Unravelling the causes of tidal asymmetry in deltas

Zhang, Wei; Cao, Yu; Zhu, Yinian; Zheng, Jinhai; Ji, Xiaomei; Xu, Yong; Wu, Yao; Hoitink, A.J.F.

doi:10.1016/j.jhydrol.2018.07.023

Cited by 73 publications

(39 citation statements)

References 61 publications

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“…Tide-river interactions and resulting residual water level profiles play a crucial role in large-scale river deltas (e.g. the Mississippi River delta in the US, the Rhine-Meuse delta in the Netherlands, the Pearl River delta and the Yangtze H. Cai et al: Tide-river dynamics in the Yangtze River estuary River delta in China and the Ganges-Brahmaputra delta in Bangladesh, among others) because tide-river dynamics exert a tremendous impact on delta morphodynamics, salt intrusion and deltaic ecosystems (Hoitink and Jay, 2016;Hoitink et al, 2017;Zhou et al, 2017). However, it has only been in recent years that substantial effort has been devoted to the nonlinear interaction between tidal waves and riverine flow in estuaries (e.g.…”

Section: Introductionmentioning

confidence: 99%

Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

Cai

Savenije

Garel

et al. 2019

Hydrol. Earth Syst. Sci.

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Abstract. As a tide propagates into the estuary, river discharge affects tidal damping, primarily via a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we demonstrate a third effect of river discharge that may lead to the weakening of the channel convergence (i.e. landward reduction of channel width and/or depth). In this study, monthly averaged tidal water levels (2003–2014) at six gauging stations along the Yangtze River estuary are used to understand the seasonal behaviour of tidal damping and residual water level slope. Observations show that there is a critical value of river discharge, beyond which the tidal damping is reduced with increasing river discharge. This phenomenon is clearly observed in the upstream part of the Yangtze River estuary (between the Maanshan and Wuhu reaches), which suggests an important cumulative effect of residual water level on tide–river dynamics. To understand the underlying mechanism, an analytical model has been used to quantify the seasonal behaviour of tide–river dynamics and the corresponding residual water level slope under various external forcing conditions. It is shown that a critical position along the estuary is where there is maximum tidal damping (approximately corresponding to a maximum residual water level slope), upstream of which tidal damping is reduced in the landward direction. Moreover, contrary to the common assumption that larger river discharge leads to heavier damping, we demonstrate that beyond a critical value tidal damping is slightly reduced with increasing river discharge, owing to the cumulative effect of the residual water level on the effective friction and channel convergence. Our contribution describes the seasonal patterns of tide–river dynamics in detail, which will, hopefully, enhance our understanding of the nonlinear tide–river interplay and guide effective and sustainable water management in the Yangtze River estuary and other estuaries with substantial freshwater discharge.

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Section: Introductionmentioning

confidence: 99%

Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

Cai

Savenije

Garel

et al. 2019

Hydrol. Earth Syst. Sci.

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“…On a short timescale, gauged water level variations can result from three main factors: (a) astronomical tides; (b) storm surges (sea residuals); and (c) seiches (Mel, Viero, Carniello, Defina, & D’Alpaos, 2014). Numerous studies have shown that the storm surges are amplified in estuaries subject to considerable channel deepening (e.g., Talke, Orton, & Jay, 2014; Familkhalili & Talke, 2016; Zhang et al, 2018). It is not necessary to capture these short‐term events unless focusing on the hydrodynamics within single tidal cycles, which is beyond the scope of this study.…”

Section: Discussionmentioning

confidence: 99%

“…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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“…Previous studies on the long‐term evolution of tidal dynamics mainly focused on tidal properties in terms of the tidal range and tidal datum level (e.g., lower low water, higher high water, and MWL). The underlying causes of historic changes can then be diagnosed either by trend tests, change‐point detections (Zhang et al, , , ), or by harmonic analysis that allows to describe the tidal behaviour using tidal species or constituents (Kukulka & Jay, ; Jay, Leffler, & Degens, , , ; Zhang et al, ). However, gradients of the tidal range or tidal datum levels are of greater practical interest because they are directly related to the magnitude of tidal dynamics.…”

Section: Introductionmentioning

confidence: 99%

“…As the tide propagates into the estuary, the wave experiences distortion and damping caused by the combined effects of bottom friction and river discharge (e.g., Cai et al, 2014Cai et al, , 2016aGodin, 1999;Guo et al, 2015;Horrevoets, Savenije, Schuurman, & Graas, 2004). Moreover, due to the significant variation of the river discharge, the tidal wave becomes highly nonstationary; thus, traditionally defined harmonic constants vary as a function of the river discharge (Kukulka & Jay, 2003;Matte, Jay, & Zaron, 2013;Matte, Secretan, & Morin, 2014;Zhang et al, 2018). On the other hand, estuarine human interventions, such as channel dredging, dam construction, in-channel sand excavation, and land reclamation, may impact the long-term evolution of tidal dynamics by changing the estuarine morphology.…”

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confidence: 99%

Decadal variability of tidal dynamics in the Pearl River Delta: Spatial patterns, causes, and implications for estuarine water management

Cai

Huang

Niu

et al. 2018

Hydrological Processes

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In this study, we examine the decadal variability of tidal dynamics in terms of the tidal range in the Pearl River Delta (PRD) from the 1950s to 2016. The Mann–Kendall trend test and Empirical Orthogonal Function (EOF) method are employed to identify the long‐term trends and spatial patterns of the annual tidal range series observed at 26 stations over the whole PRD, respectively. The results show that most stations display an increasing tidal range trend, except for some stations near estuarine outlets, which corresponds to the 1st EOF mode characterized by a rapid increase of the tidal range since the 1990s. This means that the cumulative impacts of human interventions reached their peak in the 1990s, exceeding the threshold of tidal dynamics in the PRD. To quantify human‐induced alternations of the tidal range, the tidal regime shift was subsequently explored by comparing the tidal ranges of the pre‐ and post‐1992 periods reconstructed from the EOF decomposition. The mechanism causing the tidal regime shift in the PRD can be attributed to the substantially reduced residual water level slope (hence, the effective bottom friction) that greatly enhances the tidal dynamics. Our study describes the shift of spatial–temporal tidal dynamics patterns in detail, which is particularly useful to guide effective and sustainable water management in the PRD and other river deltas that are subjected to intensive human interventions.

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Unravelling the causes of tidal asymmetry in deltas

Cited by 73 publications

References 61 publications

Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

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

Decadal variability of tidal dynamics in the Pearl River Delta: Spatial patterns, causes, and implications for estuarine water management

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