Aggravation of north channels' shrinkage and south channels' development in the Yangtze Estuary under dam-induced runoff discharge flattening

Zhu, Boyuan; Li, Yitian; Yao, Yulong; Yang, Yixin

doi:10.1016/j.ecss.2016.10.048

Cited by 12 publications

(30 citation statements)

References 73 publications

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“…Datong holds long-term data on river flux and is located about 500km upstream of the estuary, with no major tributary or water abstraction works between the station and the upper entrance of the estuary at Xuliujing (Figure 1a,b). More than 50000 dams have been constructed in the watershed, causing the annual sediment load to decrease sharply and the seasonal distribution of runoff discharge to be flattened significantly, even though the annual runoff discharge has remained almost unchanged (Yang et al, 2011;Luan et al, 2016;Zhang et al, 2016a;Zhu et al, 2017). The annual average runoff discharge was about 8960 m 3 yr -1 from 1950 to 2017, whereas the annual average river sediment load was 4.25 × 10 8 tyr -1 during 1951-2002 [i. e. pre-Three Gorges Dam (pre-TGD) period, Figure 1a] and 1.37 × 10 8 tyr -1 during 2003-2017 (i.e.…”

Section: Study Areamentioning

confidence: 99%

“…Over past decades, more than 50000 dams have been constructed and a large number of local engineering projects undertaken in the river basin and its estuary. Surveys have comprehensively examined decadal to seasonal erosion-deposition processes affecting geomorphic units within estuarine and offshore areas of the Yangtze subject to significant variations in water dynamics and sediment supply caused by intense human activities (Liu et al, 2009;Yang et al, 2011;Dai et al, 2013Dai et al, , 2014Dai et al, , 2016Du et al, 2016;Luan et al, 2016;Yang et al, 2016;Zhu et al, 2017;Mei et al, 2018;Zhu et al, 2019;Zhu et al, 2020). It has been established that certain of these morphological changes have led to practical problems, including migration of navigation features (Liu et al, 2009;Dai et al, 2013), increased risk of embankment failure related to water abstraction projects (Ou et al, 2013), and recession of saltmarsh-wetland systems (Wei et al, 2015;Gu et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Improved understanding is also needed of the decadal link between longitudinal erosion-deposition patterns within the inland branching channels and movement of the offshore depo-center. Such understanding requires knowledge of spatial differences in hydrodynamics among the branching channels (Li et al, 2010;Zhu et al, 2017) and the concomitant impact on the seaward hydrodynamic field beyond the estuary mouth (Yan et al, 2007;Shen and Li, 2011;Zhang et al, 2016b).…”

Section: Introductionmentioning

confidence: 99%

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Decadal link between longitudinal morphological changes in branching channels of Yangtze estuary and movement of the offshore depo‐center

Zhu

Yao

Borthwick

et al. 2020

Earth Surf Processes Landf

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In estuaries, the morphology of inland and offshore areas usually evolves synergistically. This study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo‐center (where sediment deposition rate is maximum) of the Yangtze River estuary, under intense human interference. Integrated data analysis is provided on morphology, runoff discharge, and ebb partition ratio from 1950 to 2017. Channel‐volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects. Ebb partition ratio and duration of discharge ≥ 60 000 m3 s‐1 act as proxies for the water excavating force in branching channels and runoff intensity. It is found that deposition occurs in the lower/upper sub‐reaches (or further downstream/upstream channels) of the inland north/south branching channels, and the offshore depo‐center moves southward or southeastward, as runoff intensity grows; the reverse occurs as runoff intensity declines. This is because the horizontal circumfluence in the Yangtze estuary rotates clockwise as ebb partition ratios of the north/south branching channels increase/decrease for increasing runoff, and conversely rotates anticlockwise for decreasing runoff. Land reclamation activities, the Deepwater Channel Project, and the Qingcaosha Reservoir have impacted greatly on longitudinal changes of morphology in the North Branch and the South Passage and on ebb partition ratio variations in the North/South Channel and the North/South Passage. Dam‐induced runoff flattening has enhanced deposition in the upper/lower sub‐reaches of the north/south branching channels and caused northward movement of the offshore depo‐center, except in areas affected by estuarine engineering projects. Dam‐induced longitudinal evolution of branching channel morphology and offshore depo‐center movement will likely persist in the future, given the ongoing construction of large cascade dams in the upper Yangtze and the completion of major projects in the Yangtze estuary. © 2020 John Wiley & Sons, Ltd.

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Section: Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Decadal link between longitudinal morphological changes in branching channels of Yangtze estuary and movement of the offshore depo‐center

Zhu

Yao

Borthwick

et al. 2020

Earth Surf Processes Landf

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“…On-going land reclamation activities for house buildings at both Rukpokwu and Rumuodara wetlands which houses the Woji River source channels, construction of undersized culverts and bridges at various points of the river long profile have affected the hydrologic recharge processes of the stream. These obstructions produce damming effect since the river free flow is interrupted intermittently, with a resulting lowered hydraulic radius, unit stream power and gradual covering of the downstream channel as the river no longer have need to maintain its channel excess capacity (Zhu et al 2017). Further consequence on the channel morphology is seen in the developing sinuosity of the river channel, the midstream siltation and formation of sandbags within the channel (Fig.…”

Section: Channel Morphometric Analysismentioning

confidence: 99%

“…The morphology of a river describes the geomorphic parameters of its channel/gully and by its implication explains how the river profile has changed in shape and direction over time. A given river channel dynamics can result out of a number of processes amidst the pressing environmental conditions: such as the geologic composition of the region, the river bed and banks rock structures, vegetation availability, volume and rate of Horton's Overland Flows, the available upland loose sediments, in-channel sediment sizes and composition, net sediment transportation within the channel and the consequent depositions on the river floodplain, bed and bank, and the general basin net denudation events (Zhu et al 2017). Apart from these natural factors as mentioned, most urban situated rivers, such as the Woji River, are predominantly haunted by anthropogenic causes (Oyegun 1997, Booth 1991.…”

Section: Introductionmentioning

confidence: 99%

Morphological analysis of the Woji River in Port Harcourt, Nigeria; using temporal data and mathematical algorithm

Anya¹,

Ezekwe²,

Oyegun³

2018

Landform Analysis

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The research analysed morphological variations of the Woji River between 1986 and 2016 using mathematical extrapolations and temporal data. A 50% reduction in the River mean channel width, fullbank discharge and the stream power was found. Channel siltation occurred due to high sediment fluxes from rapid urban processes versus reduced stream power of the river. Water hyacinth invasion, domestic waste dumps and narrow culvers constricted the river channels. Finally, an impaired river status was found and extinction projected by 2043. Recommended were correction and monitoring exercises to check activities along the river channel and to restore the head stream wetlands.

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Alternate erosion and deposition in the Yangtze Estuary and the future change

Zhu

Yao

et al. 2020

J. Geogr. Sci.

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The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of topographic data from 1950 to 2015, this paper studied the erosion-deposition pattern of the entire Yangtze Estuary. An alternation between erosion and deposition was found during the past 65 years, which was in correspondence to the alternation between flood and dry periods identified by multi-year average duration days of high-level water flow (defined as discharge ≥ 60,000 m 3 /s, namely, D ≥60,000) from the Yangtze River Basin. A quantitative relationship was further developed between the erosional/depositional rate of the Yangtze Estuary and the interpreting variables of yearly water discharge, D ≥60,000 and yearly river sediment load, with contributing rates of 1%, 59% and 40%, respectively. Mechanism behind the alternate erosion and deposition pattern was analyzed by examining residual water surface slope and the corresponding capacity of sediment transport in flood and dry periods. In flood periods, a larger discharge results in steeper slope of residual water level which permits a greater capacity of sediment transport. Therefore, more bed materials can be washed to the sea, leading to erosion of the estuary. In contrast, flatter slope of residual water level occurs in dry periods, and deposition dominates the estuarine area due to the decreased capacity of sediment transport and the increased backwater effect of flood-tide. Coastal dynamics and estuarine engineering projects alter the local morphological changes, but slightly affect the total erosional/depositional rate of the whole estuarine region. Heavy sedimentation within the Yangtze Estuary after the impoundment of the Three Gorges Dam can be attributed to the

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Aggravation of north channels' shrinkage and south channels' development in the Yangtze Estuary under dam-induced runoff discharge flattening

Cited by 12 publications

References 73 publications

Decadal link between longitudinal morphological changes in branching channels of Yangtze estuary and movement of the offshore depo‐center

Decadal link between longitudinal morphological changes in branching channels of Yangtze estuary and movement of the offshore depo‐center

Morphological analysis of the Woji River in Port Harcourt, Nigeria; using temporal data and mathematical algorithm

Alternate erosion and deposition in the Yangtze Estuary and the future change

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