Influence of Seasonal River Discharge on Tidal Propagation in the Ganges‐Brahmaputra‐Meghna Delta, Bangladesh

Elahi, Md Wasif E; Jalón‐Rojas, Isabel; Wang, Xiao Hua; Ritchie, Elizabeth A.

doi:10.1029/2020jc016417

Cited by 21 publications

(10 citation statements)

References 29 publications

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“…The model results also explain why a higher river discharge hastens the high water and delays the low water in the seaward parts of the Saint Lawrence Estuary (Godin 1985(Godin , 1999. In the Ganges-Brahmaputra-Meghna Delta, model results suggested enhanced quarter-diurnal tides in the seaward regions of the delta and a transition from increase to decrease in the landward regions with increasing river discharge (Elahi et al 2020). These field data and model results confirm that the findings regarding the spatial dependence of overtide on river discharge are ubiquitous for estuaries with large river discharges.…”

Section: Comparison With Actual Estuariesmentioning

confidence: 70%

“…Numerical simulations of tidal dynamics provide an alternative approach that can fully capture the nonlinear dynamics without simplification. They include the detailed changes in estuarine geometry and are widely employed to examine tides in estuaries with more complexity in morphology and dynamics (Lu et al 2015;Elahi et al 2020). To cope with the strong nonlinearity in tidal dynamics in long estuaries with highly varying river discharges, in this work, we aim to combine the advantages of these methods by using a numerical model of a schematized estuary.…”

Section: Rationale and Objectivementioning

confidence: 99%

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River Flow Induced Nonlinear Modulation of M4 Overtide in Large Estuaries

Guo

Zhu

Cai

et al. 2023

Estuaries and Coasts

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River discharge is known to enhance tidal damping and tidal wave deformation in estuaries. While the damping effect on astronomical tides has been well documented, river impact on tidal wave deformation and associated overtide generation (shallow water harmonics of one or more astronomical constituents, such as M 4 ) remains insufficiently understood. Overtides affect tidal asymmetry, extreme water levels, and subsequent sediment transport and flooding management, thus meriting in-depth examination. Being inspired by unusual overtide changes in the landward and seaward parts of the Changjiang Estuary under low and high river discharges, in this work, we use a schematized tidal estuary model to systematically explore overtide variations under different river discharges. Model results show enhanced overtide generation in the case with river discharge compared with that without river impact. The M 4 amplitude decreases in the landward parts of the estuary, but increases in the seaward parts under increasing river discharges. The potential energy of M 4 integrated throughout the estuary shows nonlinear variations and reaches a transitional maximum when the river discharge to tidal mean discharge (R2T) ratio at the mouth is close to unity. Similar nonlinear behaviors are observed for compound tides like MS 4 when more astronomical constituents are prescribed and triad tidal interactions are enabled. The space-dependent overtide variability is more profound in large estuaries with high river discharges like the Amazon and Changjiang estuaries. It is ascribed to the inherently nonlinear river-tide interactions, specifically the twofold effects of river discharge in enhancing bottom stress, which simultaneously enhances dissipation of astronomical constituents and reinforces the energy transfer to overtides. These findings highlight the profound nonlinear impact of river discharge on overtides, and inform the study of tidal asymmetry and compound flood risk in large estuaries and deltas. KeywordsEstuary • Overtide • Bottom stress • River discharge Communicated by Arnoldo Valle-Levinson Key points 1. River discharge enhances tidal wave deformation and induces larger overtides in estuaries. 2. Overtide generation is maximal when the river discharge to tidal mean discharge ratio is close to unity. 3. The quadratic bottom stress plays a dominant role in controlling the space-dependent overtide variations.

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Section: Comparison With Actual Estuariesmentioning

confidence: 70%

Section: Rationale and Objectivementioning

confidence: 99%

River Flow Induced Nonlinear Modulation of M4 Overtide in Large Estuaries

Guo

Zhu

Cai

et al. 2023

Estuaries and Coasts

View full text Add to dashboard Cite

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“…The Meghna River estuary is one of the largest estuarine ecosystems in terms of sediment and water discharge, and characterized by high levels of hydro‐dynamics activity (Syed et al., 2018). The estuary has the highest sediment discharge and ranked third for water discharge in the world (Elahi et al., 2020). The Meghna River estuary carries a combined flow of water typically 120,000 m3/s and most of the water flow comes from the confluence of Ganga, Jamuna and Padma rivers at northwest region (Syed et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

Phytoplankton ecology in different coastal habitats along the northern Bay of Bengal

et al. 2021

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Knowledge on phytoplankton dynamics is important to understand the trophodynamics of aquatic ecosystems. But, the topic remains poorly studied in the context of tropical coastal habitats. The present study describes the community structure and drivers of phytoplankton in different coastal habitats along the northern Bay of Bengal. Data were collected on phytoplankton, zooplankton and a range of environmental variables from the estuarine, mangroves and coral habitats of Bangladesh during dry season from October 2020 to March 2021. Our study found that eco‐hydrological characteristics of the estuarine, mangroves and coral habitats differ from each other, although phytoplankton assemblages in these habitats commonly dominated by diatoms. In the estuary, the main diatom taxa included Coscinodiscus, whereas Ceratium and Chaetoceros were dominant in the coral habitat, and Coscinodiscus and Chaetoceros in the mangroves habitat. The concentration of micronutrients (silicate, nitrate and phosphate) was the most important driver of phytoplankton among all habitats. Zooplankton had a vital role in regulating the phytoplankton community composition in the coral habitat. These results suggest that the phytoplankton dynamics across tropical coastal habitats is largely driven by nutrients, which, when compared, have less influence on the growth of phytoplankton in temperate region.

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“…This model calculates the flow of water over a multi-dimensional (2D (depth averaged) and 3D) finite, rectilinear or curvilinear, boundary-fitted difference grid. Areas of application include coastal, river and estuarine settings (Delft Hydraulics 2003;Lesser et al 2004;Temmerman et al 2012;Elahi et al 2020).…”

Section: Model Setup and Data Processingmentioning

confidence: 99%

Can Managed Realignment Buffer Extreme Surges? The Relationship Between Marsh Width, Vegetation Cover and Surge Attenuation

Kiesel

MacPherson

Schuerch

et al. 2021

Estuaries and Coasts

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Managed realignment (MR) involves the landward relocation of sea defences to foster the (re)creation of coastal wetlands and achieve nature-based coastal protection. The wider application of MR is impeded by knowledge gaps related to lacking data on its effectiveness under extreme surges and the role of changes in vegetation cover, for example due to sea-level rise. We employ a calibrated and validated hydrodynamic model to explore relationships between surge attenuation, MR width(/area) and vegetation cover for the MR site of Freiston Shore, UK. We model a range of extreme water levels for four scenarios of variable MR width. We further assess the effects of reduced vegetation cover for the actual MR site and for the scenario of the site with the largest width. We show that surges are amplified for all but the largest two site scenarios, suggesting that increasing MR width results in higher attenuation rates. Substantial surge attenuation (up to 18 cm km−1) is only achieved for the largest site. The greatest contribution to the attenuation in the largest site scenario may come from water being reflected from the breached dike. While vegetation cover has no statistically significant effect on surge attenuations in the original MR site, higher coverage leads to higher attenuation rates in the largest site scenario. We conclude that at the open coast, only large MR sites (> 1148 m width) can attenuate surges with return periods > 10 years, while increased vegetation cover and larger MR widths enable the attenuation of even higher surges.

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Influence of Seasonal River Discharge on Tidal Propagation in the Ganges‐Brahmaputra‐Meghna Delta, Bangladesh

Cited by 21 publications

References 29 publications

River Flow Induced Nonlinear Modulation of M4 Overtide in Large Estuaries

River Flow Induced Nonlinear Modulation of M4 Overtide in Large Estuaries

Phytoplankton ecology in different coastal habitats along the northern Bay of Bengal

Can Managed Realignment Buffer Extreme Surges? The Relationship Between Marsh Width, Vegetation Cover and Surge Attenuation

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