Morphology and mechanism of the very large dunes in the tidal reach of the Yangtze River, China

Zheng, Shuwei; Cheng, Heqin; Wu, Shuaihu; Shengyu, Shi; Xu, Weihua; Zhou, Qin; Jiang, Yuehua

doi:10.1016/j.csr.2016.10.006

Cited by 9 publications

(7 citation statements)

References 25 publications

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“…There is no dune planform shape data in this research and little previous research on this in the Changjiang Estuary [Shuwei et al, 2017]. However, for the majority of the survey lines (except survey B and F), the lateral gap between each survey line is less than 5 meters, and the computed dune lengths are relatively constant in line with previous research (e.g.…”

Section: Dune Characteristicssupporting

confidence: 85%

“…Moreover, Lefebvre et al [2011] and Lefebvre et al [2013] conjectured that the flow separation and recirculation presumably solely occurred over the lee-side of dunes whose downstream slope is above 10° during the ebb, leading to the creation of form drag, while the secondary bedforms dominated the ܼ during the flood. However, dunes in this study have a low-angle, and there were no secondary bedforms developed over primary dunes [Shuwei et al, 2017]. The downstream slope of the LAD is too gentle to generate significant expansion loss during ebb or flood, thereby, hydraulic roughness associated with the bedforms will be weakened [Hoitink et al, 2009;Paarlberg et al, 2010;Lefebvre et al, 2011].…”

Section: How Does Roughness Length Z 0 Respond To Tides?mentioning

confidence: 80%

“…However, these studies have mainly focussed on classifying the geometric characteristics of the dunes [Li et al, 2003;Cheng et al, 2004;Shuwei et al, 2017] or exploring how to predict bedload transport rate based on dune migration [Yang et al, 1999]. But, the formative mechanisms of LADs under this specific condition has been rarely studied.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

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Low-angle dunes in the Changjiang (Yangtze) Estuary: Flow and sediment dynamics under tidal influence

Wei

Yang

et al. 2018

Estuarine, Coastal and Shelf Science

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Low-angle dunes in the Changjiang (Yangtze) Estuary: flow and sediment dynamics under tidal influence Highlights: Low-angle dunes composed of fine sediment were studied; Flow and sediment dynamics over dunes were measured in the Changjiang Estuary; Sediment composition attributes to sediment transport mechanism; Evolution process of low-angle dunes within a tidal cycle was elaborated; Clockwise hysteresis loops were found between flows and bedform features.

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Section: Dune Characteristicssupporting

confidence: 85%

Section: How Does Roughness Length Z 0 Respond To Tides?mentioning

confidence: 80%

Section: Accepted Manuscriptmentioning

confidence: 99%

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Low-angle dunes in the Changjiang (Yangtze) Estuary: Flow and sediment dynamics under tidal influence

Wei

Yang

et al. 2018

Estuarine, Coastal and Shelf Science

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“…The 681-km multi-beam measurements along the main navigation channel of the Lowermost Yangtze River were used to verify the current riverbed topography. Approximately 63.3% of the surveyed reach developed dunes, 21.8% showed eroded surface, and 14.9% was a flat riverbed 31 . Dunes distributed along the entire studied reach and the distribution density of very large dunes (wavelength greater than 100 m) showed a decreasing trend from Datong to the river mouth.…”

Section: Resultsmentioning

confidence: 99%

“…3A ). A recent study on foundation scours of the large bridges in the studied river reach pointed out that the riverbed erosion phenomenon after the TGD closure has been stronger 31 . Although we are unable to do any comparison on grain size before and after the TGD construction, a study by Luo et al .…”

Section: Discussionmentioning

confidence: 97%

Riverbed erosion of the final 565 kilometers of the Yangtze River (Changjiang) following construction of the Three Gorges Dam

Zheng

Cheng

et al. 2018

Sci Rep

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The world’s largest hydropower dam, the Three Gorges Dam (TGD), spans the upper Yangtze River in China, creating a 660-km long and 1.1-km wide reservoir upstream. Several recent studies reported a considerable decline in sediment load of the Lowermost Yangtze River (LmYR) and a rapid erosion in the subaqueous delta of the river mouth after the closure of the TGD in 2003. However, it is unknown if the TGD construction has also affected river channel and bed formation of the LmYR. In this study, we compared bathymetric data of the last 565 kilometers of the Yangtze River’s channel between 1998 and 2013. We found severe channel erosion following the TGD closure, with local riverbed erosion up to 10 m deep. The total volume of net erosion from the 565-km channel amounted to 1.85 billion m3, an equivalent of 2.59 billion metric tons of sediment, assuming a bulk density of 1.4 t/m3 for the riverbed material. The largest erosion occurred in a 100-km reach close to the Yangtze River mouth, contributing up to 73% of the total net eroded channel volume.

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Quantitative relationship between channels and bars in a tidal reach of the lower Yangtze River: Implications for river management

et al. 2021

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Deep-water navigation channels in the tidal reaches of the lower Yangtze River are affected by water and sediment fluxes that produce complex shoals and unstable channel conditions. The Fujiangsha reach is particularly difficult to manage, as it has many braided channels within the tidal fluctuation zone. In this study, hydrologic and topographic data from the Fujiangsha reach from 2012 to 2017 were used to examine the variations in deposition and erosion, flow diversion, shoals, and channel conditions. Since the Three Gorges Dam became operational and water storage was initiated, the Fujiangsha reach has shown an overall tendency toward erosion. Channels deeper than 10 m accounted for 83.7% of the total erosion of the Fujiangsha reach during 2012-2017. Moreover, the dominant channel-forming sediments have gradually changed from suspended sediments to a mixed load of suspended and bed-load sediments. Deposition volumes of these sediments has varied significantly among different channels, but has mainly occurred in the Fubei channel. Furthermore, periodic variations in the Jingjiang point bar have followed a deposition-erosion-deposition pattern, and the downstream Shuangjian shoal mid-channel bar has been scoured and shortened. Approximately 44.0% of the bed load from the upstream Fujiangsha reach is deposited within the 12.5-m deep Fubei channel. The increased erosion and river flow from the Jingjiang point bar and the Shuangjian shoal during the flood season constituted 59.3% and 40.7%, respectively, of the total amount of siltation in the Fubei channel. Keywords: tidal current; fluctuating reach; point and central bar; channel conditions; quantitative relationship; lower reaches of the Yangtze River; Fujiangsha reach

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Morphology and mechanism of the very large dunes in the tidal reach of the Yangtze River, China

Cited by 9 publications

References 25 publications

Low-angle dunes in the Changjiang (Yangtze) Estuary: Flow and sediment dynamics under tidal influence

Low-angle dunes in the Changjiang (Yangtze) Estuary: Flow and sediment dynamics under tidal influence

Riverbed erosion of the final 565 kilometers of the Yangtze River (Changjiang) following construction of the Three Gorges Dam

Quantitative relationship between channels and bars in a tidal reach of the lower Yangtze River: Implications for river management

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