Abstract
The existence of sandy beaches relies on the onshore transport of sand by waves during post-storm conditions. Most operational sediment transport models employ wave-averaged terms, and/or the instantaneous cross-shore velocity signal, but the models often fail in predictions of the onshore-directed transport rates. An important reason is that they rarely consider the phase relationships between wave orbital velocity and the suspended sediment concentration. This relationship depends on the intra-wave structure of the bed shear stress and hence on the timing and magnitude of turbulence production in the water column. This paper provides an up-to-date review of recent experimental advances on intra-wave turbulence characteristics, sediment mobilization, and suspended sediment transport in laboratory and natural surf zones. Experimental results generally show that peaks in the suspended sediment concentration are shifted forward on the wave phase with increasing turbulence levels and instantaneous near-bed sediment concentration scales with instantaneous turbulent kinetic energy. The magnitude and intra-wave phase of turbulence production and sediment concentration are shown to depend on wave (breaker) type, seabed configuration, and relative wave height, which opens up the possibility of more robust predictions of transport rates for different wave and beach conditions.
Highlights
The coexistence and interaction of hydrodynamic motions over a wide range of timescales create a rather chaotic surf zone environment
The present paper aims to provide an up-to-date review of recent experimental advances on turbulence characteristics and generation in the surf zone and its effects on sediment mobilization, suspended sediment load, and wave-driven
Aagaard and Hughes [28] observed that the impact of breaking waves on the seabed generated large sediment clouds, and under plunging breakers up to 85% of the suspended sediment load was associated with large breaker vortices
Summary
Troels Aagaard 1, *, Joost Brinkkemper 2 , Drude F. Coastal Ocean Fluid Dynamics Laboratory (COFDL), Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
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