Cargando…

Shortwave Sand Transport in the Shallow Surf Zone

Empirical parameterizations of the shortwave sand transport that are used in practical engineering models lack the representation of certain processes to accurately predict morphodynamics in shallow water. Therefore, measurements of near‐bed velocity and suspended sand concentration, collected durin...

Descripción completa

Detalles Bibliográficos
Autores principales: Brinkkemper, J. A., Aagaard, T., de Bakker, A. T. M., Ruessink, B. G.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049877/
https://www.ncbi.nlm.nih.gov/pubmed/30034978
http://dx.doi.org/10.1029/2017JF004425
_version_ 1783340244780711936
author Brinkkemper, J. A.
Aagaard, T.
de Bakker, A. T. M.
Ruessink, B. G.
author_facet Brinkkemper, J. A.
Aagaard, T.
de Bakker, A. T. M.
Ruessink, B. G.
author_sort Brinkkemper, J. A.
collection PubMed
description Empirical parameterizations of the shortwave sand transport that are used in practical engineering models lack the representation of certain processes to accurately predict morphodynamics in shallow water. Therefore, measurements of near‐bed velocity and suspended sand concentration, collected during two field campaigns (at the Sand Engine and Ameland, the Netherlands) and one field‐scale laboratory experiment (BARDEXII), were here analyzed to study the magnitude and direction of the shortwave sand flux in the shallow surf zone. Shortwave sand fluxes dominated the total sand flux during low‐energetic accretive conditions, while the mean cross‐shore current (undertow) dominated the total flux during high‐energetic erosive conditions. Under low‐energetic conditions, the onshore‐directed shortwave sand flux scales with the root‐mean‐square orbital velocity u (rms) and velocity asymmetry A (u) but not with the velocity skewness. Under more energetic conditions the shortwave flux reduces with an increase in the cross‐shore mean current [Formula: see text] and can even become offshore directed. For all data combined, the contribution of the shortwave flux to the total flux scales with [Formula: see text] , with a high contribution of the shortwave flux (∼70%) when this ratio is high (∼ 10) and low contributions (∼0%) when this ratio is low (∼1). We argue that the velocity asymmetry is a good proxy for the net effect of several transport mechanisms in the shallow surf zone, including breaking‐induced turbulence. These field and laboratory measurements under irregular waves thus support the hypothesis that the inclusion of velocity asymmetry in transport formulations would improve the performance of morphodynamic models in shallow water.
format Online
Article
Text
id pubmed-6049877
institution National Center for Biotechnology Information
language English
publishDate 2018
publisher John Wiley and Sons Inc.
record_format MEDLINE/PubMed
spelling pubmed-60498772018-07-20 Shortwave Sand Transport in the Shallow Surf Zone Brinkkemper, J. A. Aagaard, T. de Bakker, A. T. M. Ruessink, B. G. J Geophys Res Earth Surf Research Articles Empirical parameterizations of the shortwave sand transport that are used in practical engineering models lack the representation of certain processes to accurately predict morphodynamics in shallow water. Therefore, measurements of near‐bed velocity and suspended sand concentration, collected during two field campaigns (at the Sand Engine and Ameland, the Netherlands) and one field‐scale laboratory experiment (BARDEXII), were here analyzed to study the magnitude and direction of the shortwave sand flux in the shallow surf zone. Shortwave sand fluxes dominated the total sand flux during low‐energetic accretive conditions, while the mean cross‐shore current (undertow) dominated the total flux during high‐energetic erosive conditions. Under low‐energetic conditions, the onshore‐directed shortwave sand flux scales with the root‐mean‐square orbital velocity u (rms) and velocity asymmetry A (u) but not with the velocity skewness. Under more energetic conditions the shortwave flux reduces with an increase in the cross‐shore mean current [Formula: see text] and can even become offshore directed. For all data combined, the contribution of the shortwave flux to the total flux scales with [Formula: see text] , with a high contribution of the shortwave flux (∼70%) when this ratio is high (∼ 10) and low contributions (∼0%) when this ratio is low (∼1). We argue that the velocity asymmetry is a good proxy for the net effect of several transport mechanisms in the shallow surf zone, including breaking‐induced turbulence. These field and laboratory measurements under irregular waves thus support the hypothesis that the inclusion of velocity asymmetry in transport formulations would improve the performance of morphodynamic models in shallow water. John Wiley and Sons Inc. 2018-05-28 2018-05 /pmc/articles/PMC6049877/ /pubmed/30034978 http://dx.doi.org/10.1029/2017JF004425 Text en ©2018. The Authors. This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
spellingShingle Research Articles
Brinkkemper, J. A.
Aagaard, T.
de Bakker, A. T. M.
Ruessink, B. G.
Shortwave Sand Transport in the Shallow Surf Zone
title Shortwave Sand Transport in the Shallow Surf Zone
title_full Shortwave Sand Transport in the Shallow Surf Zone
title_fullStr Shortwave Sand Transport in the Shallow Surf Zone
title_full_unstemmed Shortwave Sand Transport in the Shallow Surf Zone
title_short Shortwave Sand Transport in the Shallow Surf Zone
title_sort shortwave sand transport in the shallow surf zone
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049877/
https://www.ncbi.nlm.nih.gov/pubmed/30034978
http://dx.doi.org/10.1029/2017JF004425
work_keys_str_mv AT brinkkemperja shortwavesandtransportintheshallowsurfzone
AT aagaardt shortwavesandtransportintheshallowsurfzone
AT debakkeratm shortwavesandtransportintheshallowsurfzone
AT ruessinkbg shortwavesandtransportintheshallowsurfzone