Dune‐Phase Fluvial Transport and Deposition Model of Gravelly Sand

Abstract

The importance and role of sorting processes in dune-phase bedload transport and deposition is demonstrated with flume experiments, vibracores from the River Rhine (The Netherlands) and with sediment transport and dune data from the River Rhine. The entrainment and deposition depth of the sediment depend on dune trough levels below the average bed level and therefore on the dune height. As bedload sediment transport depends partly on grain size, it will be dependent upon the relict vertical sorting left in the bed by former discharge waves. The vertical sorting is created by sorting in grain flows on the lee side of dunes and by gravel lag formation in the dune troughs. Based on these principles, a simple reach-representative process model is developed for the prediction of bed sediment reworking, vertical sorting and deposition by dunes. The model is applied to two successive discharge waves of different magnitude, and predicts qualitatively the same vertical sorting characteristics as observed in the vibracores from the River Rhine (The Netherlands) after two successive discharge waves. The effect of the sorting on the sediment transport, and how to include this feedback in future models, is discussed.

Modeling the response of the Rhine–Meuse fluvial system to Late Pleistocene climate change

“…This is the part of the bed sediment in which primary sub-aqueous bedforms such as ripples, dunes and bed load sheets form. The thickness of the active layer in all simulations is set to 0.75 m, a value that is within the same order of active layer thickness known from the present and historically described Rhine channels (Wilbers and Ten Brinke, 2003;Kleinhans, 2005).…”

What is the “active layer”?

“…Taking scour‐fill considerations into account with dunes in particular in mind, Kleinhans [; p. 78] consequently defined the active layer as follows:…”

Complex variations in sediment transport at three large river bifurcations during discharge waves in the river Rhine

“…Aspects of the Pannerdensche Kop data have previously been analysed by Wilbers & Ten Brinke (2003), Wilbers (2004), Kleinhans (2001Kleinhans ( , 2005 and Kleinhans et al (2007), but they are summarized and reanalysed here to enable comparison with the IJsselkop and Merwedekop data, which are presented here for the first time.…”

“…Nevertheless, it is often supposed that hysteresis in hydraulic roughness causes an opposite hysteresis in bed-load transport (e.g. Kleinhans, 2005;Kleinhans et al, 2007), by reasoning that a decrease in roughness reduces the amount of bed shear stress needed to overcome bed friction, leaving a larger part available for bed-load transport, and therefore increasing the bed-load transport (Fig. 1C).…”