Immediately downstream effects of Three Gorges Dam on channel sandbars morphodynamics between Yichang-Chenglingji Reach of the Changjiang River, China

Wang, Jie; Dai, Zhijun; Mei, Xuefei; Lou, Yaying; Wen, Wei; Ge, Zhenpeng

doi:10.1007/s11442-018-1495-8

Cited by 42 publications

(34 citation statements)

References 64 publications

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“…These results imply that the larger the size of MCB, the greater relative stability in area and shape variations, whereas the smaller size of the MCBs, the less stable in terms of area and shape variations. In previous studies, only one specific scale MCBs were focused (such as large-size MCBs), and the temporal dynamic patterns of other sizes of MCBs were not addressed [23,30].…”

Section: Scale Effects On the Temporal Dynamicsmentioning

confidence: 99%

“…As an essential geomorphic unit and component in a fluvial system, 3 of 21 channel morphology dynamics [17,35,36]. However, only a few studies analyzed the MCB dynamics at a large spatiotemporal scale with the help of RS technology [12,23,30,37]. For example, in the reach immediately downstream of TGD, Wang et al [23] found that the total area of MCBs extracted from Landsat images reduced dramatically by 19.23% from 2003 to 2016, accompanied with an increase of water surface width.…”

Section: Introductionmentioning

confidence: 99%

“…However, only a few studies analyzed the MCB dynamics at a large spatiotemporal scale with the help of RS technology [12,23,30,37]. For example, in the reach immediately downstream of TGD, Wang et al [23] found that the total area of MCBs extracted from Landsat images reduced dramatically by 19.23% from 2003 to 2016, accompanied with an increase of water surface width. Lou et al [12] focused on the lower reach and found the MCBs' total area exhibited a decreasing trend in the pre-TGD period, but an increasing trend in the post-TGD period.…”

Section: Introductionmentioning

confidence: 99%

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Remotely Sensed Mid-Channel Bar Dynamics in Downstream of the Three Gorges Dam, China

et al. 2020

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The downstream reach of the Three Gorges Dam (TGD) along the Yangtze River (1560 km) hosts numerous mid-channel bars (MCBs). MCBs dynamics are crucial to the river’s hydrological processes and local ecological function. However, a systematic understanding of such dynamics and their linkage to TGD remains largely unknown. Using Landsat-image-extracted MCBs and several spatial-temporal analysis methods, this study presents a comprehensive understanding of MCB dynamics in terms of number, area, and shape, over downstream of TGD during the period 1985–2018. On average, a total of 140 MCBs were detected and grouped into four types representing small (<2 km2), middle (2 km2 – 7 km2), large (7 km2 – 33 km2) and extra-large size (>33 km2) MCBs, respectively. MCBs number decreased after TGD closure but most of these happened in the lower reach. The area of total MCBs experienced an increasing trend (2.77 km2/yr, p-value < 0.01) over the last three decades. The extra-large MCBs gained the largest area increasing rate than the other sizes of MCBs. Small MCBs tended to become relatively round, whereas the others became elongate in shape after TGD operation. Impacts of TGD operation generally diminished in the longitudinal direction from TGD to Hankou and from TGD to Jiujiang for shape and area dynamics, respectively. The quantified longitudinal and temporal dynamics of MCBs across the entire Yangtze River downstream of TGD provides a crucial monitoring basis for continuous investigation of the changing mechanisms affecting the morphology of the Yangtze River system.

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Section: Scale Effects On the Temporal Dynamicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Remotely Sensed Mid-Channel Bar Dynamics in Downstream of the Three Gorges Dam, China

et al. 2020

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“…Large amounts of riverine water and SSD are discharged in the funnel‐shaped estuary during the monsoon season, developing bifurcations with migrating channels and tidal bars. Some studies indicate that the fluvial SSD input has decreased by 70% after the construction of the Three Gorges Dam (TGD) in 2003, triggering local erosion in the offshore area of the Changjiang Delta (Dai et al, 2016; Wang et al, 2018). Recent studies suggest that sediment supplied from the ocean can alleviate the current estuarine erosion, providing material to tidal flats and shoals (Dai et al, 2013, 2018; Yang et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Tropical Cyclones Significantly Alleviate Mega‐Deltaic Erosion Induced by High Riverine Flow

Wang

Dai

Mei

et al. 2020

Geophysical Research Letters

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The drastic decline in sediment discharge experienced by large rivers in recent years might trigger erosion thus increasing the vulnerability of their extensive deltas. However, scarce information is available on the erosion patterns in mega-deltas and associated physical drivers. Here a series of bathymetries in the South Passage, Changjiang Delta, were analyzed to identify morphodynamic variations during high riverine flow and tropical cyclones (TCs). Results indicate that high river flow during flood season triggers large-scale net erosion along the inner estuary, generating elongated erosion-deposition patches. Erosion magnitude gradually weakens moving seaward with few localized bottom variations in the offshore area. TCs transport sediment landward and are accompanied by an overall weak erosion, with a less organized spatial pattern of erosion-deposition. TCs can therefore significantly alleviate erosion, reducing the sediment loss induced by riverine flows by over 50%. These results highlight the role of TCs on the sediment dynamics of mega-deltas. Plain Language Summary In recent years, climate change and reduced riverine sediment inputs have significantly affected the morphology of large deltas. However, it is unknown whether typhoons cause erosion or deposition in the submerged part of a delta, due to challenge in capturing infrequent events. Here we study the impact of high river flow and typhoons on the South Passage, Changjiang Delta. Results show that high riverine flows can cause large-scale erosion. Typhoons reduce fluvial erosion by transporting offshore sediments in the delta. The relative accretion caused by a typhoon is more than half the net erosion induced by riverine floods. This research sheds light on the sediment budget of large deltas and inform policy measures that can mitigate the effect of increasing anthropogenic pressure, extreme events, and sea level rise on delta morphology.

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“…Capolongo et al coupled multitemporal remote sensing with geomorphology and hydrological modelling for post-flood recovery in the Strymonas dammed river basin [12]. There also have been many studies on the morphodynamic processes of sandbars in the Yangtze River, the channel downstream of the Three Gorges Dam (TGD) in China [13][14][15][16][17][18]. The decreased sediment load in the middle of the Yangtze River was found to be responsible for dramatic changes of channel bar morphodynamics, which could last for a long time, depending on the operation of the Three Gorges Dam in 2003 [19].…”

Section: Introductionmentioning

confidence: 99%

Long-Term (1986–2018) Evolution of Channel Bars in Response to Combined Effects of Cascade Reservoirs in the Middle Reaches of the Hanjiang River

Zhang

Cai

Yang

et al. 2019

Water

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Channel bars are essential landforms and their evolution is crucial to aquatic and riparian biodiversity, river’s water-sediment process, and economic development. With the development of water conservation facilities and hydropower projects, numerous changes have been taken place in hydrological regimes and morphology. There have been many changes on channel bars in the middle reaches of Hanjiang River due to the combined effects of cascade reservoirs. However, little was known about such dynamics and their linkages to cascade dams across the entire downstream area. Using Landsat remote sensing images from 1986–2018 and the threshold binary Otsu extraction method, this study completed comprehensive monitoring of nine mid-channel bars (DX1–DX7, XZ1, and XZ2), and three shoal group (XZ3–XZ5) dynamics. Results showed that the mid-channel bars’ area in the reach from Danjiangkou to Xiangyang (DX) decreased over the past 33 years, with the exception of DX4, while the total area decreased by 23.19%, this channel bars’ area change was mainly influenced by backwater from the Cuijiaying Reservoir with high water level after 2010 (r = −0.93, p < 0.01). The total channel bar area from Xiangyang to Huangzhuang (XZ) decreased by 16.63% from 1986 to 2018. The total channel bar area in XZ had a strong negative correlation with runoff at Huangzhuang hydrologic station (r = −0.79, p < 0.05), which was partly attributed to upstream precipitation according to the high correlation between runoff and precipitation (R2 = 0.65). In general, the DX section was under equilibrium between scouring and deposition compared to downstream Xiangyang, the bars in DX section were mainly affected by water level, and bars in XZ section during 1986–2018 were complicated because it was upstream eroded and downstream deposited. In addition, vegetation cover, revetments, flood events, sand mining, land use, and over-exploitation may cause channel bar area dynamics. Hence, more continuous investigations are suggested to focus on effects of cascade reservoir operation on hydrological regime, as well as the changing morphology of channel bars in the middle reaches of the Hanjiang River.

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Immediately downstream effects of Three Gorges Dam on channel sandbars morphodynamics between Yichang-Chenglingji Reach of the Changjiang River, China

Cited by 42 publications

References 64 publications

Remotely Sensed Mid-Channel Bar Dynamics in Downstream of the Three Gorges Dam, China

Remotely Sensed Mid-Channel Bar Dynamics in Downstream of the Three Gorges Dam, China

Tropical Cyclones Significantly Alleviate Mega‐Deltaic Erosion Induced by High Riverine Flow

Long-Term (1986–2018) Evolution of Channel Bars in Response to Combined Effects of Cascade Reservoirs in the Middle Reaches of the Hanjiang River

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