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A tidal bore is a positive surge taking place during the flood tide with a large tidal range and the bore corresponds to the leading edge of the tidal wave propagating upstream. In this study, some physical modelling was performed to investigate the upstream bore propagation over fixed and movable gravel beds. Both undular and breaking bores were tested. The free-surface and velocity measurements were complemented by some observations of particle motion beneath the bore front. In the initially-steady flow and beneath undular bores, no sediment motion was observed for the experimental set-up. Beneath breaking bores, on the other hand, some upstream gravel bed load motion was observed behind the bore. The gravel bed particles were de-stabilized by the roller toe passage and advected upstream. The unsteady velocity data showed some damping of the transient recirculation on the movable gravel bed.

The East Japan tsunami of 11 March 2011 propagated more than 100 km upstream in the Columbia River. Visual analysis of its records along the river suggests that the tsunami propagation was strongly affected by tidal conditions. A numerical model of the lower Columbia River populated with tides and a downstream current was developed. Simulations of the East Japan tsunami propagating up the tidal river reproduced the observed features of tsunami waveform transformation, which did not emerge in simulations of the same wave propagating in a quiescent-state river. This allows us to clearly attribute those features to nonlinear interaction with the tidal river environment. The simulation also points to possible amplification of a tsunami wave crest propagating right after the high tide, previously deduced from the recordings of the 1964 Alaska tsunami in the river.

Eleven repeat reciprocal sound transmission experiments for current measurements were successful carried out from April 2009 to May 2010 in the Qiantang River, China. Ubiquitous are tidal bore intrusions that occur during spring tides in Hangzhou Bay. The experimental site is about 90 km away from the mouth of Hangzhou Bay. The coastal acoustic tomography (CAT) system consisted of two acoustic transceiver units, one on each side of the river, separated by 3050 m. During the sound transmission experiments, 42 shipboard acoustic Doppler profiler (ADP) surveys were also performed along the sound transmission line to obtain validation data for reciprocal sound transmission data. The average current along the vertical section, determined from the travel time difference between the reciprocal data, was in excellent agreement with the ADP results, with a root-mean-square difference of 0.04 m s −1 . The sudden variations in river discharge caused by the passage of tidal bores were captured well by the CAT. The river discharge ( Q CAT ) measured by CAT had a mean value of 2170 m 3 s −1 but varied between −9097 m 3 s −1 and 7985 m 3 s −1 during the bore events. For the periods with no tidal bores, the water level data were well correlated with the steady river discharges estimated from the CAT data. By using the empirical relationship between these two variables, the annual river discharge ( Q WL ) was predicted in the range from 914 m 3 s −1 to 11,982 m 3 s −1 , with a mean of 2737 m 3 s −1 . A comprehensive discussion of the potential sources of error is presented. The resultant Q WL error (621 m 3 s −1 ) is small compared with the range of Q WL (11,068 m 3 s −1 ), implying that the proposed method for estimating river discharge is acceptable. The present study provides an efficient way for the long-term monitoring of river discharge in large tidal rivers with heavy shipping traffic, such as the Qiantang River.

A tidal bore is a series of waves propagating upstream in the river mouth as the tidal flow turns to rising in macro-tidal conditions. Some related geophysical processes include the tsunami-induced bores and uprushing bores on beaches. In the present study, the inception of sediment motion beneath tidal bores was investigated physically. No sediment motion was observed in the initially steady flow and beneath undular bores. A transient sheet flow motion was observed beneath breaking bores and the onset of sediment motion was closely linked with the passage of the roller toe. The forces acting on the movable gravel bed particles were estimated from the physical measurements. The results showed that the longitudinal pressure gradient force was the dominant contribution de-stabilising the particles and inducing the onset of sediment motion. The drag force added a sizeable contribution to maintain the upstream particle motion, although the entire sheet flow motion was brief.

A tidal bore is an unsteady flow motion generated by the rapid water level rise at the river mouth during the early flood tide under macrotidal and appropriate bathymetric conditions. This paper presents a study that physically investigates the turbulent properties of tidal bores. Results from some experimental measurements of free-surface fluctuations and turbulent velocities conducted on smooth and rough beds are reported. The free-surface measurements were conducted with Froude numbers of 1-1.7. Both undular and breaking bores were observed. Using an ensemble-averaging technique, the free-surface fluctuations of breaking tidal bores are characterized. Immediately before the roller, the free-surface curves gradually upwards. The passage of the bore roller is associated with some largewater elevation fluctuations; the largest free-surface fluctuations are observed during the first half of the bore roller. The turbulent velocity measurements were performed at several vertical elevations during and shortly after the passage of breaking bores. Both the instantaneous and ensemble-averaged velocity data highlight a strong flow deceleration at all elevations during the bore passage. Close to the bed, the longitudinal velocity component becomes negative immediately after the roller passage, implying the existence of a transient recirculation. The height and duration of the transient are a function of the bed roughness, with a higher and longer recirculation region above the rough bed. The vertical velocity data presented some positive, upward motion beneath the front with increasing maximum vertical velocity with increasing distance from the bed. The transverse velocity data show some large fluctuations with nonzero ensemble average after the roller passage that highlight some intense secondary motion advected behind the bore front. DOI: 10.1061/(ASCE)HY.1943-7900.0000542. © 2012 American Society of Civil Engineers.

A tidal bore may develop in an estuary during the spring tide conditions when the tidal range exceeds 5–6 m and the flood tide is confined to a narrow funnelled estuary with low freshwater levels. The tidal bore is of great importance for the geomorphology of the estuarine zone. In this study, some physical modelling was performed to investigate the sediment motion inception beneath a tidal bore on a movable gravel bed. The results show the significant impact of breaking bore propagation on the gravel bed motion. The dominant contribution to sediment transport inception is the longitudinal pressure gradient force, while the transient recirculation motion next to the bed yields to a drag force acting in the upstream direction and contributing to sediment motion.

In an open channel, a sudden rise in free-surface elevation is associated with the development of a bore. The bore front is a hydrodynamic shock with a sharp discontinuity in terms of water depth and velocity field. In this study, some turbulent velocity measurements were conducted in breaking bores. The unsteady turbulent properties were analysed using three methods: an ensemble average (EA) technique based upon 20 repeated experiments, a variable interval time average (VITA) method based upon a single experiment, and the variable interval time average (VITA) method averaged over 20 experimental runs. The instantaneous free-surface and velocity measurements showed a marked effect of the bore front passage. The longitudinal velocity components were always characterised by a rapid flow deceleration at all vertical elevations, and some large fluctuations of all velocity components were recorded beneath the surge. The EA and VITA methods showed some comparable long-term trends superposed to some rapid turbulent fluctuations, as well as close results in terms of the turbulent Reynolds stress components. The VITA data based upon a single run presented some differences with the EA median results, but all methods exhibited comparable long-term trends superposed to rapid turbulent fluctuations.

A tidal bore is a unique Earth surface process, characterized by its highly destructive energy, predictable periodicities and magnitudes, and the production of characteristic sedimentary features. Tidal bores and associated rapid flood flows are highly turbulent flows of the upper-flow regime with a velocity over several meters per second. Reynolds (Re) and Froude (Fr) numbers, respectively, are larger than 104 and 1.0, making them significantly different from regular tidal flows but analogous to turbidity currents. Until now, understanding of tidal-bore depositional processes and products has been limited because of the difficulty and hazards involved with gauging tidal bores directly. The Qiantang bore is known as the largest breaking bore in the world. Field surveys were carried out in May 2010, along the north bank of the Qiantang Estuary to observe the occurrence of peak bores, including regular observations of current, water level and turbidity at the main channel. Several short cores were sampled on the intertidal flats to study the characteristic sedimentary features of tidal bores. Hydrodynamic and sedimentological studies show that the processes of sediment resuspension, transport and deposition are controlled primarily by the tidal bores, and the subsequent abruptly accelerated and decelerated flood flows, which only account for one tenth of each semidiurnal tidal cycle in the estuary. Tidal-bore deposits are generally poorly sorted because of rapid sedimentation after highly mixed suspension by intense turbulence. This behavior is characteristic of the absence of tractive-current depositional components in a C-M diagram. It also goes along with well-developed massive bedding, graded bedding, basal erosion structures, convolute bedding and dewatering structures. Together, these sedimentary features can constitute fingerprinting of turbidites, widely distributed in the deep-water environment. However, a tidal bore is triggered by intensely deformed tidal waves propagating into a shallow-water environment, which returns to regular tidal flows rapidly after the passage of the bore head. The tidal-bore deposits are usually bounded by the intertidal-flat deposits with typical tidal beddings at the top and on both flanks. The difference between tidal-bore deposits (TBD) and tidal sandy/muddy deposits (TSD/TMD) is evident not only in sedimentary structures, but also in the grain-size composition. They can be clearly distinguished in grain-size bivariate plots, typically the plot of mean grain size vs. standard deviation (or sorting). Some trend variations generally exist in mean grain size with TBD>TSD>TMD, sorting with TMD>TBD>TSD (larger value indicating poorer sorting), and both skewness and kurtosis with TSD>TBD>TMD. These findings will undoubtedly shed new light on our understanding of tidal-bore sedimentology, ancient tidal-bore sedimentary facies and environments, and related oil-and-gas field prospecting.

The interaction of river flow, tidal mixing, basin morphology and wind produces a different type of river plume in the Pearl River Estuary. In this paper, a three-dimensional numerical model has been used to study the response of the river plume to different forcings in the Pearl River Estuary. The results indicate that river discharge determines the font size of river plume, while wind greatly affects its shape. Tidal current can restrict diluted water spreading seaward, but contributes little to the net transport of low salinity water. The flushing time can increase by 2 times when considering the Coriolis force, which delays the diluted water flowing out of the flushing area. Southwest winds can greatly decrease the flushing time, while northeast winds can increase it. This rule can also be valid when considering tides.

In the southeast coastal zone of Yellow Sea, the tide characteristics showing ebb-dominant tide and tidal flow were confirmed by analysis of observed tide and tidal currents. Physical factors generating asymmetric tide were reviewed. Influence of bottom shear stress, tidal flat, and nonlinear terms in shallow water equations was investigated by two-dimensional tide modeling. The model results gave good agreements with observed tides, but the amplitude of simulated tide was less than that of observed tide. The tidal flats existing in the study area widely have great effect on the generation of nonlinear tide. The M4 tide is mainly generated near the tidal flats. The deletion of tidal flats prevents the production of the M4 tide. We can conclude that the wide tidal flats is a primary cause of tide asymmetry in the study area.

The study details new sediment concentration measurements associated with some turbulence characterisation conducted at high-frequency in the undular tidal bore of the Garonne River (France). Acoustic Doppler velocimetry was used, and the suspended sediment concentration was deduced from the acoustic backscatter intensity. The field data set demonstrated some unique flow features of the tidal bore including some large and rapid turbulent velocity fluctuations during and after the bore passage. Some unusually high suspended sediment concentration was observed about 100 s after the tidal bore front lasting for more than 10 min. It is thought that the tidal bore passage scoured the bed and convected upwards the bed material, reaching the free-surface after the bore passage. Behind the tidal bore, the net sediment flux magnitude was 30 times larger than the ebb tide net flux and directed upstream. A striking feature of the data set was the intense mixing and suspended sediment motion during the tidal bore and following flood tide. This feature has been rarely documented.

We examine rimming flows, i.e. flows of a liquid film on the inside of a horizontal rotating cylinder. So far this problem has mostly been explored using the so-called lubrication approximation (LA). It was shown that, if the volume of the liquid in the cylinder exceeds a certain threshold, then a shock similar to a tidal bore appears in the lower half of the cylinder on its rising side. The position of the shock can be characterized by the polar angle θ s, with a value between θ s = −90° (the bottom of the cylinder) and θ s = 0° (the horizontal direction). In this study, we examine rimming flows without the LA, by solving numerically the exact Stokes equations. It is shown that a steady solution describing a (smoothed) shock exists only if $${-60^{\circ}\lesssim\theta_{\rm s}

Tidal bore is a series of waves propagating upstream as the tidal flow turns to rising. The Qiantang Bore has aroused the curiosity of scientists and tourists all over the world in the past centuries as a strong turbulent bore. We consider here tidal bore impact measurements, recorded in the Qiantang River using pressure transducers. Based on the empirical mode decomposition (EMD) algorithm, a signal processing method for impact test due to the Qiantang Bore is proposed. As a self-adaptive approach, EMD method can be used to decompose the local characteristics of the no-stationary and nonlinear signals into several fluctuations and trend items with different time scales step by step. The separation of the quasi-static and dynamic pressures is conducted by using the empirical mode decomposition method.

The Bay of Fundy in eastern Canada has the highest tides in the world. Harnessing the tidal energy in the region has long been considered. In this study, the effects of tidal in-stream energy extraction in the Minas Passage on the three-dimensional (3D) tidal circulation in the Bay of Fundy (BoF) and the Gulf of Maine (GoM) are examined using a nested-grid coastal ocean circulation model based on the Princeton Ocean Model (POM). The nested-grid model consists of a coarse-resolution (~4.5 km) parent sub-model for the GoM and a high-resolution (~1.5 km) child sub-model for the BoF. The tidal in-stream energy extraction in the model is parameterized in terms of nonlinear Rayleigh friction in the momentum equation. A suite of numerical experiments are conducted to determine the ranges of extractable tidal in-stream energy and resulting effects on the 3D tidal circulation over the Bay of Fundy and the Gulf of Maine (BoF-GoM) in terms of the Rayleigh friction coefficients. The 3D model results suggest that the maximum energy extraction in the Minas Passage increases tidal elevations and tidal currents throughout the GoM and reduces tidal elevations and circulation in the upper BoF, especially in the Minas Basin. The far-field effect of tidal energy extraction in the Passage on the 3D tidal circulation in the BoF-GoM is examined in two cases of harnessing tidal in-stream energy from (a) the entire water column and (b) the lower water column within 20 m above the bottom in the Passage. The 3D model results demonstrate that tidal in-stream energy extraction from the lower water column has less impact on the tidal elevations and circulation in the BoF-GoM than the energy extraction from the whole water column in the Minas Passage.

A positive surge results from a sudden change in flow that increases the depth. It is the unsteady flow analogy of the stationary hydraulic jump and a geophysical application is the tidal bore. Positive surges are commonly studied using the method of characteristics andthe Saint-Venant equations.Thearticle presents the results fromnewexperimental inves- tigations conducted in a large rectangular channel. Detailed unsteady velocity measurements were performed with a high temporal resolution using acoustic Doppler velocimetry and non-intrusive free-surface measurement devices. Several experiments were conducted with the same initial discharge (Q = 0.060m 3 /s) and six different gate openings after closure resulting in both non-breaking undular and breaking bores. The analysis of undular surges revealed wave amplitude attenuation with increasing distance of surge propagation were in agreement with Ippen and Kulin theory. Also, undular wave period and wave length data were relatively close to the values predicted by the wave dispersion theory for gravity waves in intermediate water depths.

Power levels available from the kinetic energy of tidal flows can be significant in coastal or estuarine regions with relatively modest tidal ranges. For example, the central Maine coast, where the mean semi-diurnal tidal range is about 3 m, includes several river estuaries with narrow interconnecting passages where tidal currents exceed 2 m s−1. A numerical circulation model applied to this region shows that the vigorous tidal flows lead to available power peaks exceeding 3 kW per square meter of turbine aperture in several sites during a spring tide. At one promising location, the peak power density is 6.5 kW/m2 near the surface and the energy capacity in a 500 m2 section under mean tidal conditions is about 2700 MWh per year, sufficient to meet the average consumption needs of about 150 homes connected to an electrical grid capable of accepting the tidal power pulses and blending them with traditional sources.

The nonlinear distortion of the astronomic tide in the Lower St. Johns River is investigated. Computed tidal elevations are analyzed at various locations within the Lower St. Johns River. The modeling approach first evaluates the boundary condition applied at the open ocean with regards to it providing a complete description of the tidal elevation, followed by numerical experimentation and a tidal constituent analysis that examines the effects of finite wave amplitude, advection, and bottom friction towards distorting the tide as it propagates upriver. The distortions caused by each nonlinear source are presented in both the time and frequency domains. Analysis at observation stations reveals a river tide with more coastal characteristics near the mouth and with more considerable distortion upriver. The spectroscopy of the astronomic tide for the Lower St. Johns River is established in terms of a custom set of tidal constituents.

The present study examines the free-surface properties of undular tidal bores observed for 1 < F < 1.5-1.8. The analysis is based on some new experimental results together with a reanalysis of both field and laboratory data. The free-surface profiles followed a pattern somehow similar to the sinusoidal and cnoidal wave shapes, although neither captures the fine details of the undulation profiles. The wave properties highlighted some maxima in amplitude and steepness for a Froude number of about 1.3-1.4 corresponding to the apparition of some wave breaking at the first wave crest.

PAN, C. and HUANG, W., 2010. Numerical modeling of suspended sediment transport in Qiantang River: an estuary affected by tidal bore. Journal of Coastal Research, 26(6), 1123–1132. West Palm Beach (Florida), ISSN 0749-0208. Study of suspended sediment transport in an estuary affected by tidal bore is important for coastal engineering and management because the tidal bore can cause strong sediment resuspension and scour in shallow waters. Numerical modeling of suspended sediment transport in a natural estuary affected by tidal bore is such a challenging research topic that there are few articles on the subject available in the literature. In this study, a two-dimensional, numerical model was developed to investigate suspended sediment transport induced by a tidal bore. The hydrodynamic component of the model employs the Godunov-type scheme with second-order accuracy in space, which effectively describes the rapid supercritical flow and sharp horizontal pressure gradients of the tidal bore. To preserve balance between the source terms and the internal forces, both the water level–bottom topography formulation (WLTF) method and a special technique for triangular mesh have been applied to solve the source term in the model equations to account for the irregular bottom topography. The wet/dry boundary issue was solved by using the improved exact-Riemann solver on the dry bed. The coupled sediment transport model incorporates more reliable equations from recent publications to characterize the rapid increase of sediment resuspension in the water column. The model test against an analytical solution of convection transport shows that the sharp gradient of scalar transport is satisfactorily estimated in the model simulations. The model in the application has been validated to simulate hydrodynamics and suspended sediment transport affected by a tidal bore in the Qiantang River of China. The results compare well with a time series of observations to characterize the rapid increases of surface elevation, currents, and suspended sediment concentration resulting from the tidal bore. Results of spatial distributions of water levels and currents indicate that the model adequately describes the sharp horizontal gradients of the surface elevation and the tidal currents during the passage of the tidal bore and characterizes the suspended concentrations in the estuary.

A tidal bore develops in an estuary when the tidal range exceeds 4.5–6 m and the estuarine bathymetry amplifies the tidal wave. The bore is an abrupt rise in water depth associated with a discontinuity in velocity and pressure fields at the front. Herein the free-surface properties and the turbulent mixing of light-weight particles were investigated during the passage of tidal bores. The free-surface properties were recorded using a non-intrusive technique, while particle tracking was performed under undular and breaking bores. A basic result was the identification of a broad spectrum of particle trajectories, linked with the existence of large-scale vortical structures. These turbulent structures were responsible for the vertical water mixing as a tidal bore propagates upstream in an estuary. The large-scale eddies were also responsible for the rapid longitudinal dispersion of particulates, such as fish eggs, with some form of preferential motion, depending upon the particle's vertical elevation.

The process of tidal bore passing through bridge piers is numerically simulated in an open channel using a pure Lagrangian method, i.e. Smooth Particle Hydrodynamics (SPH). Due to its “gridless” feature, SPH is intrinsically well-suited for the complex hydrodynamic simulation when the fluid encounters a structure. The behavior of bores propagation along the channel is illustrated herein and includes the bore's free surface properties and flow field, and in particular, the intricate behavior of unsteady flow during the passage of tidal bore. The generation of shock waves between the structures can be clearly observed in the numerical experiment. Intense vortical structures behind the bore front are generated as the bore propagate through the constriction.

Shenzhen River is a tidal river on the border between Hong Kong and Shenzhen. It flows southwest towards Deep Bay in the Pearl River Estuary in south China. In the past, Shenzhen River was narrow, meandering and only capable of conveying floods of return period 2–5 years. To alleviate the flooding hazard, Hong Kong and Shenzhen governments have carried out the Shenzhen River Regulation Project jointly since 1995. The river downstream has been trained to cater for flooding of 50-year return period. However, unexpectedly, the trained Shenzhen River has been seriously silted by 3 m of sediment 5 years after the completion of river training. This diminishes the effectiveness of river training on enhancing flood discharge capacity. We present a study on the impact of river training on Shenzhen River hydraulics by an integrated three-dimensional numerical hydrodynamic model. The model is verified against field data and shows good agreement with the observed hydrodynamics; wetting and drying of inner Deep Bay tidal flats are successfully simulated. The model simulations show that river training has drastically altered the hydraulics of Shenzhen River. Tidal propagation in the river has changed from a damped tidal oscillation to a more standing wave character with less amplitude damping. Tidal current is reduced by about 50%. Vertical salinity stratification and gravitational circulations are formed within the trained river in the dry season. The bottom upstream residual current in the two-layered residual circulation strongly suggests the input of sediment from Deep Bay and sediment trapping in the river.

In a sedimentological sense a fluvial to tidal transition zone can be defined in rivers as a zone that separates the upstream fluvial from the downstream estuarine zone. Characteristic sedimentary structures within this zone are notoriously difficult to recognize. This study demonstrates the influence of tidal modulation within the most proximal part of the fluvial-tidal transition zone (i.e. the ‘backwater zone’) of an ancient fluvial system. Criteria have been established to differentiate between purely fluvial facies and those modulated by tidal energy. The stratigraphic interval from which the data were derived is the Lourinha Formation (Late Jurassic) of the Lusitanian Basin, Western Portugal. An analysis of sedimentary features at four key localities has identified a temporal spectrum of tidal influence ranging from the daily modulation of fluvial flows to the effects of tidal bore passage. A combination of quantitative and qualitative data reveals systematic changes in the internal architecture of dune-scale bedforms deposited in a channel-floor setting. The key co-occurring features are: (i) increasing-decreasing organic particle concentration; (ii) increasing-decreasing bottomset thickness; (iii) increasing-decreasing foreset dip and shape (from convex to concave); and (iv) increasing-decreasing brinkpoint height. Collectively, these features are interpreted as having been produced by successive fluctuations in flow regime conditions from lower (during flood tidal retardation) to higher (during ebb tidal drawdown) current velocities. Bedforms showing these features occur in both meandering fluvial channels and straighter distributary systems. In addition, several examples of a specific type of stepped erosion surface and draping sediment have been recognized, the interpretation of which strongly suggests generation by the passage of tidal bores. If this interpretation is correct, then it represents one of the first published examples of tidal bore propagation in ancient fluvial systems. Palaeoclimatic evidence (cellular analysis of woody tissue, palaeosol character and plate reconstruction) indicates a warm, seasonal, winter wet to summer dry climate during deposition of the Lourinha Formation. From this evidence it is suggested that tidal modulation and tidal bore effects are more likely to develop in the ‘dry season’, when fluvial flow in the main river channels was reduced.

A numerical model was developed based on the Cubic-Interpolated Pseudo-particle (CIP) Combined Unified Procedure (CIP-CUP or C-CUP) method equipped with a Large Eddy Simulation (LES) model and a re...

A tidal bore is a wave propagating upstream as the tidal flow turns to rising. It forms during spring tide conditions when the flood tide is confined to a narrow funneled channel. To date, theoretical and numerical studies rely upon physical experiments to validate the developments, but the experimental data are limited mostly to visual observations and sometimes free-surface measurements. Herein turbulent velocity measurements were obtained in a large-size laboratory facility with a fine spatial and temporal resolution. The instantaneous velocity measurements showed rapid flow deceleration at all vertical elevations, and large fluctuations of all velocity components were recorded beneath the bore and secondary waves. A comparison between undular (nonbreaking) and breaking bores suggested some basic differences. In an undular bore, large velocity fluctuations were recorded beneath the first wave crest and the secondary waves showing a long-lasting effect after the bore passage. In a breaking bore, some la...

A tidal bore may occur in a macro-tidal estuary when the tidal range exceeds 4.5–6 m and the estuary bathymetry amplifies the tidal wave. Its upstream propagation induces a strong mixing of the estuarine waters. The propagation of undular tidal bores was investigated herein to study the effect of bridge piers on the bore propagation and characteristics. Both the tidal bore profile and the turbulence generated by the bore were recorded. The free-surface undulation profiles exhibited a quasi-periodic shape, and the potential energy of the undulations represented up to 30% of the potential energy of the tidal bore. The presence of the channel constriction had a major impact on the free-surface properties. The undular tidal bore lost nearly one third of its potential energy per surface area as it propagated through the channel constriction. The detailed instantaneous velocity measurements showed a marked effect of the tidal bore passage suggesting the upstream advection of energetic events and vorticity “clouds” behind the bore front in both channel configurations: prismatic and with constriction. The turbulence patches were linked to some secondary motions and the proposed mechanisms were consistent with some field observations in the Daly River tidal bore. The findings emphasise the strong mixing induced by the tidal bore processes, and the impact of bridge structures on the phenomenon.

Tidal models for the Bay of Fundy, Canada — site of the highest recorded modern tide — show that tidal amplification began in the early Holocene and by ca. 5000 BP the range was almost 80% of the present range. Empirical data consisting of 146 sea-level index points and other observations appear to contradict model results. Aggregated relative sea-level data for Chignecto Bay and Minas Basin show that rapid tidal expansion began ca. 3400 BP. However, if we separate these two geographically separate data sets, evidence for this rapid late-Holocene tidal expansion is confined to Minas Basin. We explain this singularity by positing a barrier at the mouth of Minas Basin, at the Minas Passage, that delayed tidal expansion. With the rapid breakdown of this barrier and near-instantaneous tidal expansion, water temperature dropped, tidal currents and turbidity increased, and the form of the inner estuary was changed from lagoonal–mesotidal to macrotidal. We argue that the catastrophic breakdown of the barrier is related in the aboriginal legend of Glooscap, showing that aboriginal peoples observed the rapid environmental changes and preserved an oral record for 3400 years.

Substantial temperature drops in the Dongsha Atoll with diurnal period have been reported and considered to be the result of an internal solitary wave (ISW). The cold water event occurs daily with duration of a few hours, a time scale much longer than that of the ISW. To further understand the physical process, a detailed numerical simulation on the interaction of the Dongsha Atoll and the ISW is carried out using the Princeton Ocean Model. Internal solitary waves are found to merge, become asymmetric, and break in the shoaling process. Then, a violent tidal bore forms and runs up the slope as a bolus, bringing up cold deep water to the shallows. The simulated temperature variation and flow field in November are very similar to the largest temperature drop in the field measurement where the flow field is dominated by the ISW. In the merging process, three ISWs become one longer wave lengthening the time scale of the cooling process compared with that of a single ISW. The step around the atoll also contributes substantially by increasing the exposure time of the local ecosystem to the cold deep water. The same calculation in the absence of the step yields a much shorter time for the cold water cycle.

A new method of integrating satellite remote sensing data and inundation models allows the mapping of extensive tidal mudflats in a sub-Arctic estuary, Cook Inlet (CI), Alaska. The rapid movement of the shorelines in CI due to the large tides (~10 m range) is detected from a series of Landsat imagery taken at different tidal stages, whereas GIS tools are used to identify the water coverage in each satellite image and to extract the coordinates of the shoreline. Then, water level along the shoreline for each satellite image is calculated from the observed water level at Anchorage and the statistics of an inundation model. Several applications of the analysis are demonstrated: 1. studying the dynamics of a tidal bore and the flood/ebb processes, 2. identifying climatic changes in mudflats morphology, and 3. mapping previously unobserved mudflat topographies in order to improve inundation models. The method can be used in other regions to evaluate models and improve predictions of catastrophic floods such as those associated with hurricane storm surges and tsunamis.

A tidal bore is a natural and fragile phenomenon, which is of great importance for the ecology of an estuary. The bore development is closely linked with the tidal range and the river mouth shape, and its existence is sensitive to any small change in boundary conditions. Despite their ecological and cultural value, little is known on the flow field, turbulent mixing and sediment motion beneath tidal bores. Indeed, some striking features can be highlighted in two-dimensional simulations, such as large velocity fluctuations and flow recirculation structures. Using Large Eddy Simulation method, the numerical results emphasised the complicated turbulent structures and their unsteadiness under a tidal bore.

Recently, an increase in the load from the land and a food scatter of aquaculture causes eutrophication in IMARI Bay. Therefore, red tides have been generated. It is necessary to decrease the red tide. So, as a basic research, we clarify the characteristics of flow structure and water quality by means of field observations and a numerical model. As a consequence, it is clear that flow structure around bay mouth is very complex. Bay water flows out in the upper layer during ebb tide, and outer sea water flows into the lower layer during flood tide. It is realized that the tidal exchange is strong comparatively in the western part of the bay, while it is weak in the central and south-eastern part.

In open channels, a sudden rise in water elevation generates a positive surge. Positive surges are commonly observed in man-made channels (Bazin 1865, Treske 1994) and a natural occurrence is the tidal bore in macro-tidal estuaries (Tricker 1965, Chanson 2011a). The positive surge may propagate upstream or downstream (Fig. D1). It is a rapidly-varied flow and the flow properties immediately upstream and downstream of the front must satisfy the continuity and momentum principles (Rouse 1938, Liggett 1994). The authors investigated positive surge waves in a long channel with a range of sidewall configuration. Their configuration corresponded to a downstream surge configuration (Fig. D1, right). The contribution is a welcome addition to the literature on rapidly-varied unsteady open channel flows. In this discussion, it is shown that the effects of boundary friction were previously documented, and a recent investigation provided some insight into the energy dissipation induced by large-scale sidewall roughness.

A tidal bore is a series of waves propagating upstream as the tidal flow turns to rising. It forms during the spring tide conditions when the tidal range exceeds 5–6 m and the flood tide is confined to a narrow funnelled estuary with low freshwater levels. A tidal bore is associated with a massive mixing of the estuarine waters that stirs the organic matter and creates some rich fishing grounds. Its occurrence is essential to many ecological processes and the survival of unique eco-systems. The tidal bore is also an integral part of the cultural heritage in many regions: the Qiantang River bore in China, the Severn River bore in UK, the Dordogne River in France. In this contribution, the environmental, ecological and cultural impacts of tidal bores are reviewed, explained and discussed.

Nonlinear shallow water equations are employed to model the inviscid slumping of fluid along an inclined plane and analytical solutions for the motion are derived using the hodograph transformation to reveal the run-up and the inception of a bore on the backwash. Starting from rest, the fluid slumps along the inclined plane, attaining a maximum run-up, before receding and forming a relatively thin and fast moving backwash. This interacts with the less rapidly moving fluid within the interior to form a bore. The evolution of the bore and the velocity and height fields either side of it are also calculated to reveal that it initially grows in magnitude before diminishing and intersecting with the shoreline. This analytical solution reveals features of the solution, such as the onset of the bore and its growth and decline, previously known only through numerical computation and the method presented here may be applied quite widely to the run-up of other initial distributions of fluid. © 2009 Cambridge University Press.

Characteristics of hydrography and tidal currents were investigated in Hampyung Bay through in situ CTD data, tidal currents and elevations. According to the seasonal weather variability, hydrography showed the lower density with high temperature and low salinity in summer and the higher density with low temperature and high salinity in winter. In particular, the thermal structure like a tidal front was formed along the central channel at the neap tide of summer. The critical value of the parameter $SH(

The hydraulic jump is the sudden transition from a high-velocity open channel flow regime to a subcritical flow motion. The flow properties may be solved using continuity and momentum considerations. In this review paper, recent advances in turbulent hydraulic jumps are developed: the non-breaking undular hydraulic jump, the positive surge and tidal bore, and the air bubble entrainment in hydraulic jumps with roller. The review paper demonstrates that the hydraulic jump is a fascinating turbulent flow motion and the present knowledge is insufficient, especially at the scales of environmental and geophysical flows.

SUMMARY In this paper, the third-order weighted essential non-oscillatory (WENO) schemes are used to simulate the two-dimensional shallow water equations with the source terms on unstructured meshes. The balance of the flux and the source terms makes the shallow water equations fit to non-flat bottom questions. The simulation of a tidal bore on an estuary with trumpet shape and Qiantang river is performed; the results show that the schemes can be used to simulate the current flow accurately and catch the stronger discontinuous in water wave, such as dam break and tidal bore effectively. Copyright q 2008 John Wiley & Sons, Ltd.

A positive surge results from a sudden change in flow that increases the flow depth. New experiments were conducted in a large channel. Most positive surge tests were conducted with a horizontal be...

In macrotidal estuaries, a tidal bore may form during spring tide conditions when the flood tide is confined to a narrow channel. Most field occurrences showed well-defined undulations behind the leading wave, that is, an undular bore process. Herein, detailed free-surface and turbulence measurements were performed beneath undular bore fronts using side-looking acoustic Doppler velocimetry and nonintrusive free-surface measurement devices in a laboratory channel. Undular bores were observed for Froude numbers less than 1.7, which compared favourably with past studies. Velocity measurements with a temporal resolution of 50 Hz showed a marked effect of the bore passage. Longitudinal velocities were characterised by rapid flow deceleration at all vertical elevations, while large fluctuations of transverse velocities were recorded beneath the front. Turbulent Reynolds stress data highlighted high levels in the lower flow region, including next to the bed. Maximum normal and tangential turbulent stres...

Hydraulic engineers and researchers deal with the scientific challenges presented by turbulent flow and its interactions with the surroundings. Turbulent flows are characterised by unpredictable behaviour, and, as yet, little systematic research has been conducted in natural systems. This paper discusses the implications of recent developments in affordable instrumentation, which was previously characterised by intrinsic weaknesses that adversely affected the quality of the signal outputs. A challenging application is the unsteady turbulence field in tidal bores. The interactions between open channel flows and movable boundaries and the atmosphere illustrate another aspect of our limited knowledge. Rapid siltation of reservoirs and air entrainment in turbulent freesurface flows are discussed. In both applications, hydraulic engineers require some broad-based expertise. In turn, the education of future hydraulic engineers is of vital importance.

The under developing estuarial port Bupsung is bounded by a river and the sea, and has several well developed tidal lands, where the littoral drift is strong due to the tide and the river discharge. The study area is located at the inner part of a concave bay and has a large tidal range due to the water discharge through the Watan-chun and Junnam-dike. In beginning stage of the ocean physical impact study, the tidal modeling is very important and difficult especially in this area. Moreover, we need a model experiment after the verification of the formulated model based on ocean survey. In this study, we constructed a numerical model to the Bupsung port coastal boundaries, which varies with the past and future development and made simulation with it. The result after development shows that there is a decrease of velocity on flood current and a increase on Ebb current and the minor variation of the tide level, compared with before development.

A new double-arch structure for the gate used as tidal barrage and sluice was adopted in Caoe River Dam in China. It was a spatial structure made up of the right arch, the invert arch, the chord, etc., and was designed to bear bilateral loads. To research the cyclic behavior of the new double-arch structure, a scale-model cyclic test was conducted. First, the test setup and test method were presented in detail, and according to the test results, the cyclic behavior and failure characteristics of this structure were discussed. Then by analyzing the test cyclic envelope curve, it was found the curve was divided into three stages: the elastic stage, the local plastic stage and the failure stage at the local yield point and structural yield point. The gate model has local yield strength and structural yield strength, with both their values being bigger than that of the designing load. Therefore, the gate is safe enough for the projects. At last, dynamic property of the gate was analyzed considering additional mass of the water. It was found that the tidal bore shock would not cause resonance vibration of the gate.

A wetting and drying (WAD) algorithm is implemented in a baroclinic three-dimensional ocean circu- lation model of Cook Inlet, Alaska, where large tidal ranges (≈10 m) regularly expose extensive mudflats. The model includes tides and wind- and buoyancy-induced flows. In the upper Inlet, the model successfully simulates large amplification of tides and propagation of fast (3∼ 4ms −1 ) tidal bores over shallow mudflats. The simulated return flows during ebb expose large areas (∼100 km 2 )o f the mudflats. Medium-resolution (250- and 500-m) images obtained from the moderate resolution imaging spectro- radiometer(MODIS) instrumentsaboardthe Terraand Aqua satelliteswereused toverify the modelresults byidentifying the location, extent, and temporal changes of the exposed mudflat regions. The results demonstrate the value of operational, medium-resolution remote sensing data in evaluating the WAD model. Sensitivity tests show that WAD produces approximately 20% larger tidal amplitude and 10% slower phase than the corresponding experiment without WAD. In the deep channel of the central Inlet, the confluence of saline water of the lower Inlet with brackish water from rivers and melting ice from land around the upper Inlet produces a salinity front. At the simulated front, strong vertical circulation cells and surface convergence and currents develop, especially during the flood. The char- acteristics resemble those of "rip tides" often observed in this region.

The tidal bore at the estuary of the Qiantang River in China is one of the most spectacular bores in the world. Although it is a famous scenic spot, it may cause disasters due to its destructive power. In this paper, a new numerical model, based on a Godunov-type scheme with the water level-bottom topography formulation combined with the improved wet/dry techniques, is constructed to numeri- cally simulate the tidal bore on the Qiantang River. The simulated results using the model agree well with observed data, which shows that the model can reproduce the formation, evolution, and dissipation of the tidal bore on the Qiantang River.

The response of the Chesapeake Bay to river discharge under the influence and absence of tide is simulated with a numerical model. Four numerical experiments are examined: (1) response to river discharge only; (2) response to river discharge plus an ambient coastal current along the shelf outside the bay; (3) response to river discharge and tidal forcing; and (4) response to river discharge, tidal forcing, and ambient coastal current. The general salinity distribution in the four cases is similar to observations inside the bay. Observed features, such as low salinity in the western side of the bay, are consistent in model results. Also, a typical estuarine circulation with seaward current in the upper layer and landward current in the lower layer is obtained in the four cases. The two cases without tide produce stronger subtidal currents than the cases with tide owing to greater frictional effects in the cases with tide. Differences in salinity distributions among the four cases appear mostly outside the bay in terms of the outflow plume structure. The two cases without tide produce an upstream (as in a Kelvin wave sense) or northward branch of the outflow plume, while the cases with tide produce an expected downstream or southward plume. Increased friction in the cases with tide changes the vertical structure of outflow at the entrance to the bay and induces large horizontal variations in the exchange flow. Consequently, the outflow from the bay is more influenced by the bottom than in the cases without tide. Therefore, a tendency for a bottom-advected plume appears in the cases with tide, rather than a surface-advected plume, which develops in the cases without tide. Further analysis shows that the tidal current favors a salt balance between the horizontal and vertical advection of salinity around the plume and hinders the upstream expansion of the plume outside the bay.

To better understand the effects of river flow and tidal stage on the propagation of realistic tsunami waves up large rivers, simulations of the Columbia River (United States) were carried out. The two-dimensional depth-averaged version of the advanced circulation model was used. The model was forced with open boundary tides, tidal potential, and river flow. Simulations without tsunami waves demonstrated excellent agreement with numerous tidal gauging stations in the domain. A Cascadia Subduction Zone earthquake and associated tsunami were then considered by prescribing a rapid temporal change in the bathymetric/topographic grid. The simulations were repeated over a wide range of river flow conditions and a wide range of tidal phases. In each simulation, the tsunami was characterized in terms of the variation of its amplitude with upriver distance, how much land was inundated, and its propagation speed up the estuary. Although river flow is a dominant mechanism in the Columbia River in terms of st...

Tidal bore loads are the main control loads for Sluice gate of Cao’e River dam. Tidal bore loads are complex and influenced by many random factors, thus the Monte Carlo method is adopted to conduct a stochastic simulation analysis on such loads. Firstly, the procedure of Monte Carlo stochastic simulation analysis on structural reliability is studied, and the random variable sampling method with improved TwoDimensional Logistic Map is introduced in our study. Then, random analysis are made for the selected typical tidal bore parameters based on field observed data, including tidal bore height, velocity and flow direction. Our random analysis results indicate that the tidal bore height and velocity follow normal distribution, and the flow direction obeys uniform probability distribution. In the end, the tidal bore loads are simulated using Monte Carlo method based on our rapids vibration test data, hence allowing the impact loads of the sluice gate to be investigated. The reliability assessment of the sluice gate is conducted finally base on sampling analysis results.

Inclined heterolithic stratification (IHS) forms the upper parts of a vegetated point-bar that forms the channel bank in the fluvial–tidal transition toward the head of the Severn Estuary. Continuing accretion of IHS occurs at the level of mean high water spring tides. The IHS overlies bar sands. The channel bank is convex upward with a tidal current-eroded scarp near the level of mean high water neap tides. At the foot of the scarp is a sandy bar reworked by tidal currents and weakly bioturbated by all but the lowest neap tides. The sandy bar is within the tidal channel and sections exhibit faint horizontal lamination with occasional ripple cross-lamination, mud flasers, reactivation surfaces, and convolutions. Convolutions are ascribed to pressure fluctuations due to tidal bores. In contrast, the IHS of the point-bar consists of distinctive thin laminations of sand, silt, and clay deposited by the higher spring tides. The channel bank top is inundated by slow currents, with little opportunity for reworking, which explains the preservation of distinctive IHS. The influence of high river discharge is not evident in the depositional signature, probably due to the intense mixing of high concentration estuarine suspended sediment in all weather and seasonal conditions.