Kato, S., Aoki, S., and Torii, H., 2007. Temporal Variation of Graded Suspended Sediment Concentration in the Surf Zone. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 302 – 306. Gold Coast, Australia, ISSN 0749.0208

Some studies have demonstrated that the relationship between suspended sediment concentration and turbidity changes according to the grain size distribution. However, to obtain a more accurate estimation of the suspended sediment concentration (SSC) and associated transport rate by surrogate measurements, such as turbidity and acoustic backscatter, a better understanding of the characteristics of the grain size distribution of the suspended sediment and its variation is necessary. In this research, a sediment size distribution sensor (LISST-100) was employed to perform field measurement of graded grain size (2.5∼500 µm by 32 log-scaled size bins) in suspended sediment and its volume concentration under storm conditions. Thirty measured particle sizes were classified into three groups, SSC₁ (2.5∼100 µm), SSC₂ (100∼200 µm) and SSC₃ (200∼300 µm), to grasp easily the characteristics of the SSC temporal variation and its relationship with the sea surface fluctuation, η. The results obtained for each group show the following: (1) The correlation coefficient between SSC₃ (given in percentage with respect to the total SSC) and the total SSC is 0.75. The grain sizes larger than 200 µm (SSC₃) are the more significant component in larger amounts of total SSC. (2) SSCs of the grain sizes smaller than 200 µm have almost constant energy of temporal fluctuation in the frequencies higher than 0.005 Hz, and this tendency is also found in the power spectral density of η_rms. On the other hand, the power spectral density of SSC of the grain sizes larger than 200 µm increases as the frequency becomes lower. This gradient of spectral shape is almost the same as that of η_rms for frequencies lower than 0.005 Hz.