2007
DOI: 10.1029/2006gl028865
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Processes of initiation of motion leading to bedload transport in gravel‐bed rivers

Abstract: Transport processes that lead to the initiation of bedload motion in gravel‐bed rivers have not yet been clarified. We report patch‐ and grain‐scale processes involved in the initiation of bedload motion in a natural gravel‐bed stream as observed through a series of video experiments. With increasing flow strength, the phases of initiation of motion that have been identified are (1) within‐patch grain instability (grain vibration, pivoting, and grain‐scale rolling), (2) within‐patch gyratory step‐and‐rest moti… Show more

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Cited by 33 publications
(34 citation statements)
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“…Protuberances on the bed have a significant influence on flow resistance through form drag (Brayshaw et al, 1983;Hassan and Reid, 1990;Robert, 1990Robert, , 1997Lawless and Robert, 2001) and also induce a complex and variable hydraulic environment, including local reversal of the boundary shear stress vector Garcia et al, 2007). A heterogeneous near-bed hydraulic environment has a significant impact on the presence and behaviour of benthic organisms that reside on the substrate (Carling, 1992;Lancaster et al, 2006;Rice et al, 2008) and on the entrainment of bed material (Schvidchenko and Pender, 2001).…”
Section: Potential Impact On Sediment Transport Of Topographic Changementioning
confidence: 99%
“…Protuberances on the bed have a significant influence on flow resistance through form drag (Brayshaw et al, 1983;Hassan and Reid, 1990;Robert, 1990Robert, , 1997Lawless and Robert, 2001) and also induce a complex and variable hydraulic environment, including local reversal of the boundary shear stress vector Garcia et al, 2007). A heterogeneous near-bed hydraulic environment has a significant impact on the presence and behaviour of benthic organisms that reside on the substrate (Carling, 1992;Lancaster et al, 2006;Rice et al, 2008) and on the entrainment of bed material (Schvidchenko and Pender, 2001).…”
Section: Potential Impact On Sediment Transport Of Topographic Changementioning
confidence: 99%
“…As flow strength was increased, entrainment began with small, occasional movements of isolated grains. However, in all our experimental runs, a step-change was clearly observed as flow was increased, whereby this occasional single-grain movement was replaced by general movement of the majority of surface grains, mimicking direct observations made in the field, where the bed has been water-lain and naturally conditioned (Garcia et al, 2007). We used the start of this latter, widespread movement of grains as our definition of the entrainment threshold.…”
Section: Entrainment Measurements and Analysismentioning
confidence: 99%
“…For instance, bed material entrainment in gravel bed rivers is often controlled by patches of fine sediments. Several phases have been described in the literature as occurring in this type of sedimentary microfeature [Garcia et al, 2007], and recent technical developments Vericat et al, 2007Vericat et al, , 2008 have aided in examining the interaction between hydraulics and bed load under such marginal transport conditions (i.e., very low bed load transport rates). These rates are also very sensitive to changing hydraulic conditions [Church and Hassan, 2005].…”
Section: Comparison With Nonuniform (Flume and Field) Sediment Datamentioning
confidence: 99%