Temporal lag effect in bed load sediment transport

Phillips, Brett C; Sutherland, Alex J.

doi:10.1080/00221689009499144

Cited by 38 publications

(19 citation statements)

References 10 publications

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“…Having said this, the plots suggest that the bed load transport rate lags modestly behind the discharge. This lag has been observed by others [Phillips and Sutherland, 1990;Habersack et al, 2001], but Graf and Qu [2004] suggest that it is usually small.…”

Section: Resultsmentioning

confidence: 84%

One‐dimensional modeling of bed evolution in a gravel bed river subject to a cycled flood hydrograph

Wong¹,

Parker

2006

J. Geophys. Res.

105

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[1] How does a mountain river adjust to accommodate repeated flood hydrographs? Do flood hydrographs cause major cycles of aggradation and degradation of the river bed? Here flume experiments are used to explore this problem. The response of a gravel bed river to repeated floods is modeled in the simplest possible way. The gravel is well sorted, the flume is operated in sediment feed mode, and the gravel feed rate is held constant. The flow discharge, on the other hand, is specified in terms of the repetition of the same hydrograph until mobile bed equilibrium (averaged over the hydrograph) is achieved. The results of the experiments demonstrate a remarkable trade-off. In a short inlet "boundary layer" (transition region) the bed elevation and bed slope fluctuate cyclically with the changing flow discharge, while the gravel transport rate remains nearly equal to the constant feed rate. Downstream of this short reach, however, the bed elevation and bed slope do not fluctuate in response to the hydrograph; all the fluctuation is transferred to the gravel transport rate. These results are verified in terms of onedimensional analytical and numerical modeling. This modeling shows that the trade-off is inevitable as long as the morphologic response time of the reach in question is sufficiently long compared to the duration of a single hydrograph. The implication is that gravel bed rivers tend to adjust to hydrographs so as to minimize the response of the bed and maximize the response of the bed load transport rate to fluctuating flow discharge.Citation: Wong, M., and G. Parker (2006), One-dimensional modeling of bed evolution in a gravel bed river subject to a cycled flood hydrograph,

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Section: Resultsmentioning

confidence: 84%

One‐dimensional modeling of bed evolution in a gravel bed river subject to a cycled flood hydrograph

Wong¹,

Parker

2006

J. Geophys. Res.

105

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“…On the other hand, in experiments done by Song and Graf (1997), the hydrograph durations ranged from 18 to 74 s with two sediment diameters of 5Ð8 mm and 12Ð3 mm, and the peak discharges ranged from 0Ð068 to 0Ð309 m 3 /s/m. A comparatively wide range of hydrograph duration was found in straight channel experiments (from 1 to 60 min) done by Phillips and Sutherland (1990) and in meandering channel experiments (from 180 to 420 min) conducted by Yen and Lee (1995), but no detailed discussions of time-scale determination were provided in these papers.…”

Section: Experimental Model Time-scalementioning

confidence: 96%

“…They found that the sediment volume was always larger than the calculated volume derived from equivalent steady flow. A series of experiments was conducted by Phillips and Sutherland (1990), an equivalent steady flow sediment transport rate was derived, and an impulse response model was used to analyse the temporal lag of the sediment movement under unsteady flow conditions. The possible effects of unsteady flow were summarized by Plate (1994).…”

Section: Introductionmentioning

confidence: 99%

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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“…These findings suggest strongly that sediment transport in unsteady flood flow becomes stronger in the rising stage than in the corresponding falling stage. Until now, research towards the influence of unsteadiness on sediment transport has been scarce and mainly focused on the bed load transport of coarse gravel in transient flow conditions in laboratory setups (Bestawy, 1997;Kabir, 1993;Phillips & Sutherland, 1990;Suszka, 1987).…”

Section: Introduction and Objectivesmentioning

confidence: 99%

Simulation of sediment transport during flood events: laboratory work and field experiments

Sutter¹,

Verhoeven²,

Krein

2001

Hydrological Sciences Journal

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This paper aims at initiating a fundamental understanding of the suspended load transport of river sediment in unsteady flow. Laboratory erosion tests as well as artificial flood experiments are used to evaluate the influence of the transient regime on the transport efficiency of the flow. The erosion experiments reveal that the transport capacity is augmented when the unsteadiness of the flow increases. However, the influence of the transient regime is counteracted by the cohesive properties of the river bed. Field experiments with artificial floods released from a reservoir into a small canal confirm these findings and show a relationship between the friction velocity and the suspended load transport. An appropriate parameter [3 is proposed to evaluate the impact of the transient regime on the transport of suspended sediment.Key words sediment transport; unsteady flow; artificial floods; suspended load; kinematic flow; friction velocity Simulation du transport de sédiment pendant des événements de crue: expériences au laboratoire et sur le terrain Résumé Cette publication se donne pour but d'arriver à une plus grande compréhen-sion fondamentale du transport des matières en suspension pendant un écoulement non-permanent. Des expériences au laboratoire et sur le terrain avec des écoulements artificiels sont réalisées pour évaluer comment un débit non-permanent peut influencer le transport de matière. Les expériences au laboratoire montrent que la capacité de transport est augmentée significativement par le régime non-permanent. Néanmoins, les propriétés cohésives du lit du cours d'eau contrebalancent cette influence. Des expériences sur le terrain, consistant en des crues artificielles issues d'un réservoir dans un petit canal, confirment ces résultats et montrent une relation entre la vitesse de cisaillement et le transport en suspension. Un paramètre (3 est introduit pour évaluer l'influence du régime non-permanent sur le transport de matières en suspension.

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Temporal lag effect in bed load sediment transport

Cited by 38 publications

References 10 publications

One‐dimensional modeling of bed evolution in a gravel bed river subject to a cycled flood hydrograph

One‐dimensional modeling of bed evolution in a gravel bed river subject to a cycled flood hydrograph

Experimental investigation of bedload transport processes under unsteady flow conditions

Simulation of sediment transport during flood events: laboratory work and field experiments

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