Two-Dimensional Numerical Simulation Study on Bed-Load Transport in the Fluctuating Backwater Area: A Case-Study Reservoir in China
Abstract
:1. Introduction
2. Mathematical Model
2.1. Shallow-Water Equations
2.2. Movable Bed Model
3. Numerical Model
4. Numerical Simulation
4.1. Study Case Description
4.2. Validation Test
4.3. Evaluation of Morphological Bed Changes in the Fluctuating Backwater Area
4.3.1. Type 1: Reservoir Storage
4.3.2. Type 2: Reservoir Drawdown
4.3.3. Type 3: Continuous Flood Process
5. Conclusions
- Sediment transport is by far the more uncertain process, which is the most significant innovation of this study. This present study shows the implementation that the river channel sedimentation morphology is changed by the change of water level in the downstream reach and provides evidence for the effect of incidental events on river bed morphology, which increases the factors driving the change of river bed morphology and challenges the traditional theory that the shape of a river channel is mainly determined by the upstream water and sediment and the physical boundary conditions of the river channel, rather than random events.
- The sedimentation in the fluctuating backwater area is mainly deposited in the main channel and the difference in elevation of the river-bed between the beach and channel decreases with time. In the river bend, the sedimentation is mainly concentrated on the convex bank, readily resulting in the growth of a convex bank beach. Although the concave bank also experiences siltation, the quantity is relatively minor.
- During the drawdown period of the reservoir, the original sedimentation is scoured, with scouring concentrated over a small width. The flow gradually erodes a deep channel in the river-bed, forming compound channels with a beach and multiple channels, which reshapes the channel of the low flow period. The deposition of bed-load from upstream to downstream and the slope of the longitudinal section of the river bed in the fluctuating backwater area are generally gradually reduced.
- There is an element of randomness in the location and morphology of sedimentation due to the effect of the downstream water level and fluctuating backwater. Under type 3, the location and bed morphology of the end of the backwater vary under the same inlet flow conditions and different downstream water levels. The location and direction of upstream flow are changed under differences in location and morphology, resulting in large differences in sedimentation under different flow conditions.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Name | Zhang RJ | Tang CB | Dou GR | Sha YQ | Sharmov | B.H. | Shields |
---|---|---|---|---|---|---|---|
K | 1.53 | 1.789 | 1.314~1.343 | 1.277 | 1.33 | 1.58 | 1.272 |
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Luo, M.; Yu, H.; Huang, E.; Ding, R.; Lu, X. Two-Dimensional Numerical Simulation Study on Bed-Load Transport in the Fluctuating Backwater Area: A Case-Study Reservoir in China. Water 2018, 10, 1425. https://doi.org/10.3390/w10101425
Luo M, Yu H, Huang E, Ding R, Lu X. Two-Dimensional Numerical Simulation Study on Bed-Load Transport in the Fluctuating Backwater Area: A Case-Study Reservoir in China. Water. 2018; 10(10):1425. https://doi.org/10.3390/w10101425
Chicago/Turabian StyleLuo, Ming, Heli Yu, Er Huang, Rui Ding, and Xin Lu. 2018. "Two-Dimensional Numerical Simulation Study on Bed-Load Transport in the Fluctuating Backwater Area: A Case-Study Reservoir in China" Water 10, no. 10: 1425. https://doi.org/10.3390/w10101425