AN ENERGETIC TYPE MODEL FOR THE CROSS-SHORE DISTRIBUTION OF TOTAL LONGSHORE SEDIMENT TRANSPORT

Cüneyt Baykal,Işıkhan Güler,Ayşen Ergin

doi:10.9753/icce.v33.sediment.40

Cüneyt Baykal, Işıkhan Güler + Show 1 more

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https://doi.org/10.9753/icce.v33.sediment.40

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Abstract

This paper presents an energetic-based simple approach for the computation of cross-shore distribution of total longshore sediment transport (LST) rates. The proposed approach (Baykal 2012) follows similar assumptions with the given formula of Bayram et al. (2007) for the total LST rate (Qlst,t) across the surf zone and is applied to investigate the relation between the rate of dissipation in wave energy flux due to wave breaking and total longshore sediment flux using the available laboratory measurements of Wang et al. (2002) and Gravens and Wang (2007) and the field measurements carried out at Duck site, North Carolina, USA between years 1995-1998 (Miller 1999). The proposed approach is also compared with some of the available distributed total load models. From the comparative studies, it is found that the proposed approach shows good agreement with both the laboratory and field measurements, using a single empirical constant, both qualitatively and quantitatively, especially for the cases where the wave conditions are highly energetic (both for plunging and spilling type breakers) and the suspended load is the main mode of sediment transport in the surf zone.

Highlights

Over the years, numerous approaches have been developed for the prediction of longshore sediment transport (LST) rates within the surf zone due to waves and currents
In the proposed approach, the total work (w*) needed to keep sediments in suspension per unit length in cross-shore direction is done by a certain part (ε) of the rate of dissipation in wave energy flux due to wave breaking (w*=ε∙Db), and the steady state conditions prevail for the respective unit length and the sediment concentration in the water column is carried with a depth-averaged longshore current velocity (v)
It has been observed that 91% and 74% of the predicted transport rates using the SED1 approach lies within a factor of 0.25-4.0 of the measured values for the selected laboratory and field experiments, respectively, using a constant coefficient (ε=0.002) for both, where such empirical coefficients might show variability for laboratory and field conditions as given in Table 3 and Table 4 for the Watanabe (1992), Bagnold (1963) and Bodge (1989) expressions

Summary

Introduction

Numerous approaches have been developed for the prediction of longshore sediment transport (LST) rates within the surf zone due to waves and currents. Bagnold (1963), Bijker (1967, 1971), Engelund and Hansen (1967), Ackers and White (1973), Bodge (1989), Van Rijn (1984), Watanabe (1992) and more recently Camenen and Larson (2005, 2007 and 2008), Kobayashi et al (2007) and Kuriyama (2010) are some of these distributed sediment transport rate formulas These approaches are mainly divided into two categories; the “energetics” models, which assume the mobilizing mechanism is a function of wave energy dissipation, and “stress” models, in which shear stress exerted on the bottom by waves and currents mobilize sediment. Bodge and Dean (1987), Bayram et al (2001) and Van Maanen et al (2009) give evaluation of the various distributed sediment transport approaches and compare their capabilities in predicting the cross-shore distribution of LST rates for the selected data sets

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