Suspended Sediment Concentration on Beaches Under Three Different Mechanisms

Abstract

A set predictive models is formulated for computing suspended sediment concentration in and outside the surf zone under three different mechanisms:(1) suspension due to turbulence motion over sand ripples,(2) suspension from sheet flow layer, and(3) suspension due to turbulence motion under breaking waves. Dimensional analysis and best-fit technique are the main methods for the formulation of reference concentration and diffusion coefficient and the model parameters are calibrated with the help of a large amount of published data. Time-averaged concentration profiles are derived from the steady diffusion equation, Published experimental data from 19 sources from 1977 to 1966 are better explained by the proposed formulae than the preceding formulae of Sleath [1982], Nielsen [1986 and 1988] and, Rattanapitikon and Shibayama [1994]. Due to scale effects, models are given for small-scale and large-scale cases separately. Predominance of each suspension mechanism is verified with a newly developed explicit formula. Finally, the applicability of the above sub models for irregular waves is also confirmed by the measured data sets.