Abstract

To quantify the effect of wave breaking turbulence on sediment transport in the nearshore, the vertical distribution of time-averaged suspended sediment concentration (SSC) in the surf zone was parameterized in terms of the turbulent kinetic energy (TKE) at different cross-shore locations, including the bar crest, bar trough, and inner surf zone. Using data from a large-scale laboratory experiment, a simple relationship was developed between the time-averaged SSC and the time-averaged TKE. The vertical variation of the time-averaged SSC was fitted to an equation analogous to the turbulent dissipation rate term. At the bar crest, the proposed equation was slightly modified to incorporate the effect of near-bed sediment processes and yielded reasonable agreement. This parameterization yielded the best agreement at the bar trough, with a coefficient of determination R2 ≥ 0.72 above the bottom boundary layer. The time-averaged SSC in the inner surf zone showed good agreement near the bed but poor agreement near the water surface, suggesting that there is a different sedimentation mechanism that controls the SSC in the inner surf zone.

Highlights

  • Cross-shore sediment transport models have been developed based on energetic-type models (e.g., [1])

  • The relationship between the time-averaged turbulent kinetic energy per unit mass and the sediment concentration was examined at the bar crest, trough, and inner surf zone of a beach using data from a large-scale laboratory experiment

  • Equation (5) describes the relationship between the time-averaged turbulent kinetic energy and the sediment concentration near the bottom, which suggests that the mixing length scale at the bar crest is rather related to the bottom boundary layer thickness

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Summary

Introduction

Cross-shore sediment transport models have been developed based on energetic-type models (e.g., [1]). Time-averaged cross-shore sediment transport model that includes a sediment suspension effect due to wave breaking turbulence. Butt et al [12] modified the energetic-type cross-shore sediment transport model by including turbulent kinetic energy (TKE) terms for the swash and inner surf zones. They showed that the model capability was improved by 55% when bore events (i.e., TKE) were included, suggesting that TKE significantly affects sediment transport. To quantitatively express the effect of turbulence on sediment suspension, this paper proposes a simple relationship between the time-averaged SSC and TKE based on the results of moveable beach observations from a large-scale laboratory experiment.

Observations
Experimental Procedures for Erosive and Accretive Morphological Changes
Velocity and Turbulence Extraction
Sediment Concentration
Cross-Shore Variations of Hydrodynamics
Findings
Summary and Conclusions
Full Text
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