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Beach Morphology Monitoring Program
Sediment Samples
Four sediment samples are collected at each beach profile location during the summer profiling campaign. Surface samples are collected by hand (typically several hundred grams of beach sand) within the dune, at the dune toe, at mid-beach and within the swash zone at low tide. Sand grain size distributions are determined using ASTM (American Society for Testing and Materials) -approved dry sieves at quarter-phi intervals following current EPA protocols for sediment analysis in the state of Washington (Tetra Tech Inc., 1986).
Sediment samples collected at each of the beach profile sites in the CRLC reveal a trend of fining median grain size with increased distance from the Columbia River as shown in this plot of the beach state parameters. This trend is interrupted near the mouth of Grays Harbor where a coarse sediment lag is evident. Beaches with the smallest mean grain size typically have the flattest beach slopes. Beach slopes in turn influence how a beach responds to storm events, the extent of wave runup on the beach, and the probability of coastal flooding. For a given set of environmental forcing conditions, the rate of sediment transport is primarily determined by sediment size distribution. Sediment size data are used in the models that predict shoreline change (Kaminsky et al., 1999).
References
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Kaminsky, G.M., Buisjman, M.C., Gelfenbaum, G., Ruggiero, P., Jol, H.M., Gibbs, A.E., and Peterson, C.D. 1999. Synthesizing geological observations and processes-response data for modeling coastal change at management scale, Proceedings of Coastal Sediments '99, ASCE, pp. 1708-1723.
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Tetra Tech Inc., 1986. Recommended protocols for measuring conventional sediment variables in Puget Sound, for the U.S. Environmental Protection Agency, 46 p.
