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Abbr. NB: North Branch SB: South Branch NC: North Channel SC: South Channel NP: North Passage SP: South Passage
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The analytical expression for residual coarse sediment transport of Van de Kreeke and Robaczewska (1993) is extended for estuaries. The major extension concerns the contribution to sediment transport by residual current, which is ignored by Van de Kreeke and Robaczewska (1993). Tidal constituents M0, M2, S2, N2, M4, MS4, MN4, M6, K1 and O1 are used...
Contexts in source publication
Context 1
... Yangtze Estuary is located halfway China's coastline (Fig. 4). It has ample water and sediment supply from upstream and obvious tidal influence, creating an estuary characterized by three major bifurcations and four outlets, with well-developed shoals, alternating channels, expanding sandbars and a vast submerged delta. The spatial-temporal dynamics of river runoff and tidal current dominate the ...Context 2
... directions are clearly determined by the orientation of the river. These features agree well with the description in the literature (Chen, 1998). Table 3 lists the amplitudes and phases of tidal current constituents along the principal axis of M 2 tidal current constituent at four selected stations, viz. Tr-XLJ, Tr-NC, Tr-NP and Tr-SP (see Fig. 4). Station Tr-XLJ is located in the middle of the Xuliujing cross-section and can be regarded as representative of the upper part of the estuary. The other three stations represent the middle parts of the North Channel, the North Passage and the South Passage, respectively. As expected, M 2 tidal current, with a magnitude of about 1 ...Similar publications
Aerial ortophotos taken in 1995 have been examined using GIS software to assess the situation of saltmarsh areas in the Tagus estuary. Partial analyses have been made concerning: (a) the right bank, between Lisboa and Vila Franca; (b) Mouchão da Póvoa; (c) Mouchão de Alhandra; (d) Mouchão do Lombo do Tejo; (e) left bank, north of rio Samora; (f) le...
Citations
... The coupled hydrodynamic and sediment transport model was realized based on previous studies, which have been calibrated and validated for water level, flow velocity, flow direction, SSC, and water salinity (Chu et al., 2015(Chu et al., , 2020. Manning coefficients in the Changjiang River and the deltaic-offshore areas were calibrated to 0.019 and 0.011 s/m 1/3 , respectively; the horizontal viscosity and diffusivity were calibrated to 2 and 1 m 2 /s (Chu, 2019;Zhao et al., 2023). ...
... The sediment transport model in this study is based on Chu et al. (2015), which has been calibrated well. Many sediment transport models have been established to investigate sediment dynamics in the YE (Hu et al., 2009;Kuang et al., 2013;Zhu et al., 2021). ...
... In addition to examining the influence of SLR on amplitude and phase changes, many studies have evaluated residual tidal currents in the context of SLR for areas with large residual tidal currents. For tidal basins and estuaries, residual tidal currents dominate the direction of sediment transport, which plays a vital role in long-term morphological changes (Boon 2013; Chu et al. 2015;Cruz and Noernberg 2020;Davies and Jones 1996;Van et al. 2004). Wisha et al. (2019) determined the character of the tidal current during the southwest monsoon in Mandeh Bay. ...
The regional dynamics of the coastal area in Ho Chi Minh City affected by the river and sea hydrodynamic factors are incredibly complex. These factors such as tides, waves, and river flow strongly influence the process of accretion-erosion in both estuary and coastal areas. In this study, the characteristic changes in four main tidal constituents (K1, O1, M2, and S2) influenced by sea-level rise are investigated using a numerical model in the curvilinear coordinate system. The 2050 and 2100 sea-level rise scenarios are considered to evaluate the change in tidal harmonic constants and tidal ellipses. The results show that the amplitude of the four constituents significantly increases; however, there is a declining trend in the tidal phase for both the 2020 and 2100 scenarios. As the highest value in amplitude, the M2 constituent indicates that the tidal regime is the dominant semidiurnal tide in the study area. Despite a smaller amplitude than the M2 constituent, K1 has a higher value than both the O1 and S2 constituents. Tidal ellipses in the study area indicate the orientation of the major axes parallel to the shoreline, and the offshore axes that move clockwise are more circular than those in the river mouth. The strongest semidiurnal M2 velocity of ellipses in the Dong Tranh Gulf ranges from 0.6 to 0.7 m/s in 2020 and records an increase of 0.046 m/s in 2050 and 0.082 m/s in 2100. Most tidal ellipse velocities gradually increase under the influence of sea-level rise in 2050 and 2100.
... Tidal asymmetry in estuaries and lagoons (tidal basins) is the main contributor to the residual current and sediment transport. For coarse-grained coasts, the sediment grains immediately respond to the tidal current so that the residual sediment transport is in line with the residual flow [16,17]. It is worth noting that for coarse-grained coasts (i.e., those with a sand-dominated bed), the sand supply from the rivers, which mainly moves in a bedload transport or bedform migration, is also a crucial factor in the sedimentary budget of a beach [18]. ...
Residual sediment transport, which is influenced by many factors including tide, wind, and waves, controls coastal morphological changes on different time scales. For fine-grained coasts where the wave effects are limited, it is still unclear to what extent the wind-driven current can impact the residual sediment transport. Taking the fine-grained Jiangsu Coast as an example, this study aimed to identify the contribution of wind on residual sediment transport over different time scales using a newly developed model. On a seasonal scale, wind-induced sediment transport shows strong seasonal characteristics, where the residual transport is more significant in the winter and summer. Nevertheless, the tide plays a dominant role in both residual current and sediment transport and the annual sediment budget over the coast. On the scale of tidal cycles, the extreme winds overwhelm the tides, controlling the residual sediment transport. However, the net sediment transport caused by the northerly winds (representing cold waves) is comparable to that of the southerly winds (representing typhoons). Therefore, although extreme winds can drive massive sediment transport in a short period, their contribution to annual sediment transport is limited.
... The hydrodynamic model used in this study was based on Chu et al. (2015), and is well calibrated. The Manning coefficient plays a key role in hydrodynamic simulations (Yu et al., 2014b) and was set as 0.011 s/m 1/3 for the YE and HZB model domain. ...
Salinity distributions and gradients within an estuary are of great socioeconomic and ecological importance. In this study, a well-validated and process-based hydrodynamic model (Delft3D) was applied to investigate the salinity distributions and variations in the Yangtze Estuary subject to river discharge regulation by the Three Gorges Reservoir and morphological evolution of the estuary. The results indicate that the regulation of river discharge is the controlling factor for salinity variations in the estuary. Following construction of the Three Gorges Reservoir, the salinity significantly decreased during the dry season and slightly increased during the flood season. The morphological evolution of the estuary induced spatial salinity variations and affected the salinity in the estuarine wetlands (the Jiuduansha Shoal and East Chongming Mudflat). The salinity in the Jiuduansha Shoal increased from 1998 to 2010, whereas it decreased from 2010 to 2018. During the period 1998 to 2018, the salinity in the East Chongming Mudflat exhibited an increasing trend. These findings provide implications for management of water resources and wetlands in the Yangtze and other similar estuaries.
... The calibrated and validated process-based model for the Yangtze Estuary based on Delft3D was used in this study to simulate the water level [6,19,20]. The flow model domain extends over about 800 km in the longitudinal direction and about 400 km in the lateral direction. ...
... It is noted that this application only focuses on the wind-induced water setup. Previous research proposed that the radius of maximum winds and the wave-induced water setup have a significant effect on the simulation of storm surges [20,21]. The purpose of this research is to propose a wind correction method suitable for estuarine areas. ...
High-quality wind field data are key to improving the accuracy of storm surge simulations in coastal and estuarine water. These data are also of great significance in studying the dynamic processes in coastal areas and safeguarding human engineering structures. A directional correction method for ECMWF reanalysis wind data was proposed in this paper based on the correlation with the measured wind speed and direction. The results show that the accuracies of wind speed and direction were improved after being modified by the correction method proposed in this paper. The modified wind data were applied to drive the storm surge model of the Yangtze Estuary for typhoon events, which resulted in a significant improvement to the accuracy of hindcasted water levels. The error of the hindcasted highest water levels was reduced by 16–19 cm.
... In particular, the R 2 for the prescribed water lever at 19S0 is only 0.82, which could be the reason why the fit to SSC was poor at this station. Although the absence of more tidal constituents (especially with SNR >1) in the analytical model could result in poor fit in SSC, incorporating more tidal components into the model will make it very complex (e.g., Chu et al., 2015). ...
Coastal turbidity maxima (CTMs) have been recognized on open coastal seas with elevated suspended sediment concentrations. Tidal pumping is often considered the major contributor to turbidity maxima in well‐mixed estuaries. However, its role in CTM formation on well‐mixed coasts remains unclear. Here, we propose a two‐dimensional depth‐averaged analytical model to explore residual sediment transport influenced by interactions between cross‐shore and along‐shore tidal currents. Observation data collected on the well‐mixed central Jiangsu coast (southern Yellow Sea), China, are analyzed by the model. The results display a persistent CTM close to the shore and show that the large along‐shore tidal velocity strongly influences the cross‐shore tidal pumping flux. The model calculation presents landward tidal pumping flux under horizontally homogeneous bed sediment distribution, illustrating the dominant role of tidal pumping in CTM formation within well‐mixed coastal water bodies. The model suggests that the significance of alongshore tidal current to cross‐shore sediment transport should be addressed in similar coastal environments.
... Sediment dynamics conditions created present-day estuaries consisting of channels, mudflats, and saltmarshes underlying by consolidated sediments (Perillo and Cuadrado, 2013). Around the world, these systems experience increasing rates of change in their geomorphology, mainly due to coastal erosion attributed to rising sea levels, reduced amount of sediment delivery to the coast as well as anthropogenic degradation (Chu et al., 2015;Picado et al., 2010). ...
A wide range of processes determine the hydrodynamics and sedimentary balance in tide-dominated estuarine environments. Tidal channels can be subject to the most energetic processes. Therefore, changes in their geomorphology require continuous updates. Through oceanographic surveys, were collected in situ hydrodynamic, bathymetric, and sedimentological data in a section of the Canal del Medio in the Bahia Blanca Estuary (southwest of the Buenos Aires Province, Argentina) to examine the possible effect that the presence of a sediment bank can have on the tidal current pattern within a specific meander. An unusual elliptical deep scour hole was detected with a depth of 12.60 m in the thalweg of the meander (tidal range is about 3 m). Based on the data, it was found that the maintenance of the scour hole is possible because of a vortex forced by the presence of an elongated sandy bank connected to the tidal channel bank that acts as a hydrodynamic barrier to the currents, inducing the modification of the meander pattern.
... M2, S2 and M4). The amplitudes of other tidal constituents are comparatively small and hence not considered for simplicity (Chu et al., 2015). ...
Understanding sediment sorting and bedding dynamics has high value to unravelling the mechanisms underlying geomorphological, geological, ecological and environmental imprints of tidal wetlands and hence to predicting their future changes. Using the Nanhui tidal flat on the Changjiang (Yangtze) Delta, China, as a reference site, this study establishes a schematized morphodynamic model coupling flow, sediment dynamics and bed level change to explore the processes that govern sediment sorting and bedding phenomena. Model results indicate an overall agreement with field data in terms of tidal current velocities, SSCs, deposition thicknesses and sedimentary structures. Depending on the variation of tidal current strength, sand-dominated layers (SDLs) and mud-dominated layers (MDLs) tend to form during spring and neap tides, respectively. Thinner tidal couplets are developed during daily-scale flood-ebb variations. A larger tidal level variation during a spring-neap tidal cycle, associated with a stronger tidal current variation, favours the formation of SDLs and tidal couplets. A larger boundary sediment supply generally promotes the formation of tidal bedding, though the bedding detail is partially dependent on the SSC composition of different sediment types. Sediment properties, including e.g. grain size and settling velocity, are also found to influence sediment sorting and bedding characteristics. In particular, finer and coarser sediment respond differently to spring and neap tides. During neap tides, relatively small flow velocities favour the deposition of finer sediment, with limited coarser sediment being transported to the upper tidal flat because of the larger settling velocity. During spring tides, larger flow velocities transport more coarser sediment to the upper tidal flat accounting for distinct lamination formation. Model results are qualitatively consistent with field observations, but the role of waves, biological processes and alongshore currents need to be included in further studies to establish a more complete understanding.
... They assumed M 2 to be the dominant tidal current constituent, and the transport of coarse sediment was proportional to the third power of the depth-averaged current speed, and then concluded that the interactions of M 2 and the Eulerian mean current (M 0 ), M 2 and M 4 and the triple interaction of M 2 , M 4 and M 6 lead to a tidally-averaged residual coarse sediment transport. Chu et al. (2015) suggested that the expression by van de Kreeke and Robaczewska (1993) is only applicable in the cases with a relatively small residual current, and re-derived an approximate expression including higher-order terms. Explanations were proposed thereafter of why the original expression may underestimate the residual transport of coarse sediment in cases of large residual currents. ...
... The velocities were decomposed into the orthogonal X and Y directions, i.e., the cross-shore and alongshore directions, respectively. Because M 2 is the dominant astronomical tide along much of the world's coasts, and the interactions of M 2 and M 0 and M 2 and M 4 are sufficient to calculate RST in situations with small residual current, which is true for the present study area (Table 1); thus, the tidal velocity can be modeled by a superposition of the M 2 tide, its most significant overtide M 4 , and the tidal residual M 0 in this study (Friedrichs and Aubrey, 1988;van de Kreeke and Robaczewska, 1993;Yu et al., 2012;Chu et al., 2015). ...
... The positive and negative gradients represent the spatial variation of erosion and deposition, respectively. Chu et al. (2015) suggested that the analytical solution by van de Kreeke and Robaczewska (1993) works well in the Dutch estuaries, where the residual current (M 0 ) is sufficiently small. It is necessary to include a full-time series for situations with a significant residual current. ...
The residual sand (D > 62.5 μm) transport (RST) refers to the tidally averaged rate of horizontal sand transport. Albeit much smaller than the peak rates, it determines the morphological evolution. The analytical expression for the tide-induced RST has been reported in the condition of one-dimensional tidal currents by van de Kreeke and Robaczewska (1993). Here we extended the analytical solution to two-dimensional. The constituents of the residual, M2, and M4 tidal current velocities were used to characterize the collinear tidal current in the orthogonal X and Y directions, i.e., cross-shore and alongshore, respectively, while the M 2 tidal constituent is dominant in both directions. Based on the solution, RST is controlled by a series of triple interactions of the M 2 tidal velocity in the X direction, M 2 tidal velocity in the Y direction, and the residual or M 4 velocity in the X or Y direction. The solution was applied to the tide-dominated continental shelf of the Jiangsu coast, China, where the alongshore current is much stronger than the cross-shore component. The results show that the triple interactions of the cross-shore M 2 tidal velocity (U M2), the alongshore M 2 tidal velocity (V M2), and the alongshore residual velocity account for the major parts of both the alongshore and cross-shore RST in the nearshore area. The RST patterns promote sand accumulation in the shallow nearshore area and generate a narrow and active conduit of coastal alongshore sand transport. These findings can be applied in similar marine environments to understand the effects of non-linear tidal interactions in RST.
