TY - JOUR
T1 - Observations on sandbar behaviour along a man-made curved coast
AU - Rutten, J.
AU - Ruessink, B. G.
AU - Price, T. D.
PY - 2018
Y1 - 2018
N2 - Sandbars, submerged ridges of sand parallel to the shoreline, affect surfzone circulation, beach topography and beach width. Under time-varying wave forcing, sandbars may migrate onshore and offshore, referred to as two-dimensional (2D) behaviour, and vary in planshape from alongshore uniform ridges to alongshore non-uniform ridges through the growth and decay of three-dimensional (3D) patterns, referred to as 3D behaviour. Although 2D and 3D sandbar behaviour is reasonably well understood along straight coasts, this is not the case for curved coasts, where the curvature can invoke spatial variability in wave forcing. Here, we analyse sandbar behaviour along the ∼3000 m man-made curved coastline of the Sand Engine, Netherlands, and determine the wave conditions governing this behaviour. 2D and 3D behaviour was quantified within a box north and west of the Sand Engine's tip, respectively, using a 2.4-year dataset of daily low-tide video images and a sparser bathymetric dataset. The northern and western sides behaved similarly in terms of 2D behaviour, with seasonal onshore and offshore migration, resulting in a stable position on inter-annual timescales. However, both sandbar geometry and 3D behaviour differed substantially between both sides. The geometric differences (bar shape, bar crest depth and wavelength of 3D patterns) are consistent with computed alongshore differences in breaker height due to refraction. The differences in the timing in growth, decay and morphological coupling of 3D patterns in the sandbar and shoreline are likely related to differences in the local wave angle, imposed by the curved coast. Similar dependency of bar behaviour on local wave height and angle may be expected elsewhere along curved coasts, e.g. shoreline sandwaves, cuspate forelands or embayed beaches.
AB - Sandbars, submerged ridges of sand parallel to the shoreline, affect surfzone circulation, beach topography and beach width. Under time-varying wave forcing, sandbars may migrate onshore and offshore, referred to as two-dimensional (2D) behaviour, and vary in planshape from alongshore uniform ridges to alongshore non-uniform ridges through the growth and decay of three-dimensional (3D) patterns, referred to as 3D behaviour. Although 2D and 3D sandbar behaviour is reasonably well understood along straight coasts, this is not the case for curved coasts, where the curvature can invoke spatial variability in wave forcing. Here, we analyse sandbar behaviour along the ∼3000 m man-made curved coastline of the Sand Engine, Netherlands, and determine the wave conditions governing this behaviour. 2D and 3D behaviour was quantified within a box north and west of the Sand Engine's tip, respectively, using a 2.4-year dataset of daily low-tide video images and a sparser bathymetric dataset. The northern and western sides behaved similarly in terms of 2D behaviour, with seasonal onshore and offshore migration, resulting in a stable position on inter-annual timescales. However, both sandbar geometry and 3D behaviour differed substantially between both sides. The geometric differences (bar shape, bar crest depth and wavelength of 3D patterns) are consistent with computed alongshore differences in breaker height due to refraction. The differences in the timing in growth, decay and morphological coupling of 3D patterns in the sandbar and shoreline are likely related to differences in the local wave angle, imposed by the curved coast. Similar dependency of bar behaviour on local wave height and angle may be expected elsewhere along curved coasts, e.g. shoreline sandwaves, cuspate forelands or embayed beaches.
KW - Alongshore variability
KW - Mega-nourishment
KW - Nearshore sandbars
KW - Surfzone morphology
KW - Video analysis
UR - http://www.scopus.com/inward/record.url?scp=85019067094&partnerID=8YFLogxK
U2 - 10.1002/esp.4158
DO - 10.1002/esp.4158
M3 - Article
AN - SCOPUS:85019067094
SN - 0197-9337
VL - 43
SP - 134
EP - 149
JO - Earth Surface Processes and Landforms
JF - Earth Surface Processes and Landforms
ER -