Variable source areas of bedload in a gravel-bed stream

García, Carmen; Laronne, Jonathan B.; Sala, María

doi:10.2110/jsr.69.27

Cited by 55 publications

(54 citation statements)

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“…This supports results from other field studies (e.g. Lisle & Madej 1992, Garcia et al 1999. The tracer studies also show that the patches exchange particles with the through going bedload, yet can remain unchanged.…”

Section: Discussionsupporting

confidence: 90%

“…As the stage rises, do the patches experience the onset of transport at the same discharge? It seems likely that fine patches would be more mobile than coarse ones, as Lisle & Madej 1992) have suggested and Garcia et al (1999) have inferred. If so, does sediment released from the fine patch cross into the coarser patches and influence the mobility of particles there?…”

Section: Sediment Dynamics In Patches: a Field Studymentioning

confidence: 84%

“…Lisle & Madej 1992, Lisle 1995, Garcia et al 1999). The widely used bedload transport equation of Parker (1990) captures the observed stagedependent mobility through a non-linear dependency of bedload flux on a hiding function and boundary shear stress.…”

Section: Inroductionmentioning

confidence: 99%

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Sediment patches, sediment supply, and channel morphology

Dietrich¹,

Nelson²,

Yager³

et al. 2006

River, Coastal and Estuarine Morphodynamics

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Bed surface particle size patchiness may play a central role in bedload and morphologic response to changes in sediment supply in gravel-bed rivers. Here we test a 1-D model (from Parker ebook) of bedload transport, surface grain size, and channel profile with two previously published flume studies that documented bed surface response, and specifically patch development, to reduced sediment supply. The model over predicts slope changes and under predicts average bed surface grain size changes because it does not account for patch dynamics. Field studies reported here using painted rocks as tracers show that fine patches and coarse patches may initiate transport at the same stage, but that much greater transport occurs in the finer patches. A theory for patch development should include grain interactions (similar size grains stopping each other, fine ones mobilizing coarse particles), effects of boundary shear stress divergence, and sorting due to cross-stream sloping bed surfaces.

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Section: Discussionsupporting

confidence: 90%

Section: Sediment Dynamics In Patches: a Field Studymentioning

confidence: 84%

See 1 more Smart Citation

Sediment patches, sediment supply, and channel morphology

Dietrich¹,

Nelson²,

Yager³

et al. 2006

River, Coastal and Estuarine Morphodynamics

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“…As with the fine sediment found in patches between coarse particles (Garcia et al, 1999 Discharge, flow velocity and shear stress at sites A and B are also illustrated. Note that the scales 8 differed for the total bed-load rate and the bed-load rate for each size fraction (y-axis).…”

Section: Discussionmentioning

confidence: 87%

Changes in bedload transport rate associated with episodic sediment supply in a Japanese headwater channel

Imaizumi

Gomi

Kobayashi

et al. 2009

CATENA

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2We conducted field monitoring of bedload transport rate associated with experimental sediment 3 release in a natural channel to clarify behavior of the supplied sediment on mixed size bed. 4Observation of bedload rate at two sites along the 30 m channel reach revealed that downstream 5 migration of finer particles delay compared with coarser particles. Ratio of the bedload sediment that 6 deposited during the migration was higher for finer sediments. These behaviors of the mixed size 7 particles were clear during passage of the sediment wave without changes in water discharge. Flashing 8 peak of discharge that caused artificially by opening of the dam gate did not destroy channel bed 9 structure including steps and pools formed by coarser sediments, and only small amount of bedload 10 was mobilized. Both reach scale channel features including steps, pools, and riffles as well as fine 11 scale features (i.e., armor coat) likely increased critical shear stress of particles and decreased bedload 12 rate during our experiment. Extreme sediment supply induced two types of sediment deposition; (1) 13 filling the pools in reach sales and (2) the intrusion of fine particles into the coarser sediment that 14 formed an armour layer. The all grain size fractions can deposit as type (1) when shear stress of stream 15 water is not enough to entrain bedload particles, while deposition type (2) occurs when finer sediment 16 pass over channel bed on which armor coat is well-developed. Deposition of finer sediment into 17 coarser sediment that forms armor coat is affected by grain size distribution of bed surface sediment. 18Thus, impact of the sediment supply on downstream channel depends on both bedforms and grain size 19 distribution of bed surface sediment over which the supplied sediment pass. 20 21

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“…Holding other influences constant (e.g., local boundary shear stress, bed roughness), patches composed of finer material will experience during competent flows higher rates of grain entrainment and transport than coarser patches (Paola and Seal 1999). Previous research on bed material patches has shown that fine patches could contribute the majority of sediment measured in transport during highfrequency flow events (Lisle and Madej 1992;Garcia et al 1999;Vericat et al 2008). In these circumstances, it might be unnecessary to treat the grains located in the coarse patches as an equally significant sediment source as the grains located in fine patches.…”

Section: Introductionmentioning

confidence: 99%

Predicting Coarse Sediment Transport from Patchy Beds in Ephemeral Channels

Yuill¹

2012

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Seven 1-D sediment transport formulae are employed to predict coarse sediment transport in a low-order, ephemeral channel with patchy bed material. Sediment transport is modeled through two different methods to characterize the sediment supply: by using a channel-averaged grain-size distribution (GSD) and by using the mean GSDs from the relatively coarse and fine textured patches that compose the channel bed.Modeling results show that the two different characterizations of the sediment supply produce significantly different values of predicted coarse sediment yield. The relative differences in the predicted yield values are dependent on the assumptions of each formula, including how the sediment supply is parameterized within the model. Modeled sediment yield values are contrasted to observed values for seven flashflood-type runoff events. The formulae accuracies typically are comparable to past analyses in fluvial systems more reminiscent of the hydraulic environments in which the models were derived (perennial flow, gravel-bed material).Study results reaffirm that the method by which sediment supply is characterized significantly impacts the performance of sediment transport formulae and that a single GSD might not adequately describe the sediment supply originating from patchy beds.

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Variable source areas of bedload in a gravel-bed stream

Cited by 55 publications

References 0 publications

Sediment patches, sediment supply, and channel morphology

Sediment patches, sediment supply, and channel morphology

Changes in bedload transport rate associated with episodic sediment supply in a Japanese headwater channel

Predicting Coarse Sediment Transport from Patchy Beds in Ephemeral Channels

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