Graded bed load transport in sediment supply limited channels under unsteady flow hydrographs

Wang, Le; Cuthbertson, Alan; Zhang, Shang Hong; Pender, Gareth; Shu, An Ping; Wang, Yong Qiang

doi:10.1016/j.jhydrol.2021.126015

Cited by 8 publications

(17 citation statements)

References 47 publications

(73 reference statements)

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“…In fact, this assumption inherently violates the principle of hysteretic behaviour, particularly when considering clockwise and counterclockwise loops that have been reported extensively for bed load sediment transport in a wide range of single-peaked hydrograph flows including in the current study. In addition, it has been found from our earlier studies (e.g., Wang et al, 2019;2021) that the difference between bed load transport rates on both limbs decreased with increasing flows, implying that the difference tends to be more pronounced during more rapidlychanging (low) flow conditions (i.e., where dQ/dt > 0 on the rising limb and dQ/dt < 0 on the falling limb) than either side of the peak flow condition (i.e. where dQ/dt ≈ 0).…”

Section: Thresholds and Hysteresis Of Sediment Motionsupporting

confidence: 69%

“…This upstream boundary setup helps simplify the experimental procedure between different runs, as well as our interpretation of bed load sediment transport hysteresis that is generally known to vary with many external factors (e.g., sediment feed mode, flow conditions, sediment type and grading, and bed conditions), as mentioned earlier. The experimental configurations and protocols are exactly the same as described in Wang et al (2021). The flume was segmented into three sections, including an effective working length covered with a uniform bed layer of the fine-grained sediment mixture, whereas the remaining part in the upstream and downstream flume channel were artificially roughened to prevent local scour and ensure the turbulent boundary layer is fully developed in the erodible test bed section.…”

Section: Flume Set-up and Bed Sedimentsmentioning

confidence: 99%

“…Three groups of design flow hydrographs were simulated in the current study, with full details of these hydrographs reported in the earlier work of Wang et al (2021). In this study, we focus specifically on the bed load transport hysteresis under symmetrical hydrograph flows, for which hydrograph U1/ V1/U1a-V1a (highlighted in Table 1) serves as a benchmark for the design of other hydrograph flow conditions tested.…”

Section: Hydrograph Flowsmentioning

confidence: 99%

“…In our experiments, we observed bed load sediment transport to have clockwise, no/mixed and counterclockwise hysteresis, with these different sediment hysteresis patterns particularly noticeable in experimental hydrograph group UV. More details on the temporal variations in fractional transport rates (Wang et al, 2021). q b,i in groups V1 and U1 can be found in Wang et al (2021).…”

Section: Bed Load Sediment Transport Hysteresismentioning

confidence: 99%

“…More details on the temporal variations in fractional transport rates (Wang et al, 2021). q b,i in groups V1 and U1 can be found in Wang et al (2021).…”

Section: Bed Load Sediment Transport Hysteresismentioning

confidence: 99%

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Hysteretic Implications for Graded Bed Load Sediment Transport in Symmetrical Hydrograph Flows

Wang

Cuthbertson

et al. 2021

Front. Environ. Sci.

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Differential parametric values associated with bed load sediment transport, that result at the same discharge levels on the rising and falling limbs of a flood hydrograph, are usually defined as bed load hysteresis. This hysteresis in bed load sediment transport rates is of considerable interest in the field of fluvial hydraulics. Within this study, a series of well-defined, symmetrical hydrograph flows are generated over a graded, mobile sediment bed to fully examine the hysteresis of the resulting bed load sediment transport in terms of the threshold of motion, and differential bed load transport rates and bed load yields during the hydrographs. The experiments are conducted in a titling flume without sediment supply specified at the upstream inlet, thereby representing typical river reach conditions immediately downstream of a dam that are exclusively subject to net in-channel bed degradation from sediment transport initiated during flood events. Our results show that the fractional bed load transport of defined fine, medium and coarse size classes within the graded sediment bed generally display clockwise, no/mixed and counter-clockwise hysteresis patterns, respectively, with clockwise hysteresis most commonly found for the coarse size class mobilised by hydrographs with long durations. By contrast, counter-clockwise hysteresis is usually observed for fine size class transported by hydrographs with short durations. Accordingly, the corresponding reference stresses for each size class vary between different hydrographs and are primarily controlled by the hydrograph flashiness (i.e. unsteadiness) and magnitude (i.e. total water work). Moreover, it is shown that the hysteresis effect, particularly for those size classes and hydrograph combinations that result in clockwise and counter-clockwise behaviour, should be fully accounted for when reproducing bed load transport rates using separate-limb based method. Finally, we investigate the relative fractions of the overall bed load yields generated during the rising and falling limbs of all symmetrical hydrographs (i.e. the bed load yield ratio), which are found to be primarily dependent on bed load transport hysteresis. Finally, the relationship between the bed load yield ratio and the ratio of reference stresses for the fractional sediment motion of each size class on both limbs is found to follow a power law.

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Section: Thresholds and Hysteresis Of Sediment Motionsupporting

confidence: 69%

Section: Flume Set-up and Bed Sedimentsmentioning

confidence: 99%

Section: Hydrograph Flowsmentioning

confidence: 99%

Section: Bed Load Sediment Transport Hysteresismentioning

confidence: 99%

“…More details on the temporal variations in fractional transport rates (Wang et al, 2021). q b,i in groups V1 and U1 can be found in Wang et al (2021).…”

Section: Bed Load Sediment Transport Hysteresismentioning

confidence: 99%

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