TY - JOUR
T1 - Observations on decadal sandbar behaviour along a large-scale curved shoreline
AU - Gijsman, R.
AU - Ruessink, Gerben
AU - Visscher, J.
AU - Schlurmann, T.
N1 - Funding Information:
The authors gratefully acknowledge the Coastal Authority of Schleswig‐Holstein (LKN.SH), in particular Arfst Hinrichsen, for the provision of the wave buoy and coastal profile data, the discussion on the findings and the comments on the draft manuscript. We acknowledge Finn Mielck of the Alfred‐Wegener‐Institute (AWI) for sharing the grain size measurement. The study was funded through project STENCIL (Contract No. 03F0761) of the German Ministry of Education and Research (Bundesministerium für Bildung und Forschung or BMBF). We acknowledge the reviewers for their thoughtful comments on the manuscript.
Funding Information:
The authors gratefully acknowledge the Coastal Authority of Schleswig-Holstein (LKN.SH), in particular Arfst Hinrichsen, for the provision of the wave buoy and coastal profile data, the discussion on the findings and the comments on the draft manuscript. We acknowledge Finn Mielck of the Alfred-Wegener-Institute (AWI) for sharing the grain size measurement. The study was funded through project STENCIL (Contract No. 03F0761) of the German Ministry of Education and Research (Bundesministerium f?r Bildung und Forschung or BMBF). We acknowledge the reviewers for their thoughtful comments on the manuscript.
Publisher Copyright:
© 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd
PY - 2021/2
Y1 - 2021/2
N2 - Nearshore sandbars are characteristic features of sandy surf zones and have been observed with a variety of geometries in cross-shore (e.g. location) and longshore direction (e.g. planform). Although the behaviour of sandbars has been studied extensively on spatial scales up to kilometres and timescales up to years, it remains challenging to observe and explain their behaviour on larger spatial and temporal scales, especially in locations where coastline curvature can be prominent. In this paper, we study a data set with 38 years of coastal profiles, collected with alongshore intervals of 50 m, along the 34 km-long curved sandy shoreline of Sylt island, Germany. Sylt's shoreline has an orientation difference of ~20° between the northern and southern half of the island. We found that the decadal coastal profiles on the southern half show features of a low-tide terrace and a sandbar located further from the shoreline (~441 m). On the nothern half, the sandbar was located closer to the shoreline (~267 m) and was less pronounced, while the profiles show transverse bar and rip features. The alongshore planform also differed systematically and significantly along the two island sides. The sandbar on the southern island half, with alongshore periodicity on a larger length scale (~2240 m), was coupled out-of-phase to the shoreline, while no phase coupling was observed for the sandbar with periodicity on a shorter length scale (~670 m) on the northern half. We related the observed geometric differences of the sandbars to the difference in the local wave climate along Sylt, imposed by the shoreline shape. Our observations imply that small alongshore variations in wave climate, due to the increasing shoreline curvature on larger spatial scales, can lead to significant alongshore differences in the decadal evolution of coastal profiles, sandbars and shorelines.
AB - Nearshore sandbars are characteristic features of sandy surf zones and have been observed with a variety of geometries in cross-shore (e.g. location) and longshore direction (e.g. planform). Although the behaviour of sandbars has been studied extensively on spatial scales up to kilometres and timescales up to years, it remains challenging to observe and explain their behaviour on larger spatial and temporal scales, especially in locations where coastline curvature can be prominent. In this paper, we study a data set with 38 years of coastal profiles, collected with alongshore intervals of 50 m, along the 34 km-long curved sandy shoreline of Sylt island, Germany. Sylt's shoreline has an orientation difference of ~20° between the northern and southern half of the island. We found that the decadal coastal profiles on the southern half show features of a low-tide terrace and a sandbar located further from the shoreline (~441 m). On the nothern half, the sandbar was located closer to the shoreline (~267 m) and was less pronounced, while the profiles show transverse bar and rip features. The alongshore planform also differed systematically and significantly along the two island sides. The sandbar on the southern island half, with alongshore periodicity on a larger length scale (~2240 m), was coupled out-of-phase to the shoreline, while no phase coupling was observed for the sandbar with periodicity on a shorter length scale (~670 m) on the northern half. We related the observed geometric differences of the sandbars to the difference in the local wave climate along Sylt, imposed by the shoreline shape. Our observations imply that small alongshore variations in wave climate, due to the increasing shoreline curvature on larger spatial scales, can lead to significant alongshore differences in the decadal evolution of coastal profiles, sandbars and shorelines.
KW - alongshore variability
KW - coastal profiles
KW - curved coastlines
KW - nearshore morphology
KW - nearshore sandbars
KW - sandbar–shoreline coupling
UR - http://www.scopus.com/inward/record.url?scp=85099367180&partnerID=8YFLogxK
U2 - 10.1002/esp.5041
DO - 10.1002/esp.5041
M3 - Article
SN - 0197-9337
VL - 46
SP - 490
EP - 503
JO - Earth Surface Processes and Landforms
JF - Earth Surface Processes and Landforms
IS - 2
ER -