Author(s): Le Wang, Alan J. S. Cuthbertson, Deyu Zhong, Gareth Pender, Zhixian Cao
Linked Author(s): Le Wang
Keywords: Bedload transport, double-peaked hydrograph, bed elevation, quasi-uniform and graded sediments, flume experiments
Abstract: In natural rivers, significant bedload transport and variability in sediment bed geomorphology are generally observed to occur under unsteady flows, especially during flood events. In this study, a double-peaked hydrograph event, consisting of two identical and consecutive flood waves (i. e. sub-hydrographs), is performed in a large titling flume to investigate the behavior of bedload transport and response of sediment bed change within both quasi-uniform and fine-graded sediment beds, respectively. The results indicate that the total bedload transport rates for both quasi-uniform and fine-grained sediment beds tend to be reduced during the second sub-hydrograph, in comparison to the first sub-hydrograph, with more significant reductions observed to occur during the rising limb compared to the falling limb. In terms of fractional transport rates for the fine-graded sediment, the results also show that the bedload transport rates for the coarsest fraction are most significantly reduced in the second sub-hydrograph, compared to the first, during the rising limb. A similar overall trend is also shown for the corresponding fine and medium sediment fractions. In terms of the bed evolution over the duration of the double-peaked hydrograph, detailed measurement of bed surface elevation within both quasi-uniform and graded sediment beds runs reveals that the well-defined alternate bars are generated in quasi-uniform sediment bed, while only slight variations in elevation are found to occur in the fine-graded sediment bed with no indication of the generation of bed forms
Year: 2017