EM 1110-2-1100 (Part III)
30 Apr 02
Figure III-2-6.
Coefficient K versus median grain size D50 (del Valle, Medina, and Losada 1993)
(c) Researchers at CHL (unpublished) used sand tracer data from Santa Barbara and Torrey Pines,
California, and profile and dredging records from Santa Barbara Harbor, California, to compare 20 longshore
sediment transport models. They concluded that the CERC equation performed as well or better than the
other models. Of the six models including effects of grain size evaluated (they did not evaluate del Valle,
Medina, and Losada's (1993) relationship), they concluded that Bailard's (1984) relationship (given in
Equation 2-8) performed the best. However, the data set used for comparison only represented grain sizes
in the range 0.15 to 0.25 mm, and therefore was not particularly suited for testing the dependence of
longshore sediment transport relationships on grain size outside this limited range.
b. Longshore current method. Early workers such as Grant (1943) stressed that sand transport in the
nearshore results from the combined effects of waves and currents; i.e., the waves placing sand in motion and
the longshore currents producing a net sand advection. Walton (1980, 1982) proposed a longshore sediment
transport calculation method using the breaking-wave-driven longshore current model of Longuet-Higgins
(1970) from which the longshore energy flux factor becomes
ρ g Hb W VR Cf
PR '
(III-2-11)
5π
V
2
Vo
Longshore Sediment Transport
III-2-15
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