cross-correlated concentration measurements from a pair of concentration probes horizontally separated by 15 mm.…”

Section: Introductionmentioning

confidence: 99%

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Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches

O’Donoghue

Kikkert

Pokrajac

et al. 2016

Coastal Engineering

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The paper reports on dambreak-type swash experiments in which intra-swash hydrodynamics and sediment flux are measured for swash on a coarse sand beach and a gravel beach. Flow velocity and depth are measured using PIV and LIF respectively; the intra-swash sediment flux is measured using sediment traps. Comparison of measured hydrodynamics with the immobile, permeable bed experiments of Kikkert et al. (2013) indicate that bed mobility impacts on the swash hydrodynamics, reducing the maximum run-up by approximately 8% for both beaches, compared to the maximum run-up on the corresponding immobile beach. The measured intra swash sediment flux at a given location is characterised by high flux at the moment of bore arrival, followed by rapid decay during uprush, becoming zero at some time before flow reversal. For the gravel beach, the backwash sediment flux is negligibly small, while for the sand beach the backwash flux increases slowly as the flow accelerates down the beach, and peaks at about the time of maximum backwash velocity. Intraswash sediment flux calculated using the Meyer-Peter and Müller bed load transport formula, with measured hydrodynamics as input and bed shear stress estimated using both the Swart and Colebrook formulae, are within a factor 2 of the measured intra-swash flux. The agreement between the calculated and measured flux is better for the sand beach than for the gravel beach, and better for uprush than for backwash. For the sand beach there is good agreement between calculated and measured total uprush and total backwash sediment volumes. The agreement is less good for the gravel beach, for which calculated and measured uprush volumes show a similar trend but the calculated backwash volumes over-estimate the (negligible) volumes observed in the experiments. Field experiments investigating swash hydrodynamics and sediment dynamics have developed substantially over the last two decades in terms of the sophistication of the instruments deployed and the degree to which detailed processes are captured by the measurements. Regarding sediment flux, sediment trapping has been used to measure total uprush and total backwash transport volumes (Hughes et al., 1997;Masselink and Hughes, 1998;Austin & Masselink, 2006;Masselink et al., 2009) and high-resolution bed elevation measurements across the swash zone have been used to obtain net sediment transport volumes for individual swash events (e.g. Blenkinsopp et al., 2011). These measurements are extremely valuable in terms of quantifying sediment fluxes and morphological change for swash events in the field. However, they do not provide a complete picture since they reveal little (in the case of traps) or nothing (in the case of bed elevation measurements) of the sediment flux during a swash event. In principle, measurements of intra-swash sediment flux can be obtained from co-located measurements of velocities and concentrations, but obtaining these measurements sufficiently accurately over the complete water column to give total sediment flux...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches

O’Donoghue

Kikkert

Pokrajac

et al. 2016

Coastal Engineering

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“…1b). Two CCM + tanks ( Van der Zanden et al, 2015) were installed slightly offshore from the bar crest to measure sheet flow concentration and particle velocity. The water surface elevation was measured by sidewall-deployed resistive wave gauges (RWGs) and PTs.…”

Section: Methodsmentioning

confidence: 99%

Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

Zanden

O’Donoghue

et al. 2017

Int. Conf. Coastal. Eng.

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This paper presents results obtained during a large-scale wave flume experiment focused at measuring hydrodynamics and sediment transport processes in the wave breaking region. The experiment involved monochromatic plunging breaking waves over a mobile bed barred profile consisting of D 50 = 0.24 mm sand. Vertical profiles of velocity, turbulence, sand concentration and sand fluxes were measured at 12 cross-shore locations, covering the shoaling region up to the inner surf zone. Particularly high-resolution profiles were obtained near the bed within the wave bottom boundary layer, using an acoustic sediment concentration and velocity profiler (ACVP). Sheet flow concentration and particle velocities were measured at two locations near the bar crest using two conductivity-based concentration measurement tanks (CCM+). Total transport rates, obtained from the evolving bed profile measurements, were decomposed into suspended and bedload transport contributions across the bar. The present paper presents a summary of the key findings of the experiment, which are used to discuss existing approaches for modeling suspended and bed load transport in the surf zone.

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“…Bedload in sheet flow conditions has been extensively studied in wave flumes under non breaking waves (Dohmen Janssen and Hanes, 2002;Schretlen, 2012) and oscillatory flow tunnels (see van der Werf et al, 2009, for an overview). Observations in the swash zone revealed that bore turbulence and cross shore sediment advection may lead to increased sheet flow layer thicknesses compared to non breaking wave observations (van der Zanden et al, 2015a;Lanckriet and Puleo, 2015). Due to a lack of high resolution measurements, it is still unclear if and how wave breaking affects sheet flow transport rates and processes around the breaker bar.…”

Section: Introductionmentioning

confidence: 99%

“…Data from the same experiment were used before to study wave breaking effects on wave bottom boundary layer hydrodynamics (Chapter 2) and on suspension processes (Chapter 3). The present study particularly addresses four matters: (i) the potential effects of wave breaking on sheet flow dynamics, which are measured using a novel conductivity based concentration measurement system (CCM + ; van der Zanden et al, 2015a); (ii) the cross shore variation in bedload transport rates in relation to the hydrodynamic forcing and to the suspended transport; (iii) the contributions of net bedload and suspended sand transport to the morphological evolution of the breaker bar; (iv) grain size sorting of suspended sediment and of the sand bed.…”

Section: Introductionmentioning

confidence: 99%

Sand transport processes in the surf and swash zones

Zanden¹

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Bed level motions and sheet flow processes in the swash zone: Observations with a new conductivity-based concentration measuring technique (CCM + )

Cited by 31 publications

References 41 publications

Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches

Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches

Suspended and Bedload Transport in the Surf Zone: Implications for Sand Transport Models

Sand transport processes in the surf and swash zones

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