Dynamic channel adjustments in the Jingjiang Reach of the Middle Yangtze River

Xia, Junqiang; Deng, Shanshan; Lu, Jinyou; Xu, Quanxi; Zong, Quanli; Tan, Guojun

doi:10.1038/srep22802

Cited by 90 publications

(96 citation statements)

References 25 publications

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“…In such fluvial environment, sediment erosion or storage are mostly induced by suspended load transportation and the amounts of sand bedload were less than 4% of the suspended load during 2003-2013 (Wang et al, 2007;Xia et al, 2016). In such fluvial environment, sediment erosion or storage are mostly induced by suspended load transportation and the amounts of sand bedload were less than 4% of the suspended load during 2003-2013 (Wang et al, 2007;Xia et al, 2016).…”

Section: Calculation Methods Of Temporal Distributionmentioning

confidence: 99%

“…The average ratio of sand material bedload to suspended load at the Zhicheng station was less than 4% for 2003-2013; thus, the effect of bedload transport on the riverbed evolution usually was ignored (Xia et al, 2016). The topographic change method can identify the erosion amounts of channels corresponding to different stages, but the calculations are affected by the section spacing and calculation error of channel storage volume.…”

Section: Role Of the Tgd On Erosion Intensity Distributionmentioning

confidence: 99%

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Distribution of erosion intensity in the Jingjiang reach influenced by the Three Gorges Dam

Han

Sun

2018

Earth Surf Processes Landf

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Elucidation of the fluvial processes influenced by dams provides better understanding of river protection and basin management. However, less attention has been given to the erosion intensity distribution of riverbeds and its association with channel morphology and hydrological conditions. Based on hydrological and topographic data, the spatial and temporal distributions of erosion intensity (2002–2014) influenced by the Three Gorges Dam (TGD) were analyzed for the Jingjiang reach of the Yangtze River. The mechanisms underlying the distribution of erosion intensity in response to hydrological conditions were investigated. The results are as follows: (1) The erosion intensities of different discharges were not uniform, and moderate flow (10 000–27 000 m3/s) produced the largest erosion magnitude among all flow ranges. Owing to the hydrological changes caused by flood reduction and prolongation of moderate flow duration after the TGD began operating, up to 70% of the erosion amount was caused by moderate flows. (2) The lateral distribution of erosion intensity was extremely uneven, as the proportion of cumulative erosion of the low‐flow channel within the bankfull channel reached 88% in 2013. This caused the channel to become narrower and deeper. (3) The longitudinal distribution of erosion intensity was inhomogeneous. The erosion intensity in the wide reaches was greater than that in the narrow reaches, leading to smaller differences in channel morphology along the river. (4) Changes in hydrological conditions influenced by the TGD, significant reduction of sediment concentration along with flood abatement, and increased duration of moderate flow discharges were the main factors affecting erosion distribution in the post‐dam period. Our conclusions can be applied to the Yangtze River as a basis for riverbed change estimations, and river management strategies. Copyright © 2018 John Wiley & Sons, Ltd.

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Section: Calculation Methods Of Temporal Distributionmentioning

confidence: 99%

Section: Role Of the Tgd On Erosion Intensity Distributionmentioning

confidence: 99%

Distribution of erosion intensity in the Jingjiang reach influenced by the Three Gorges Dam

Han

Sun

2018

Earth Surf Processes Landf

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“…In addition, the reservoir intercepts a large amount of sediment from upstream, leading to a dramatic decrease in the transported load downstream (Dai & Lu, ; Yang, Xu, Milliman, Yang, & Wu, ; Dai, Fagherazzi, Mei, & Gao, ; Zhou, Xia, Lu, Deng, & Lin, ). Since impoundment of the reservoir, erosion has occurred in downstream river channels, and the thalweg has become incised (Dai & Liu, ), most significantly in the dam‐proximal part of the Jingjiang reach (Xia et al, ; Xia, Deng, Zhou, Lu, & Xu, ). As riverbeds exhibit different compositions, different patterns of river channel adjustment exist (Petts, ).…”

Section: Introductionmentioning

confidence: 99%

Impact of the operation of a large‐scale reservoir on downstream river channel geomorphic adjustments: A case study of the Three Gorges

Yang

Zhang

Zhu

et al. 2018

River Research & Apps

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To evaluate the effects of reservoir construction on the geomorphology of downstream reaches, a case study is performed on the Three Gorges Reservoir (TGR) by comparing data collected before and after impoundment of the reservoir. This study focuses on a 1,183‐km‐long reach downstream from the TGR and investigates the temporal and spatial characteristics and patterns of geomorphic adjustment in the downstream reaches. The amount of erosion in flood plain channels and the annual average intensity of erosion in downstream reaches after 12 years of impoundment are larger than the predicted values before the impoundment of the TGR. The maximum intensity of erosion was found at 410 km from the dam, with an average thalweg incision of 1.5 m, and the main zone of erosion migrated approximately 80 km downstream. At both preimpoundment and postimpoundment, erosion occurred the along beaches and channels in the Yichang–Chenglingji reach. The pattern of erosional channels and depositional river floodplain changed to erosional channels and erosional river floodplain in the Chenglingji–Hankou reach after the trial impoundment stage. In the Hankou–Hukou reach, the erosional channels and depositional river floodplain pattern changed to erosional deep channels, erosional low beaches, and depositional high‐river floodplain during the early impoundment stage. After the trial impoundment stage, erosion continued in the deep channels, but minor deposition occurred on the river floodplain. Moreover, the discharge of clear water increased, and the duration from middle to low‐water levels increased, leading to more concentrated erosion in low‐water channels. The intensity of the erosion along the river floodplain decreased due to the shortened duration of high‐water levels and reduced human activity.

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“…The TGD is the world's biggest dam built on the largest river in China, the YR [14]. With impoundment of the TGD, channel reach downstream of the reservoir has adjusted to a changed flow and sediment situation, especially in the Jingjiang reach [29,44].…”

Section: Connection With Dongting Lakementioning

confidence: 99%

Quantifying the Effects of Near-Bed Concentration on the Sediment Flux after the Operation of the Three Gorges Dam, Yangtze River

2017

Water

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Abstract:The regime of sediment transport in the Jingjiang Reach has significantly changed from quasi-equilibrium to sub-saturation since the impoundment of the Three Gorges Dam (TGD), and vertical profiles of suspended sediment concentration (SSC) have changed accordingly. Vertical profiles of SSC data measured at three hydrological stations in the Jingjiang Reach (Zhicheng, Shaishi, and Jianli), before and after the impoundment of TGD, were collected and analyzed. Analytic results indicate a remarkably large concentration in the near-bed zone (within 10% of water depth from the river-bed) in a sub-saturated channel. The maximum measured concentration was up to 15 times the vertical average concentration, while the ratio in quasi-equilibrium channel was less than four times that. Concentrations normalized with reference concentration at the same height, and may decrease with increasing values of suspension index (settling velocity over shear velocity). In addition, concentration near the water surface may be larger than concentration in the near-bed region when the suspension index is smaller than 0.01. Sediment flux transported in the near-bed zone may be up to 35% of the total sediment flux in unsaturated flows. The relationship between deviations of estimating sediment flux when ignoring the near-bed concentration and discharge in flood season and non-flood season are different in unsaturated and quasi-equilibrium channels. Analysis indicates that, in the quasi-equilibrium channel, more attention should be paid to near-bed concentration during non-flood season, the same as measurements during flood season with larger discharge.

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Dynamic channel adjustments in the Jingjiang Reach of the Middle Yangtze River

Cited by 90 publications

References 25 publications

Distribution of erosion intensity in the Jingjiang reach influenced by the Three Gorges Dam

Distribution of erosion intensity in the Jingjiang reach influenced by the Three Gorges Dam

Impact of the operation of a large‐scale reservoir on downstream river channel geomorphic adjustments: A case study of the Three Gorges

Quantifying the Effects of Near-Bed Concentration on the Sediment Flux after the Operation of the Three Gorges Dam, Yangtze River

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