Publication

Influence of immobile boulders on bedload transport in a steep flume

Anton Schleiss, Tamara Ghilardi
2011
Conference paper
Abstract

When applied to mountain torrents, sediment transport formulae habitually overestimate the bedload by several orders of magnitude, even if they have been developed for steep slopes. The reason is that the influence of macro-roughness elements, such as large immobile boulders which have an impact on flow conditions, is not taken into account. Larger roughness elements induce an increased form drag, implying a lower shear stress available for sediment entrainment. Preliminary tests carried out in a laboratory flume with a slope of 6.7%, reveal that the surface occupied by boulders need to be considered in order to obtain a good estimation of the sediment discharge. With 15% of the surface occupied by boulders, the bedload is reduced by 61% compared to transport rate without boulders. The influence of the immobile boulders on flow conditions and sediment transport has been studied as a function of spatial density of the boulders. The results are discussed in comparison with existing empirical bedload transport formula.

About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Related concepts (21)
Sediment transport
Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural systems where the particles are clastic rocks (sand, gravel, boulders, etc.), mud, or clay; the fluid is air, water, or ice; and the force of gravity acts to move the particles along the sloping surface on which they are resting.
Bed load
The term bed load or bedload describes particles in a flowing fluid (usually water) that are transported along the stream bed. Bed load is complementary to suspended load and wash load. Bed load moves by rolling, sliding, and/or saltating (hopping). Generally, bed load downstream will be smaller and more rounded than bed load upstream (a process known as downstream fining). This is due in part to attrition and abrasion which results from the stones colliding with each other and against the river channel, thus removing the rough texture (rounding) and reducing the size of the particles.
Fluvial processes
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used. Fluvial processes include the motion of sediment and erosion or deposition on the river bed. The movement of water across the stream bed exerts a shear stress directly onto the bed.
Show more
Related publications (42)

Influence of channel geomorphic units on bedload transport and river morphology during low‐magnitude bed‐forming floods coupled with sediment augmentation

Giovanni De Cesare, Severin Stähly, Christian Mörtl, Robin Schroff

In this study, we map different types of channel geomorphic units in a sediment-starved, residual-flow reach before and after an artificial flood. Bedload particles of a previous sediment augmentation measure are tracked with passive integrated transponder ...
2023

Dynamics of Dual-Mode Bedload Transport With Three-Dimensional Alternate Bars Migration in Subcritical Flow: Experiments and Model Analysis

Mehrdad Kiani Oshtorjani, Zhipeng Li, Yong Zhang

Bedload transport often exhibits dual-mode behavior due to interactions of spatiotemporal controlling factors with the migrating three-dimensional bedforms (characterized by the fully developed patterns in the bed, such as alternate bars, pools, and cluste ...
AMER GEOPHYSICAL UNION2023

p Spatio-temporal deposition profile of an experimentally produced turbidity current with a continuous suspension supply

Giovanni De Cesare, Shun Nomura

A turbidity current is a turbulent, particle-laden gravity current that is driven by density differences resulting from the presence of suspended sediment particles. The current travels downslope, bearing a large amount of sediment over a great distance, a ...
IRTCES2022
Show more
Related MOOCs (2)
Fluid Mechanics
Ce cours de base est composé des sept premiers modules communs à deux cours bachelor, donnés à l’EPFL en génie mécanique et génie civil.
Water quality and the biogeochemical engine
Learn about how the quality of water is a direct result of complex bio-geo-chemical interactions, and about how to use these processes to mitigate water quality issues.