Relationship between the equilibrium morphology of river islands and flow-sediment dynamics based on the theory of minimum energy dissipation

Yang, Xuhai; Sun, Zhilin; Deng, Jinyun; Li, Dongfeng; Li, Yitian

doi:10.1016/j.ijsrc.2021.12.001

Cited by 11 publications

(3 citation statements)

References 39 publications

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“…In another case, the bends are formed when the river scouring continuously the area of its course, while deposition occurs in the opposite side. This is happened due to the spiral movement of water current when the main water is rapidly moving and collides with the concave area [23]. A reactionary water current is down warded and works slowly with a quantity of sediments that have been deposited in the convex side [24].…”

Section: Changes In Meanders and Bendsmentioning

confidence: 99%

Morphological Evolution of Euphrates River Cross-Sections in Central Iraq: Response to Streamflow and Sediment Load Variability

Al Bayaty,

Al Zubaidy,

Almansory

2024

IJDNE

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In recent years, the Euphrates River in Iraq has experienced a noticeable change in its morphological system. The presence of sediment has created some problems in spite of rehabilitation and maintenance process have been put into practice. Therefore, the aim of this research is identifying the morphological evolution in a part of Euphrates River as response to streamflow and sediment load variability due to climate change. To this end, a field survey was conducted along a part of Euphrates River in center of Iraq start from station 605+554 km northern Al Hindiyah Barrage and extend about 25 km downstream until station 630+00 km. Approximately 40 cross-sections were surveyed along river reach with distance between one cross section and another from 0.4 to 2 km. The meandering changes and river migration were estimated with support of Satellite images, besides provided maps and aerial photographs to investigate which river segments that remained steady or changed between 2019 and 2022. The field surveying was included of explore morphologic manifestations of channel such as; meanders, bends, bars and islands and measured the change in geometry shape of selected cross sections. For analysis, a comparison was done with historical field data approved in 2019. The results have indicated that the channel has multiple morphology course of river consists of straight, curved and braided parts and the curvature occur according to the stage of the flow. The average width of displacement is changed between 130 m and 930 m and the variation in centerline distance due to variations in the radius of curvature caused by the internal arc's reduction 880 m and 2035 m. The river is varied in the ratio of sinuosity SI between 1.005 and 1.149 "straight" and "winding" sections; and there is one meander formation the maximum percentage of sinuosity 1.62. The geometry of cross sections, sediment and water conditions are mightily connected and varied relatively over the time scale. The variation in shape has associated with constructing floodplains, riparian vegetation, and boundary conditions. Besides, the quantity of sediment that input river reach. Several factors have helped to widen floodplains over along time of centuries like; flood deposition, river flow, presence of plants, branching, bends and meanders, and the presence of river islands. The results of survey can have important effects on the development, operation, and maintenance of river basin for sustainable use in an environmentally and economically sound manner.

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Section: Changes In Meanders and Bendsmentioning

confidence: 99%

Morphological Evolution of Euphrates River Cross-Sections in Central Iraq: Response to Streamflow and Sediment Load Variability

Al Bayaty,

Al Zubaidy,

Almansory

2024

IJDNE

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“…Tong [32] derived two formulas for calculating the diversion ratio of branching rivers by using the equal sediment concentration method and the momentum balance method and considered the formula based on the momentum balance method more accurate. Based on the theories of minimum energy dissipation theory of fluid movement and river morphodynamics, Yang [33] analyzed the relationship between river island shape coefficient and flow and sediment dynamics under stable equilibrium conditions. Some researchers proposed two different forms of power law, hydropower station hydraulic geometry (AHG) and downstream hydraulic geometry (DHG), and derived the theoretical expressions of AHG and DHG [34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Hydraulic Geometry and Theory of Equilibrium Water Depth of Branching River

Gao

et al. 2023

Water

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Based on the flow continuity formula, resistance formula, sediment transport capacity formula and width-depth ratio relationship, the hydraulic geometry relationship and theory of equilibrium water depth for a branching river are established and are suitable for arbitrary section shape. The ratio of cross-sectional area of a distributary channel and the main stream is a power function of its bifurcation ratio with an exponent of 6/7. This was applied to a 12.5 m deep-water channel of the Yangtze River (the North Passage, Fujiangsha Waterway and Shiyezhou Waterway). The reliability of the equilibrium water depth was verified and the construction effect of the channel regulation project was predicted. The results show that the regulation project has achieved certain results on the whole, but some waterways still cannot meet the requirement of 12.5 m navigation depth. It is necessary to adjust the layout of the regulation project and focus on increasing the bifurcation ratio and reducing the flow resistance so as to increase the maximum equilibrium water depth.

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“…Vegetation can also contribute to island erosion, including by locally focusing flood flows into island margins or across island surfaces, or by adding mass that increases the potential for bank collapse (Simon & Collison, 2002;Thorne, 1990). In recent decades, an increasing number of field, laboratory experimental, and computational modelling approaches have focused on documenting and quantifying these diverse vegetative influences on island dynamics, and also on examining the impacts of vegetated islands on local-to reach-scale flow hydraulics, sediment transport and channel behaviour (Bennett & Simon, 2004;Diehl et al, 2017;Harvey & Bertoldi, 2015;Heidari et al, 2021;Nicholas et al, 2013;Yang et al, 2022). Timescales of island dynamics (e.g., age of initiation, growth rates, longevity) vary widely.…”

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confidence: 99%

Timescales of tree‐covered island dynamics on the mixed bedrock‐alluvial anabranching Vaal River, South Africa

Tooth,

Keen‐Zebert,

Grenfell

et al. 2024

River Research & Apps

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Previous research on mixed bedrock‐alluvial anabranching rivers has documented how alluvial islands commonly grow under vegetation influences atop slowly eroding bedrock templates, but timescales of island dynamics remain poorly constrained. We focus on the Vaal River near Parys, South Africa, and combine field investigations, aerial image analyses and optically stimulated luminescence (OSL) dating to establish timescales of initiation, growth and erosion for nine bedrock‐cored, tree‐covered, alluvial islands. For each island, two OSL samples were collected in vertical succession from sand‐rich exposures up to 4 m in thickness to establish minimum ages for island initiation (~1802 to 243 years) and to estimate local vertical aggradation rates (~0.20 to 1.8 cm year−1). The diachronous lower ages and lack of systematic upstream‐downstream trend in island age support an interpretation of patchwork initiation, growth, and erosion of islands throughout the late Holocene. Following island initiation, vertical island aggradation occurs in association with establishment of reeds, shrubs and trees, but erosion of island margins or dissection by cross‐cutting channels also can occur. Observations during and after recent large floods (peak discharges >3000 m3 s−1) provide further insights into island dynamics, including the influence of exotic trees (e.g., Eucalyptus spp.) that have colonised many islands in the postcolonial era (last ~150 years). Our findings extend previous conceptual models by constraining timescales of island dynamics and providing new insights into island stability and longevity in mixed bedrock‐alluvial anabranching rivers. Improved communication of findings regarding island geomorphology, ecology and stability can benefit local community engagement, geo/eco‐tourism and education activities, and land use planning.

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Relationship between the equilibrium morphology of river islands and flow-sediment dynamics based on the theory of minimum energy dissipation

Cited by 11 publications

References 39 publications

Morphological Evolution of Euphrates River Cross-Sections in Central Iraq: Response to Streamflow and Sediment Load Variability

Morphological Evolution of Euphrates River Cross-Sections in Central Iraq: Response to Streamflow and Sediment Load Variability

Hydraulic Geometry and Theory of Equilibrium Water Depth of Branching River

Timescales of tree‐covered island dynamics on the mixed bedrock‐alluvial anabranching Vaal River, South Africa

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