Effect of sediment pulse grain size on sediment transport rates and bed mobility in gravel bed rivers

This paper presents a novel 2D-depth average model especially developed for gravel-bed rivers, named Lican-Leufú (Lican=pebble and Leufu=river, in Mapuche’s language, the native inhabitants of Central Patagonia, Argentina). The model consists of three components: a hydrodynamic, a sedimentological, and a morphological model. The flow of water is described by the depth-averaged Reynolds equations for unsteady, free-surface, shallow water flows. It includes the standard k-e model for turbulence closure. Sediment transport can be divided in different size classes (sand-gravel mixture) and the equilibrium approach is used for Exner’s equation. The amour layer is also included in the structure of the model and the surface grain size distribution is also allowed to evolve. The model simulates bank slides that enable channel widening. Models predictions were tested against a flume experiment where a static armour layer was developed under conditions of sediment starvations and general good agreements were found: the model predicted adequately the sediment transport, grain size of transported material, final armour grain size distribution and bed elevation.

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Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers

Water ◽

10.3390/w11030550 ◽

2019 ◽

Vol 11 (3) ◽

pp. 550 ◽

Cited By ~ 5

Author(s):

Van Bui ◽

Minh Bui ◽

Peter Rutschmann

Keyword(s):

Grain Size ◽

Sediment Transport ◽

Size Distribution ◽

Grain Size Distribution ◽

Morphological Changes ◽

Relative Size ◽

Size Fraction ◽

New Model ◽

Gravel Bed ◽

Gravel Bed Rivers

Understanding the alterations of gravel bed structures, sediment transport, and the effects on aquatic habitat play an essential role in eco-hydraulic and sediment transport management. In recent years, the evaluation of changes of void in bed materials has attracted more concern. However, analyzing the morphological changes and grain size distribution that are associated with the porosity variations in gravel-bed rivers are still challenging. This study develops a new model using a multi-layer’s concept to simulate morphological changes and grain size distribution, taking into account the porosity variabilities in a gravel-bed river based on the mass conservation for each size fraction and the exchange of fine sediments between the surface and subsurface layers. The Discrete Element Method (DEM) is applied to model infiltration processes and to confirm the effects of the relative size of fine sediment to gravel on the infiltration depth. Further, the exchange rate and the bed porosity are estimated while using empirical formulae. The new model was tested on three straight channels. Analyzing the calculated results and comparing with the observed data show that the new model can successfully simulate sediment transport, grain sorting processes, and bed change in gravel-bed rivers.

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The influence of microform bed roughness elements on flow and sediment transport in gravel bed rivers: A reply

Earth Surface Processes and Landforms ◽

10.1002/esp.3290170512 ◽

1992 ◽

Vol 17 (5) ◽

pp. 535-538 ◽

Cited By ~ 10

Author(s):

Ian Reid ◽

Marwan A. Hassan

Keyword(s):

Sediment Transport ◽

Gravel Bed ◽

Roughness Elements ◽

Flow And Sediment Transport ◽

Gravel Bed Rivers ◽

Bed Roughness

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Geometry of meandering and braided gravel-bed threads from the Bayanbulak Grassland, Tianshan, P. R. China

Earth Surface Dynamics ◽

10.5194/esurf-4-273-2016 ◽

2016 ◽

Vol 4 (1) ◽

pp. 273-283 ◽

Cited By ~ 9

Author(s):

François Métivier ◽

Olivier Devauchelle ◽

Hugo Chauvet ◽

Eric Lajeunesse ◽

Patrick Meunier ◽

...

Keyword(s):

Grain Size ◽

Scaling Laws ◽

Sedimentary Basin ◽

Bedload Transport ◽

Braided River ◽

Statistical Distributions ◽

Meandering Rivers ◽

Gravel Bed ◽

Threshold Theory ◽

Gravel Bed Rivers

Abstract. The Bayanbulak Grassland, Tianshan, P. R. China, is located in an intramontane sedimentary basin where meandering and braided gravel-bed rivers coexist under the same climatic and geological settings. We report and compare measurements of the discharge, width, depth, slope and grain size of individual threads from these braided and meandering rivers. Both types of threads share statistically indistinguishable regime relations. Their depths and slopes compare well with the threshold theory, but they are wider than predicted by this theory. These findings are reminiscent of previous observations from similar gravel-bed rivers. Using the scaling laws of the threshold theory, we detrend our data with respect to discharge to produce a homogeneous statistical ensemble of width, depth and slope measurements. The statistical distributions of these dimensionless quantities are similar for braided and meandering threads. This suggests that a braided river is a collection of intertwined threads, which individually resemble those of meandering rivers. Given the environmental conditions in Bayanbulak, we furthermore hypothesize that bedload transport causes the threads to be wider than predicted by the threshold theory.

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