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. However, selective transport of sediments also plays a role in relation to downstream fining: smaller-than average particles are more easily entrained than larger-than average particles, since the shear stress required to entrain a grain is linearly proportional to the diameter of the grain. However, the degree of size selectivity is restricted by the hiding effect described by Parker and Klingeman (1982), wherein larger particles protrude from the bed whereas small particles are shielded and hidden by larger particles, with the result that nearly all grain sizes become entrained at nearly the same shear stress.
Experimental observations suggest that a uniform free-surface flow over a cohesion-less plane bed is unable to entrain sediments below a critical value of the ratio between measures of hydrodynamic (destabilizing) and gravitational (stabilizing)
forces acting on sediment particles, the so-called Shields stress . This quantity reads as:
where is the friction velocity, s is the relative particle density, d is an effective particle diameter which is entrained by the flow, and g is gravity. Meyer-Peter-Müller formula for the bed load capacity under equilibrium and uniform flow conditions states that the magnitude of the bed load flux for unit width is proportional to the excess of shear stress with respect to a critical one . Specifically, is a monotonically increasing nonlinear function of the excess Shields stress , typically expressed in the form of a power law.
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This course aims to provide theoretical fundamentals in flow measurement science, and advanced knowledge regarding measurement methods, tools and instrumentation applied to experimental hydraulics, in
Le cours donne aux étudiants des solides connaissances théoriques en hydraulique fluviale, et enseigne les bases de l'ingénierie fluviale dans le but de concilier la protection contre les crues et la
Les aménagements hydrauliques sont indispensable pour garantir l'approvisionnement en énergie écophile et renouvelable, de même que l'approvisionnement en eau de bonne qualité et en quantité suffisant
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.
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification.
Explores sediment transport, river structures, and hydraulic platforms for river development.
Explores river hydraulics, bedload transport, and hydraulic construction platforms, emphasizing the challenges of predicting sediment movement in rivers and the impact of floods on infrastructure.
Explores hydraulic constructions, wave propagation, and bedload analysis for project design.
In computational hydraulics models, predicting bed topography and bedload transport with sufficient accuracy remains a significant challenge. An accurate assessment of a river's sediment transport rate necessitates a prior understanding of its bed topograp ...
Field surveys and laboratory experiments show that bedload transport rates may vary to within one order of magnitude for a given water discharge. One of today's major challenges is to account for these large transport rate fluctuations in computational hyd ...
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 ...