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A comprehensive observational data set was used to examine shoreward propagating semidiurnal internal tides as they shoal, break and run-up as turbulent boluses across the edge of the Australian North West Shelf (NWS), offshore Dampier, during late winter 2013. The measured waveforms and wavefields supported the grouping of events into two distinct categories: (1) pre-; and, (2) post- wave breaking. It was found that the transition from (1) to (2) was marked by the rise of nonlinear steepening (α) and reduction in dispersion (β), both coefficients that parameterize nonlinear wave effects on the Korteweg-de Vries (KdV) equation. We introduced a criterion for wave breaking from the dimensionless parameter (δ) that relates these two terms: wave breaking occurs when δ < 1. In the first group, dispersive effects were dominant to spread energy out of the semidiurnal wave to a dispersive wave packet of short-period internal solitary waves (ISWs). In the second, dispersion was considered small compared to the cumulative effect of nonlinear steepening. Here, the semidiurnal wave built sufficient energy at its rear face to generate wave breaking, which has been known to produce multiple turbulent boluses. Similar observations have not been described for this region during winter months and highlight that the nonlinear internal wave field is an important feature on the NWS throughout the year. Additionally, measurements obtained through autonomous ocean glider profiles revealed some of the post-breaking characteristics that included intensive vertical mixing and transport of dense water and suspended material onshore of the shelf break.

Fu, L.; Wang, J.M., and Peng, Z.H., 2020. Simulation of wastewater discharge in a coastal plain river network considering different boundary conditions. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 529–534. Coconut Creek (Florida), ISSN 0749-0208.Owing to a rapidly developing economy and society, coastal cities along the East China Sea face serious water pollution problems. A number of sewer plants were recently constructed to improve the water quality in the region. This study investigated the environmental effects of wastewater discharge from a newly constructed sewer plant as the wastewater passes through a typical coastal plain river network. Ammonia nitrogen (NH3-N) was selected as the typical pollutant, which was monitored and simulated using a two-dimensional model to demonstrate the effects of wastewater discharge. Different kinds of boundary conditions and the effects of tidal bores were represented in the simulation, and the risk of wastewater discharge in the coastal plain river network was also analyzed. An emergency plan is recommended to minimize the risk of wastewater discharge and prevent potential damage to the regional river network environment.

Extreme climatic/environmental events associated with sea level rise in the context of global warming are a prime concern in coastal management. Kuahuqiao, the type-site for the early Neolithic cul...

A tidal bore normally occurs in an estuarine zone, as a combined result of the spring tide and the trumpet-shaped river mouth. During flood tide, the inland flow is amplified by the gradually-narrowing funnelled estuary, forcing the leading edge to grow steeper until forming an upstream propagating discontinuous wave that is the tidal bore. Tidal bores in natural rivers usually contain enormous energy and induce intense turbulent mixing, posing a threat to hydraulic structures and seriously affecting the fluvial environment. The current study of tidal bores focused on the physical modelling of their turbulent propagation and transformation as well as the bore-induced sediment transport. The experiments were conducted in a 15 m long 0.5 m wide rectangular channel, with ten flow conditions encompassing various flow rates, channel slopes and bed materials (smooth PVC, fixed/mobile gravel). High-frequency sampling of instantaneous unsteady free-surface elevation and turbulent velocity was realised using acoustic displacement meters and acoustic Doppler velocimeters at 200 Hz. High-definition video recording and photographic observation were applied to track the bore propagation and transformation along the test section. Ultra-high-speed video camera recordings were undertaken at 1,200 fps, to capture the bore-induced sediment particle motion from the side view. For each series of flow conditions, the experiment was repeated at least 25 times to derive some ensemble-averaged results of flow turbulence properties and sediment particle motion characteristics. Two different kinds of decelerating bores were recorded in the inclined channel: (a) decelerating bores transformed into stationary hydraulic jumps (arrested bores) when propagating against supercritical flows; (b) decelerating bores vanished when travelling opposite to subcritical flows. The arrival of bores induced an abrupt free-surface rise and a rapid decrease of streamwise velocity. The near-bed flow was observed to reverse direction towards upstream beneath breaking bores. The instantaneous free-surface and all flow velocity components experienced some drastic fluctuations during the bore front passage. Large-amplitude Reynolds stresses and extreme Reynolds stress fluctuations occurred in the same phase during and after the passage of decelerating bores.The sediment transport in the bore-induced rapidly-varied flows was investigated focusing on the bed particle motion and diffusion processes. The frame-by-frame analysis of slow-motion videos demonstrated three basic motion modes of individual pebbles: rotation, rolling and saltation. More complicated pebble motion included a combination of 2 or 3 basic modes. Most moving particles were entrained underneath the bore front between the bore roller toe and the first crest. Based upon a Lagrangian approach, more than 550 complete trajectories of the moving bed particles were extracted from the videos recorded at 1,200 fps. These particles were set into motion by bore passages and shortly reposed into the static gravel bed without intermediate rest. The instantaneous particle velocity and acceleration were derived from the particle trajectories. The forces exerted on the moving particles were estimated based on the combination of instantaneous particle kinematics and fluid properties. The adverse longitudinal pressure gradient force was the major force for the particle acceleration from entrainment, while the drag force induced by transient flow reversal played an important role in the further upstream advection of bed particles. The time series of particle kinematic parameters were superimposed using their starts and ends respectively as the reference points, which enabled the ensemble-average analysis of particle dynamics since entrainment and before disentrainment. The ensemble-averaged particle motion included two major stages: acceleration phase at onset and deceleration phase before stoppage. There was no quasi-steady phase between the two stages. The particle motion was more diffusive immediately after entrainment than before disentrainment. Super-ballistic diffusion was observed during the transient particle motion. This study demonstrated very complicated fluid-particle-bed interactions in the rapidly-varied flows during bore events. In summary, the current physical modelling characterised the turbulent propagation and transformation processes of tidal bores, as well as the bore-induced transient sediment motion in the rapidly-varied flows. Future researches on this topic should focus on the simultaneous flow velocity measurements through the entire water column, to reveal the flow structure and its interactions with sediment materials. The combination of numerical modelling and physical measurements may provide further detailed information on these complicated phenomena.

The Qiantang Estuary is characterized by strong tidal bore, high sediment concentration, severe erosion/deposition and frequent human activities. The law of saltwater intrusion is different from other general tidal estuary. This chapter reveals the law of interaction among runoff, channel volume and salinity by means of the analysis of the long-term hydrological and measured salinity data of the Qiantang Estuary. Based on the concept of water, sand and salt mixture density, the muddy water control equations have been derived, and the mathematical model coupling with strong tidal bore-sediment-salinity has been developed as a result, and the model has also been verified, which shows that the result adopting movable-bed numerical simulation model in calculation agrees more with the actual condition.

Short review of recent research of propagation of tidal waves into an estuary and examples of estuaries where bore is formed are presented. Criterion of tidal bore formation and the cross section of its inception are discussed. In estuaries under consideration the bore is formed in cross sections at distances from the mouth site larger than the convergence length. Abrupt changes of water level and pressure gradient in a flow result in intensive sediment suspension and bottom erosion at the cross section of bore inception. Bottom deposits in the estuaries and low-landing marshes take a wave form with parameters corresponding to the bore waves. Bore waves contribute to the sediment accumulation in the upper parts of the estuary and its shallowing.

A tidal bore is a compressive wave, advancing upstream in an estuary when the flood tidal flow starts. It is observed when a macro-tidal flood flow enters the funnel shaped river mouth with shallow waters. Its upriver propagation impacts the natural system, with sediment scouring and suspension. The tidal bores of the Garonne and Selune Rivers in France were extensively investigated between 2010 and 2016. Instantaneous velocity measurements were conducted continuously at high-frequency (50 to 200 Hz) during each bore event. In the Garonne River, instantaneous sediment concentration data were obtained and the sediment properties were systematically tested. The nature of the observations was comprehensive, regrouping hydrodynamics and turbulence, sedimentology and suspended sediment transport. The key outcomes show that the tidal bore occurrence has a marked effect on the velocity field and suspended sediment processes, including a sudden flow deceleration and flow reversal during the bore passage. The turbulent Reynolds stresses present large instantaneous amplitudes, with rapid fluctuations, during the tidal bore. The sediment flux data imply considerable mass transport rates during the first hour of flood tide. This unique review of field data further shows a number of common features, as well as the uniqueness of each individual event.

Decelerating bores are commonly seen in shorelines, estuaries and rivers in forms of swash run-up, tidal bores, tsunami bores. A decelerating bore propagating upstream can gradually change its shap...

A tidal bore is a natural estuarine phenomenon forming a positive surge in a funnel-shaped river mouth during the early flood tide under spring tide conditions and low freshwater levels. The bore p...

A tidal bore is perhaps the most spectacular tidal phenomenon that can be readily observed. When a large tide enters a shallow, funnel-shaped estuary with a gently sloping bottom, its waveform is distorted and this can lead to an impressive rolling ‘wall of water’, travelling upriver. ‘Tidal bores’ explains that estuary shape and a large tidal range are important for tidal bore formation. Tidal bores can be smooth, non-breaking ‘undular’ waves or a variety of breaking forms of increasing violence. Famous examples are seen along the Qiantang River in China, the Amazon River in Brazil, and the River Severn in the UK. The impact of tidal bores on estuarine processes and ecosystems is also discussed.

The Yangtze River Delta characterized by a dense population and a rapidly developing economy is highly vulnerable to sea-level rise. The data from the China Oceanic Information Network and the Zhejiang Provincial Hydrology Bureau are used to analyze sea-level rise. The rate of sea-level rise in the delta was 2.4 mm per year in 1981–2015. The annual sea-level at Daishan, Dinghai, and Dongtou stations in the south wing of the delta were 4.3, 3.1, and 5 mm per year respectively over the same period. The 10-year averaged results at each station also indicate a perceptible trend of sea-level rise. Sea-level rise is contributed to a larger proportion of intensified erosion, ranging from 3% to 14% in the delta. Meanwhile, the 100-year return period of tidal level has decreased to the 50-year rank at Dongtou and Dinghai stations. Moreover, the arrival time of tidal bores at Yanguan is 4 min earlier under sea-level rise of 0.145 m than that of 0 m. The height of tidal bores and the velocities at the surface and bottom layers have an increase under sea-level rise. The maximum increases of high and low tide levels are 0.122 m and 0.016 m while the maximum increases of the velocities at the surface and bottom layers are 0.07 m s−1 and 0.05 m s−1, respectively. Sea-level rise will bring about the damage of seawall, thus the design standard of constructing seawalls should adopt a higher level to minimize the associated risks in the Yangtze River Delta and its south wing. Keywords: Coastal erosion, Sea-level rise, Saltwater intrusion, Tidal bore, Yangtze River Delta, Zhejiang province

Ni X.; Huang S.; Feng W., and Yao W., 2018. Numerical simulation of tidal bores using SPH method. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 951–956. Coconut Creek (Florida), ISSN 0749-0208. A tidal bore is a natural hydraulic phenomenon normally formed in funnel-shaped estuaries with large tidal ranges. Water levels and flow velocities change rapidly in both magnitude and direction when a tidal bore arrives. These strongly nonlinear water body movements have significant influences on scouring and deposition processes along the riverbed and produce hydrodynamic impacts on piers and dikes. In this paper, a mesh-free numerical method known as the smoothed particle hydrodynamics (SPH) method is used to implement a numerical model capable of handling complex free-surface flows and solve the Navier-Stokes equations with a large-eddy simulation. A tida...

A persistent semidiurnal internal tidal bore feature occurs at the head of the Monterey Bay Submarine Canyon and drives regular intrusions of cold, subthermocline waters onto the adjacent shelf. In this study, we examine the influence of this internal tidal bore feature on the larval fish community using over a year of periodic larval fish samples collected coincidently with physical measurements. Larval samples were categorized into one of two water mass periods: a “warm period” representative of shallow coastal shelf waters and a “cold period” characteristics of colder waters present during internal bore forcing. Using multivariate statistical methods, we show warm and cold periods, along with seasonality, are the primary drivers of larval fish community composition. A significantly different community composition was observed between warm and cold water mass periods. This difference was primarily due to decreased abundance in most taxa during the cold periods, and did not indicate an obvious shift in the assemblage of the taxa. However, our data do indicate that some taxa may show higher abundance during cold periods compared to warm periods, but further studies are warranted. Along with seasonality, the presence/absence of subthermocline waters driven by internal bores appears to be a key control on nearshore larval fish community composition at this location.

A major tsunami-like event, locally known as ‘marrobbio’, impacted the southwestern coast of Sicily on 25–26 June 2014. The event was part of a chain of hazardous episodes in the Mediterranean and Black seas during the last week of June 2014 resulting from an anomalous atmospheric system (“tumultuous atmosphere”) propagating eastward over the region. The synoptic patterns and vertical structure of the atmosphere over Sicily at the time of the event indicate that atmospheric wave ducting was responsible for the generation of tsunamigenic air pressure disturbances that produced especially high sea level responses (“meteotsunamis”) at certain sites along the Sicilian coast. The strongest sea level oscillations were observed at Mazara del Vallo, where a 1-m meteotsunami bore, propagating upstream in the Mazaro River, was generated. The combined effects of external resonance (Proudman resonance on the western Sicilian shelf) and internal resonant conditions (bathymetric and topographic characteristics of specific sites) were found to be the key factors that caused the meteotsunami (marrobbio phenomenon) on the coast of Sicily and the meteobore at Mazara del Vallo.

Most of the numerical methods used for shallow water flow calculation are not applicable to the numerical calculation of the discontinuous flows. High precision resolution is a difficult problem in simulate discontinuous flows. This paper adopts Roe scheme approximate Riemann solver to deal with normal vector through interface, apply TVD–MUSCL scheme and Hancock scheme to increase the precision of space and time to second order using in tidal bore simulation. In order to verify the accuracy of the model and simulate the ability of discontinuous flows, some numerical examples are simulated in this paper, the results of simulation and other scholars’ results are compared to check the applicability and accuracy of the model for discontinuous flow. With the generalized river course tidal bore experiment to prove the model has the ability to capturing shock wave and better calculative precision.

Many alluvial estuaries worldwide include an inside bar system, a large sediment deposit deeply stretched into the estuary. A good example of such a system is the large sediment deposit in the Qiantang Estuary, China. Its length and height reach 130 km and 10 m, respectively. Bathymetrical comparison reveals that the large bar has moved seaward by around 15 km over the last decades, probably related to the large-scale coastal embankment project. This motivated a quantitative investigation of the impact of estuarine planform on the inside bar development. The bar morphology is reproduced by means of an idealized 1-D morphodynamic model. Model results suggest that the bar movement is related to a decreasing tidal prism, increasing flood dominance in the lower reach and enhanced ebb currents in the upper reach, in response to the embankment. The timescale of the morphological response is only several years. The rapid response is related to the strong tidal currents and large sediment fluxes within the estuary. Sensitivity experiments show that the location and dimensions of the bar are related to the convergence length of the estuary. A decrease of the convergence length causes seaward movement and shortening and lowering of the bar. The bar dimensions also depend on the ratio between river and tidal discharges. When the ratio increases, the bar apex moves seaward and the elevation decreases. The bar movement has significantly influenced the tidal bore in the Qiantang Estuary.

The highly controversial relationship among the chemical weathering of silicate rocks, climatic variability and human activities on various temporal scales has become a hot research topic given the booming interest in global climate change. This study of the Holocene Qiantang River incised-valley fill investigates the variability of weathering intensity and its controlling factors based on geochemical analysis. Results indicate that the variations of chemical weathering indices throughout the studied succession are chiefly climate-controlled, although partly influenced by source-rock lithology, grain-size effects, hydraulic sorting and sediment recycling by tidal bores. Over the last 12 ka, 8 periods with distinct characteristics and weakened weathering intensity are identified. The abruptly weakened weathering intensity documented by chemical weathering indices in the last 2 ka is ascribed to the intensification of human activities and/or EI-Nino activities. Noteworthy, small catchments located near land-ocean boundaries respond more rapidly to climate change and human activities on a millennial (even centennial) timescale. The climatic cooling events (e.g., Younger Dryas, 10.3 ka and 9.3 ka) are better reflected in the study interval as the sediments of units U5, U4 and U3 (before 8.2 ka BP) are sourced from the Qiantang River watershed. Slightly weakened chemical weathering related to climatic events is also documented by the coarser sediments of unit U1, which are primarily derived from the Changjiang (Yangtze River).

The tidal bore of the Garonne River (France) was investigated on 29 August, 31 August and 27 October 2015, during which instantaneous velocity measurements were performed continuously at high-frequency (200 Hz). The tidal bore occurrence had a marked effect on the flow field and turbulent Reynolds stress data, indicating large shear stresses, together with large and rapid fluctuations, during the bore passage and the early flood tide. Like many natural process flows, the tidal bore flow motion was dominated by coherent structure activities and turbulent events, with significant impact on the natural systems including in terms of sediment processes. Herein a new turbulent event analysis was developed for the highly-unsteady rapidly-varied tidal bore flow. The analysis was based upon basic concepts, in which turbulent bursting events were defined in terms of the instantaneous relative turbulent flux, and the method was extended to the rapidly-varied, highly-unsteady tidal bore motion. The turbulent event data showed relatively close results for most fluxes during the tidal bores. The event duration showed some tidal trend, with longer turbulent events immediately after the tidal bore passage, occurring simultaneously with major sediment erosion processes. The field data set and analyses suggested that a turbulent event analysis may be applicable to highly-unsteady rapidly-varied flows, providing quantitative details into the turbulent bursts that are responsible for major mixing and sedimentary processes.

In a natural estuary, a tidal bore may progress on a small sloping bed from the downstream to the upstream. In this study, a simple analytical solution for tidal bore formed in a small slope channel was developed using the finite control volume analysis. New unsteady experiments were conducted to verify the theoretical model. The model predictions generally agree with the observations. A general relation is obtained for the conjugate depth ratio as a function of the Froude number and the channel slope from the experimental data. The results indicate that the conjugate depth ratio increases with an increasing Froude number as well as with a decrease in channel slope. On a negative slope, the Froude number increases as the bore propagates along the channel, and decreases for a positive slope. The theoretically based model is accurate and simple to estimate the celerity of the tidal bore progressing along a small slope channel.

The factors that govern the distribution and transformation of tidal waves in the macrotidal estuary of the Mezen River have been considered, including tide range in the mouth section, water discharge in the river’s lower reaches, estuary shape, and bed resistance coefficient. Data on variations of water discharge over period 1920–2008 are given. The parameters of estuary channel narrowing in horizontal and vertical sections have been considered. The effect of narrowing and bed hydraulic friction on tide wave amplitude has been evaluated. Froude number values for the tidal estuary suggest that tidal bore can form at the Mezen mouth. The conditions of the propagation of tidal waves to the mouths of different rivers and tidal bore formation in them are considered.

International audience; Surface wave breaking induces strong turbulence in the two-phase flow region. Detailed turbulence statistics were experimentally obtained using non-intrusive optical techniques in a breaking bore roller, at relatively large scale, with a bore Froude number Fr1 = 2.15 and Reynolds number Re = 2.3 × 105. These novel velocity data were ensemble-averaged based upon an instantaneous dataset of 24,320 images. In terms of the velocity field, the breaking bore roller was classified into three regions: the impinging jet, developing shear layer and flow reversal region. The vertical profiles of the longitudinal velocity data exhibited some self-similarity. The Reynolds stress data showed an anisotropic turbulent flow immediately downstream of the roller toe, and tended towards isotropy away from the roller toe. The vorticity data suggested that the breaking at the roller toe was responsible for the generation of vortices. The turbulent structures in the shear layer presented significantly smaller length and time scales with higher dissipation rate than other regions. A discussion between present turbulence statistical data and bubble dynamics from literature was developed. The comparison between present and past studies suggested a similarity in two-phase physical processes in the breaking roller region between the tidal bore, hydraulic jump, swash zone bore and breaking wave.

Turbulence dynamics and sediment suspension, under intense tidal bore conditions are investigated using field observations from the Qiantang Estuary, China. During the passage of the bore the tidal current bottom generated turbulence is augmented by turbulence injection from the surface as part of the breaking processes of both bore front and the bore associated secondary waves. These processes lead to enhanced vertical mixing and vertical distribution of the advected sediments. The latter contributes to increased sediment transport in the direction of the bore propagation that potentially modifies the normal tidally-driven estuarine sediment dynamics and morphology. The results show that turbulence intensity increases with increased tidal currents and oscillating motions associated with the breaking processes. At the early stage of the tidal bore, the vertical mixing of suspended sediment is more convective than diffusive due to the elevated length scales associated with bore and breaking secondary wave generated turbulence. Turbulent momentum and vertical sediment flux are determined by intermittent, large magnitude turbulent events (i.e., turbulent bursting). At early period of the tidal bore (~ 40s), inward and outward interactions contribute most to the Reynolds stress and vertical sediment flux, in contrast to later periods when sweep and ejection become more important. Negative vertical sediment flux (i.e., toward the bed) is observed, indicating that the sediment buoyancy acts as a source of turbulent kinetic energy, possibly due to the modification of vertical distribution of suspended sediment by the bore. These observations, in flow conditions under intense tidal bore breaking, reveal different sediment dynamics from traditional boundary process by injecting breaking induced turbulence which modifies the distribution and transport of the suspended sediment.

In this paper, the three-dimensional photogrammetry is introduced in the tidal bore height observation of Yanguan station for the thread-shape bore near the Qiantang River estuary. The three-dimensional scene of the tidal bore is restored by remote control and post-solution. The measurement of tidal bore’s height in three-dimensional environment is realized, and the auxiliary measurement of tidal bore’s upper bound, the foot line, the tidal curve and other vector data are extracted. The accuracy of the measurement is compared with the result of the tidal bore height measured by the Water gauge observations on the same station. The results show that not only the tidal bore’s shape can be captured but also the tidal bore’s height can be quantitatively calculated by three-dimensional photogrammetry. The three-dimensional photogrammetry can be used to quantitatively observe the tidal bore’s height in Qiantang River Estuary and the measurement accuracy is reliable.

It is the best time to view tidal bores in lunar August in the Qiantang River Estuary, but it happens to be a time of typhoon occurs frequently. The effect of typhoons on the Qiantang bore still remains to be studied. Herein, typhoon Yagi making landfall in the Zhejiang coast during astronomical spring tide in 2018 was chosen to study the effect of typhoon on tidal bores. Based on the validation of wind speed, tidal level and tidal bore height during typhoon Yagi, a three-dimensional typhoon model combined with a parametric hurricane model is developed to investigate the effect of this typhoon on tidal bores. Numerical results demonstrate that the direct effect of wind-pressure field plays a significant role in the upper reach of the estuary. Affected by typhoon Yagi, the height of both the line-shape tidal bore and the back-flow tidal bore was remarkably increased. The enhanced tidal bore is earlier to be formed in the Yanguan reach during typhoon Yagi. The Qiantang bore is indirectly affected by increasing tidal range in the lower reach. The typhoon-induced storm surge progresses into Hangzhou bay and induces to form a more spectacular tidal bore in the inner estuary.

Contiguous mudflats exist along the coast zone of the Bohai Bay in the western part of the Bohai Sea of China. They are generally suitable for land reclamation, which can ease the contradiction between land resource shortage and the demand for development, because mudflats are important geomorphological systems which provide land resources. The shoreline at the Bohai Bay has experienced significant changes since 2003 due to high intensity reclamation. Environmental impacts of reclamation at different stages, especially on the tidal wave system, have attracted worldwide attention. However, there is still a lack of understanding on the cumulative response process of the tidal wave system and its response mechanism to high intensity development of mudflats. In this study, six periods were selected as representative reclamation stages in the Bohai Bay: 2003, 2006, 2012, future planning, and 0 m and −5 m reclamation stages. A two-dimensional tidal wave mathematical model was developed to analyze the cumulative changing process and dominant mechanism of the change of the tidal wave system by comparing effects of reclamation of the entire bay and cumulative effects of sequential reclamation projects, as well as studying the relations between the tidal wave change and tidal range on the shore segment where the reclamation project is located. Based on the analysis results, the influence of reclamation in the Bohai Bay on the M2 constituent tide was much greater than that on the K1 constituent tide, especially on the M2 constituent tide amphidromic point outside of the Yellow River mouth. The movement distance of the M2 constituent tide amphidromic point outside the Yellow River mouth for the aforementioned reclamation stages compared to its location in 2003 was about 1, 10, 22.5, 27.3, and 83.8 km, respectively. In contrast, the maximum movement distance of the other M2 constituent tide amphidromic point outside Qinhuangdao and the unique K1 constituent tide amphidromic point in the Bohai Sea for the aforementioned reclamation stages compared to their conditions in 2003 were about 5.9 and 6.3 km, respectively. With the increase of the reclamation scale, the M2 constituent tide amphidromic point outside of the Yellow River mouth first moved southeastward, and then moved northeastward, and the tidal range of the western Bohai Bay first increased and then decreased, while the speed of tidal wave propagation first accelerated and then stabilized during the 0 m reclamation stage. During the −5 m reclamation stage, the tidal wave system experienced obvious changes, however, the tidal properties inside the bay remained the same. The average tidal current velocity of the bay decreased with the increase of the reclamation scale, and the tidal current velocity of 2003, 2012, future planning and −5 m reclamation stages were 0.33–0.37, 0.3–0.34, 0.29–0.31, and 0.16–0.17 m/s, respectively. When reclamation projects were performed one by one counterclockwise from Caofeidian (future planning) in the north to south until all the future planned reclamation projects were completed, the M2 constituent tide amphidromic point first moved southwestward, and then moved southeastward. In semi-closed bays influenced by rotational tidal wave, the impact intensity of reclamation projects to the tidal wave system depends mostly on the tidal range of the coast where the reclamation projects are located. The greater the tidal range, the more obvious the effects of the reclamation projects will be on the tidal wave system. Continuous reclamation will increase flooding risks and tendency of siltation in the bay, weaken the water exchange rate in the bay, affect scouring and silting, as well as impact the design and defense standards of coastal engineering projects near the Yellow River mouth.

Flow division at bifurcations in the Yangtze Estuary has received ample attention, since it may control the pathways of terrestrial sediments over downstream river branches including the 12.5 m Deepwater Navigation channel. While some efforts have been made to interpret flow division at the bifurcations of the Yangtze Estuary, little attention has been paid to the role of tides. Flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta. To quantify the tidal influence on the distribution of river discharge, and more generally, to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the Yangtze River Delta, a two-dimensional hydrodynamic model is employed. In this model, the landward boundary is chosen beyond the tidal limit, where the tidal motion has faded out entirely. The seaward boundary is chosen such that the river discharge does not influence the water level. Subtidal discharges are decomposed using the method of factor separation, to distinguish between the effects of tides, river discharge and river-tide interactions on the subtidal flow division. Results indicate that tides modify the river discharge distribution over distributary channels in the Yangtze River Delta, particularly in the dry season. A significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude. By varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model, the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail. Generally, the tidal impacts on the subtidal flow division are around 12% to 22%, with river discharge varying from 30,000 m3s-1 to 20,000 m3s-1. This effect on the flow distribution can even overwhelm the effects induced by river discharge based on geometry only, when the flow discharge is lowest. Furthermore, the fortnightly tidal cycle plays an important role in enhancing the inequality of the subtidal flow division caused by the M2 tidal component solely at the tidal bifurcation in the Yangtze River Delta during low flow.

The purpose of this study was to develop a two-dimensional shallow water flow model using the finite volume method on a combined unstructured triangular and quadrilateral grid system to simulate coastal, estuarine and river flows. The intercell numerical fluxes were calculated using the classical Osher-Solomon's approximate Riemann solver for the governing conservation laws to be able to handle wetting and drying processes and to capture a tidal bore like phenomenon. The developed model was validated with several benchmark test problems including the two-dimensional dam-break problem. The model results were well agreed with results of other models and experimental results in literature. The unstructured triangular and quadrilateral combined grid system was successfully implemented in the model, thus the developed model would be more flexible when applying in an estuarine system, which includes narrow channels. Then, the model was tested in Mobile Bay, Alabama, USA. The developed model reproduced water surface elevation well as having overall Predictive Skill of 0.98. We found that the primary inlet, Main Pass, only covered 35% of the fresh water exchange while it covered 89% of the total water exchange between the ocean and Mobile Bay. There were also discharge phase difference between MP and the secondary inlet, Pass aux Herons, and this phase difference in flows would act as a critical role in substances’ exchange between the eastern Mississippi Sound and the northern Gulf of Mexico through Main Pass and Pass aux Herons in Mobile Bay.

Due to accelerated anthropogenic activity, a significant amount of pollutants has been directly or indirectly discharged into coastal estuaries of Kampar. Nutrient pollution along the river to the estuary that adversely affects coastal and estuary ecosystem mainly originates from inland such as industrial effluent, household, and agricultural waste as well as a naturally derived pollutant from biogeochemical cycle, which is controlled by the propagation of undular bore ( Bono ) . The purpose of this study is to determine the environmental impact of distribution of nutrients caused by the mechanism of Bono. This research employed a purposive quantitative method, the concentration of dissolved phosphate, nitrate, nitrite and ammonia was analyzed using a spectrophotometer, tidal data retrieval was measured for 30 days’ near the estuarine area, while, current flow was measured for 24 hours’ measurement. Phosphate concentrations ranged from 0.02-0.1 mg.L -1 , nitrate concentrations ranged from 0.76-5.73 mg.L -1 , ammonia concentrations ranged from 0.2-0.41 mg.L -1 , nitrate concentrations ranged from 0.001-0.03 mg.L -1 . The tidal type is mixed tide prevailing semidiurnal with tidal range reach 4.2 m during spring tide condition. At the time of Bono propagate, drastically enhance the surface elevation and directly increase the drift of velocity with the flow direction from estuary into the river upstream, that mechanism affects the nutrient distribution in Kampar river. Keywords : Bono, Fluid dynamics, Nutrient distribution, Tidal bore, Water quality

Recent studies suggest that tidal forcing can be as important as gravitational circulation in maintaining an estuarine turbidity maximum (ETM). It is further postulated that a long-term mass balance between the import and export of sediment in an estuary may require episodic large river discharges or ‘freshets’ to flush sediment out of the ETM towards the open sea. In this study, we use a 2-month data set from a mooring in a tidal river that drains into a large drowned-river-valley estuary (Kaipara Harbour, New Zealand) to investigate interactions between tidal-current asymmetry and gravitational circulation. During baseflow river discharge and on spring tides, suspended-sediment transport was directed up-channel (landwards), driven by tidal pumping due to tidal-current asymmetry. During neap tides, the suspended-sediment flux was approximately zero. The data suggest that the bed was not locally erodible and that bed sediments at the site were being supplied by an ETM. The ETM only migrated far enough down channel to be observed at the mooring site during spring tides when the tidal excursion was longer. Suspended sediments were effectively trapped and recycled within the ETM. During and after two freshets, high river discharge displaced saline water from the tidal river, water-column stratification strengthened and the surface and bed current speeds increased. As a result, the advective component of the down-channel directed suspended-sediment flux increased. This provided a transport pathway for sediment out of the otherwise tidally pumped, flood-dominant system. We conclude that largest export of sediments out of the tidal river would potentially occur when a large freshet coincides with an apogean spring tide.

Although there have been studies on the tide in convergent bay (or estuary), the tide change in terms of phase speed, amplitude, and phase difference between elevation and tidal current from a coastal ocean to a convergent bay has not been clearly shown so far. This study systematically examines the change of tidal wave characteristics from the eastern Yellow Sea to the Asan Bay, a strongly convergent bay on the west coast of Korea, using observations and an analytical model. As the tidal wave propagates from the eastern Yellow Sea into the Asan Bay, the phase speed, amplitude, and phase difference between elevation and tidal current increase along the channel. Such a phenomenon represents a unique example of tide change from a coastal ocean to a convergent bay, indicating dominance of convergence over friction in the Asan Bay. Both analytically computed tidal amplitude and travelling time compare well with observations. In the Asan Bay, the influence of the reflected wave is only felt in the upper one fifth of the bay and is almost unperceivable in the rest of the bay. The analytical analyses presented in this paper are particularly useful for understanding the relative importance of channel convergence, bottom friction, and reflected wave on the tidal characteristics change along the channel and the proposed method could be applicable to other estuaries.

In this paper, the effect of the dike line adjustment on the Qiantang Tidal Bore (QTB) is studied by physcial experiments. A lab-scale physical model of the Qiantang Estuary is built and the tidal bore is generated. With this model, the formation and pro-pagation processes of the tidal bore are simulated with or without the dike line adjustment. It is shown that the adjusted dike line changes the direction of the reflected tidal bore. The height of the tidal bore increases in the upstream region where the dike line is contracted. In the tested bent and forking regimes, the bore height at the upstream station is increased by 0.10 m and 0.04 m, respectively. Furthermore, the crossing bore still exists near the Daquekou station and the location slightly moves by about 3 km to the downstream region.

A field study was undertaken to understand the possible effect of stratification on the vertical structure of the M 2 semidiurnal tidal ellipses in the Changjiang River estuary. A pycnocline occurs at each station along the North Passage on a neap tide only. Calculated potential energy anomalies within the North Passage are 100–200 J·m−3 larger on a neap tide than on a spring tide. The tidal ellipses degenerate to rectilinear motion at each layer of the water column at each station along the North Passage, while they rotate clockwise at each station over the Hengsha Shoal. The surface-to-bottom inclination angle difference of the tidal ellipse at a seaward station is 40° on a neap tide but a few degrees on a spring tide. The vertical phase shifts of the tidal ellipses range from 20° to 50° at most stations along the North Passage on a neap tide, while they are less than 10° on a spring tide. Rapid changes in the inclination angles and phase shifts of the tidal ellipses occur at the pycnocline. An abrupt reduction in the vertical eddy viscosity at the pycnocline seems to be the major cause for the vertical variability of ellipticity, inclination angle and phase of the tidal ellipses on a strongly stratified neap tide. The surface-to-bottom ellipticity difference appears to have a positive linear relation with the overall Richardson number mainly along the North Passage on a neap tide. A one-dimensional coastal model with vertical turbulence closure scheme seems to be able to reproduce the major features of the vertical structure of the tidal ellipses at a seaward station on a spring tide.