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

T. O'Donoghue, G. A. Kikkert, D. Pokrajac, N. Dodd, R. Briganti

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Abstract

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.
Original languageEnglish
Pages (from-to)113-130
Number of pages18
JournalCoastal Engineering
Volume112
Early online date12 Apr 2016
DOIs
Publication statusPublished - Jun 2016

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Beaches
Sediments
Hydrodynamics
Fluxes
Gravel
Sand
Sediment traps
Experiments
Flow velocity
Shear stress

Keywords

  • swash
  • hydrodynamics
  • sediment transport
  • shear stress
  • laboratory
  • dambreak

Cite this

Intra-swash hydrodynamics and sediment flux for dambreak swash on coarse-grained beaches. / O'Donoghue, T.; Kikkert, G. A.; Pokrajac, D.; Dodd, N.; Briganti, R.

In: Coastal Engineering, Vol. 112, 06.2016, p. 113-130.

Research output: Contribution to journalArticle

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abstract = "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 M{\"u}ller 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.",
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note = "Acknowledgements The research reported in this paper was conducted as part of a collaborative research project involving the Universities of Aberdeen and Nottingham in the UK, funded by the UK's Engineering and Physical Sciences Research Council (EPSRC grants EP/E011330/1 and EP/E010407/1). Riccardo Briganti acknowledges support through an EPSRC Career Acceleration Fellowship (EP/I004505/1). The paper has benefitted from the helpful comments provided by Professor Tom Baldock and an anonymous reviewer.",
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AU - Pokrajac, D.

AU - Dodd, N.

AU - Briganti, R.

N1 - Acknowledgements The research reported in this paper was conducted as part of a collaborative research project involving the Universities of Aberdeen and Nottingham in the UK, funded by the UK's Engineering and Physical Sciences Research Council (EPSRC grants EP/E011330/1 and EP/E010407/1). Riccardo Briganti acknowledges support through an EPSRC Career Acceleration Fellowship (EP/I004505/1). The paper has benefitted from the helpful comments provided by Professor Tom Baldock and an anonymous reviewer.

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N2 - 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.

AB - 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.

KW - swash

KW - hydrodynamics

KW - sediment transport

KW - shear stress

KW - laboratory

KW - dambreak

U2 - 10.1016/j.coastaleng.2016.03.004

DO - 10.1016/j.coastaleng.2016.03.004

M3 - Article

VL - 112

SP - 113

EP - 130

JO - Coastal Engineering

JF - Coastal Engineering

SN - 0378-3839

ER -