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

Joep van der Zanden, J.M. Alsina, I. Caceres, René Buijsrogge, Jan S. Ribberink

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Detailed measurements of bed level motions and sheet flow processes in the lower swash are presented. The measurements are obtained during a large-scale wave flume experiment focusing on swash zone sediment transport induced by bichromatic waves. A new instrument (CCM+) provides detailed phase-averaged measurements of sheet flow concentrations, particle velocities, and bed level evolution during a complete swash cycle. The bed at the lower swash location shows a clear pattern of rapid erosion during the early uprush and progressive accretion during the middle backwash phase. Sheet flow occurs during the early uprush and mid and late backwash phases. Sheet flow sediment fluxes during these instances are highest in the pick-up layer. Sediment entrainment from the pick-up layer occurs not only during instances of high horizontal shear velocities but also in occurrence of wave–backwash interactions. As opposed to oscillatory sheet flow, the pivot point elevation of the sheet flow layer is time-varying during a swash event. Moreover, the upper sheet flow layer concentrations do not mirror the concentrations in the pick-up layer. Both differences suggest that in the lower swash zone the dynamics of the upper sheet flow layer are not only controlled by vertical sediment exchange (such as in oscillatory sheet flows) but are strongly affected by horizontal advection processes induced by the non-uniformity of the flow.
Original languageEnglish
Pages (from-to)47-65
JournalCoastal engineering
Volume105
DOIs
Publication statusPublished - 2015

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Sediments
Phase measurement
Sediment transport
Advection
Erosion
Mirrors
Fluxes
Experiments

Keywords

  • IR-100796
  • METIS-311701

Cite this

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title = "Bed level motions and sheet flow processes in the swash zone: observations with a new conductivity-based concentration measuring technique (CCM+)",
abstract = "Detailed measurements of bed level motions and sheet flow processes in the lower swash are presented. The measurements are obtained during a large-scale wave flume experiment focusing on swash zone sediment transport induced by bichromatic waves. A new instrument (CCM+) provides detailed phase-averaged measurements of sheet flow concentrations, particle velocities, and bed level evolution during a complete swash cycle. The bed at the lower swash location shows a clear pattern of rapid erosion during the early uprush and progressive accretion during the middle backwash phase. Sheet flow occurs during the early uprush and mid and late backwash phases. Sheet flow sediment fluxes during these instances are highest in the pick-up layer. Sediment entrainment from the pick-up layer occurs not only during instances of high horizontal shear velocities but also in occurrence of wave–backwash interactions. As opposed to oscillatory sheet flow, the pivot point elevation of the sheet flow layer is time-varying during a swash event. Moreover, the upper sheet flow layer concentrations do not mirror the concentrations in the pick-up layer. Both differences suggest that in the lower swash zone the dynamics of the upper sheet flow layer are not only controlled by vertical sediment exchange (such as in oscillatory sheet flows) but are strongly affected by horizontal advection processes induced by the non-uniformity of the flow.",
keywords = "IR-100796, METIS-311701",
author = "{van der Zanden}, Joep and J.M. Alsina and I. Caceres and Ren{\'e} Buijsrogge and Ribberink, {Jan S.}",
year = "2015",
doi = "10.1016/j.coastaleng.2015.08.009",
language = "English",
volume = "105",
pages = "47--65",
journal = "Coastal engineering",
issn = "0378-3839",
publisher = "Elsevier",

}

Bed level motions and sheet flow processes in the swash zone: observations with a new conductivity-based concentration measuring technique (CCM+). / van der Zanden, Joep; Alsina, J.M.; Caceres, I.; Buijsrogge, René; Ribberink, Jan S.

In: Coastal engineering, Vol. 105, 2015, p. 47-65.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Bed level motions and sheet flow processes in the swash zone: observations with a new conductivity-based concentration measuring technique (CCM+)

AU - van der Zanden, Joep

AU - Alsina, J.M.

AU - Caceres, I.

AU - Buijsrogge, René

AU - Ribberink, Jan S.

PY - 2015

Y1 - 2015

N2 - Detailed measurements of bed level motions and sheet flow processes in the lower swash are presented. The measurements are obtained during a large-scale wave flume experiment focusing on swash zone sediment transport induced by bichromatic waves. A new instrument (CCM+) provides detailed phase-averaged measurements of sheet flow concentrations, particle velocities, and bed level evolution during a complete swash cycle. The bed at the lower swash location shows a clear pattern of rapid erosion during the early uprush and progressive accretion during the middle backwash phase. Sheet flow occurs during the early uprush and mid and late backwash phases. Sheet flow sediment fluxes during these instances are highest in the pick-up layer. Sediment entrainment from the pick-up layer occurs not only during instances of high horizontal shear velocities but also in occurrence of wave–backwash interactions. As opposed to oscillatory sheet flow, the pivot point elevation of the sheet flow layer is time-varying during a swash event. Moreover, the upper sheet flow layer concentrations do not mirror the concentrations in the pick-up layer. Both differences suggest that in the lower swash zone the dynamics of the upper sheet flow layer are not only controlled by vertical sediment exchange (such as in oscillatory sheet flows) but are strongly affected by horizontal advection processes induced by the non-uniformity of the flow.

AB - Detailed measurements of bed level motions and sheet flow processes in the lower swash are presented. The measurements are obtained during a large-scale wave flume experiment focusing on swash zone sediment transport induced by bichromatic waves. A new instrument (CCM+) provides detailed phase-averaged measurements of sheet flow concentrations, particle velocities, and bed level evolution during a complete swash cycle. The bed at the lower swash location shows a clear pattern of rapid erosion during the early uprush and progressive accretion during the middle backwash phase. Sheet flow occurs during the early uprush and mid and late backwash phases. Sheet flow sediment fluxes during these instances are highest in the pick-up layer. Sediment entrainment from the pick-up layer occurs not only during instances of high horizontal shear velocities but also in occurrence of wave–backwash interactions. As opposed to oscillatory sheet flow, the pivot point elevation of the sheet flow layer is time-varying during a swash event. Moreover, the upper sheet flow layer concentrations do not mirror the concentrations in the pick-up layer. Both differences suggest that in the lower swash zone the dynamics of the upper sheet flow layer are not only controlled by vertical sediment exchange (such as in oscillatory sheet flows) but are strongly affected by horizontal advection processes induced by the non-uniformity of the flow.

KW - IR-100796

KW - METIS-311701

U2 - 10.1016/j.coastaleng.2015.08.009

DO - 10.1016/j.coastaleng.2015.08.009

M3 - Article

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