Bedload transport for heterogeneous sediments

Abstract

A large panel of instruments was deployed in the Eastern English Channel to measure the evolution of bedload fluxes during a tidal cycle for two different sites. The first one was characterized by a sandy bed with a low dispersion in size while the other study site implied graded sediments with grain sizes ranging from fine sands to granules. The in situ results obtained were compared with predictions of total bedload fluxes by classical models. A good agreement was found for homogeneous sediments with these formulas. In the case of size heterogeneous sediments, a fractionwise approach, involving a hiding-exposure coefficient and a hindrance factor, provided better predictions of bedload fluxes, but still some discrepancies were noticed. Present results revealed that the consideration of particle shape in formulas through the circularity index enhanced the estimations of bedload transport rates. A new adjustment of Wu et al.’s (J Hydraul Res 38:427–434, 2000) formula was proposed and a very good agreement was obtained between the measured and predicted values.