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Form Resistance Prediction in Gravel-Bed Rivers
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
The values of friction factor in gravel-bed rivers depend on the particle size of the bed material, bedforms, channel geometry, longitudinal slope, and non-dimensionalized flow depth (flow depth/sediment size, usually defined by h/d84) as a hydraulic condition. Among these parameters, grain size and bedforms have the greatest influence on the friction factor and the transport of sediment in most gravel-bed rivers with deep flow (Garcia, 2008). Also, bedforms have direct ecological implications, with great effects on aquatic animals' life (Crowder and Diplas, 2006). Yang et al. (2005) deliberated on the impacts of bedforms on the total bed shear stress and the slope of the energy grade line. The study proposed an equation for computing the total bed shear stress as a function of the grain and bedform friction. Their model was tested and verified against bulk field data observations and proved the indisputable impact of bedforms on flow resistance calculations.
Hydraulics, Sediment Transportation and Structures of Mechanical Origin
Published in Supriya Sengupta, Introduction to Sedimentology, 2017
Water flowing over a plane, non-cohesive sediment surface throws it into a series of rhythmic patterns called bedforms. Observations in streams reveal that the nature and magnitude of bedforms are dependent on parameters such as the flow velocity and sediment grain-size. The precise manner in which these variables influence the shape and magnitude of bedforms, however, remained unclear until the natural processes could be simulated to some extent under controlled conditions in the laboratory. The results of one such pioneering study, carried out in the United States (Simons, Richardson and Nordin 1965) are reproduced in Fig. 5.9. The nature of the bedform generated at various combinations of stream power and fall velocity of sedimentary particles is shown in this diagram. Stream power (τ0⋅v¯) was used by the experimenters as a measure of the erosive power of the stream and fall velocities were used as an index of the hydraulic behaviour of the grains. The flows responsible for generation of bedforms were divided into three regimes according to Froude number: a lower flow regime (F < 1), a transitional flow regime (F ≈ 1) and an upper flow regime (F > 1).
Hydraulic Flows: Overview
Published in Marian (Editor-in-Chief) Muste, Dennis A. Lyn, David M. Admiraal, Robert Ettema, Vladimir Nikora, Marcelo H. Garcia, Experimental Hydraulics: Methods, Instrumentation, Data Processing and Management, 2017
Marian (Editor-in-Chief) Muste, Dennis A. Lyn, David M. Admiraal, Robert Ettema, Vladimir Nikora, Marcelo H. Garcia
These bedforms have an important influence on sediment transport and on flow resistance. Best (2005) highlights recent year’s great progress in our knowledge and understanding regarding bedform characteristics due to the increased ability to monitor flow and dune morphology in the laboratory and the field as well as the development of increased sophistication numerical modeling to capture not only the characteristics of the mean flow field but realistically simulate the origins and motions of coherent flow structures above bedforms. These advances are summarized in the work by Reynolds (1976), Engelund and Fredsøe (1982), Ikeda and Parker (1989), McLean (1990), Southard (1991), Kennedy and Odgaard (1991), Seminara (1995), Best (1996), Seminara and Blondeaux (2001), Yalin and da Silva (2001), ASCE (2002), Bridge (2003), Best (2005), and Parker and Garcia (2006) and Garcia (2008). Since the effect of the bedforms both on sediment and flow is so important, it is impossible to cover all the material needed in detail. Instead, a brief introduction on the major bedform types and some of their characteristics are presented below. Interested readers are guided to consult the references of this section for more details.
Bulk Flow Characteristics of a Gravel Bed River with Instream Emergent Vegetation
Published in ISH Journal of Hydraulic Engineering, 2023
Sadegh Derakhshan, Hossein Afzalimehr, Vijay P. Singh
The study of river systems is of utmost importance as they are directly and indirectly involved with the sustenance of life. Aquatic vegetation and morphology are integral components of river systems, aquatic vegetation alters the flow field and the fluvial and morphological behavior of rivers (Nepf 2012; Curran and Hession 2013), and through this alteration, it provides various ecosystem services such as removal of contaminants in aquatic environments and improving water quality, channel erosion control, creating habitats and promoting biodiversity (Osterkamp and Hupp 2010; Folkard 2011; Wang et al. 2014). Bedforms are essential in engineering and ecological aspects of rivers, effecting sediment transport, aquatic habitat and the flow resistance (Julien 2010; Afzalimehr et al. 2017; Hassan et al. 2018). Aquatic vegetation and morphology are highly interrelated and play a critical role in river management and restoration (Harvey and Gooseff 2015; Rowiński et al. 2018).
Particle image velocimetry validation for quantifying bedload movement
Published in Journal of Applied Water Engineering and Research, 2019
Muhammed T. Mustafa, Amanda L. Cox, Kyle Mitchell
Within the past decade, the use of PIV techniques in the field of sediment transport has significantly increased (e.g. Diplas et al. 2010; Hergault et al. 2010; Micheaux et al. 2015; Rébillout et al. 2016; Agudo et al. 2017). Transport of bedload material occurs when the moments exerted by the hydrodynamic forces on the upper layer of particles on a loose granular bed exceed that of the resisting gravitational force caused by the particle weight (Fernandez Luque and Van Beek 1976). Transport of bedload particles generally occurs through rolling of particles across the bed (Van Rijn 1984; Parker 1990; Chiew and Parker 1994). Different studies have shown the effect of bedslope and bedforms on transport of bedload particles (Chiew and Parker 1994), while the flow acts to accelerate the sediment particles, the bed decelerates them (Campbell et al. 2005).
Erosional and depositional subglacial streamlining processes at Skálafellsjökull, Iceland: an analogue for a new bedform continuum model
Published in GFF, 2018
Jane K. Hart, Alexander I. Clayton, Kirk Martinez, Benjamin A. Robson
However, where flutes and MSGL are formed of bedrock or composite till and bedrock, they may be stationary in the landscape and may show no relationship between elongation and velocity. At Skálafellsjökull both large flutes and drumlins were probably formed under the same velocity regime, but related to different bedrock configurations. Under these conditions, increased velocity may lead to increased erosion, and increased relief of the bedforms, which has been reported from the literature (Spagnolo et al. 2014). In this way flutes may develop directly into MSGL’s rather than passing through a drumlin phase.