Does flow variance affect bedload flux when the bed is dominated by grain roughness?

Cooper, James R.

doi:10.1016/j.geomorph.2011.12.039

Cited by 5 publications

(4 citation statements)

References 48 publications

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“…This difference in submergence may be important when extrapolating the transport‐capacity relationships from one river to another, or one from hillslope to another, for the following reason. Within the fluvial literature there is strong evidence that the mean fluid shear stress at which sediment is entrained is inversely correlated to relative submergence [e.g., Bathurst et al ., , ; Bettess , ; Shvidchenko and Pender , ; Mueller et al ., ; Parker et al ., ] because the structure of the near‐bed flow changes with submergence [ Ashida and Bayazit , ; Graf , ; Lamb et al ., ; Cooper , ]. Wainwright and Thornes [] found a similar pattern for coarse particles on hillslopes.…”

Section: Discussionmentioning

confidence: 99%

The concept of transport capacity in geomorphology

Wainwright

Parsons

Cooper

et al. 2015

Reviews of Geophysics

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Section: Discussionmentioning

confidence: 99%

The concept of transport capacity in geomorphology

Wainwright

Parsons

Cooper

et al. 2015

Reviews of Geophysics

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“…[6] A small number of studies have examined the change in spatial variance in time-averaged streamwise velocity with submergence, but the results are inconsistent. The studies have observed an increase in variance with a rise in flow depth [Clifford, 1996;Cooper, 2012], a decrease [Buffin-B elanger et al, 2006], and little or no change above [Legleiter et al, 2007] and within the roughness layer [Aberle et al, 2008]. Aberle et al [2008] further showed that relative submergence had little influence on the magnitude of form-induced stress.…”

Section: Introductionmentioning

confidence: 99%

Influence of relative submergence on spatial variance and form-induced stress of gravel-bed flows

et al. 2013

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[1] Spatial flow variance has a strong control on sediment transport, sediment-water interface exchange mechanisms, and the distribution and behavior of aquatic organisms in rivers. Thus, being able to quantify spatial flow variance, and how it varies with different water levels, is important for understanding how fluvial processes change during periods of time varying flow. In this paper, laboratory flume measurements of near-bed flow velocity were used to quantify spatial flow variance and form-induced stress, and their variation with flow submergence, within and above the surface of porous, gravel beds with differing grain roughness. The analysis revealed spatial flow variance was usually four or five times higher within the roughness layer than above. A rise in relative submergence resulted typically in a decrease in spatial variance-relative to bed shear velocity-in streamwise form-induced intensity, streamwise turbulence intensity, and form-induced momentum flux, both within and above the roughness layer. Flow submergence had no consistent influence on spatial variance in the vertical flow direction and in Reynolds stress. Form-induced stress was significant within the roughness layer, more so at shallow depths. The greater significance was driven primarily by higher spatial flow variance in time-averaged streamwise velocity at these depths. The implication is the relative role of momentum transfer mechanisms within the roughness layer, and thus, sediment-water interface exchange processes in rivers will change during periods of time varying flows.

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“…This difference in inundation may be important when extrapolating the transport relationships from the river to the hillslope for the following reason. Within the fluvial literature there is strong evidence that the mean fluid shear stress at which sediment is entrained is inversely correlated to the inundation ratio [e.g., Bathurst et al , 1983, 1987; Shvidchenko and Pender , 2000; Mueller et al , 2005; Parker et al , 2011] because the structure of the near‐bed flow changes with this ratio [ Ashida and Bayazit , 1973; Graf , 1991; Lamb et al , 2008; Cooper , 2012]. Therefore the difference in the flow‐inundation ratio between river and overland flows is likely to result in flow detachment rates on hillslopes being overestimated by fluvial transport equations.…”

Section: Discussionmentioning

confidence: 99%

A new approach for simulating the redistribution of soil particles by water erosion: A marker‐in‐cell model

et al. 2012

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[1] There are currently no process-based approaches that allow detailed spatial information on soil redistribution on hillslopes to be modeled at spatial scales that are appropriate for studying slope processes. In response, we developed a new type of soil-erosion model, a marker-in-cell model, which simulates the redistribution of soil during rainfall events. The model is a hybrid of cell-and particle-based techniques. A cell-based model is used to determine the hydrology and hydraulics occurring at the cellular scale on the hillslope. Markers, representing sediment, are then moved through the grid according to these properties. The spatial pattern of erosion is determined directly by the properties of the markers. The model allows two-dimensional spatial patterns of individual particle movement on a hillslope to be simulated within a computationally efficient framework. We have tested the model using data collected from a plot-scale, rainfall-simulation experiment. We measured the redistribution of 137 Cs-rich tracer soil to resolve the spatial patterns of erosion caused by a single, high-intensity, rainfall event. The model was able to recreate the key temporal and spatial aspects of the hydrology and hydraulics occurring on the plot, as well as the spatial redistribution of 137 Cs-rich tracer soil. The development of the model was used to probe our understanding of how to investigate soil-erosion processes. The lack of empirical underpinnings of the different model components highlighted the need to understand the spatiotemporal dynamics of soil erosion processes at the grain-scale so to provide a better process-based understanding of detachment and transport can be sought.

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Does flow variance affect bedload flux when the bed is dominated by grain roughness?

Cited by 5 publications

References 48 publications

The concept of transport capacity in geomorphology

The concept of transport capacity in geomorphology

Influence of relative submergence on spatial variance and form-induced stress of gravel-bed flows

A new approach for simulating the redistribution of soil particles by water erosion: A marker‐in‐cell model

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