Spatial lag effects in bed load sediment transport

Phillips, Brett C; Sutherland, Alex J.

doi:10.1080/00221688909499247

Cited by 109 publications

(61 citation statements)

References 15 publications

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“…As reported by previous researchers (Bell and Sutherland, 1983;Phillips and Sutherland, 1989;Jain, 1992), a spatial lag effect can be identified from the difference between the measured local sediment transport rate and the equilibrium sediment transport rate. To confirm a possible spatial lag effect on our experimental data, we examined the lag distance using the equation suggested by Jain (1992).…”

Section: Presentation Of Datamentioning

confidence: 95%

Experimental investigation of bedload transport processes under unsteady flow conditions

Lee

Liu

Cheng

2004

Hydrological Processes

130

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Abstract:Hydraulic engineering is usually based on theoretical analysis and/or numerical modelling simulation. As the dynamic behaviour of sediment movement under unsteady flow is still unclear, and field measurement is comparatively difficult during a large flood, prior investigations through flume experiments are required. A series of flume experiments, conducted using different inflow hydrographs without sediment supply from upstream, was carried out to investigate the sediment transport process under unsteady flow conditions.A series of triangular hydrographs were performed in the experiments. The results indicate that a temporal lag was found between the flow hydrograph peak and the sediment hydrograph peak because large size sand dunes lasted for a short period in the falling limb of the flow hydrograph. The temporal lag was found to be about equal to 6-15% of the flow hydrograph duration. Owing to the temporal lag, the total bedload yield in the rising period was less than that in the falling period. Furthermore, the measured total bedload yield in the unsteady flow experiments was larger than the predicted value, which was estimated by using the results obtained from the equivalent steady flow experiment. The peak bedload transport rate for unsteady flow conditions was also larger than the predicted value. The ratios of the measured to the predicted quantities mentioned above were found to be constant values for different shapes of hydrographs. It is, therefore, expected that the analytical results of sediment transport from equivalent steady flow can be a good reference for sediment transport under unsteady flow conditions.

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Section: Presentation Of Datamentioning

confidence: 95%

Experimental investigation of bedload transport processes under unsteady flow conditions

Lee

Liu

Cheng

2004

Hydrological Processes

130

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“…To tackle this shortcoming, the non-equilibrium approach is used [5,30,55]. In this context, the non-equilibrium equation is formulated assuming a space and time-lag between Q s and Q cap s [2,4,19,43,44]. RubarBE assumes only a space-lag between Q s and Q cap s through the equation of Daubert and Lebreton [19] (Eq.…”

Section: Governing Equationsmentioning

confidence: 99%

One-dimensional numerical modelling of dam-break waves over movable beds: application to experimental and field cases

Abderrezzak

Paquier

2008

Environ Fluid Mech

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This paper reports a numerical study on dam-break waves over movable beds. A one-dimensional (1-D) model is built upon the Saint-Venant equations for shallow water waves, the Exner equation of sediment mass conservation and a spatial lag equation for nonequilibrium sediment transport. The set of governing equations is solved using an explicit finite difference scheme. The model is tested in various idealized experimental cases, with fairly good agreement between the numerical predictions and measurements. Discrepancies are observed at the earlier stage of the dam-break wave and around the dam location due to no vertical velocity component being taken into account. Sensitivity tests confirm that the friction coefficient is an important parameter for the evaluation of sediment transport processes operating during a dam-break wave. The influence of the non-equilibrium adaptation length (or the lag distance) is negligible on the wavefront celerity and weak on the free surface and bed profiles, which indicates that one may ignore the spatial lag effect in dam-break wave studies. Finally, the simulation of the Lake Ha!Ha! dyke-break flood event shows that the model can provide relevant results if a convenient formula for computing the sediment transport capacity and an appropriate median grain diameter of riverbed material are selected.

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“…(5) proposed by Greimann, et al, (2008) is used to estimate the approximate velocity ratio for weak sediment transport; for the severe sediment transport, we assume the sediment and flow velocity to be approximately equivalent. Furthermore, the non-equilibrium adaptation length L has been investigated by many researchers (Armanini and Di Silvio, 1988, Greimann, et al, 2008, Phillips and Sutherland, 1989, Wu, 2004, but still warrants further study. Here, following the previous research, L is calculated by Eq.…”

Section: Stm1: Bedload Dominant Sheet Flow Modelmentioning

confidence: 99%