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In meandering rivers, interactions between flow, sediment transport, and bed topography affect diverse processes, including bedform development and channel migration. Predicting how these interactions affect the spatial patterns and magnitudes of bed deformation in meandering rivers is essential for various river engineering and geoscience problems. Computational fluid dynamics simulations can predict river morphodynamics at fine temporal and spatial scales but have traditionally been challenged by the large scale of natural rivers. We conducted coupled large‐eddy simulation and bed morphodynamics simulations to create a unique database of hydro‐morphodynamic data sets for 42 meandering rivers with a variety of planform shapes and large‐scale geometrical features that mimic natural meanders. For each simulated river, the database includes (a) bed morphology, (b) three‐dimensional mean velocity field, and (c) bed shear stress distribution under bankfull flow conditions. The calculated morphodynamics results at dynamic equilibrium revealed the formation of scour and deposition patterns near the outer and inner banks, respectively, while the location of point bars and scour regions around the apexes of the meander bends is found to vary as a function of the radius of curvature of the bends to the width ratio. A new mechanism is proposed that explains this seemingly paradoxical finding. The high‐fidelity simulation results generated in this work provide researchers and scientists with a rich numerical database for morphodynamics and bed shear stress distributions in large‐scale meandering rivers to enable systematic investigation of the underlying phenomena and support a range of river engineering applications.
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Modelling shear stress distribution in ice-covered streams
Abstract Distribution of bed shear stress is the critical factor in regulating the meandering of single-thread rivers. However, the impact of ice cover on bed shear stress is largely unknown. In this study, we develop a theoretical model of cross-stream momentum balance to examine the distribution of bed shear stresses in ice-covered meandering rivers. To validate the theoretical model, field surveys were carried out in a river reach of the Red River in Fargo, North Dakota. Data monitoring was completed using an Acoustic Doppler Current Profiler to obtain time-averaged velocity profiles. Our theoretical model indicates that an ice covering develops high-shear zones near both the inner and outer banks, which might exacerbate sediment transport and enhance bank erosion. Velocity measurements confirm the results of the proposed model and demonstrate a clear impact of meandering river banks on velocity profiles and secondary flow patterns under ice cover. Based on our results, we hypothesize that ice cover increases turbulent stresses near banks, which in turn lead to the enhancement of the bed shear stress. Our work provides new insights into the impact of ice cover on bed shear stress distribution, which could play an important role in driving sediment-transport processes and the long-term morphodynamic evolution of meandering rivers seasonally covered by ice.
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- PAR ID:
- 10514375
- Publisher / Repository:
- Geological Society Publications
- Date Published:
- Journal Name:
- Geological Society, London, Special Publications
- Volume:
- 540
- Issue:
- 1
- ISSN:
- 0305-8719
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1144/SP540-2022-161
