History‐Dependent Threshold for Motion Revealed by Continuous Bedload Transport Measurements in a Steep Mountain Stream

Masteller, Claire; Finnegan, N. J.; Turowski, Jens M.; Yager, E.; Rickenmann, Dieter

doi:10.1029/2018gl081325

Cited by 71 publications

(91 citation statements)

References 56 publications

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“…This theory suggests that low, inter-flood flow periods will have no effect on bed stability and bed restructuring will only occur during flood events which result in active bedload transport modifying surface stability. However, field Reid et al, 1985;Masteller et al, 2019) and flume (Paphitis and Collins, 2005;Monteith and Pender, 2005;Haynes and Pender, 2007;Ockelford and Haynes, 2013;Masteller and Finnegan, 2017) data suggests that both uniform and graded beds appear to progressively stabilize even when subjected to the low shear stresses experienced during inter-flood flow periods.…”

Section: Introductionmentioning

confidence: 99%

The impact of inter‐flood duration on non‐cohesive sediment bed stability

Ockelford

Woodcock

Haynes

2019

Earth Surf Processes Landf

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Limited field and flume data suggests that both uniform and graded beds appear to progressively stabilize when subjected to inter‐flood flows as characterized by the absence of active bedload transport. Previous work has shown that the degree of bed stabilization scales with duration of inter‐flood flow, however, the sensitivity of this response to bed surface grain size distribution has not been explored. This article presents the first detailed comparison of the dependence of graded bed stability on inter‐flood flow duration. Sixty discrete experiments, including repetitions, were undertaken using three grain size distributions of identical D50 (4.8 mm); near‐uniform (σg = 1.13), unimodal (σg = 1.63) and bimodal (σg = 2.08). Each bed was conditioned for between 0 (benchmark) and 960 minutes by an antecedent shear stress below the entrainment threshold of the bed (τ*c50). The degree of bed stabilization was determined by measuring changes to critical entrainment thresholds and bedload flux characteristics. Results show that (i) increasing inter‐flood duration from 0 to 960 minutes increases the average threshold shear stress of the D50 by up to 18%; (ii) bedload transport rates were reduced by up to 90% as inter‐flood duration increased from 0 to 960 minutes; (iii) the rate of response to changes in inter‐flood duration in both critical shear stress and bedload transport rate is non‐linear and is inversely proportional to antecedent duration; (iv) there is a grade dependent response to changes in critical shear stress where the magnitude of response in uniform beds is up to twice that of the graded beds; and (v) there is a grade dependent response to changes in bedload transport rate where the bimodal bed is most responsive in terms of the magnitude of change. These advances underpin the development of more accurate predictions of both entrainment thresholds and bedload flux timing and magnitude, as well as having implications for the management of environmental flow design. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

The impact of inter‐flood duration on non‐cohesive sediment bed stability

Ockelford

Woodcock

Haynes

2019

Earth Surf Processes Landf

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“…Modeling flow and bed load transport in mountain stream is complex because patches of mobile sediments coexist with immobile structures such as steps or isolated boulders (Green et al, 2015; Laronne et al, 2001; Yager et al, 2012). Furthermore, critical dimensionless shear stress in mountain streams (i.e., Shields stress) is very difficult to model, due to its high variability in time (Masteller et al, 2019) and space (Monsalve et al, 2016), modulated by changes in local channel slope (Lamb et al, 2008) and relative submergence of sediments (Lenzi et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Controls Over Particle Motion and Resting Times of Coarse Bed Load Transport in a Glacier‐Fed Mountain Stream

et al. 2020

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Coarse bed load transport is a crucial process in river morphodynamics but is difficult to monitor in mountain streams. Here we present a new sediment transport data set obtained from 2 years of field-based monitoring (2014)(2015) at the Estero Morales, a high-gradient stream in the central Chilean Andes. This stream features step-pool bed geometry and a glacier-fed hydrologic regime characterized by abrupt daily fluctuations in discharge. Bed load was monitored directly using Bunte samplers and by surveying the mobility of passive integrated transponder (PIT) tags. We used the competence method to quantify the effective slope, which is the fraction of the topographical slope responsible for bed load transport. This accounts for only 10% of the topographical slope, confirming that most of the energy is dissipated on macroroughness elements. We used the displacement lengths of PIT tags to analyze displacement lengths and virtual velocity of a wide range of tracer sizes (38-415 mm). Bed load transport in the Estero Morales shown to be size-selective, and the distance between steps influences the displacement lengths of PIT tags. Displacement lengths were also used to derive the statistics of flight distances and resting times. Our results show that the average length of flight scales inversely to grain size. This contradicts Einstein's conjecture about the linear relationship between grain size and intervals between resting periods in a steep step-pool stream in ordinary flood conditions.

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“…To further study such "memory" effect of antecedent flow on the sediment transport during a subsequent flood, a number of flume experiments as well as field surveys have been conducted in the past decade, and different terms have been proposed, including "stress history effect" (Monteith and Pender, 2005;Paphitis and Collins, 2005;Haynes and Pender, 2007;Ockelford and Haynes, 2013), "flood history effect" (Mao, 2018), "flow history" (Masteller et al, 2019), etc. Given that all these terms are similar, here we adopt the term "stress history" in this paper.…”

Section: Introductionmentioning

confidence: 99%

“…However, most of the previous research about stress history is either under conditions with relatively low sediment transport or with relatively short durations of sediment transport in order to capture the threshold of sediment motion (Monteith and Pender, 2005;Paphitis and Collins, 2005;Haynes and Pender, 2007;Ockelford and Haynes, 2013;Masteller and Finnegan, 2017;Ockelford et al, 2019). On the other hand, other researchers have found that exceptionally high discharge events can reduce critical shear stress by disrupting particle interlocking and breaking of bed structure (Turowski et al, 2011;Yager et al, 2012;Ferrer-Boix and Hassan 2015;Masteller et al, 2019). Flume experiments by Masteller and Finnegan (2017) also indicate an increase in the number of highly mobile, highly protruding grains in response to sediment transporting flows.…”

Section: Introductionmentioning

confidence: 99%

Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

An¹,

Hassan²,

Ferrer‐Boix³

et al. 2020

Preprint

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Abstract. With the increasing attention on environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this paper, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.

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History‐Dependent Threshold for Motion Revealed by Continuous Bedload Transport Measurements in a Steep Mountain Stream

Cited by 71 publications

References 56 publications

The impact of inter‐flood duration on non‐cohesive sediment bed stability

The impact of inter‐flood duration on non‐cohesive sediment bed stability

Controls Over Particle Motion and Resting Times of Coarse Bed Load Transport in a Glacier‐Fed Mountain Stream

Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers

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