Bedform characteristics in a gravel-bed river

Afzalimehr, Hossein; Maddahi, Mohammad Reza; Sui, Jueyi

doi:10.1515/johh-2017-0023

Cited by 10 publications

(7 citation statements)

References 29 publications

(29 reference statements)

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“…; Afzalimehr et al. ). There is still great demand for a reliable technique for characterizing gravel‐bed forms.…”

Section: Methodsmentioning

confidence: 99%

“…Contrary to sand-bed rivers where accepted classifications of bedforms (e.g. ripples, dunes, antidunes) exist (Simons and Richardson, 1966;van Rijn, 1984;Coleman and Nikora, 2011), bedforms in gravel-bed rivers are not always specific or easy to identify (Singh et al, 2012;Afzalimehr et al, 2017). There is still great demand for a reliable technique for characterizing gravel-bed forms.…”

Section: Evaluation Of the Bed Morphologymentioning

confidence: 99%

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How does the bed surface impact low‐magnitude bedload transport rates over gravel‐bed rivers?

Perret

Berni

Camenen

2020

Earth Surf Processes Landf

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Bedload transport is a complex phenomenon that is not well understood, especially for poorly sorted sediment and low transport rates, which is what is typically found in alpine gravel‐bed rivers. In this paper, the interaction between bedload rate, bed stability and flow is investigated using flume experiments. Significant differences in bedload rates were observed for experiments conducted on beds formed with the same gravel material but presenting diverse arrangements and bedforms. Tests were performed under regimes of low transport rate, which are mainly controlled by gravel‐bed roughness. Different scales of roughness were identified using the statistical characteristics of detailed bed elevation measurements: grain, structure and large bedform scales. The role played by these different roughness scales in bedload dynamics was examined. For quasi‐flat beds, bed stability was quantified using a combination of bed surface criteria describing grain and structure scales. It was found that bed stability affects the bedload rate directly and not only through its influence on the flow or on the incipient motion. For beds with large bedforms, the analysis of bedload dynamics also showed the importance of accounting for effective bed shear stress distributions. An empirical bedload model for low transport regimes was suggested. Compared with previous formulae developed for alpine rivers, this model accounts for bed stability and distribution of effective bed shear stress. It significantly improves the understanding of gravel dynamics over complex beds such as arranged beds or those with large bedforms. However, further tests are needed to use the model outside the range of conditions of this study. © 2019 John Wiley & Sons, Ltd.

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“…; Afzalimehr et al. ). There is still great demand for a reliable technique for characterizing gravel‐bed forms.…”

Section: Methodsmentioning

confidence: 99%

Section: Evaluation Of the Bed Morphologymentioning

confidence: 99%

How does the bed surface impact low‐magnitude bedload transport rates over gravel‐bed rivers?

Perret

Berni

Camenen

2020

Earth Surf Processes Landf

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“…Accordingly, the surveying operation was done carefully on the entire riverbed along the desired reaches. Afzalimehr et al (2017) applied a type of networking with dimensions of 0.8 m × 0.5 m in river bed to obtain suitable result; this method was used in this study. In total 1244 points in reach 1 and 981 points in reach 2 were surveyed.…”

Section: Reach2mentioning

confidence: 99%

Incipient motion of sediment particles in the presence of bed forms under decelerating and accelerating flows

Dodangeh

Afzalimehr

2022

Journal of Hydrology and Hydromechanics

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This paper investigates the incipient motion of sediment particles under non-uniform flow in river and laboratory. In rivers, the non-uniform flow is often observed due to the presence of various bed forms. Threshold condition has been examined by using the Shields diagram based on the uniform flow assumption, however, this approach can be led to fallacious results for non-uniform flows where the effect of pressure gradient is significant due to bed forms. This study investigates the chronological order of incipient motion of the particles, the average threshold velocity (Ucr ), and Shields parameter for non-uniform flows. River data collection with gravel is used for investigating the incipient motion of surface layer of river bed and the laboratory data collection is considered studying the incipient motion of sub-surface layer of river. Both river and laboratory data collections are conducted in the presence of bed forms. Results reveal that the Shields diagram underestimates the particle incipient motion under accelerating and decelerating flows for the both case of laboratory and river. In both weak and general motion in the laboratory, the values of the critical Shields parameter are located below the Shields diagram, showing no particle motion. Our analysis shows that the incipient motion in river is affected by the presence of bed forms, river width changes, and flow non-uniformity conditions. The results show that in the accelerating flow (the bed form exit with a negative slope), the incipient motion is greater than the decelerating flow (the bed form entrance with a positive slope).

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“…Sedimentation that occurred on the bed of the river producing a conducive ecosystem for vegetation to grow. These plants grow naturally in the channel and are very important to aquatic life by supplying oxygen and removing excess nutrients to the ecosystem [1].…”

Section: Introductionmentioning

confidence: 99%

The Hydrodynamic Characteristics for Vegetative Channel With Gravel Bed Dunes

2022

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Aquatic plants are known to provide flow resistance and impact the turbulence intensity and turbulent kinetic energy within the vegetated area. This paper further investigates the impact of both vegetation and dunes in open channels to the hydrodynamic characteristic of flow. Emergent vegetations were built from rigid wooden rod in staggered arrangement with 0.5% vegetations density were applied in the flume. Experiments were conducted with flow rate of 0.0058 m3/s throughout the experiments. Dunes were constructed from gravel of 2 mm size diameter in the shape of standing waves of three different lee slope angles of 3⁰, 6⁰ and 9⁰. Flow velocities are measured by using a velocimeter to get the raw data for the three-dimensional flow velocity in the x, y, and z directions. The velocities data were then analysed to calculate the mean velocity, turbulence intensity and turbulent kinetic energy. Experimental results showed that, for all three lee slope angles presented higher flow velocity in the vegetated channel compared to the non-vegetated channel. It was also found that greater lee slope angle dunes generate higher velocity for both channels with and without vegetation. Higher turbulence intensity can be found near the bed area and greater turbulence intensity also shown in the positive slope of a dunes compared to negative slope area. Higher turbulent kinetic energy values were recorded within the vegetated channel compared to the non-vegetated channels.

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Bedform characteristics in a gravel-bed river

Cited by 10 publications

References 29 publications

How does the bed surface impact low‐magnitude bedload transport rates over gravel‐bed rivers?

How does the bed surface impact low‐magnitude bedload transport rates over gravel‐bed rivers?

Incipient motion of sediment particles in the presence of bed forms under decelerating and accelerating flows

The Hydrodynamic Characteristics for Vegetative Channel With Gravel Bed Dunes

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