Secular bathymetric variations of the North Channel in the Changjiang (Yangtze) Estuary, China, 1880–2013: Causes and effects

Mei, Xuefei; Dai, Zhicong; Wen, Wei; Li, Weihua; Wang, Jie; Sheng, Hao

doi:10.1016/j.geomorph.2017.11.014

Cited by 52 publications

(35 citation statements)

References 40 publications

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“…Thereafter, data from each survey were gridded by the Kriging scheme at 20 × 20 m resolution to produce digital elevation models (DEMs) (Dai et al, 2016). Previous studies have shown that the morphological adjustments observed at Datong are part of a phase of erosion that extends throughout the reach downstream of the TGD and which have been induced as a result of sediment trapping by the dam (Luan et al, 2016;Mei et al, 2018;Yang et al, 2007). The timing and reach-wide nature of these adjustments (supporting information Figure S6), which extend even to the estuarine delta front, means that the observed morphological adjustments at Datong can confidently be attributed to the impacts of the TGD, as opposed to reflecting local adjustments.…”

Section: Estimation Of Shifts In Flood Levels Due To Morphological Chmentioning

confidence: 99%

“…Previous studies have shown that, as a result of the TGD trapping sediment, significant erosion has occurred in the reaches downstream of the TGD since its closure in 2003 (Luan et al, 2016;Mei et al, 2018;Yang et al, 2007). The extent of the morphological adjustment is sufficiently great to potentially affect flow conveyance in the reach downstream of the dam, but the relationship between these morphological adjustments and flood risk has not yet been evaluated.…”

Section: Introductionmentioning

confidence: 99%

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Modulation of Extreme Flood Levels by Impoundment Significantly Offset by Floodplain Loss Downstream of the Three Gorges Dam

Mei

Dai

Darby

et al. 2018

Geophysical Research Letters

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River flooding—the world's most significant natural hazard—is likely to increase under anthropogenic climate change. Most large rivers have been regulated by damming, but the extent to which these impoundments can mitigate extreme flooding remains uncertain. Here the catastrophic 2016 flood on the Changjiang River is first analyzed to assess the effects of both the Changjiang's reservoir cascade and the Three Gorges Dam (TGD), the world's largest hydraulic engineering project on downstream flood discharge and water levels. We show that the Changjiang's reservoir cascade impounded over 30.0 × 103 m3/s of flow at the peak of the flood on 25 July 2016, preventing the occurrence of what would otherwise have been the second largest flood ever recorded in the reach downstream of the TGD. Half of this flood water storage was retained by the TGD alone, meaning that impoundment by the TGD reduced peak water levels at the Datong hydrometric station (on 25 July) by 1.47 m, compared to pre‐TGD conditions. However, downstream morphological changes, in particular, extensive erosion of the natural floodplain, offset this reduction in water level by 0.22 m, so that the full beneficial impact of floodwater retention by the TGD was not fully realized. Our results highlight how morphological adjustments downstream of large dams may inhibit their full potential to mitigate extreme flood risk.

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Section: Estimation Of Shifts In Flood Levels Due To Morphological Chmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modulation of Extreme Flood Levels by Impoundment Significantly Offset by Floodplain Loss Downstream of the Three Gorges Dam

Mei

Dai

Darby

et al. 2018

Geophysical Research Letters

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“…The retreat in the north and progradation around the cusp between 1999 and 2013 resulted from the DWP‐induced increase in ebb flow intensity and were supported by the suspended sediment transport mode (Figure ). The response of the NHS to the estuarine regime adjustment stems from channel–shoal interactions (Scully & Friedrichs, ) and indicates the long‐lasting impact of extreme events, despite their short duration, in determining the morpho‐sedimentary dynamics of estuaries (Mei et al, ; Törnqvist, Bick, Klaas, & de Jong, ).…”

Section: Discussionmentioning

confidence: 99%

“…Hughes et al () documented a rapid headward erosion of marsh creeks away from equilibrium in South Carolina under fast sea‐level rise. Mei et al () diagnosed development/disruption cycle in midchannel shoals in relation to extreme floods. For the NHS, a mode of planar geometry alteration regulated by estuarine regime adjustment has been replaced by a mode of landward siltation controlled by estuarine engineering since 1989 (Figure ).…”

Section: Discussionmentioning

confidence: 99%

Multi‐decadal morpho‐sedimentary dynamics of the largest Changjiang estuarine marginal shoal: Causes and implications

et al. 2019

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Understanding the long-term evolution of estuarine shoals given natural variations and human modifications is a key issue for wetland protection and shoal management. Here, the multi-decadal morpho-sedimentary dynamics of the Nanhui Shoal (NHS), the largest Changjiang estuarine marginal shoal, are studied using a suite of hydrological, sedimentological, and bathymetric data. The results show that the tidal flow regime and sedimentary mode around the NHS changed slightly after the 1980s. Moreover, the NHS experienced a siltation-induced volume increase of 4.1 × 10 8 m 3 , concentrated in the landward region, and seaward progradation, producing an increase in gross area of 33 km 2 , during 1958-2013. Even so, the actual tidal flat resource decreased by 29% due to the reclamation of 202 km 2 . Transition in the development of the NHS is detected: a planar geometry transformation from a triangular cusp to an arcuate cusp during 1958-1989; vertical siltation in the landward region under a stable arcuate-shaped geometry thereafter. Furthermore, a steeply sloping profile with grades of 2-11‰ formed in the northern section, which limits future reclamation to 80 km 2 there. Estuarine regime adjustment, inducing hydrodynamic alterations in the South Passage, dominated the geometric changes in the NHS during 1958-1989, whereas substantial siltation promotion projects led to the landward siltation after 1989. The decrease in sediment input downstream of the Three Gorges Dam has played a minor role in the shoal evolution. This work provides new insights into the long-term morpho-sedimentary responses of estuarine shoals to natural and artificial forcings and their implications for shoal exploitation.

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“…Temporal–spatial tidal forcing affects not only the transport of sediments, nutrients, and contaminants (Falcão, Santos, Drago, Serpa, & Monteiro, 2009; Bonaldo et al, 2014) in estuaries but also salt intrusion and storm surge propagation (Zhang, Savenije, Wu, Kong, & Zhu, 2011; Zhang, Savenije, Chen, & Mao, 2012; Li, Zhu, Wu, & Guo, 2014). In recent decades, intensive human activities (e.g., dredging for navigation, sand excavation, and land reclamation) have dramatically changed the morphology of many estuaries and, have caused the erosion of estuarine saltmarshes (Bendoni et al, 2016; Francalanci, Bendoni, Rinaldi, & Solari, 2013; Tommasini, Carniello, Ghinassi, Roner, & D'Alpaos, 2019) and altered the tidal regimes and hydrodynamics (Zhang et al, 2017; Mei et al, 2018; Wu et al, 2018; Zhang et al, 2018; Finotello Canestrelli, Carniello, Ghinassi, & D'Alpaos, 2019). For these reasons, the response of tidal forcing to human activities has attracted worldwide research attention.…”

Section: Introductionmentioning

confidence: 99%

Tidal regime shift in Lingdingyang Bay, the Pearl River Delta: An identification and assessment of driving factors

Wang

Ping

Zhou

et al. 2020

Hydrological Processes

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Both natural changes (e.g., tidal forcing from the ocean and global sea level rise) and human‐induced changes (e.g., dredging for navigation, sand excavation, and land reclamation) exert considerable influences on the long‐term evolution of tidal regimes in estuaries. Evaluating the impacts of these factors on tidal‐regime shifts is particularly important for the protection and management of estuarine environments. In this study, an analytical approach is developed to investigate the impacts of estuarine morphological alterations (mean water depth and width convergence length) on tidal hydrodynamics in Lingdingyang Bay, Southeast China. Based on the observed tidal levels from two tidal gauging stations along the channel, tidal wave celerity and tidal damping/amplification rate of different tidal constituents are computed using tidal amplitude and phase of tidal constituents extracted from a standard harmonic analysis. We show that the minimum mean water depth for the whole estuary occurred in 2006, whereas a shift in tidal wave celerity for the M2 tide component occurred in 2009. As such, the study period (1990–2016) could be separated into pre‐human (1990–2009) and post‐human (2010–2016) phases. Our results show that the damping/amplification rate and celerity of the M2 tide have increased by 31% (from 7 to 9.2 m−1) and 28% (from 7 to 9 m·s−1) respectively, as a consequence of the substantial impacts of human interventions. The proposed analytical method is subsequently applied to analyse the historical development of tidal hydrodynamics and regime shifts induced by human interventions, thus linking the evolution of estuarine morphology to the dominant tidal hydrodynamics along the channel. The observed tidal regime shift is primarily caused by channel deepening, which substantially enlarged the estuary and reduced effective bottom friction resulting in faster celerity and stronger wave amplification. Our proposed method for quantifying the impacts of human interventions on tidal regime shifts can inform evidence‐based guidelines for evaluating hydraulic responses to future engineering activities.

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Secular bathymetric variations of the North Channel in the Changjiang (Yangtze) Estuary, China, 1880–2013: Causes and effects

Cited by 52 publications

References 40 publications

Modulation of Extreme Flood Levels by Impoundment Significantly Offset by Floodplain Loss Downstream of the Three Gorges Dam

Modulation of Extreme Flood Levels by Impoundment Significantly Offset by Floodplain Loss Downstream of the Three Gorges Dam

Multi‐decadal morpho‐sedimentary dynamics of the largest Changjiang estuarine marginal shoal: Causes and implications

Tidal regime shift in Lingdingyang Bay, the Pearl River Delta: An identification and assessment of driving factors

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