The fascination of a shallow-water theory for the formation of megaflood-scale dunes and antidunes

Bohorquez, Patricio; Cañada-Pereira, Pablo; Jimenez-Ruiz, P.J.; Moral-Erencia, José David del

doi:10.1016/j.earscirev.2019.03.021

Cited by 30 publications

(39 citation statements)

References 87 publications

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“…where k a is the streamwise wavenumber of antidunes (2π/λ a ). Yokokawa et al (2010) advocated that rather than the migration direction of antidunes, Equation 6 roughly represents the wavelength of downstream-migrating antidunes, as shown in Figure 2 of Bohorquez et al (2019) and our experimental results. The Taylor approximation of Equation 6 gives us…”

Section: Theoretical Wavelength and Transverse Wavenumber Of 3d Antidmentioning

confidence: 51%

“…Bedforms are characterized in terms of streamwise length scale of deformations, with ripples having the shortest length, dunes and antidunes having an intermediate length, and bars having the longest length (e.g. Colombini and Stocchino, 2012;Charru et al, 2013;Bradley and Venditti, 2017;Bohorquez et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

“…The dynamics of both dunes and antidunes have been investigated experimentally (e.g. Fukuoka et al, 1982;Carling and Shvidchenko, 2002;Recking et al, 2009;Núñez-González and Martín-Vide, 2011;Cartigny et al, 2014;Bohorquez et al, 2019), analytically (e.g. Kennedy, 1961Kennedy, , 1963Engelund, 1970;Hayashi, 1970;Parker, 1975;Colombini, 2004;Andreotti et al, 2012;Charru et al, 2013), and computationally (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Three‐dimensional antidunes coexisting with alternate bars

Inoue

Watanabe

Iwasaki

et al. 2020

Earth Surf Processes Landf

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Antidunes are fluvial bedforms that form in rivers with supercritical flows. The water surface over antidunes is strongly in phase with the bed surface, and the water surface is amplified to produce large surface waves. Many experimental studies have addressed antidunes; however, the shapes of three‐dimensional antidunes in a wide channel with alternate bars have not yet been appropriately understood. In this study, we experimentally investigated the streamwise and transverse length scales of antidunes under conditions with a large width–depth ratio. Our experimental results provide evidence for the coevolution of antidunes and free alternate bars, and show for the first time that the development of free bars greatly alters the three‐dimensional shape of water surface waves over antidunes. In the absence of free bars in a wide channel, multiple longitudinal wave trains form, and the number of wave trains counted in the transverse direction increases with increases in the width–depth ratio. However, the presence of free bars affects the local flow characteristics, resulting in a decrease of the number of wave trains in the transverse direction. Therefore, we propose a simple model for predicting the reduction in the number of wave trains by combining two previous theories for antidunes and free bars. Results obtained by the model were found to largely agree with experimental observations. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Section: Theoretical Wavelength and Transverse Wavenumber Of 3d Antidmentioning

confidence: 51%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Three‐dimensional antidunes coexisting with alternate bars

Inoue

Watanabe

Iwasaki

et al. 2020

Earth Surf Processes Landf

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“…The third solution to the dispersion equation is called the sediment mode because it describes the bed's slow evolution. This mode is stable when empirical bedload equations q s are explicit one-to-one functions ofū and h (Balmforth & Provenzale, 2001;Bohorquez et al, 2019). The only effect of bedload transport is to slightly alter the dynamics of water waves.…”

Section: Interplay and Feedback Loopsmentioning

confidence: 95%

“…The first two solutions to the dispersion equation are called the hydrodynamic modes as they describe the propagation of fast-evolving water waves. They are barely modified by the erodible bed (Balmforth & Provenzale, 2001;Bohorquez, Cañada Pereira, Jimenez-Ruiz, & del Moral-Erencia, 2019), and they are thus stable for Froude numbers F lower than 2. The third solution to the dispersion equation is called the sediment mode because it describes the bed's slow evolution.…”

Section: Interplay and Feedback Loopsmentioning

confidence: 99%

A new front condition for non-Boussinesq gravity currents

Sciortino

Adduce

Lombardi

2018

Journal of Hydraulic Research

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This paper outlines the various approaches used to calculate bedload transport. As bedload transport exhibits considerable spatial and temporal variations, computing the bedload transport rates and morphological changes experienced by streambeds is difficult. A large body of experimental work has revealed scaling laws relating the mean transport rate q s to hydraulic conditions (that is, water discharge q w , bottom shear stress τ b or stream power ω): q s ∝ q w , q s ∝ τ 3/2 b or q s ∝ ω. The most common approach used to calculate bedload transport has thus long involved determining the one-to-one function q s = f (q w) (or any other dependence of q s on τ b or ω) from experiments or theoretical considerations. However, the predictive power of such relationships is limited: scientists are unable to predict q s to within better than one order of magnitude, and morphodynamic models based on q s = f (q w) fail to explain the development of bedforms without the use of additional assumptions. Progressively, other calculation approaches have appeared, with many relying on the idea that bedload transport is a macroscopic transport process that primarily reflects random particle motion at the grain scale. The present paper reviews the main ideas being explored today.

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The variability of antidune morphodynamics on steep slopes

Pascal

Ancey

Bohorquez

2021

Earth Surf Processes Landf

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Steep streams on rough beds are generally characterised by supercritical flow conditions under which antidunes can develop and migrate over time. In this paper, we present flume experiments that we conducted to investigate the variability of antidune geometry and migration celerity, a variability observed even under steady‐state conditions. Quantifying this variability is important for river morphodynamics, hydraulics and paleohydraulics. We imposed moderate to intense bedload transport rates at the flume inlet to assess their effects on antidune morphodynamics for near‐constant values of the mean bed slope. The bed elevation profile was monitored for each experiment with high spatial and temporal resolution. Upstream migrating antidunes were observed along most of the flume length. Considering single values for wavelength and celerity was not sufficient to describe the antidune behaviour in these experiments. By using spectral analysis, we identified the variability ranges of bedform shape and celerity. Interestingly, migration celerity increased with increasing antidune wavelength; the opposite trend was reported for dunes in other studies. Antidunes were more uniform and migrated faster for higher sediment feeding rates. Scaling the spectra made it possible to find a general dimensionless relationship between antidune wavelength and celerity. This framework provides a novel method for estimating the mean bedload transport rate in the presence of upstream migrating antidunes.

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The fascination of a shallow-water theory for the formation of megaflood-scale dunes and antidunes

Cited by 30 publications

References 87 publications

Three‐dimensional antidunes coexisting with alternate bars

Three‐dimensional antidunes coexisting with alternate bars

A new front condition for non-Boussinesq gravity currents

The variability of antidune morphodynamics on steep slopes

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