Author(s): Hao Zhang; Hajime Nakagawa; Hideaki Mizutani
Linked Author(s): Hajime Nakagawa
Keywords: Non-uniform sediment; Spur dyke; Local scour
Abstract: Natural riverbeds are characterized by non-uniform sediment covering a wide spectrum of particle sizes. Investigation on the transport of non-uniform sediment is of practical value to estimate and to characterize responses of channel morphologies as well as riverine habitats. In this paper, bed variations around a spur dyke under non-uniform sediment transport are studied experimentally. A series of laboratory experiments are conducted with sediment beds consisting of different particle sizes and size distributions. It is found that the local scour in a non-uniform bed is smaller compared with that in a uniform bed of the same sediment mean diameter. In the local scour hole, the bottom part is rather coarser than the upper part. Due to the sediment sorting process, the bed materials generally become coarser in the neighborhood of the spur dyke and armor layers form there. Furthermore, there exist two longitudinal belts consisting of relatively fine sediment, which is not observed for any uniform sediment bed.
Year: 2010