The Influence of Slipface Angle on Fluvial Dune Growth

Naqshband, Suleyman; Giri, Sanjay; Bradley, R. W.; Kostaschuk, Ray; Venditti, Jeremy G.; Hoitink, A.J.F.

doi:10.1029/2020jf005959

Cited by 6 publications

(9 citation statements)

References 96 publications

(169 reference statements)

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“…In addition, unlike laboratory conditions, water discharge and depth constantly change in natural rivers. Thus, bedform fields are often out of equilibrium since bathymetric evolution requires a much longer adjustment time‐scale as compared to the flow (Martin & Jerolmack, 2013; Myrow et al., 2018; Naqshband et al., 2017, 2021; Leary & Ganti, 2020; R. Bradley & Venditti, 2021). The cases discussed above suggest that the local water depth might not always be able to serve as a flow boundary condition constraining the dune growth in natural fluvial systems.…”

Section: Discussionmentioning

confidence: 99%

“…The bedform turnover time scale T t was used to evaluate the dynamic equilibrium state, which indicates the transient period between step increases of flow and sediment discharge (Martin & Jerolmack, 2013;Myrow et al, 2018;Leary & Buscombe, 2020;R. Bradley & Venditti, 2021).…”

Section: Methodsmentioning

confidence: 99%

Section: The Spectral Range Of Transporting-bedform Scales and The Ca...mentioning

confidence: 99%

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Reconstructing Sediment Transport by Migrating Bedforms in the Physical and Spectral Domains

Lee

Singh

Guala

2022

Water Resources Research

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: The Spectral Range Of Transporting-bedform Scales and The Ca...mentioning

confidence: 99%

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Reconstructing Sediment Transport by Migrating Bedforms in the Physical and Spectral Domains

Lee

Singh

Guala

2022

Water Resources Research

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“…Dune hysteresis varies spatially because the controlling variables, such as discharge, depth and slope, vary spatially within and between river systems. Additionally, experimental evidence indicates that processes of dune adaptation, such as enhanced sediment bypass, have the potential to change the nature and recurrence of dune scour, which ultimately determines the thicknesses of the preserved dune sets (Reesink et al ., 2018; Naqshband et al ., 2021).…”

Section: Introductionmentioning

confidence: 99%

The thickness variability of fluvial cross‐strata as a record of dune disequilibrium and palaeohydrology proxy: A test against channel deposits

Colombera,

Reesink,

Duller

et al. 2023

Sedimentology

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Strata produced by fluvial dunes can provide insight into the hydrological regime of ancient rivers. Recent experiments indicate that conditions of disequilibrium between bedforms and formative flows may be inferred from the coefficient of variation of preserved dune cross‐set thickness, suggesting that this quantity may act as a proxy for the flashiness of river floods relative to the time required for full bedform translation. To assess whether this idea is applicable to interpretations of the stratigraphic record, this study examines published data relating to more than 2600 cross‐sets from 53 sedimentary units of 19 river systems. The presented analyses must not be over‐interpreted, because the considered rivers span different environmental settings, the data sources are heterogeneous in terms of type and dimensionality, and some variables were established by applying empirical relationships. Yet, significant findings are revealed. Larger rivers exhibit discharge and bedform characteristics that are more conducive to disequilibrium; however, a modest increase in the coefficient of variation of cross‐set thickness, CV(Dst), as opposed to the expected decrease, is seen as a function of river size. Crucially, smaller CV(Dst) values are not systematically associated with conditions that should favour dune disequilibrium. Meanwhile, only ca 25% of the studied examples demonstrate cross‐set thickness statistics compatible with quantitative formulations of the autogenic control by variable dune topography – the notion of ‘variability‐dominated’ preservation. These findings indicate that the variability in cross‐set thickness may be a poor predictor of discharge variability, perhaps because of the multiplicity of factors controlling dune preservation, such as bedform hierarchy, transport stage and depth‐dependent variations in dune disequilibrium. To improve interpretations of cross‐stratified deposits, further research is needed: (i) to establish the value of process‐to‐product models for reverse product‐to‐process interpretations; and (ii) to define representative samples for preserved dune deposits accounting for temporal and spatial variability in preservation potential.

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“…respectively, where

\bar{z}

is the root‐mean‐squared amplitude of the bed profile, λ is the wavelength (defined as the mean distance between crests), t is time and a z , b z , a λ , and b λ are fitted constants. This empirical model has since been applied to both subaqueous (Baas, 1999; Bradley & Venditti, 2019; Naqshband et al., 2021; Venditti et al., 2005b) and aeolian (Swanson et al., 2017) dunes, although the precise measures of amplitude and wavelength vary (amplitude: peak‐to‐peak, root‐mean‐squared; wavelength: crest‐to‐crest, mean, or mode from spectral analysis). Recent work has further found that, for larger shear stresses, the time of applicability of this exponentially saturated model can be preceded by a transient linear stage (Bradley & Venditti, 2019).…”

Section: Introductionmentioning

confidence: 99%

Coarsening Dynamics of 2D Subaqueous Dunes

et al. 2022

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Fluid flow over an initially flat granular bed leads to the formation of a surface‐wave instability. The sediment bed profile coarsens and increases in amplitude and wavelength as disturbances develop from ripples into dunes. We perform experiments and numerical simulations to quantify both the temporal evolution of bed properties and the relationship between the initial growth rate and the friction velocity u∗. Experimentally, we study underwater bedforms originating from a thin horizontal particle layer in a narrow and counter‐rotating annular flume. We investigate the role of flow speed, flow depth and initial bed thickness on dune evolution. Bedforms evolve from small, irregular disturbances on the bed surface to rapidly growing connected terraces (2D equivalent of transverse dunes) before splitting into discrete dunes. Throughout much of this process, growth is controlled by dune collisions which are observed to result in either coalescence or ejection (mass exchange). We quantify the coarsening process by tracking the temporal evolution of the bed amplitude and wavelength. Additionally, we perform Large Eddy Simulations (LES) of the fluid flow inside the flume to relate the experimental conditions to u∗. By combining the experimental observations with the LES results, we find that the initial dune growth rate scales approximately as u∗5 ${u}_{\ast }^{5}$. These results can motivate models of finite‐amplitude dune growth from thin sediment layers that are important in both natural and industrial settings.

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The Influence of Slipface Angle on Fluvial Dune Growth

Cited by 6 publications

References 96 publications

Reconstructing Sediment Transport by Migrating Bedforms in the Physical and Spectral Domains

Reconstructing Sediment Transport by Migrating Bedforms in the Physical and Spectral Domains

The thickness variability of fluvial cross‐strata as a record of dune disequilibrium and palaeohydrology proxy: A test against channel deposits

Coarsening Dynamics of 2D Subaqueous Dunes

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