Consequences of Abrading Bed Load on Vertical and Lateral Bedrock Erosion in a Curved Experimental Channel

Mishra, Jagriti; Inoue, Takuya; Shimizu, Yasuyuki; Sumner, Tamaki; Nelson, Jonathan M.

doi:10.1029/2017jf004387

Cited by 38 publications

(70 citation statements)

References 43 publications

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“…Nevertheless, our first‐order considerations (Figures A and B) yield a strong dependence of lateral migration rates on water discharge (

M_{L} ~ Q_{w}^{1.13 \pm 0.42}

according to Equation and

M_{L} ~ Q_{w}^{0.92 \pm 0.22}

according to Equation ), and only a weak dependence on sediment discharge (

M_{L} ~ Q_{s}^{- 0.13 \pm 0.42}

and

M_{L} ~ Q_{s}^{0.08 \pm 0.22}

) (Figures A and B). In contrast with these braided‐channel system in non‐cohesive sediment, the input sediment discharge may have a greater control on lateral migration where channel banks are cohesive, for example, due to the presence of clays or plants, and where sediment impacts are needed to erode the banks, such as in bedrock channels (Sklar & Dietrich, ; Fuller et al, ; Beer et al, ; Mishra et al, ). Our experiments have much lower Reynolds numbers and relatively large grain sizes (~1–12% of the average channel‐bank height [Table S2]) compared to natural streams.…”

Section: Discussionmentioning

confidence: 99%

Controls on the lateral channel‐migration rate of braided channel systems in coarse non‐cohesive sediment

Bufe

Turowski

Burbank

et al. 2019

Earth Surf Processes Landf

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Lateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. In a two‐step process, we develop here an expression for the lateral migration rate of braided channel systems in coarse, non‐cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel‐system geometry (i.e. channel‐bank heights, water depths, channel‐system width, and channel slope) on channel‐migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, the laterally reworked volume of sediment is constant and lateral channel‐migration rates scale inversely with the channel‐bank height. Furthermore, when channel‐bank heights are accounted for, lateral migration rates are independent of the remaining channel geometry parameters. These constraints allow us, in a second step, to derive two alternative expressions for lateral channel‐migration rates under different boundary conditions using dimensional analysis. Fits of a compilation of laboratory experiments to these expressions suggest that, for a given channel bank‐height, migration rates are strongly sensitive to water discharges and more weakly sensitive to sediment discharges. In addition, external perturbations, such as changes in sediment and water discharges or base level fall, can indirectly affect lateral channel‐migration rates by modulating channel‐bank heights. © 2019 The Author. Earth Surface Processes and Landforms published by John Wiley & Sons, Ltd. © 2019 The Author. Earth Surface Processes and Landforms published by John Wiley & Sons, Ltd.

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“…Nevertheless, our first‐order considerations (Figures A and B) yield a strong dependence of lateral migration rates on water discharge (

M_{L} ~ Q_{w}^{1.13 \pm 0.42}

according to Equation and

M_{L} ~ Q_{w}^{0.92 \pm 0.22}

according to Equation ), and only a weak dependence on sediment discharge (

M_{L} ~ Q_{s}^{- 0.13 \pm 0.42}

and

M_{L} ~ Q_{s}^{0.08 \pm 0.22}

Section: Discussionmentioning

confidence: 99%

Controls on the lateral channel‐migration rate of braided channel systems in coarse non‐cohesive sediment

Bufe

Turowski

Burbank

et al. 2019

Earth Surf Processes Landf

View full text Add to dashboard Cite

show abstract

“…6B in Johnson and Finnegan, 2015). The experiments of Mishra et al (2018) also show that when sediment supply is low, the alluvial point bar is narrow and an inset channel is eroded at the toe of the point bar, leaving an exposed bedrock bench on the outer part of the bend. 10…”

Section: Cross-sectional Averages Of Alluvial Covermentioning

confidence: 89%

“…During the last two decades, particular attention to the previously-described phenomenon has motivated experimental (e.g. Mishra et al, 2018;Johnson andWhipple, 2010, 2007;Chatanantavet and Parker, 2008;Finnegan et al 2007;Sklar and Dietrich, 1998), theoretical or numerical (e.g. Turowski 2018; Turowski and Hodge, 2017;Zhang et al 2015;Inoue et al 2014;Johnson 2014;Nelson et al 2014;Nelson and Seminara, 2012;Lague, 2010;Chatanantavet and Parker, 2009;Turowski et al, 2007;Whipple et al, 2000), and field (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Turowski (2018) presents a model that links alluvial cover to the width, slope and sinuosity of mixed bedrock alluvial rivers 30 and postulates that change in channel width and sinuosity over time depends only on the amount of alluvial bed cover. Finally, Mishra et al (2018) conducted experiments in a U-shaped meandering channel with constant curvature and showed that: i) lateral erosion increases with sediment supply ratio, ii) vertical incision initially grows with sediment supply but shows a more Earth Surf. Dynam.…”

Section: Introductionmentioning

confidence: 99%

“…In spite of these developments, the cover factor definitions used so far by the different authors lack one or more important aspects required for the development of a model of bedrock incision in mixed bedrock-alluvial meandering rivers, namely: 5 (i) What is the role of sediment supply and local curvature and how do they affect the areas of potential erosion in meandering bedrock-alluvial channels? With the exception of the recent work by Mishra et al (2018), Inoue et al (2017) and Nelson et al (2014, all models of bedrock incision by abrasion are either '0D' or '1D' and all experiments have been conducted in straight channels (Johnson andWhipple, 2010, 2007;Chatanantavet and Parker, 2008;Finnegan et al, 2007). There is still no baseline set of experiments describing how the pattern of spatial cover is established in a meandering channel, and how it 10 varies with local curvature and sediment supply.…”

Section: Introductionmentioning

confidence: 99%

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Experiments on patterns of alluvial cover and bedrock erosion in a meandering channel

Fernández¹,

Parker²,

Stark³

2019

Preprint

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In bedrock rivers, erosion by abrasion is driven by sediment particles that strike bare bedrock while traveling downstream with 10 the flow. If the sediment particles settle and form an alluvial cover, this mode of erosion is impeded by the protection offered by the grains themselves. Channel erosion by abrasion is therefore related to the amount and pattern of alluvial cover, which are functions of sediment load and hydraulic conditions, and which in turn are functions of channel geometry, slope and sinuosity. This study presents the results of alluvial cover experiments conducted in a meandering channel flume of high fixed sinuosity. Maps of quasi-instantaneous alluvial cover were generated from time-lapse imaging of flows under a range of below-15 capacity bedload conditions. These maps were used to infer patterns of particle impact frequency and likely abrasion rates.Results from eight such experiments suggest that: (i) abrasion through sediment particle impacts is driven by fluctuations in alluvial cover due to the movement of freely-migrating bars, (ii) patterns of potential erosion are functions of sediment load and local curvature, (iii) low sediment supply ratios are associated with regions of potential erosion located closer to the inner bank but this region moves toward the outer bank as sediment supply increases, and (iv) the threads of high erosion rates are 20 located at the tow of the alluvial bars, just where the alluvial cover reaches an optimum for abrasion rate.

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Width control on event‐scale deposition and evacuation of sediment in bedrock‐confined channels

Cook

Turowski

Hovius

2020

Earth Surf Processes Landf

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In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory and numerical modelling to address this gap. First, we present observations from the Daan River gorge in western Taiwan, where the river flows through a 1km long 20-50m wide bedrock gorge bounded upstream and downstream by wide braidplains. We documented two flood events during which coarse sediment evacuation and redeposition appear to cause changes of up to several metres in channel bed elevation. Motivated by this case study, we examined the relationships between discharge, channel width and bedload transport capacity, and show that for a given slope narrow channels transport bedload more efficiently than wide ones at low discharges, whereas wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modelling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. The fluctuations in sediment transport rates that result from width variations can lead to intermittent bed exposure, driving incision in different segments of the channel during different portions of the hydrograph.

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Consequences of Abrading Bed Load on Vertical and Lateral Bedrock Erosion in a Curved Experimental Channel

Cited by 38 publications

References 43 publications

Controls on the lateral channel‐migration rate of braided channel systems in coarse non‐cohesive sediment

Controls on the lateral channel‐migration rate of braided channel systems in coarse non‐cohesive sediment

Experiments on patterns of alluvial cover and bedrock erosion in a meandering channel

Width control on event‐scale deposition and evacuation of sediment in bedrock‐confined channels

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