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Longshore Transport Variability of Beach Face Grain Size : Implications for Dune Evolution

Hallin, Caroline LU ; Almström, Björn LU ; Larson, Magnus LU and Hanson, Hans LU (2019) In Journal of Coastal Research 35(4). p.751-764
Abstract
This study investigates grain-size sorting through longshore transport processes and how it influences dune evolution.The analysis is based on a data set of 58 sediment samples distributed alongshore over a 6.5-km-long sandy beach in Ängelholm, Sweden. Grain size differs significantly from north to south, where median grain size varies from about 0.4–0.15 mm. The long-term coastal evolution is derived from shoreline change analysis of a series of aerial photos from the1940s until today and from longshore sediment transport rates calculated on the basis of wave data simulated by the SWAN wave model employed in the Coastal Engineering Research Center (CERC) formula. The results show an almost unidirectional longshore transport from north to... (More)
This study investigates grain-size sorting through longshore transport processes and how it influences dune evolution.The analysis is based on a data set of 58 sediment samples distributed alongshore over a 6.5-km-long sandy beach in Ängelholm, Sweden. Grain size differs significantly from north to south, where median grain size varies from about 0.4–0.15 mm. The long-term coastal evolution is derived from shoreline change analysis of a series of aerial photos from the1940s until today and from longshore sediment transport rates calculated on the basis of wave data simulated by the SWAN wave model employed in the Coastal Engineering Research Center (CERC) formula. The results show an almost unidirectional longshore transport from north to south; the beach is eroding in the northern part and accreting in thesouthern part. The McLaren model, a grain size–based model to predict transport direction, was tested against the grainsize data. The test indicated transport in the opposite direction. This result supports previous studies suggesting that the McLaren model has limited applicability for sandy beaches with a dominant longshore transport. The sediment sampleswere collected at the mid–beach face position in an area where sediment is supplied to the beach during accreting conditions. Sediment in the appropriate grain size to build dunes—at this beach, 0.2–0.3 mm—was found in the parts ofthe beach where the dunes are growing. In the eroding parts, the sediment was coarser, suggesting that the longshore transport influences the supply of sediment for aeolian transport. The gradients in longshore transport rate were also found to affect dune morphology; the dunes were higher in the eroding and stable parts of the beach and lower in the accreting parts. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Coastal Research
volume
35
issue
4
pages
14 pages
publisher
Coastal Education and Research Foundation
external identifiers
  • scopus:85068465235
ISSN
0749-0208
DOI
10.2112/JCOASTRES-D-18-00153.1
language
English
LU publication?
yes
id
27bfa8aa-bae9-445c-b579-c569c9591385
date added to LUP
2019-05-21 11:37:39
date last changed
2019-08-06 03:19:43
@article{27bfa8aa-bae9-445c-b579-c569c9591385,
  abstract     = {This study investigates grain-size sorting through longshore transport processes and how it influences dune evolution.The analysis is based on a data set of 58 sediment samples distributed alongshore over a 6.5-km-long sandy beach in Ängelholm, Sweden. Grain size differs significantly from north to south, where median grain size varies from about 0.4–0.15 mm. The long-term coastal evolution is derived from shoreline change analysis of a series of aerial photos from the1940s until today and from longshore sediment transport rates calculated on the basis of wave data simulated by the SWAN wave model employed in the Coastal Engineering Research Center (CERC) formula. The results show an almost unidirectional longshore transport from north to south; the beach is eroding in the northern part and accreting in thesouthern part. The McLaren model, a grain size–based model to predict transport direction, was tested against the grainsize data. The test indicated transport in the opposite direction. This result supports previous studies suggesting that the McLaren model has limited applicability for sandy beaches with a dominant longshore transport. The sediment sampleswere  collected  at  the  mid–beach  face  position  in  an  area  where  sediment  is  supplied  to  the  beach  during  accreting conditions. Sediment in the appropriate grain size to build dunes—at this beach, 0.2–0.3 mm—was found in the parts ofthe beach where the dunes are growing. In the eroding parts, the sediment was coarser, suggesting that the longshore transport influences the supply of sediment for aeolian transport. The gradients in longshore transport rate were also found to affect dune morphology; the dunes were higher in the eroding and stable parts of the beach and lower in the accreting parts.},
  author       = {Hallin, Caroline and Almström, Björn and Larson, Magnus and Hanson, Hans},
  issn         = {0749-0208},
  language     = {eng},
  number       = {4},
  pages        = {751--764},
  publisher    = {Coastal Education and Research Foundation},
  series       = {Journal of Coastal Research},
  title        = {Longshore Transport Variability of Beach Face Grain Size : Implications for Dune Evolution},
  url          = {http://dx.doi.org/10.2112/JCOASTRES-D-18-00153.1},
  volume       = {35},
  year         = {2019},
}