Constraints of salinity- and sediment-induced stratification on the turbidity maximum in a tidal estuary

Lü, Ting; Wu, Hao; Zhang, Fan; Li, Jiasheng; Zhou, Linfeng; Jia, Jianjun; Li, Zhanhai; Wang, Ya Ping

doi:10.1007/s00367-020-00670-8

Cited by 12 publications

(4 citation statements)

References 52 publications

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“…Vertical salinity stratification induces flocculation settling, thereby contributing to sediment accumulation owing to the low current velocity (Wan & Zhao, 2017; Wu et al., 2012). The stable density stratification interface is near the location of the ETM in the Yangtze River Estuary (Lu et al., 2020). The suspended sediment transport is strongly affected by the salinity distribution and salinity‐gradient‐induced stratification in the Deep Navigational Channel (Song et al., 2013).…”

Section: Discussionmentioning

confidence: 99%

Formation of Turbidity Maximum in the Modaomen Estuary of the Pearl River, China: The Roles of Mouth Bar

Li¹,

Yang²,

Mo³

et al. 2022

JGR Oceans

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An estuarine turbidity maximum (ETM) functions as a filter and plays a key role in transporting suspended sediment. The features of ETM and their formation mechanisms vary with different types of estuaries. Their responses to morphological factors require further study. In this study, the Modaomen Estuary of the Pearl River was selected to examine the formation mechanisms of the ETM and roles of the mouth bar. Hydrodynamics, suspended sediment concentration, and sediment size distribution were measured via cruise shipboard in the mouth bar zone during the dry season of 2020, which indicated that the ETM occurred in the central and western bars. Furthermore, numerical modeling of an idealized estuary based on Delft3D was performed to explore the effects of the existence of a mouth bar on the dynamic structures causing the ETM, including saltwater intrusion, residual longitudinal circulation, and bed sediment resuspension. The results indicated that the existence of a mouth bar contributed to the occurrence of double residual circulations and enhanced bed shear stress on the mouth bar, which favor the ETM formation. In general, two different dynamic regimes were responsible for the ETM formation, that is, sediment trapping by saltwater intrusion and sediment resuspension induced by tidal currents. The mouth bar played a key role in these two mechanisms, including altering the estuarine circulation and bed shear stress. The results contribute to a better elucidation of the ETM formation in estuaries and provide scientific guidelines for estuarine management and engineering.

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Section: Discussionmentioning

confidence: 99%

Formation of Turbidity Maximum in the Modaomen Estuary of the Pearl River, China: The Roles of Mouth Bar

Li¹,

Yang²,

Mo³

et al. 2022

JGR Oceans

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“…Therefore, the weak hydrodynamic favored the settling of suspended sediment. Moreover, the in-situ floc particle size in the South Passage of Yangtze estuary can reach 80 mm during slack water, and the settling velocity is approximately 1 mm/s (Lu et al, 2020), which also facilitates the formation of fluid mud in a short period of time. Bed shear stress (t cw ) was mainly contributed by tidal-induced shear stress (t c ) rather than wave-induced shear stress (t w ).…”

Section: Formation and Breakdown Of Fluid Mudmentioning

confidence: 99%

Fluid mud induced by periodic tidal advection and fine-grained sediment settling in the Yangtze estuary

Wu,

Tang,

et al. 2023

Front. Mar. Sci.

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This study presents in-situ observations of fluid mud in the Yangtze Estuary via a bottom tripod. Six occurrences of periodic fluid muds (F1-F6) were observed at high slack water, with suspended sediment concentration (SSC) exceeding 10 kg/m3. The thickness of the fluid mud varied across the six occurrences, reaching a maximum of 0.32m. Notably, temperature and salinity anomalies were observed within the fluid mud. The formation of fluid mud was found to be influenced by turbulence, with turbulence kinetic energy (TKE) below 5×10-4 m2/s2 favoring settling as the primary cause of formation. The critical shear stress (τcw) for fluid mud formation was estimated to be approximately 0.09 Pa. The formation of fluid muds during early tidal cycles was attributed to liquefaction and bed erosion resulting from strong waves. However, in most cases, the wave energy was insufficient for erosion, suggesting that advection played a role in sediment supply during the subsequent tide cycles. The increased cross-channel current velocity during flood facilitated the lateral transport of a significant amount of eroded sediment from shallow water into the channel. Due to its short duration, the fluid mud layer was entrained by the current before consolidation. Enhanced turbulence led to the breakdown of fluid mud at the early ebb. The critical τcw for fluid mud breakdown depended on the density and duration of the fluid mud, with a maximum value of up to 0.70 Pa. The absence of the fluid mud layer during low slack water and neap tide was associated with a reduction in advection and tidal pumping, disrupting the original sediment balance between supply and demand. These data provide valuable insights into the formation and breakdown of fluid mud, contributing to estuarine hydrodynamic modeling studies and enhancing the understanding of estuary dynamics.

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“…The sediments carried by the YZR were served as the most crucial element of the HZB (He et al, 2016). There was a sharp decrease in the SSD of the YZR during the following 5 years after the Three Gorges Dam construction in 2002 (Figure 9) (Gao and Wang, 2008;Yang et al, 2018;Lu et al, 2020). Comparatively, the QTR was 2 orders of magnitude smaller than the YZR and had a weak impact on geomorphological changes and shoreline expansions (Figure 9B).…”

Section: Sediment Supply and Interface Exchangementioning

confidence: 99%

“…Offshore on the middle Jiangsu Coast (MJC), radial sand ridges diverge in the adjacent waters (Xing et al, 2012;Xiong et al, 2017), with approximately a length of 90 km from the east to the west and a width of 200 km from the northwest to the southeast (Liu et al, 1989;Wang et al, 2012), which is the largest sand ridges on the Chinese continental shelf (Xu et al, 2016;Chen et al, 2020). Located in the YRE, the estuarine turbidity maximum with a length of about 25-46 km from the northwest to the southeast and a width of about 90 km from the north to the south, is formed by the accumulation of finegrained sediments within the water column (Li and Zhang, 1998;Lu et al, 2020). The HZB shows a significant turbid water state on the suspension of extremely high concentrations (Shi, 2011;He et al, 2016), with 70% of the fine-grained particles coming from the YZR sediment transport (He et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Mapping the most heavily reclaimed shorelines of the Yangtze River delta urban agglomerations

et al. 2022

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Objectively understanding the characteristics and evolution of coastal geomorphology, and predicting the growth potential of intertidal flats are the prerequisites for the effective conservation and development of shoreline resources. However, the vulnerability of shorelines in the long term and large space scale needs to be assessed since human intervention in recent decades has intensified the double oppression of river delta system transformation and land reclamation. The Yangtze River Delta Urban Agglomerations (YRDUA) is a highly developed global economy, therefore, the YRDUA with the most intense reclamation, and their dynamic shoreline changes before and after the sharply decreasing sediment supply were detected based on 4,596 remote sensing images and corresponding hydrodynamic data. We found that the sediment replenishment from the radial sand ridges on the middle Jiangsu Coast made the shoreline expansion rate reach 4–5 times that of other Jiangsu coasts. Specifically, a close correlation between the shoreline accretion rate and the amount of sediment supply was found on the eastern Chongming Wetland. Generally, there were still sufficient sediments on the Yangtze River Estuary and Hangzhou Bay interface to support the shoreline expansion despite the upstream sediment reduction. The longshore sediment transport from the delta-front erosion and the land reclamation including vegetation ecological responses were the main factors promoting the shoreline advance. Human interventions, dominated mainly by reclamation, formed positive feedback with local hydrodynamic processes and promoted continuous shoreline accretion. This study focused on the external and internal drivers and their interactions of long-term shoreline evolution with very intensive human activities, which can provide the decision-making reference for the regional coastal zone management and conservation.

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Constraints of salinity- and sediment-induced stratification on the turbidity maximum in a tidal estuary

Cited by 12 publications

References 52 publications

Formation of Turbidity Maximum in the Modaomen Estuary of the Pearl River, China: The Roles of Mouth Bar

Formation of Turbidity Maximum in the Modaomen Estuary of the Pearl River, China: The Roles of Mouth Bar

Fluid mud induced by periodic tidal advection and fine-grained sediment settling in the Yangtze estuary

Mapping the most heavily reclaimed shorelines of the Yangtze River delta urban agglomerations

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