Proceedings of Coastal Dynamics 2009

The following sections are included:

• Foreword

• Contents

The causes of beach erosion in Japan are classified into four main types: (a) obstruction of longshore sand transport, (b) beach changes associated with the formation of wave-shelter zones, (c) decreased fluvial sediment supply, and (d) offshore sand mining or dredging. Of these, examples associated with the formation of wave-shelter zones and decreased fluvial sediment supply were studied, typified by the changes in beaches at Otsu and Shimobara fishing ports, Takahama Port, and along the Enshu-nada coast caused by decreased fluvial sediment supply from the Tenryu River. Such erosion is closely related to land management and the "sector-by-sector" administrative system in Japan. The prevention of beach erosion thus requires both scientific research and improved coastal management through enhancing the public consensus.

Field, laboratory and modelling studies generally agree that the rate at which bedforms develop in response to changing conditions depends upon the pre-existing state of the bed but there is currently no consensus about the nature of this dependence. This study uses a simple abstracted model to investigate the way a field of ripples responds to a step change in forcing conditions. The results show that the influence of pre-existing bedforms is significant but subtle. Large pre-existing bedforms retard the growth of new bedforms but defects in the old bedform pattern increase the rate of development even above the growth rate from a flat bed. Wavelet analysis correctly identifies the sites of new ripple growth at defects. We suggest that defects trigger new bedform growth because they are regions of relatively flat bed, with upstream perturbations. Prediction of non-equilibrium bedforms will require information on defect densities.

The performance of most operational nearshore models is less limited by the quality of model physic or numerics than by the availability of input data for initial and boundary conditions. For example, circulation and sediment transport are very sensitive to the details of bathymetry, a data field that is notoriously hard to measure well and changes rapidly. Remote sensing approaches offer an increasingly attractive solution. While active sensors like radar and LIDAR have some advantages and will be discussed, this paper will focus more on optical remote sensing through the Argus program. Starting with a discussion of the required capabilities of an ideal sampling system, the paper will discuss the technical capabilities and future directions of optical remote sensing of the nearshore. Sampling gaps will be identified and possible solutions discussed.

This study developed a real-time wave prediction system by using SWAN (Simulating WAves Nearshore) together with 10 meter wind data from "Hourly Available GPV (Grid Point Value) Atmospheric Analysis". Validation of this system was carried out by comparing predictions with observations from NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS) wave gauges during the month of December, 2007. The predicted wave heights and periods corresponded well to observed values. This system provides current and near future ocean condition estimations for locations where observational wave data is unavailable.

The parallel, unstructured-mesh SWAN model has been employed to study a tidal inlet with complex bathymetry in the Dutch Wadden Sea. The unstructured grid resolves the large-scale, O(1km) wave dynamics in the open sea whereas employing 15-20m grid-resolution over the tidal basins and flats to gain an insight of surf breaking, local wind-wave and wave-current interactions and to assess the performance of SWAN through hindcasts of storm events. Previous studies and the present study show that the default source term settings routinely underestimate the low-frequency peak energy in the wind-sea part of the spectrum and the finite-depth wave growth over nearly horizontal beds. High-resolution simulations have indicated that the accuracy is directly affected by parameterization of bottom friction, whitecapping dissipation and depth-induced wave breaking.

Waves entering the surf zone initially develop higher harmonics which disappear after two or three wave lengths. The default Lumped Triad Approximation (LTA) in the SWAN wave model generates only (persistent) second harmonics. An alternative approximation (DCTA) is suggested which is based on an analogy with quadruplet wave-wave interactions. It initially generates all (transient) higher harmonics and subsequently a smooth universal spectral tail, in agreement with observations. The DCTA is calibrated with 31 published laboratory cases and then applied to 20 other, one- and two-dimensional cases, including field cases. The conclusion is that using the DCTA instead of the LTA barely affects the significant wave height but improves the mean period and spectral tail of the computed spectra. Further improvements are expected with enhanced high-frequency dissipation.

The paper presents improved MPS methods for the prediction of wave impact pressure on a coastal structure. By focusing on the momentum conservation properties of original MPS formulations, a new pressure gradient term is proposed in a momentum conservative form. As the first modification the original MPS formulation for pressure gradient is replaced by the new term which conserves both linear and angular momentum. Second modification is made by introducing a new source term for Poisson Pressure Equation (PPE). By revisiting the derivation of the PPE in MPS method, a higher-order source term is derived based on calculating the time differentiation of particle number density. Both first and second modifications are shown to significantly reduce the spurious fluctuations in particle number density (and thus pressure) field. The improved performance of the improved methods is demonstrated through the simulations of: a static fluid, a dam break with impact, a flip-through impact, and a slightly-breaking wave impact.

The paper presents a three-dimensional Corrected MPS (3D-CMPS) method for improvement of water surface tracking in breaking waves. The Corrected MPS (CMPS; Khayyer and Gotoh, 2008) has been extended to three dimensions and a 3D-CMPS method has been developed on the basis of the 3D-MPS method by Gotoh et al. (2005b). The improved performance of the 3D-CMPS method with respect to the 3D-MPS method has been shown by simulating a plunging breaking wave and resultant splash-up on a plane slope. Furthermore, the parallelization of 3D-CMPS method with two different solvers of simultaneous linear equations, namely, namely, the PICCG-RP (Parallelized ICCG with Renumbering Process; Iwashita and Shimasaki, 2000) and SCG (Scaled Conjugate Gradient; Jennings and Malik, 1978) techniques, has been performed to enhance the computational efficiency of the calculations. This study also applies a simple dynamic domain decomposition for an optimized load balancing among the processors.

The paper presents a weakly compressible Smoothed Particle Hydrodynamics (SPH) model to investigate the wave breaking of coastal slope. The SPH method is a mesh-free Lagrangian approach which is capable of tracking the large deformations of the free surface with good accuracy. To verify this numerical simulation, three different types of wave breaking, namely, spilling, plunging and surging breaking are successfully simulated. The computations are validated against the experimental data and a good agreement is observed. The velocity and pressure distributions are analyzed and visualized. The turbulent transport mechanism including vorticity and turbulent kinetic energy on the simulation results are also investigated in further detail. The SPH modeling is shown to provide a promising tool to predict the breaking characteristics of different waves.

This paper investigates the concept of modeling cliff stability and collapse during extreme erosion events using a hybrid model method combining Weakly Compresible Smoothed Particle Hydrodynamics (WCSPH) with a particle based geotechnical stability module (GeoSPH). The WCSPH model has been developed to include a sediment transport and morphological model to predict erosion of a beach slope under a wave climate. The GeoSPH model is based on a displacement stepping method and due to its particle nature it sidesteps the mesh straining and distortion that hinders many traditional models. The model concept and future research direction is investigated and the initial results of erosion and collapse in a storm event are presented. Conventional methods of bluff collapse are often probabilistic, based on extrapolation bluff retreat rates, or reliant on an equilibrium profile, and as such struggle to adapt the predicted movement when changes occur to either the bluff or to the wave climate. Using a hybrid model of wave-driven erosion and bluff stability allows for site by site analysis and can be run without any data of past events.

It is widely assumed that incident bound long waves are released during short wave breaking, subsequently propagating to the shore as a free wave. Statements asserting this release are either unattributed, or loosely attributed to Longuet-Higgins and Stewart (1962). However, the author is unaware of convincing evidence of such release of bound long waves as a result of short wave breaking, while there appears to be strong evidence to the contrary. The author's interpretation is that Longuet-Higgins and Stewart (1962) suggest that the bound wave will decay in amplitude following short wave breaking. This is in agreement with a number of the author's data sets and some data from other recent data sets, including field observations of strong nearshore dissipation of long waves. A surf beat similarity parameter is also suggested, which distinguishes different regimes of surf beat generation.

The formation of secondary wave in a coastal zone was investigated on examples of waves measured in numerical, laboratory and field experiments. It was found that formation of secondary waves is essentially part of transformation of weakly nonlinear-dispersive waves, and it is determined by a periodic exchange of energy between the first and second harmonics. The formation of secondary waves depends on a stage of wave transformation determined of run of wave. The increasing of a dispersion caused by peculiarities of a bottom relief, not always leads to formation of a secondary waves. Ursell number cannot be a criterion of formation of secondary waves because it does not account a stage of wave transformation. In real irregular waves, which are being at different stages of transformation, visible secondary waves are the result of an interference of the secondary waves formed by different waves.

This paper investigates the spectral characteristics of low frequency fluctuations of natural wind velocity and atmospheric pressure, and the resonant evolution of long period waves by low frequency fluctuations of winds in a laboratory experiment. Laboratory experiments on the responses of wind waves under periodically fluctuating winds have been conducted to find an alternative generation mechanism for long period waves. The experiments show that the long period waves developed at the peak frequency of the low frequency fluctuations of wind speed and air pressure. Through the spectral analysis of fluctuating components of wind speed, air pressure and water surface elevation, the long period waves are found to be generated and resonantly developed by the fluctuating components of surface shear stress due to periodically fluctuating wind speed.

The highly transient initial shapes of 1D forced long waves are described in analogy with the swinging up of a mass on a spring forced by a simple harmonic force. That is, the complete solution is seen as the asymptotic, steady forced wave plus free waves which cancel it in the initial state of rest. The highly transient, complete wave form subsequently grows as the free waves separate from the forced wave. This approach gives a clear understanding of many of the characteristics of storm surge, tsunami and surfbeat.

The evolution of waves and wave-induced currents over porous submerged breakwaters is studied by applying a numerical model based on a truncated version of Chen (2006) Boussinesq-type equations for waves and currents over porous bottoms. The equations of motion for the porous medium include an empirical Forchheimer-type term for laminar and turbulent frictional losses and an inertial term for acceleration effects following Sollitt and Cross (1972). Comparisons between simulations and new set of laboratory experimental data show excellent agreement for wave field in one-dimensional horizontal wave propagation and qualitatively good agreement for wave and current field in horizontal two-dimensional wave propagation.

A numerical model of nearshore waves and wave-induced currents was developed to predict the wave and current fields in the vicinity of coastal structures. The wave model EBED (Mase, 2001) was modified in order to improve simulation of the wave conditions in the surf zone. The surface roller was modeled following the approaches by Dally and Brown (1995) and Larson and Kraus (2002). The wave-induced current and water level were determined from the depth-averaged momentum equations and the continuity equation. Model validation was based on high-quality data sets from experiments with structures in the Large-Scale Sediment Transport Facility (LSTF) basin of the Coastal and Hydraulics Laboratory (CHL), U.S. The computational results showed that the model can produce good agreement with the measurements for nearshore waves and currents.

A new approach for prediction of wave-induced current over submerged breakwaters/reefs based on artificial neural networks (ANNs) is proposed. An ANN was designed and trained using artificial current data generated by analytical current model of Gourlay and Colleter (2005). Calculated discharge using the proposed model was compared with the measured experimental data collected by Tajziehchi and Cox (2006). Comparison of calculated and measured discharge over submerged breakwater reveals the accuracy of the proposed model and its capability in predicting discharge over submerged breakwaters/reefs.

A 2-D RANS-VOF model has been employed to investigate the wave shape changes over low-crest breakwaters under regular waves. Our analysis demonstrate that wave skewness increases on the incident side, and then decreases to the minimum magnitude on the seaward slope of LCBs, it then increases above the crown crest and leeward slope to attain a maximum magnitude around the toe of structural leeward slope, and finally it decreases as wave propagating on the transmission side. Wave asymmetry decreases gradually from around zero values to negative values on the incident side, attains a maximum magnitude on the crest of LCBs, and then dramatically increases from negative values to positive values on the transmission side. We found that wave asymmetries increase with increasing wave heights and wave period; effects of water depths on wave shape changes can be ignored; the crest width of breakwaters influences the rate of increase of wave skewness above the crest and the leeward slope and affects the location of maximum magnitude of wave asymmetry. Calculated surface elevations and wave asymmetries are in good agreement with laboratory measurements collected in the small scale wave channel tests at the University of Cantabria (UCA).

The response of composite caisson breakwaters against a partial failure of the armour layer is not well understood at present. Observations in the field have indicated that higher levels of damage can be observed in the caisson, and to try to understand the mechanisms at work laboratory experiments were carried out on a range of regular waves (including breaking waves) and solitary waves (to simulate tsunami type waves). The results show how for partially failed armour layers when a high energy wave acts directly onto the caisson much higher pressures can be expected than for when a full armour layer is present. Analysis of video recordings show how the wave changes shape by "piling-up" on top of the failed armour, and as a result their destructive potential is substantially increased.

When a mooring chain is broken due to a high wave, a moored ship can be drifted and stranded. In order to attenuate damages to facilities in a port, it is important to predict the movement of a moored floating object driven by high waves. In some previous numerical methods for this kind of prediction, it was difficult to simulate a floating object appropriately under high waves including a fragmentation and a coalescence of water like a breaking wave. On the other hand, the particle method is suitable for analysis under such a complicated water surface change. Therefore, in this study, a simulation model of moored buoy based on a particle method is developed.

Computations of the Boussinesq-type wave model TRITON of wave propagation over a shallow foreshore with a varying low-tide terrace configuration were carried out. The results were compared with Scheldt flume physical experiments, using the same settings and post processing. The comparisons show that TRITON can model the wave propagation along shallow foreshores quite accurately as long as highly nonlinear effects do not play a significant role. Furthermore, the level of the low-tide terrace was found to influence the wave conditions at the toe of a fictive structure as follows: a) As the level of the low-tide terrace increases there is more energy dissipation and the significant wave height at the toe decreases, decreasing the hydraulic load. b) On the other hand, as the waves dissipate low-frequency energy is released and the spectral wave period at the toe increases, increasing the hydraulic load.

A numerical model based on nonlinear shallow water equations is applied to study oscillations in harbors of various shapes including L-type harbors, I-type harbors with a narrowed area, a C-type harbor, a T-type harbor, and I-type harbors with a seabed crest or trough. The second mode shows a higher amplification factor at the head of an L-type harbor as its bending position is nearer to the harbor mouth. As a narrowed area of an I-type harbor is located nearer to the harbor mouth, amplification factors of the first and second modes at the harbor head are lower and higher, respectively. A C-type harbor shows rather complicated amplification because the phase difference between waves propagating through two harbor mouths depends on the position inside the harbor. The oscillation in an actual bay, i.e., Urauchi Bay, which has a shape similar to that of a T-type harbor, is also numerically simulated; damping processes are compared between Urauchi Bay and a T-type harbor.

A numerical simulation of a storm surge is useful to prevent or reduce a storm surge disaster. There are, however, unknown factors in the simulation which brings information errors. The storm surge of tropical cyclone Sidr in Bengal bay in the year of 2007 was not able to be described by the standard simulation method using the track information of a storm surge. This study shows the several results of the storm surge by 11 cases of wind field expression as uncertainty factor. Using the best case comparing with field measured data, the process of generation of the high storm surge which was over 7 m was shown with how uncertain factor affect to the simulation results. Finally, impact assessment of storm surge with sea level rise along the coast of Bengal bay in 21st century was carried out, taking into account of uncertainty of the wind fields, uncertainty of projections of sea level rises and uncertainty of population growth.

The storm surge residual of 2.35m was measured during Typhoon Anita in 1970 in the Tosa bay, Japan. Since the Tosa bay widely open to the Pacific Ocean, surge heights are usually small. The present study examined the reasons why the abnormal storm surge was generated due to Typhoon Anita 1970 by numerical simulations using a coupled model of surge, wave and tide with six levels computational domains of which grid sizes are from 12150m to 50m. The storm surge simulation driven by only wind and pressure fields was not able to compute the measured sea surface levels. However, when wave radiation stress terms were included in the storm surge model the computed sea surface levels showed a good agreement with the measurement data. This study clarified that the effect of wave-induced radiation stress is significant on water level rising of up to 0.5m-1.0m in the Tosa bay.

Since major driving forces of storm surge are pressure depression and wind stresse, a set of depth integrated equations is widely used for storm surge simulations to estimate anomaly sea level rise. However, there are several phenomena should be taken into consideration. This study estimates effects of wave radiation stress, vertical mixing models and boundary conditions at ocean upper layers on storm surge. The three dimensional hydro-static model including turbulence mixing and diffusion are used to predict the sea surface elevation in the storm surge. The numerical results show that the wave radiation stress and the turbulent flux significantly influence on sea levels and currents, respectively.

Storm surge is influenced by many factors including environmental and geographical conditions. However, laboratory experiments and filed measurements were not easy to carry due to danger and difficulties. In this study, we conducted a numerical study with a verified storm surge model. Storm surge was impacted by track, tide, water depth and sea level rise. The track of storm is related to size of storm and the range of impact could be estimated by their relationship. One of the characteristics on storm surge is that storm surge is strongly affected by water depth and surface elevation. We found that variation of storm surge could be different at each tide and depth and it makes a big difference in the western sea of Korean Peninsula whose averaged depth is about 40 m and tidal range is about 10 m. An increasing sea level rise by climate change can cause a little reduction of storm surge by its own characteristics.

Cuspate topography provides a variation in the beachface slope, which can be used as a natural laboratory to study the influence of slope and downwash convergence on each swash cycle. The steeper-sloped cusp horns are likely to be characterized by smaller, faster swash cycles than the bays. The longer swash cycles in bays are more likely to collide with subsequent uprushes, and be influenced by increased downwash mass-flux caused by channeling. Here we use non-linear forecasting techniques for detecting non-linearities to determine the main controls on longshore swash variability. The outcome is a measure of the degree of localness in the timeseries, where local timeseries are governed by non-linear processes leading to non-stationarity whereas global timeseries are generally linear (or noise-dominated). The results of the forecasting analysis indicate that the swash from the day with generally greater beach slope, lower wave and longer period conditions was more local then the swash from the day with smaller average beach slope, higher wave conditions and shorter wave periods. Moreover, the alongshore variation in topography associated with beach cusps was associated with a longshore variability in the forecasting results, with the timeseries from the bay being better forecast with a more local model then the timeseries from the horn. These results are consistent with interactions between swash events causing the variability in forecasting results. Tests indicate that it is not one simple characteristic of the timeseries that varies locally, but some combination of magnitude, period, shape and absolute location on the beachface. Results may explain why variations in infragravity energy are observed to occur on cuspate beaches.

Detailed measurements of the hydrodynamics of bore-generated swash on steep beaches with different roughness have been obtained. They were used for investigating a number of approaches to determine the bed shear stress in order to assess their theoretical and practical viability. The relationship between the bed shear stress in the swash zone and the main flow parameters is further discussed.

Some twenty ultrasonic wave gages were employed to measure the water surface level as well as the bottom sand level near the shoreline in the field. Obtained data during a storm reveals that the long period waves were really dominant in and just outside the swash zone. It is also shown that the long waves provided the swash oscillation in the form of the loop by standing waves. In addition, data recorded for different conditions of beach slopes and incident waves are also presented for comparison with some analysis.

The shoreline along sandy beaches is located at a unique position on the earth's surface where marine and terrestrial processes converge. The swash zone distinguishes the landward-most reach of wave action. Field observations from this shallow and highly energetic region reveal that individual waves regularly deposit or remove hundreds of kilograms of sand per meter width of beach. Such high rates of sand movement represent several centimeters of bed-level change and far exceed the underlying pace of beach evolution. Relatively large morphological changes caused by single swashes might suggest that very rapid beach erosion or accretion is a common occurrence. The contrasting reality shown by these new observations is that beaches generally exhibit a state of dynamic equilibrium.

This paper studies on interactions between morphological changes and wave and current fields around the Tenryu River mouth during a severe storm. Installing six cameras, authors successfully captured collapse of sand bar around the Tenryu River mouth when typhoon T0704 hit the Pacific Coast of Japan in July 2007. Obtained images were analyzed based on several image processing techniques and, coupled with the other hydrodynamic data, showed clear evidence for interactive features of bathymetry changes and surrounding wave and current fields. Finally, a numerical model based on depth-integrated non-linear shallow water equations and energy balance equations were applied to the observed conditions and it was found that topography changes during the storm was one of the most essential factors that determine the characteristics of surrounding wave and current fields.

A state-of-art process-based model is applied to simulate the hydrodynamics in the Yangtze Estuary in China, as a basic step to acquaint ourselves with the morphological development and the effect of human interference in the estuary. A major improvement with respect to previous models for the Yangtze Estuary is that the present model covers the entire tidal region of the Yangtze River. Two curvilinear grids are used to adapt to the complex geomorphologic setting and the large spatial magnitude of the study area by applying domain decomposition techniques. The calibration of the model against extensive hydrodynamics data shows a good representation of observed hydrodynamics. With the present calibrated and validated model, the morphological evolution, as well as the effects of discharge regime change and sediment load reduction on the Yangtze Estuary can be carried on.

Seasonal variation of residual currents in the Meghna Estuary, located at the northern part of the Bay of Bengal, has been investigated through the use of a 3D numerical model. Residual current in the Meghna Estuary appears to be strongly influenced by tidal currents and Coriolis Effect under average meteorological and hydrological conditions of four different seasons considered,. Average seasonal variation of wind speed and direction as well as fresh water inflow does not seem to have significant influence on residual current. Only under the influence of average of maximum wind speeds of different seasons, residual currents in the Meghna Estuary show their dependency on wind stress. In general, at the surface layer northward and northwestward flow is created during the pre-monsoon and monsoon periods and southwest and southeastward flow is created during the post-monsoon and winter periods.

In the design of sand control facilities and in the assessment of beach erosion due to global climate change, long-term morphological changes should be estimated and evaluated. Wave and wind time series are important factors for the estimation of long-term shoreline change. This study proposes a method to model the long-term time series of wave and wind by using observation data, weather and wave prediction models in a physical sense and the Monte Carlo method in a statistical sense.

Sediment transport caused by a tsunami was investigated by a simple experiment. We measured the horizontal velocities and suspended concentrations caused by one solitary wave, which is assumed to represent a tsunami passing on a planar sand bed without breaking or splitting. It was found that there are phase lags between peaks of suspended concentration and velocity, and the time variations of the vertical distribution of suspended sediment concentration are in good agreement with curve approximated with the exponential function. We found that Brown's formula is inconsistent with the time variations of sediment flux measured in the experiment because it cannot explain the phase lag between velocities or the total sediment flux. The bed load formula by Ashida-Michiue shows a close agreement with the amount of bed load.

A real-time tsunami prediction method is established in this study by an inverse method which only uses offshore observed water level variation without using the fault information. The analyzed results showed overall good performance and accuracy. Tsunami sources were estimated when compared with the initial displacement of tsunami calculated by the earthquake model. The tsunami profiles can be predicted with high accuracy fore inshore points of interests and information is easily updated by using longer observation data. The accurate prediction of initial tsunami source can estimate long term tsunami fluctuation, and it can serve as useful information for a decision making the release time of warning.

Tsunami flow and sediment transport is simulated using Delft3D, a three-dimensional coupled hydrodynamic/sediment transport/morphological model. Tsunami flow characteristics and sediment erosion and deposition are recorded in 1 second intervals, and the temporal and spatial variations are examined to determine which phases of inundation dominate sediment transport and morphological change. For the simulations conducted here, most of the sediment deposited onshore originates in shallow water. While some sediment is eroded by the passing wave front, sediment is predominantly eroded during backwash and advected onshore by the subsequent wave. The extent, composition, and structure of the onshore sediment deposit is a function of the tsunami wave form, as well as the local conditions, including the nearshore morphology, local topographic variations, sediment source characteristics, and bed roughness.

In this study, we investigated the sediment transport due to the 2004 Indian Ocean tsunami along the natural coast at Hambantota, Sri-lanka. Bathymetry and topography surveys before and after the tsunami were conducted and results showed significant erosion by the tsunami, especially around the places where shoreline discontinuations were observed. We conducted a numerical simulation of tsunami propagation as well as the bathymetry change induced by the tsunami. Furthermore, we also estimated the bathymetry change due to the usual sea waves at the coast. Our numerical results suggested that the tsunami has strong bottom shear stress at specific landform such as a river mouth and a cape. We also found that the sediment erosion and accretion due to the tsunami had been mitigated by usual waves after the tsunami.

Previous numerical modelling studies based on 2DH morphodynamical model show that oblique waves tend to inhibit the formation of rip channel systems, but the mechanisms were not investigated. Field observations do not always agree with this model result, thus, understanding the mechanisms seems essential. To this end, the global analysis technique, originally developed to describe the long term behavior of bars (saturation of the bar growth), is also applied here to the initial stage of the bar evolution (formation of the bars). As a result, rip channels grow slower for larger wave angle because of the weakening of the instability mechanism that only depends on the cross-shore current-rather than the increase of the damping due to the diffusive bedslope transport.

This study aims at improving the computation of the wave-driven longshore currents in the surf zone. The vertical distribution of wave-driven currents often deviates from a logarithmic vertical distribution, due to the vertical mixing induced by wave breaking. 3D modeling of these currents provides the opportunity to take this vertical variation into account. The current method of computing the bed shear stress in the 3D approach of Delft3D is dependent on the thickness of the near-bed vertical computational layer: the thinner this layer, the larger the bed shear stress and the smaller the wave-driven longshore currents. Computing the bed shear stress using the velocity at the edge of the wave boundary layer avoids this layer dependency. With this method good agreement with measured velocity data from laboratory experiments and field experiments is obtained, except for very close to the shore. Although Delft3D in 2DH and 3D model have similar skill in simulating longshore currents, the 3D approach is recommended for wave-driven sediment transport related problems as it more realistically represents the cross-shore current and suspended concentration profile.

The shore behind the offshore fishing port has never been attached to the facility for 15 years after the construction. The main object is to investigate the littoral drift behavior around the port. As the result of wave and current observation, the differences in the time-averaged surface elevation were found at the right and left sides during typical storm. By using a volumetric analysis and a simple method to estimate the longshore sediment transport rate, 55 percents of the net longshore sediment transport is estimated to go through behind the port. In this study, a numerical simulation is applied and gives a good validation against the observed data and estimates the current field and suspended sediment transport during typical storm to understand the littoral drift behavior.

On the Shizuoka coast, many detached breakwaters have been constructed since the 1970s as a measure against beach erosion. After their construction, the movement of a body of sand, which is mainly composed of gravel, with a velocity of 250 m/yr was observed in the zone shoreward of these detached breakwaters. In addition to this, fine sand movement was also found in the zone offshore of the detached breakwaters. A model for predicting the movement of both the sand body shoreward of the breakwaters and fine sand offshore of the detached breakwaters is developed. The predicted velocity of the sand body is 252 m/yr, which is in almost perfect agreement with the measured velocity of 250 m/yr. In contrast, the rate of expansion of the accretion zone composed of fine sand in the offshore zone is 372 m/yr, which is 1.48 times the velocity of the sand body. This is also in good agreement with the measured ratio of 1.50.

It has been suggested that vertical perforated tubes placed below the beach surface will increase the drainage of the beach, and hence increase the deposition of sand on the beach. The system is called the PEM-system, Pressure Equalization System, and the Danish company SIC (www.shore.dk) is doing the marketing. Although it for a coastal engineer seems obvious that such a device can't drain the beach (nearly no driving forces ), SIC has succeeded in installing the system in more than 75 locations around the world (according to the company). In Denmark a full scale experiment at the exposed west coast has been performed through 2005-08, and a similar Dutch test is going on right now at Egmond, Holland. In this paper, we model the flow in the beach taking into account the presence of (high-permeable) tubes and demonstrate that the drainage effect is negligible. Further, the morphodynamic behavior of the coast in relation to the Danish field test is described, and it is concluded that all morphological changes can be explained by natural causes.

Numerical computations are made for the nearshore currents and beach morphology around a system of multiple submerged groins. They function in decreasing the speed of longshore currents and controlling beach erosion. Nearshore currents are computed with the PEGBIS model by Goda (2004) for directional random wave transformation, and beach morphology is estimated with the suspended sediment transport model by Katayama and Goda (2000). The computation indicates the efficacy of a submerged groin system for beach erosion control. Discussions are made on several aspects of the submerged groin system to be clarified through further investigations.

Time variations of coastal bathymetry and sand grain size were investigated at the north Kashimanada Coast, a 40km long section of coast located between Oarai Port and Kashima Port, Japan. From the change of coastline position obtained from aerial photographs and bathymetrical surveys, it was found that the beaches located just next to Oarai Port and Kashima Port had been depositional and the areas next to those depositional beaches had been heavily eroded. Grain size distributions at the shoreline showed a tendency that grain size became coarser in the eroded areas and the areas were expanding. From analyses of the bathymetrical surveys, it was found that in almost 2/3 of the coast, offshore longshore sandbars diminished from 1984 to 2004, and it can be considered that the sediment movement caused by the headland system might be responsible for the extinction of the offshore sandbars.

In this paper, we discuss the applicability of a numerical wave channel CADMAS-SURF/3D with regard to hydrodynamics on a salt marsh by comparing numerical experimental results with previous studies for both flow and wave conditions. The present results indicate that the model is promising as long as appropriate values for numerical parameters such as the grid size are used. We present results for the bottom velocity and turbulence kinetic energy around a cylinder which are important understanding deposition in salt marsh vegetations. Furthermore, this paper shows that the drag coefficient and inertia coefficient for circular cylinders in waves depend on the density of the cylinders.

Various new types of seawalls have been adopted instead of existing seawalls such as vertical and block mound seawalls, from the comprehensive viewpoints of disaster prevention, coastal environment and utilization. However, a practical estimation procedure for wave overtopping rate of complex-shaped seawalls has not been established yet. The purpose of this study is, therefore, to numerically examine countermeasures against wave overtopping around road revetment in Okinawa Main Island by conducting numerical simulation using a two-dimensional numerical wave flume 'CADMAS-SURF'. As a result, it is revealed that the CADMAS-SURF can represent wave overtopping phenomena at actual fields. Moreover, numerical computations with the CADMAS-SURF are found to be useful in comprehensively discussing the prevention of wave overtopping disaster.

This paper numerically studies the wave field under a typical 6-column floating platform in terms of wave amplification. With the aim of serving model test better and helping locate air gap probes in the preliminary stage, the degree of wave amplification together with associated air-gap at several potential locations are specially investigated to figure out the vulnerable positions. The results show that the local surface elevation will be significantly amplified at certain critical point. It is suggested that exploring the local wave amplification and air-gap response will be great help for the design of floating systems. The effect of wave spectrum parameter on the prediction of air gap is also discussed in this study. It is found that the air gap response under deck increases with the peak factor of target spectrum.

This paper describes the hydraulic characteristics of the flap gate-type breakwater subjected to tsunami and waves. The structural features represents the type that gates moored by tension-rods with stabilizer plate are sloped contrary to direction of the waves. In this study, we investigated the measurement of wave pressure and rotation moment that acted on the gate in tsunami and waves using the water tank test. In an experiment, the experimental results revealed a positive correlation between the rotational moment and wave pressure. Stabilizer plate is decreased the rotational moment and wave pressure. We concluded that the type with stabilizer plate is the most available for the structural strength of the gate.

In this paper, the effects of tsunami condition, forest density and forest width on tsunami flow velocity behind the coastal forest with an open gap were investigated by numerical simulations. A numerical model based on two-dimensional nonlinear long-wave equations was developed to account for the effects of drag and eddy viscosity forces due to the presence of vegetation. The numerical model was validated with good agreement by the experimental results. The numerical model was then applied to the coastal forest of Pandanus odoratissimus with a straight open gap (gap width=15m) perpendicular to the shoreline. It is found that the normalized maximum velocity behind the gap and vegetation¹ patch are greatly different. When tsunami period becomes large, the increase of velocity at the gap exit becomes large. Both forest width and forest density primarily influence on the velocity; as those increase, the normalized maximum velocity at the gap exit increases, while it decreases at the behind the vegetation patch. The enhancement of velocity at the gap exit is strongly dependent on the forest density but it is weakly influenced by the tsunami height.

During their propagation tsunamis often traverse continental slopes that are relatively steep compared to deeper oceans. Further due to the change of bed slope from offshore to near shore, there is every likely possibility that a tsunami might steepen and eventually break, thereby generating large pressure gradients that could enhance the likelihood of liquefaction of the seabed. In the drawdown, high shear stresses could trigger debris flow in submarine canyons and on steep ridges. Therefore estimation of the bed stress is important in estimation of the forces induced during tsunami wave propagation, both on the seabed as well as on the subsurface installations. Bed and shear stresses generated by wave forms that represent tsunami (a solitary wave and broken solitary wave in the form of a bore) are measured using a shear cell. This paper deals with the measurements and modeling of the bed stress under the solitary waves.

A one-dimensional model for beach profile change was developed to predict longshore bar migrations. The cross-shore sediment transport was assumed to be composed of suspended load due to wave breaking and bed load due to velocity skewness, velocity atiltness, and beach slope. Beach profiles at the Hasaki coast in Japan during a 2-year period from 1989 to 1990 were predicted with a grid size of 5 m and time interval of 2 hours. The simulated profiles were compared with beach profile data, obtained along the 400-m-long pier of the Hazaki Oceanographical Research Station at 5-m intervals every workday and showing cyclic seaward bar migrations with a period of 1 year. The comparisons of the measured and predicted beach profiles and bar crest positions show that the model reasonably predicted the repeated seaward bar migration for about 2 years.

The south part of the Gulf of Lions coast (Mediterranean Sea) and its double crescentic sandbar system has been observed monthly during a 3-year long period (2005-2008) and yearly from 2000. This paper proposes a conceptual model of the morphodynamic evolution of this microtidal bar system supported by field bathymetric surveys and hydrodynamics measurements. This model is based on the different evolutive sequences observed. It is then compared with other observations made in the literature.

Sandbars are often present in the nearshore zones of sandy coasts. As a result of the interaction with the incoming waves, sandbars change in shape and location over time. Trends in cross-shore sandbar behavior can often be observed on many timescales, ranging from a few months to several years. Models for sandbar behavior can be specified on different abstraction levels and corresponding scales. In the present work we investigate the ability of two models specified on different abstraction levels to predict long-term (several months) sandbar behavior, using a high-resolution 15 year-long profile dataset collected at the Hasaki Oceanographic Research Station in Japan. We find that it is very difficult to predict the rate of offshore-directed trends in sandbar behavior on the timescales of months, resulting in overall poor model performance. We discuss the implications of our findings for the application of models in the understanding of long-term sandbar behavior.

The development and evolution of crescentic patterns in double-barred systems is explored using a morphodynamic stability model. The description of the surf zone hydrodynamics is based on depth and wave averaged conditions while sediment transport is calculated using a total load formula. The linear stability analysis predicts that an initially rectilinear coast, subject to infinitesimal perturbations and under normal wave incidence, is unstable and can result in the development of crescentic shapes that can be coupled either in-phase (highs and lows of both sandbars are at the same alongshore position) or out-of-phase (highs and lows of one sandbar correspond to lows and highs of the other sandbar). Results of numerical simulations are sensitive to some of the parameterizations used in the description of hydrodynamics. Changes in the breaker index can have an effect not only on the spacing and growth rate of the pattern but also on the type of pattern that develops. An increase in the breaker index leads to a faster growth of the pattern but also to a smaller alongshore spacing. The role of parameterizations in lateral mixing and roughness length appear to be limited.

A 40 year data set collected annually and a 3.4 data set with a daily resolution both collected at Noordwijk in The Netherlands are compared with results obtained with a process based profile model over a 3.3 year simulation period. The simulation period approximately encompasses a complete bar cycle of generation in the intertidal zone, migration through the surf zone and decay at the seaward extend of the active profile. Evaluation of the model is aimed at obtaining insight in the ability of the model to predict the characteristics of such cyclic bar behavior by comparing bar amplitude, migration rates and dominant time scales using analysis techniques such as CEOF. The observed maximum bar amplitudes, its cross-shore position and the distance between bars were accurately predicted by the model. Weekly, seasonal and annual migration rates were over-predicted quantitatively, but showed good qualitative agreement. The quantitative disagreement is probably the combination of model error and the fact that the considered periods in the data analysis and model simulation were different.

A morphodynamic model has been developed to gain more fundamental knowledge about the formation of transverse finger sand bars. The model describes the feedback between waves, rollers, depth-averaged currents and bed evolution, so that self-organized processes can develop. The wave and bathymetric conditions measured at Egmond site are firstly applied and the modeled longshore current and wave height are compared with field data of that beach. Subsequently, the wave and bathymetric conditions measured at Noordwijk site are used to compare model results with the up-current oriented bars observed there. Realistic positive feedback leading to formation of the observed bars only occurs if the resuspension of sediment due to bore turbulence is included in the model. The modeled wavelength, crest orientation and growth rate agree with data but the model overestimates the migration rates.

The utility of numerical models of beach morphodynamics is constrained by our ability to establish that the theoretical dynamics match reality. The inherent difficulty in collecting suitable validation data for spatial and temporal bathymetric models of beach evolution has resulted in relatively few studies which perform empirical validation of nearshore morphological models. The present study addresses the validity of morphological modelling of an exposed beach by qualitatively comparing the evolution of a numerically modelled beach state transition with data observed using remote imaging. The application of the numerical model was broadly validated, in that, when forced with parameterised wave conditions, the morphological development is consistent with that observed via optical sensing.

Investigation on the sediment movement characteristics was conducted in a broad research area with a 150-kilometer stretch along the Enshunada Coast and the Suruga Bay, Japan based on feldspar thermoluminescence (TL) properties. River sand grains (primary source) present a higher TL signal than beach sand. Along the nearshore area, local TL intensity peaks are observed at the river mouth and sample TL intensity gradually deceases with increasing distance from the river mouth, which indicates sediment longshore transport features. Far away from the river mouth, the decreasing trend on TL intensities terminates. Taking the spatial distribution of TL intensities into account, a quantitative estimation on the longshore sediment flux was carried out based on the total river sand discharge. A sunbath test was implemented to help to distinguish the beach sand constituents. Identification of coastal sand sources was achieved in terms of the profile and magnitude of the measured TL glow curves.

The establishment of an accurate sediment budget, including both inter-tidal sand and mud deposition, requires a reliable chronology for the deposits. This study investigates the application of Optically Stimulated Luminescence (OSL) dating to determine sedimentation rates on a sandy tidal flat, since these sandy deposits are very difficult to date using other techniques (e.g. ¹⁴C and ²¹⁰Pb). An absolute OSL chronology for four sediment cores, recovered from the Danish part of the Wadden Sea is presented. Despite vertical mixing and bioturbation of the tidal sediments, OSL ages ranging from a few years up to ~16,300 years are obtained. The average overall accumulation rates are found to be similar to the local relative sea-level rise, estimated as ~0.7 mm.a^-1 in this area. The tidal flat is concluded to have had a positive sediment budget during the last 100 years and the new approach, using OSL dating, shows promising results.

A methodology for the detection, field investigation and the establishment of a management procedure is developed over a strategic borrow site off the Mediterranean coast of Spain in deep waters. It is intended to state the volume of the deposit, the features of the sediments, mainly grain size and mineral richness, the assessment of the potential pollution by contaminants, as well as the identification of benthic communities to determine its fulfillment with the requirements of the Spanish Administration to eventually dump to the open sea the fraction with no economic interest and to be used in beach nourishment projects the fraction with interest. This investigation is in accordance with the recommendations of the European Union project "Eurosion" that suggested that Member States should identify strategic sources of sand, suitable for the long term and regional scales maintenance nourishment.

A Geological model of continental shelf sand ridges is combined with a numerical modeling system designed for shallow marine physical processes to assess the potential for recovering beach quality sand. The shelf sand ridge geological model includes a coarsening upward sequence beginning with silts, clay and silty fine sand grading upward into relatively coarse sands having minimal silt and clay fraction. The upper meter of the sequence includes a clean cross-bedded sand unit that is reworked by episodic storms and waves on the inner to mid-continental shelf. Results of a numerical model investigation of modern sand ridges on the inner continental shelf of northeast Florida are consistent with the elements of the geological model. Sand ridge crests at relatively shallow depth activated by passing storms are predicted to be subject to topographic changes of up to 1 m consisting of both deposition and erosion. It is concluded that numerical modeling combined with the appropriate geological modeling can be applied as a tool for identifying potential sand and gravel deposits on the inner continental shelf.

This study is the further application of the one-line shoreline-change model of Weesakul and Rasmeemasmuang (2002). The model applies the combination of Cartesian and polar coordinate system to simulate the time-varying shoreline change between headlands. The model is a sophisticated method of performing a sand budget calculation based on the continuity equation of mass. The alongshore sand transport rate was evaluated by two formulas, i.e. the so-called CERC and Kamphuis (1991) and their results are compared and discussed. This paper also presents the modification of Kamphuis (1991) expression. In the modified formula, the transport due to alongshore variation in the breaking wave heights as caused by the diffraction at structures as well as the flexibility of the calibration are taken into account.

This paper presents a numerical model capable of reproducing fairly complicated beach profile changes. For this the present model classifies the sediment transport processes into that due to the asymmetrical on-offshore sheet-flow, that caused by breaking waves and mean flow, and that owing to bore-induced vortex and turbulence in the surf zone. Quantitative evaluations of these three transport processes are expected to lead us to appropriate beach profile changes. Trial calculations show a fairly good agreement with large tank experiments and support the cross-shore transport forms reported up to the present. Calculations by the model also explains the beach change processes both of bar formation by huge steep waves and of bar disappearance during a swell period. It is concluded that whether a beach is accreted or eroded will be determined by the balance of these three transport processes and the gravitational effect.

A series of mobile bed experiments on small-, medium and large-scales using identical wave conditions based on Froude scaling showed the erosion of the upper beach by swash motions and the generation of a submerged breaker bar for erosive test data. The accretive test data shows onshore movement of the breaker bar. A Delft3D two-dimensional-vertical (2DV) profile model was used with default model settings to model beach profile development under erosive and accretive conditions at the three different laboratory scales. It was shown from Brier Skill Scores for the model predictions that the model is capable of simulating wave-induced erosion along plane sloping beaches at laboratory scales under erosive conditions. Model computations for accretive wave conditions were in qualitative agreement with the observed onshore bar movement of the breaker bar.

The nearshore hydrodynamic and morphological model CSHORE has been under development for the past several years, utilizing a multitude of laboratory data sets. Although the model has a physically-based foundation, all practical morphological models, including CSHORE require empirical parameters. The model is compared with a large set of field data and two representative examples are provided in detail. The storm response data sets, one from the east coast of the US and one from the west coast, are similar in bulk wave statistic but differ in that the East Coast case has a significant storm surge. The model performs reasonably well without site-specific calibration, but some improvement is realized by increasing the effect for the dissipation due to breaking waves on the West Coast.

A novel hybrid model for predicting medium- to long-term morphodynamic responses of estuaries is developed using a hybrid approach between top-down and bottom-up models. The model is based on a two-dimensional diffusion formulation. Effects of non-diffusive processes on medium- to long-term estuary morphology are modeled by a source function in the governing equation. The source function is determined by solving an inverse problem using historical bathymetry data. The model is then applied to predict future evolution of morphology of the Humber Estuary, UK. Comparison of predicted morphologies with measured values shows that despite the simplified dynamics of the morphological processes used, the model provides encouraging predictions of future morphological changes of the Humber Estuary.

In this paper, results of sediment transport at Exe Estuary, Devon, UK, obtained from a process-based model under a number of wave and tide scenarios, are presented. This study uses a nested modelling system, which consists of an oceanic scale wave model WAM and a tide/surge model POLCOMS, to transform the meteorological information to nearshore wave and tide conditions for a fine resolution local coastal process-based model to carry out detailed predictions of nearshore hydrodynamics and morphodynamics at the study area. The work is focused on studying the impacts of yearly and 1 in 50 year return period storm events on morphology at the mouth of the Exe Estuary and the adjacent coasts. Comparisons of model results are made with the beach survey data carried out by the local authorities in March 2008, in addition to the model tests on both yearly calm and storm conditions in November 2006.

Sediment movement around the river mouth is intensive and complicated, owing to the combined effects of short waves, long waves, tide currents and river discharge, which usually leads to great and frequent topography change. This study aims to describe the sediment movement in a river mouth, further to distinguish the contribution of each hydrodynamic component to sediment movement, and to get better understanding on the nonlinear effects to sediment transport and their interactions. A numerical model was developed to simulate the hydrodynamic environment and the movement of color sand tracers. Both field survey and numerical modeling were carried out around the Magome River mouth, which is located on the Enshu Coast, Shizuoka Prefecture, Japan and drains into the Pacific Ocean.

A hydrodynamic and sediment transport model for the Mouth of the Columbia River was constructed using the Delft3D modeling system to examine and isolate the physical processes responsible for sediment transport and morphological change in this dynamic estuary entrance. The model is able to simulate the dominant features in the tidal flow, salinity and wave fields observed in field measurements. Results show that a spatially and temporally varying balance of physical processes governs the transport of sand through the MCR. In the absence of salinity gradients, flows induce a large sediment export. Including salinity reduces the net sediment export at the Columbia River Mouth to near zero. Wave-driven transports are minor compared to the tides during typical summer conditions. In winter, during severe storm events, waves govern the transport patterns increasing the transports by an order of magnitude.

The general increase of human activities, including the exploitation of the hydraulic and sediment resources of rivers, has caused extensive coastal erosion throughout the world, especially during the last 150 years or so. The true costs and impacts of this erosion have not been reflected in the price of providing commodities such as sand and gravel. These impacts and their estimated costs are presented using information from the states of Washington, Oregon, and California on the Pacific Coast of the United States of America.

Beach changes of five pocket beaches located on the west shore of Miura Peninsula were investigated through the comparison of aerial photographs and bathymetric survey data. The clockwise rotation of the shoreline was observed in every case, resulting in shoreline recession in the north part of the beach and accretion in the south part. It was found that a port breakwater was extended at the south end of the pocket beach to form a wave calm zone under the conditions of the oblique wave incidence from the southwest. A small river also flows into the sea at the south end of the pocket beach because of the wave calmness by the natural headland, but sand supplied from the river became difficult to move out of the wave-shelter zone of port breakwater, accelerating sand deposition near the port immediately offshore of the river mouth. The dredged sand was disposed offshore, resulting in the decrease in sand volume of the beach. These are the common anthropogenic factors related to the beach erosion of the pocket beaches. To soundly maintain these pocket beaches, sand backpass is necessary along with the construction of some auxiliary facilities to prevent longshore sand transport from returning to the port.

On the basis of bathymetric survey data, aerial photographs and sampling data of seabed materials, sand budget analysis considering the grain size is carried out, taking the Shonan coast as an example. A diagram showing sand budget is proposed, in which longshore sand transport, rate of windblown sand, and grain sizes not only near the shoreline zone, but also in the offshore zone are shown. The loss and input of sand across the shoreline due to windblown sand and dredging in the ports are also summarized. This diagram can be effectively used for the coastal management of the coast.

The coastal erosion causes and their relative importance are site specific, changing from place to place. In the Portuguese Northwest coast, namely between Douro River and Nazaré, coastal erosion is mainly due to sediment supply reduction from Douro River. The present study analyzed the anthropogenic impacts on the river, identifying the type and time history of Human actions, the flow changes and the impact on the sediment transport along the years. Numerical formulations of sediment transport estimation allow defining the relative importance of the different interventions on the Douro River and its basin. The major importance of the dams constructed in the Douro River basin led to laboratory works on a hydraulic flume, evidencing the sediment transport reduction related with the lower flow velocities caused by the reservoirs of the dams on the upstream side.

This paper examines profile equilibration and longshore spreading associated with beach nourishment based on weekly to monthly profile surveys along the west-central Florida coast. Profile equilibration occurred rapidly and was largely completed after the first post-fill storm, typically with the formation of a nearshore bar and the overall beach-profile slope approaching the pre-nourishment slope. The bar moved offshore and onshore in response to subsequent storm and calm-weather conditions, respectively, while shoreline position remains largely stable. Longshore spreading is strongly influenced by grain size. Fine sand (~ 0.20 mm) tends to be transported and deposited along the nearshore bar resulting in little change along the shorelines and on the dry beach. The coarser shell debris tends to spread along the shoreface through the growth of a diffusion spit, which abruptly changed the shoreline orientation at the ends of project.

This paper examines the two year temporal and spatial performance of several beach nourishment projects constructed in 2006 along three microtidal low-wave energy barrier islands in west central Florida, based on monthly surveys of 145 beach profiles. The performance relates to background transport gradients, localized morphology variations, and project length. The performance of the different projects varied spatially and temporally, relating to a shoreline orientation change of 65 degrees, variations in the general depth of the inner continental shelf, and longshore sediment transport interrupted by two tidal inlets. Short projects adjacent to inlets, with large longshore transport gradients, resulted in 20-70 % volume loss of the initial-fill after 2-years. Along the longer projects further from inlets, 80 % of the fill-volumes remained.

On the Akiya coast a breakwater of Kuruwa fishing port was extended, inducing longshore sand transport from outside to inside the wave-shelter zone. Sand accumulated inside the wave-shelter zone, whereas beach erosion occurred on the nearby coast. A tracer test using sand of d₅₀=0.5, 1.5 and 15 mm showed that coarse material was deposited near the shoreline and slowly moved alongshore, whereas fine material was carried offshore. The contour-line-change model considering changes in grain size was applied to the coast to predict the effect of beach nourishment using material with different grain sizes. Gravel nourishment was confirmed to be effective for recovering a stable beach without damage to the offshore fishing ground. Beach nourishment using 7,600 m³ of gravel with d₅₀=15 mm was carried out in 2007 on the Akiya coast. The nourishment gravel was deposited near the shoreline forming a steep slope of 1/5, indicating that the nourished beach is very stable.

This study focuses on barred beach shoreface nourishments physically simulated in a wave flume. The attack of a schematic storm on three different nourishments is analysed. The apex and waning storm phases lead respectively to off-shore and on-shore sediment transport. The trough and outer bar nourishments are feeding the bar and increase wave dissipation off-shore. The bar acts as a wave filter and reduces shore erosion (lee effect). In contrast, nourishment in the inner zone leads mostly to shore feeding and beach face reconstruction (feeder effect). Along the successive nourishments, the upper beach face is clearly steepening and on-shore sediment transport is reduced during moderate wave climates. The surface sedimentological analysis reveals marked variations. Coarser sediments are sorted on the bar and the upper beach face. These locations correspond to large wave dissipation zones during the storm apex.

This paper presents a discussion on the role of impulsive pressures induced by plunging breakers acting on gravel beaches. In previous works, this process has been hypothesized to play a major role in the observed sediment transport on these beaches. Thus, a diagnostic investigation is carried out here in order to elucidate, in more detail, the anatomy of the impulsive signature in the pressure signal. For this purpose, we employ an integrated approach, which comprises full scale laboratory measurements and their comparison against model results from a well-validated phase/depth resolving numerical model based on the Reynolds-Averaged Navier-Stokes (RANS) equations. Agreement between observations and model predictions allows us to investigate the contribution of each of the acceleration terms in the momentum balance under the wave-impact event by means of the numerical model. The discussion is presented in order to understand how impulsive pressures are generated under plunging waves and their role in sediment mobilisation. Consistent with prior studies, numerical results show that under plunging breakers the local acceleration (du/dt) alone cannot be used as a proxy for pressure gradients. In addition, the importance of the term w du/dz of total acceleration is recognised for first time. Results from this study suggest that for different types of breaking a different characterisation of the pressure gradient may be sought.

There is a general lack of knowledge of combined cross-shore and longshore changes in gravel barrier beach morphology due to storms. A cluster analysis followed by a multidimensional scaling ordination revealed that the storms affecting a gravel barrier in the southwest of England (Slapton Sands) fall into two very distinct groups: easterlies with mainly wind waves, and southerlies dominated by swell. The morphological response of the barrier to these two typical storm conditions was found to be opposite. Easterly storms induce upper beach erosion and lower beach accretion, while southerly storms cause upper beach accretion and lower beach erosion. In addition, the net alongshore sediment transport for southerlies is northward, while for easterlies it is southward. Video-derived shorelines over three years indicate that the barrier has rotated significantly, as demonstrated by widening of the northern end, and narrowing of the middle section. It is argued that the rotation is caused by a recent change in dominance of one storm type over the other.

In this study, we investigated the characteristics of wave breaking on a gravel beach, considering the effects of the groundwater table. Wave breaking in 835 hydraulic model tests is studied. The experimental results of breaking index including the breaking wave height and breaking water depth in a gravel beach are compared with the existing breaking wave formula for computing breaker height and depth. The experimental results indicate that breaking wave heights and water depths are smaller than those in a sandy beach. Further, the higher the groundwater table, the higher breaking wave height and water depth.

The cross-shore numerical model CSHORE developed for the wet zone seaward of the mean water shoreline is extended to the wet and dry zone for the prediction of wave overtopping and overwash. The probability distribution of the water depth is assumed to be exponential for the wet duration with an explicit account of the wet probability. The horizontal velocity and water depth are related using a formula for a bore. The continuity and momentum equations are used to predict the cross-shore variations of the mean depth and steady current in the wet and dry zone. The formulas for the suspended sand and bedload transport rates in the wet zone are modified for the different hydrodynamics in the wet and dry zone. The extended CSHORE is compared with two small-scale tests on berm and dune erosion with minor overwash and three large-scale tests on dune erosion. The computed suspended sand and bedload transport rates appear to be physically reasonable but will need to be verified in future experiments.

In this paper we present the first results of beach profile hindcasting with XBeach using recently measured coastal data acquired under storm conditions at eight European sites, including a comparison to model results obtained with off-the-shelf models. The results show consistently that the XBeach has skill in predicting the coastal profile, albeit that in most cases the erosion around the mean water line is overpredicted and the depositions at the lower beach face are overpredicted. The causes for this model effect are under active investigation but not resolved yet. Likely candidates are the modeling of onshore (asymmetry) transports which reduces the offshore transports due to undertow (currents) or the modeling of sediment motion in the swash zone.

The morphological development of washover systems on the West Frisian barrier islands was studied over a period of almost a century. Inundation overwash still regularly occurs and the hydrodynamic processes such as mean flows and low-frequency waves are capable of transporting sufficient amounts of sediment However, the actual transport on the barrier island of Schiermonnikoog appears to be limited and is reduced by local factors such as extreme wave dissipation, the presence of vegetation and algal mats.

This paper presents video-based measurements of morphological experiments in the Vinjé wave basin. The experiments were carried out to study effects of fixed structures on dune erosion. We developed a new measurement method based on video images, that successfully uses the differences between two succeeding images to derive detailed and accurate measurements of the bathymetry. We also developed a method to monitor the position of the dune crest during the experiments by using the variations of the color intensities along a cross-shore transect to determine the dune crest position. Measurements nicely represent the episodic collapsing dune front. The measurements also show an increased erosion near a connection between a dune and a dike compared to an undisturbed dune section. The additional amounts of dune erosion are larger at breaches in a dike and in a dune foot revetment.

The Eastern Scheldt tidal basin has changed drastically in the past five centuries under the influence of both human interventions as well as extreme events. In 1530 A.D. a storm-surge inundated large parts in the landward end of the basin, and in the following four centuries local inhabitants reclaimed about as much land as was inundated in that storm. To investigate the effects of these processes on basin morphology, several different simplified geometries of the basin are used in order to gain insight into the evolution of the tidal currents over the centuries. From this model it appears that the large-scale inundations cause the basin to scour to greater depth. This in turn causes the ebb-tidal delta to grow, and causes the disappearance of the tidal watershed between the Eastern Scheldt and the Grevelingen tidal basins. Land reclamations have not been able to turn these trends around.

A new forecasting technique is presented and applied to a set of historic bathymetric surveys of sandbanks and channels off Great Yarmouth, UK, which is an extension of the method proposed by Reeve et al. (2008). The method combines three procedures. The first one consists of an Empirical Orthogonal Function (EOF) analysis to identify principal bathymetric patterns and their dynamics. The second is to use a jack-knife resampling technique to produce an ensemble of bathymetric realisations from 1846 to 1998. Finally, two distinct Auto Regression (AR) methods are used to find an ensemble of forecasts for 2006. The two AR techniques both give comparable results which agree well with measurements of the 2006 bathymetry, which indicates a useful level of robustness in the forecasting methodology.

The Great Yarmouth sandbanks are highly dynamic, and of considerable economic importance due to the presence of a wind farm and their close proximity to two busy ports. The processes driving bank evolution are poorly understood. We investigate the hypothesis that bank reconfigurations are driven by the evolution of neighbouring banks within the group, through changes to local tidal flows. 30 years of survey data are analysed, and tidal currents and sediment transport are simulated under 'everyday' wave conditions. Model results suggest that sediment transport is dominated by residual tidal flows. Modelled bed evolution is in partial agreement with observed bank changes. We conclude that everyday wave conditions can only account for limited bank evolution and suggest that storm conditions may be responsible for the remainder.

We present a three-dimensional sediment transport model implemented within the Proudman Oceanographic Laboratory Coastal Ocean System (POLCOMS). An unlimited number of sediment classes can be transported both as suspended load and bed load. Suspended sediment concentration is calculated following advection-diffusion schemes similar to those used for other scalar quantities. The location of the sediment bed is obtained from near-bed sediment mass conservation and the sediment bed is represented in the model by a layered structure. The ability to reproduce suspended concentration profiles and morphological evolution for a simple case is tested against laboratory experiments of trench migration in a flume.

The net sediment transport rate beneath waves that possess both velocity and acceleration skewness is explored using a one-dimensional model solving the Reynolds-averaged Navier-Stokes and advection-diffusion equations in conjunction with a k-ε model for turbulence closure. The model is forced with a parameterization of free-stream oscillatory flow in which the degree of velocity versus acceleration skewness, the magnitude of the total wave non-linearity, the oscillatory flow amplitude, and the wave period can be varied. For conditions that the near-bed concentrations are predicted to vary (nearly) in-phase with the oscillatory flow, the resulting transport rates are in the direction of wave advance and are largest under velocity-skewed oscillatory flow that contains some acceleration skewness. When the grain size is less than about 200 µm, however, sediment stirred during a particular wave half-cycle has not completely settled before flow reversal and tends to be transported during the next half-cycle. Consistent with earlier work, these phase-lag effects reduce transport rates under oscillatory flow dominated by velocity skewness (sometimes even leading to transport rates opposing wave advance), while they enhance net transport rates under oscillatory flow dominated by acceleration skewness. When phase-lag effects are important, the largest transport rates are thus found under acceleration-skewed waves. Our work suggests that nearshore sediment transport equations based on the instantaneous bed shear stress may be restricted in applicability to situations when the grain size exceeds about 200 µm.

Most of simulations of a vertical sorting under an oscillatory flow condition have been conducted by using one-way model without considering solid-liquid interaction. In this paper, a simulation by two-way model is performed to treat the solid-liquid and solid-solid interactions. The solid-liquid two-phase model is coupled the distinct element method (DEM) for tracking particle motion and the Eulerian fluid dynamic model. The influence on the vertical sorting process due to the fluid motion reproduced by the one-way and two-way models was investigated numerically from the particle-scale point of view.

In this contribution a discussion is presented on the development of self-organized coastal morphodynamic patterns which are due to the joint action of gradients in the depth-integrated concentration and the flow. This is done in the context of a depth-averaged shallow water model. Two physical mechanisms produce deposition-erosion patterns. Deposition either occurs where the current flows from high to low depth-averaged concentrations (1) or where the flow diverges (2). If flow conditions are quasi steady (i.e., the time scale on which bedforms evolve is much larger than the hydrodynamic time scales) only the former mechanism contributes to the formation of bottom patterns.

For constructing mound on a sea bottom, such as an artificial reef or large-scale landfill, many blocks are dumped into sea by a barge. An accurate prediction of behavior of blocks can save construction cost and time. Many studies have been performed to predict a sedimentation process of blocks from viewpoints of hydraulic experiment and numerical simulation. Most of studies by numerical simulation have been performed by using coarse computational grids in comparison with a representative solid-particle scale. Hence, a wake generated behind solid-particle could not be calculated precisely. In this study, the direct numerical simulation (DNS) is considered as a highly-resolving numerical method for flow analysis. The solid-liquid two-phase flow model based on the DNS has been developed. In addition, a numerical simulation for a sedimentation process of blocks was performed and flow around settlement blocks were shown in detail.

On September 6, 2007, the Seisho Bypass extending along the Seisho coast was severely damaged over a length of 1.1 km owing to storm waves associated with Typhoon 0709, resulting in roads being closed to traffic for urgent repairs. During the typhoon, severe beach erosion occurred owing to both strong offshore sand transport and westward longshore sand transport by storm waves, and the foreshore was rapidly narrowed. However, the foreshore was recovered except the damaged area of the highway as a result of the effect of normal waves. These beach changes were predicted using the contour-line-change model incorporating Fukuhama et al.'s concept. The predicted results were in good agreement with the measured beach changes.

This work deals with analysis of hydrographic observations and results of numerical simulations. The data base includes ADCP observations, continuous measurements on data stations and satellite data originating from the Medium Resolution Imaging Spectrometer (MERIS) onboard the ESA satellite ENVISAT with a spatial resolution of 300 m. Numerical simulations use nested models with horizontal resolutions ranging from 1 km in the German Bight to 200 m in the East Frisian Wadden Sea coupled with a suspended matter transport model. Modern satellite observations have now a comparable horizontal resolution with high-resolution numerical model of the entire area of the East Frisian Wadden Sea allowing to describe and validate new and so far unknown patterns of sediment distribution. The two data sets are consistent and reveal an oscillatory behaviour of sediment pools to the north of the back-barrier basins and clear propagation patterns of tidally driven suspended particulate matter outflow into the North Sea. The good agreement between observations and simulations is convincing evidence that the model simulates the basic dynamics and sediment transport processes, which motivates its further use in hindcasting, as well as in the initial steps towards forecasting circulation and sediment dynamics in the coastal zone.

Atoll islands are low-lying and consist of the biological organisms such as corals and foraminifers. These islands have high vulnerability to the coastal erosion and need the conservation plan. Sato and Yokoki (2008) developed the sediment transport model in Majuro atoll. Although they had a good agreement with realistic sediment volume change, the extreme large accretion and erosion were also calculated at some points. Toward accurate estimation of future land changes, we improved the model by considering the interaction between waves and land changes in this study. The calculated results showed no extreme accretion and erosion and better agreement with the realistic sediment volume during 10 years. The present model enabled reasonable estimation for the future land change in Majuro atoll.

The well-known empirical relationship between the equilibrium cross-sectional area of tidal inlet entrances (A) and the tidal prism (P), first developed by O'Brien (1931), has been extensively reviewed. A theoretical investigation indicates that a unique A-P relationship should only be expected for clusters of inlets that are phenomenologically similar (i.e. fairly similar hydrodynamic and morphological conditions), and that the exponent q in the A-P relation should be larger than 1. However, the relevant published data available to date do not clearly support this theoretical finding. A re-analysis of the available data sets indicates that they may not be sufficiently reliable to verify our theoretical finding with regard to q>1 due to the violation of the condition of phenomenological similarity, and possibly also due to violating the initial definitions given by O'Brien (1931) in estimating the tidal prism. The resolution of this issue is important because slightly different values of q result in significantly variable values for the equilibrium cross-sectional area of the tidal entrance. This may have significant implications in determining the true stable equilibrium entrance cross-sectional area. We advocate a careful re-scrutiny of the datasets available as a necessary first step in evaluating the robustness of the theoretical considerations presented herein.

Chilaw inlet, with the affiliated lagoon, is located on the west coast of Sri Lanka about 120 km north of the capital Colombo. Each year during the summer monsoon, which lasts from May to September, the inlet closes due to a sand spit forming across the inlet. The morphological evolution at Chilaw inlet was studied during the summer monsoon in order to understand the physical mechanisms governing the process of closure and how to mathematically model it. A measurement campaign was performed from May to July, 2006, resulting in high-resolution topographic maps, from which the morphological changes at the inlet during the monsoon could be deduced. A mathematical model was developed based on the identified sediment pathways at the inlet using a reservoir-type model description to simulate the morphological elements including the spit and its growth across the inlet.

Four inlets (Johns Pass and Blind Pass; and New Pass and Big Sarasota Pass) in two multi-inlet systems along the West-central Florida coast were studied. Johns Pass, New Pass, and Blind Pass are dredged every 4-9 years, whereas Big Sarasota Pass has never been dredged. The goal of this study was to investigate the morphodynamics of the four inlets and the influences of channel dredging on the flow patterns over the ebb tidal delta and sediment bypassing. Time-series aerial photographs and bathymetric maps starting from the 1920s were analyzed to assess the pathways of sand bypassing and morphodynamics at the inlets. The Coastal Modeling System (CMS), computing wave, current, sediment transport, and morphology change of tidal inlets, was applied and reproduced the observed medium-term morphology changes. CMS is then used to investigate influences of channel dredging on inlet morphodynamics.

A two-dimensional horizontal numerical model is presented for irregular wave propagation on fluid mud seabed on a frequency-by-frequency and direction-by-direction basis of the wave spectrum. A multilayered wave-mud interaction model is used to calculate wave damping rate with the constitutive equations of visco-elastic-plastic for the rheological behavior of fluid mud. Simulations of wave propagation over a mud berm off Dauphin Island in Alabama demonstrate favorable agreement between observation and simulation results. The results show that wave spectral modeling can be applied for propagation of irregular wave over a fluid mud layer.

The stratification of upper layer of coastal water can be regarded as an unused energy source in summer. In addition, the coastal water has capability to store the urban heat owing to the heat capacity difference to the atmosphere. This study assesses the usage and capacity of coastal water for heat storage. A set of numerical simulations of the urban heat release into coastal zone is performed for Osaka bay of Japan. The estimated urban heat along Osaka Bay is 1 kGJ/h within the distance from 500 m to 5000 m from the coastal line. The urban heat released within 2000 m from the coastal line had little influence on sea surface temperature of Osaka Bay.

The temporal and spatial variations of a hypoxic water mass in Tokyo Bay were investigated through intensive field surveys coupled with numerical simulations in summer 2007. The measurement results showed that the hypoxic water mass developed in the bottom layer from the head to the bay mouth in the first half of August. This water mass rose to the middle layer in the last half of August and had disappeared by the beginning of September. The analysis of observed seawater characteristic variations (temperature and salinity) and numerical simulation results suggested that these variations of the hypoxic water mass were regulated by a combination of the oceanic water variations at the mouth of Tokyo Bay and the wind-driven current.

The dispersion of point and nonpoint source pollutants may be complicated by the existence of coastal geographical features such as headlands. When coastal flow passes a headland on the coastal line, a recirculation zone will be formed as the flow separates at the headland toe. The experimental investigation was carried out in a purpose-built flume, located at the Manchester Tidal flow Facility (MTF). From the experiments, if pollutant is discharged at different locations around the perimeter of a headland, the potential of pollutant trapping around the headland and its generated recirculation zone will change accordingly. This study investigates the characteristics of pollutant dispersion in the region around the headland perimeter. Effective pollutant dispersion at the recirculation zone will be crucial to maintain the water quality of the region.

The present contribution aims to give insight into the sediment dynamics of the Bay of Marseille, under the general context of assessing the origin and fate of pollutants. Towards the objectives of the study, bed cover information was obtained from sediment samples and erodibility tests in flumes; while in-situ measurements (ADCP//Turbidity/bed level) were combined with satellite images and hydrodynamic models. The results showed that a) the estimated critical bed shear stress was in general lower than the one obtained following a theoretical Shields approach; b) sediment suspension was wave dominated and for conditions beyond the 90% annual exceedence values, bottom sediments can be active along most of the study area. Sinks and sources are scarce and fine suspended sediments from the Rhone River plume can episodically contribute to the sediment budget of the Bay of Marseille.

Mixed beaches are generally rare worldwide however they are common coastal features along the south coast in the UK and constitute the best natural defence to protect littoral environments against flooding and coastal erosion. To date, only a few investigations have attempted to estimate the LST rate for coarse grain size beaches, using models derived from the CERC equation giving K values of about 8% of those obtained for sandy beaches. In this work an impoundment technique has been applied for the first time on a mixed beach to calibrate the CERC equation using field data. Volumetric estimations from beach profile surveys and wave measurements recorded at the field site, Milford-on-Sea (South UK), are being used to estimate the LST rate, thus enabling model calibration for future shoreline change scenarios.

A new data-driven method for morphodynamic seabed modelling and prediction that is able to account for morphological relationships across space is presented. The new method uses a two-dimensional spatial statistical model that first derives surfaces that are representative of the spatial morphological properties in both the cross-shore and alongshore directions simultaneously. It evaluates the spatial changes that occur between successive surfaces across the time series to derive a spatial-temporal function of the behaviour evolution. The resulting function is then extrapolated to obtain a prediction. The model is initially applied to idealised morphological scenarios with known morphological and evolution properties to assess its validity for morphological applications. The outcome from the idealised cases indicates that the model is relevant to such applications as it was able to identify morphological properties and evolution behaviour. It was also able to predict future states of the idealised morphology within a margin that is less than the natural variability of the feature.

Morphodynamics over a shore-parallel sand shoal off south-central Louisiana, USA, have been recognized as complex given the occasional infusion of fine sediments, frequent winter storm passage, and complex shoal bathymetry. Results from field surveys and numerical model studies unveiled spatially-varying morphodynamics; Occasional infusion of fine sediments (i.e. fluid mud) created sediment heterogeneity on the shoal; the bottom sediments on the shoal further interacted with storm-induced hydrodynamics. Shallower depths on the western flank of the shoal had high sediment re-suspension, energetic flow velocity, and resultant high sediment transport; the result favored exposure of sandy material on the bottom; the eastern flank of the shoal, located in deeper water, experienced the accumulation of fine sediments. The results had potential implications for some benthic biological variables that spatially change across the shoal. Our results suggest complex bio-physical interaction with uncertainties and further implications for potential future sand mining for restoring rapidly deteriorating Louisiana barrier islands, essential for protecting wetlands along coastal Louisiana.

The sediment supply to the delta and adjacent beaches of the Elwha River in Washington State, USA is expected to increase significantly after removal of two dams. This paper describes the initial implementation of a process-based hydrodynamic and sediment transport model to predict sediment transport pathways and delta morphological response to changes in sediment supply in a mixed sediment system. The hydrodynamic model is calibrated and validated against water levels and currents measured in the Strait of Juan de Fuca and on the Elwha delta. Strong instantaneous and residual tidal currents are responsible for the transport and dispersal of fine-grained and sand-sized sediments across the delta. If sediment supply is large enough, some sediment will accumulate on the delta, modifying the delta substrate, which is presently dominated by hardbottom and coarse sediments.

On a basis of experiments the evolution of irregular waves (wave group structure) in coastal zone are studied. It was revealed that during the transformation of the waves the amplitude-frequency structure of individual waves varies quasi-periodically in space and in time due to nonlinear interactions between harmonics. The phase shift between the first and second harmonics strongly depend on the main direction of energy transfer. The ratio between the amplitudes of the first and second harmonics of waves also varies in time: waves with small first harmonics can have large higher harmonics, and there is the effect of "filling" of intervals between wave groups with large amplitudes of first harmonics by wave groups with large amplitudes of highest wave harmonics. It was shown that construction of the model describing variability of individual waves in a coastal zone is possible only at an initial stage of deformation of waves.

Sizes and numbers of sprays vertically ejected by wave overtopping through a flip-through process were measured using a back-light imaging technique in this experimental study. It has been found from the measured spray size and population that there are three primary mechanisms to form the sprays in the flip-through overtopping; (a) fine sprays are formed at the initial stage of overtopping and are vertically transported at very high speed. (b) large numbers of sprays with wide-ranging sizes are formed via disruption of an air-pocket compressed under breaking waves. (c) sprays are fragmented from the vertically extending, overtopping jets. The spray number density exponentially decreases with vertical level, and fine sprays (smaller than 1mm) predominate at the early stage of the event. Then, the mean spray size gradually increases up to 1.5 – 2.0 mm until the sprays begin to fall. The maximum spray-size spectrum occurs at 0.7 – 0.8 mm at any measurement level. There are two representative spectrum slopes to characterize the size spectrum for the relatively large sprays, which may also be resulted from the different mechanisms to form the sprays during the event — the sprays directly produced in flip-through process and the ones fragmented from the overtopping jet.

When a planar water jet obliquely splashes on still water, a secondary jet is ejected from the front face of the initial jet and is extended to be so-called finger jets. The formation of finger jets and evolution into sprays were visualized using a fluorescent imaging technique. Two different mechanisms to form sprays have been found in this study: (A) The sprays ejected by a moving contact between the splashing jet and receiving water surface, and (B) fragmentation of the finger jets into the sprays due to surface tension effect. The sprays formed in (A), having small diameter and high velocity, precede those formed in (B). Size distributions of the both fingers and sprays are found to be approximated by log-normal distributions. Transport and dispersion of the finger jets and sprays are described by the three representative velocities of (i) the moving contacts, (ii) the wave front preceding the moving contact and (iii) the secondary jet.

This paper presents four computer programs to calculate the physical characteristics of the progressive wave using linear, Stokes second order, Stokes third order, and cnoidal of Keulegan and Patterson theories: profile of water surface, celerity, wave length, horizontal and vertical orbital velocity, horizontal and vertical orbital acceleration, horizontal and vertical displacements, and under water surface pressure; in some theories energy, potency, group velocity and mass transport. An equation was developed to relate directly the full elliptical integrals of first and second class with their modulus, necessary for the cnoidal computer program. Results after application these four computer programs validate the application region proposal by Littman and Struik and the experimental works of Le Méhauté, Divoky and Lyn. Were compared results between different theoretical wave models and direct measurements made in some Mexican ports.

A method to determine swash zone boundary conditions is developed using remote sensing by video and ARGUS. Guard and Baldock (2007) proposed new numerical solutions for swash hydrodynamics, where the flow field varies according to a free parameter, k. k=0 in the Shen and Meyer swash solution but k=1 appears more realistic for real swash. This study has developed a semi-automated method to obtain values for k from multiple waves in field conditions using ARGUS video data and image analysis techniques. The results indicate that k is greater than 0 and close to 1 for natural swash. No trends were observed between k and run-up length, offshore significant wave height or tidal phase, consistent with the self-similarity of the swash hydrodynamics. In conjunction with modelling, the method offers the possibility of remote sensing of the asymmetry in the swash zone hydrodynamics.

In order to install the coastal camera observation system economically, a coastal observation system using WEB camera is newly developed. This system covers wide area, controlling the camera's pan, tilt and zoom periodically. Image processing like time exposure is also applied to observe surf zones. Using this system, we conducted long term continuous observation on tidal flats, river front and surf zone. Web camera is also controlled by many people on real time and sometime it is difficult to obtain periodical images. In order to complement loss images, a shore line estimation method using ABIC (Akaike's Bayesian information criterion) is considered. This method estimates the trend of shoreline erosion of Hasaki beach in the autumn of 2006.

X-Band radar observation has been conducted to observe morphology, flow and waves at the river mouth of Tenryu River, Japan. This imaging radar captures spatial distributions and temporal variation of water lines of the river channel and coast lines, and wave propagation in the shallow area. Breaching of the sand bar by a storm event and its recovery process, and behavior of the front formed at the river mouth by the river discharge are displayed in the study. The river flows into Enshu Coast which is suffering from severe erosion and enhancement of sediment supply from the catchment is planned to ease the degraded coast. The observation, in this context, aims to offer basic understanding of the behavior of the river mouth in morphological and hydrodynamic aspects.

Shoreline identification using satellite images is compared with in situ shoreline measurements in the Yucatan Peninsula to evaluate its potential for studying shoreline changes in places with a paucity of data. This study firstly tests the detection limits of shoreline identification by comparing a SPOT image with ground shoreline measurements, and secondly we show examples of overlaying satellite-derived shorelines from three different years to assess the ability of the technique to quantify real shoreline changes. The mean (-0.19 m) and the standard deviation (4 m) between the ground and satellite-derived shoreline are much smaller than the pixel size. Shoreline changes of more than 30 m were measured between images spanning several years (2004, 2006 and 2008) in areas near to coastal structures and near urban areas without coastal vegetation.

The characteristics of nonlinear wave decay over a fluidized bed in coastal waters were investigated by applying the HHT method to analyze the measurements from wave flume experiments. The Ensemble EMD (EEMD) was adopted to decompose the wave and pore pressure data into the intrinsic mod functions (IMF). In a resonantly fluidized response, the results of Hilbert amplitude spectrum of waves derived by the HHT illustrate that wave decay obviously occurs mainly on the fundamental component. In following non-resonantly fluidized tests, the wave decay becomes relaxed with thinner fluidized-layer. Furthermore, the wave decay is immediately due to fluidized response, but the decay along propagation over a fluidized bed is relatively insignificant. The wave-decay ratio is found to be directly proportional to the magnitude of Ursell number (Ur).

Coastal areas support many human activities and represent a very important habitat for many marine and bird species. The Dee estuary, located in the eastern Irish Sea, is 20 km long, 8 km wide at the mouth and is characterized by a 10 m tidal range. Suspended and seabed sediments in the Dee contain a diverse assemblage of non-cohesive and cohesive sediments, and therefore the threshold of motion at the bed could be a complex process, dependent on several factors. In this paper, we present data collected during 2 deployments in the Dee, including both acoustic and optical instruments to study the link between the hydrodynamics, turbulence, and suspended sediments. Suspended sediment concentration is clearly controlled by tides following the flood/ ebb and spring/neap cycle. Moderate wave events were observed to increase sediment concentration, though mainly near the bed. High concentrations of silt and very fine sand were found that could support the flocculation processes during the flood and ebb cycle. Sediment concentrations at heights above 1 m from the bed do not present direct relation with bottom stress.

The effect of the properties of oscillatory flow such as the Reynolds number and the KC number, on turbulence generated by a porous media was investigated. Violent turbulence was generated when interstitial velocity exceeded a critical level. Turbulence energy generated in pores increased with increase in the Reynolds number. The difference between minimum and maximum values of turbulence energy in a porous media increased with increase in the KC number. The turbulence energy spread wider outside a porous media with increase in the KC number. The maximum turbulence energy generated by a porous media in oscillatory flow was larger than that of unidirectional steady flow Finally, a modeling of the Reynolds stress in a porous media using velocity gradient and pore scale length was proposed.

In this paper, we highlight the various properties of wind-blown sand within a coastal dune, which is located on an eroded beach on the Enshu-Nada coast of Japan. Short term topographic changes of the Nakatajima dune have investigated with continuous field surveys over two years period (2007-2009). Measurements of wind and wind-blown sand transport rate were also carried out several times in winter. We found that the windward slope/dune crest in middle part of the dune is an actively eroding region by wind. The windward slope/dune crest of the dune was also migrated eastward as predominant wind direction in years or decades. The source of the sand transported mostly from the dune itself and limited amount of sand come from the shoreline, resulting the decreased in the elevation significantly in the West side of the dune.

The present paper presents a laboratory experiment of rip current circulations over a moveable bed. The rip current characteristics over four distinct beach morphologies, exhibiting more or less developed nature-like bar-rip morphology, were investigated. For each video run, the same offshore shore-normal waves were generated by the wavemaker with the same mean water level in order to study the sensitivity of the rip current characteristics as a function of the beach morphology only. In each case, a 1-hour video run was used to track a large number (~30) of drifters released within the surf zone. Image coordinates were then rectified to still water level Cartesian coordinates to compute drifter velocities, mean characteristics and surf zone retention rates. Results show the presence of classic rip current patterns with counter-rotating cells and a relatively narrow offshore-directed jet with, for three of the situations, a reasonably symmetric shape. Non-surprisingly, it was found that rip current intensity increases with increasing relative depth of the rip channel. The wave-driven circulations were strongly unstable. Computed standard deviation in flow intensity and direction provides high resolution information on the spatial variability of the rip current instabilities with, for instance, highly-pulsating and weakly directionally variable offshore-directed flow in the rip channel. Conversely to what was previously hypothesized in the literature, there was hardly trace of vortices being shed offshore and drifters exiting the surf zone compartment were not systematically caught by a pulsating jet. The cause for drifter exiting the semi-enclosed surf zone compartment remains, however, elusive and deserves further investigations. The computed surf zone retention rates (~90%) were of the order of those previously observed in the field, with no clear relationship with the mean rip current velocity or relative depth of the rip channel. Further video-runs will have to be analyzed to explore potential explanations.

Existing models for wave-related (cross-shore) sand transport are primarily based on data from oscillatory flow tunnel experiments. However, theory and former experiments indicate that flow differences between full scale surface waves and oscillatory flow tunnels may have a substantial effect on the net sand transport. In this paper, high resolution measurements of both boundary layer flow characteristics and net sand transport rates under full scale surface waves are presented. These experiments were performed for different wave conditions with medium (D₅₀ = 0.25 mm) and fine (D₅₀ = 0.14 mm) sand. It is shown that, especially under sheet-flow conditions, small wave induced net currents are of large importance for sand transport rates.

Laboratory measurements have been obtained in a large scale wave flume under erosive wave conditions. The focus was on the nearshore area (inner surf and swash zones). The experiment consisted of 47 erosive tests with around 500 irregular waves per test. The same wave time series was generated at each test. A sandbar was formed during the initial test which progressively moved off-shorewards, slowing down its migration velocity until it reached a relatively more stable condition. Flow velocity and sediment concentration have been obtained and analyzed. Data analysis shows that the sediment is set in suspension in an event-like manner, symptomatic of the stochastic processes driving the suspension. However a repeatable pattern of sediment suspension could be observed during successive tests, suggesting that a suspension process might be unraveled under the stochastic pattern. It is found that sediment concentration does not correlate well with flow velocity either at incident wave frequencies or at lower frequencies. The computed power spectrum of velocity and concentration shows that sediment is set in suspension at frequencies lower than those of the velocity. Computed turbulent kinetic energy (TKE) time series show patterns similar to suspended sediment, although no significant correlation between concentration and TKE was found. Preliminary analyses suggest that wave-wave interaction is an important mechanism inducing sediment stirring.

The confidence interval for the extreme wave height of longer return period is good for nothing. Unreasonable uncertainty of estimation has been accepted. We were helpless against this difficulty. We engineers believe in a certain limitation of extrapolation, but they have been bothered with a problem: how much wide interval is no worth being considered. This study proposes a new index to use for this judgement.

A methodology to estimate storm-induced morphodynamic risks is presented. The storm-induced coastal response is separately assessed in terms of inundation, beach profile and transport potential. Inundation is calculated by means of the run-up Ru_2% at the peak of the storm. Erosion is characterized by the eroded volume from a beach profile and, overall sediment transport is parameterized in function of the integrated wave power during the storm impact. These three parameters are used to calculate the resulting risk by estimating their probabilities of occurrence using the event and response methods. In the first one, the probability of occurrence is assigned from the extreme wave distribution (events) which is used to calculate the corresponding morphodynamic processes. In the response approach, storm wave data are used to build a data set of storm-induced responses which are later fitted to an extreme distribution. These two methods have been applied to characterize storm wave-induced morphodynamic risks at Costa Brava (NE Spanish Mediterranean coast). Results show that for this case, the use of the event approach significantly under-predicts the morphodynamic response for any probability of occurrence and, in consequence, its use will under-predict storm risks.

Strong low-pressure systems traveled along Japanese Main Island in October 2006. High waves and storm surge attacked Kashima Coast resulting huge erosion over the area. The extent of the study area is 38 km long for the northern Kashima Coast and 15 km long for the southern Kashima Coast. This study analyzed the foreshore erosion caused by the storms using airborne laser data measured in October 2005 and November 2006. The results are compared with the distributions of longshore component of wave power and wave run-up which estimated using SWAN wave model. The results indicate that the amount of erosion and its distribution are in agreement with the longhsore component of the wave power along the coast and the most of the high wave run-up values appear within the high eroded sections. These were especially prominent at the untreated sections, which should be close to the natural response by wave action.

Field surveys were performed in the southwest part of Bangladesh to learn lessons out of severe disasters due to Cyclone Sidr. Spatial distributions of inundation heights were measured around the most damaged area. Inundation heights along the Baleshwar River and the Burishwar River were relatively high compared to those observed on the coast of Kuakata although these sites are far from the coast. Detailed surveys were thus performed in these three areas and there found several residents who witnessed bore-like waves hitting on the damaged area. Embankments along the river had been eroded before the storm while dikes on the coast significantly functioned to reduce the damages of the coastal area behind.

ECORS is managed by the French Hydrographic Office (SHOM) and aims at improving the description of the nearshore environments for naval amphibious operations, including a demonstration of short-term prediction on the morphodynamics of sandy coasts. The understanding of hydrodynamic and morphodynamic processes that will be generated by the project will certainly find many other applications, including coastal management. Over the years 2006 to 2011, the ECORS program include three main tasks: theoretical research, experiments and numerical modeling. The project include both field and laboratory experiments. Such a wide scope was made possible by the additional contributions from many research institutes and local authorities. The first step is to improve the quality of nearshore and offshore models over timescales ranging from one day to some months. Based on these research and campaigns, a coastal forecasting simulator will be created.

Acoustic measurements of the flow, suspended sediments and bedforms were collected under regular waves above a sandy bed in a large scale flume facility. The objective of the study was to obtain simultaneous collocated near bed profiles of the horizontal and vertical flow and the suspended concentration, as bed forms changed due to increasing wave height. To obtain the measurements a recently developed dual frequency acoustic Doppler velocity profiler was deployed to provide concurrent measurements of the hydrodynamics, the entrained sediments and the location of the bed. Here we present some of the preliminary results from the study.

Accurate determination of the sediment transport budget is difficult to achieve. The aim of this study is to measure the bedload sediment transport using densitometry parameters (CT-scanning), flow velocity, sediment grain-size and porosity. An open-water channel, with an inner rectangular section, passes trough the CT-scanner's mobile gantry. The lower part of the flume is filled with a layer of quartz sand. The CT-scanner measures slices of 300 by 300 mm, 0.6 mm thick, separated by a constant time interval to produce a 4D volumetric representation of the sand ripple. Density profiles inside the volume record variations from the bottom layer of the sediment bed to the top of the water column without hydraulic interference. The sediment mass measured, over a datum and inside the upper bedload transport zone, indicates a transport below the datum. Under estimation of bedload measurements results in a new lower porosity value.

Waves in the surf zone are characterised by their forward-leaning sawtooth shape, which leads to stronger acceleration and higher net sand transport in the onshore direction compared to the offshore direction. Present understanding of acceleration effects on sand transport is poor due to a lack of measurements of the detailed processes. The paper reports new large-scale oscillatory flow tunnel experiments with sawtooth-shaped flows over a fine sand bed under sheet flow conditions. Sand concentrations and velocities were measured using CCMs and PIV respectively. Results are presented showing concentration and velocity measurements extending deep into the sheet flow layer and intra-wave erosion depth, sheet flow layer thickness and flux. The significant effect of acceleration skewness is seen in all of the results.

Accelerated sea level rise in the 21st century and beyond will result in unprecedented rates of coastal recession which will threaten $ billions worth of coastal developments and infrastrucure. Therefore, we cannot continue to depend on the controversial Bruun rule for estimating coastal recession due to sea level rise. Furthermore, the emergence of risk management style coastal planning frameworks is now requiring probabilistic estimates of coastal recession. This paper describes the development and application of an innovative process based, probabilistic model for the estimation of coastal recession due to sea level rise. The method requires as input long term water level and wave data which are now available via widespread tide gauges and global hind cast models respectively. This method is proposed as a more appropriate and defensible alternative for the determination coastal recession due to SLR for planning purposes.

The influence of global climate change due to green house effects on the earth environment will be required impact assessment, mitigation and adaptation strategies for future our society. This study predicts future ocean wave climate in comparison with present wave climate based on the atmospheric general circulation model and global wave model. The annual averaged and extreme sea surface winds and waves are analyzed in detail. There are clear regional dependence of annual average and extreme value from present to future climate. The wind speeds and wave heights of future climate are increased in middle latitudes and the Antarctic ocean, and these are decreased in the equator. The annual averaged winds and waves are decreased off coast of Japan but their maxima are increased than those of present climate.

Using the maximum significant wave in a year from the NOWPHAUS dataset, the influence of global warming was examined. The examination indexes of global warming and indexes of the maximum significant wave were carefully prepared. Cluster analysis performed considering typhoons showed that the maximum significant observed wave in August and September is effective. Several stations were selected under this condition. The scattered plot matrix, WAST is effective. These two values were checked by Spearman's rank correlation coefficient of 694. Next, Median was selected as the representative value of the maximum significant observed wave based on correlation coefficients. A linear regression model to estimate the maximum significant wave was calculated using WAST. Adjusted R-squared: was 0.3234. The model indicates that if temperature is increased 1 ^°C, the median of the maximum significant wave increases 3.35m.

One of the most commonly observed swash zone morphological patterns on coarse-grained beach is beach cusps. This study applied the new numerical implementation to improve the calculation accuracy in the shallow water depth region of a process-based morphodynamical model provided by Dodd et al. (2008). This numerical model used to simulate beach change in the swash zone in order to understand the long-term formation and evolution of beach cusp patterns in this study. Not only the phase-averaged flow field is illustrated in this study, but the tracking particle technique is also introduced to investigate flow behaviour in beach cusp area. In addition, as the infiltration term plays an important role of beach cusp shape, thus the sensitivity tests of infiltration are also provided in this study.

Greater insight in delta evolution can be acquired by linking the fields of hydraulic engineering and geology. The process of sediment reworking in the deltaic environment under wind-generated wave conditions is investigated with a two dimensional (depth-averaged) process-based model, set up in Delft3D. With upscaling methods for bed-level dynamics, it is possible to simulate long-term delta morphodynamics. In addition, a bookkeeping method allows for monitoring changes in stratigraphy. Herein, simulated morphology and stratigraphy of a pre-defined delta under wave forcing are presented. Further, a sensitivity analysis on some important parameters of the developed model is provided. The model shows great potential for future development and is expected to perform well for specific case studies.

Coastal wetlands are under a great deal of pressure from forces of human population's intervention. It is important to measure and assess erosion and deposition rate of suspended sediment in coastal zones. To measure the suspended sediment transport along and across a tidally-dominated river, Ota River, we deployed 3 AquaDopps in two different arrangements, one in 3 stations along the river in right, left, and center of the Ota Floodway for a month, and the second was 3 stations in one cross sections at the same time. The first experiment managed to be done in the winter of 2008 and the latter in Aug. 2008. Surveying the results points out that continuous suspended sediment settlement happens along the most length of the river; in some areas in consequence of meander shape of the river, incessant transversal suspended sediment transport formed sandbars in one side of the river.

Long-term migrations of sandbars on Chirihama Beach, Japan, have been investigated using a set of field surveys collected over 9 years. The typical profile configurations are characterized by the presence of multiple bars. The height of the outer bar exceeds 4 m, when the bar evolves most significantly. The movements of the bars are significant. For the time variation, it is shown that the net offshore periodic migrations of bars have been repeated. The length of one cycle is approximately 8 years, and the interval between each cycle is approximately 3 to 4 years.

The three-dimensional spatial characteristics of velocity and turbulence of tidal flow around an offshore wind turbine model have been measured using the technique of Particle Image Velocimetry, (PIV). This approach allows for the instantaneous velocity measurement in large volumes of water. This paper presents analysis of velocity and turbulence parameters in the wake flow behind a cylinder for different tidal stages. The wake flow behind a cylinder is highly complex making it difficult to characterise using point measurement techniques in the laboratory, and model numerically. The PIV measurements enabled the derivation of detailed velocity vector maps, turbulence intensities, kinetic energy and Reynolds stresses across the water column. Results showed a clear flow separation zone between reversed and stream-wise flow in the wake, the structure of which depends on flow velocity and water depth.

A series of physical model tests were conducted in a wave flume to investigated the Bragg scattering for waves propagating over a series of poro-elastic submerged breakwaters. The main purpose of this study is to develop a motion visualization analysis system for laboratory observation based on a CCD camera. Instead of intrusive wave gauges and linear displacement sensors, a high speed camera is used to capture images for observing wave motions and poro-elastic structure deformation. Subsequent image processing techniques are employed to analysis the wave characteristics and the motions of elastic submerged breakwaters. In order to overcome the insufficient image resolution for the motions of poro-elastic breakwaters in vertical direction, a polynomial regression for the gradient of image gray level is employed in this study.

An experimental investigation is presented of a turbulent round jet is discharged into regular progressive waves. The particle image velocimetry (PIV) technique was employed to measure the instantaneous velocity field of a turbulent jet in a wave environment. Three different wave conditions were used to examine the effects of wave amplitude on a turbulent jet with water waves. The experimental results showed that the jet width, magnitude of the mean flow and RMS velocity fluctuation increase significantly when the jet was under a wave environment. It is found that the mean profile of the jet near the nozzle is similar to that of a free jet, but the shape of the profile changes with the jet decayed and spread downstream in the wave environment. The magnitude and profile of the RMS velocity fluctuation of the jet increased rapidly and seemed to reach a self-similar state with the increase of wave height.

This paper presents results of experiments conducted with water waves breaking over a bottom topography resembling a bar. The experiments were conducted in a glass walled laboratory wave flume. The instantaneous water levels along the flume were measured using resistive wave gauges, providing estimates of the mean wave-heights and water levels at various positions along the flume. The instantaneous velocity fields for positions shorewards of the bar crest were measured using a video based digital correlation image velocimetry (DCIV). The mass (/velocity) and momentum fluxes were computed from the velocity flow fields by means of phase ensemble averaging followed by time averaging. These parameters reached a maximum value some distance shorewards of the break point on the bar. The relative density of the fluid in the crest of the wave, estimated using the forward and reverse velocity fluxes, was found to be in the range from 0.4 to 0.8. Time-averaged turbulence intensities and turbulent kinetic energies are also presented.

Hvide Sande harbour on the exposed North Sea coast is protected by shore-normal breakwaters and experiences considerable sedimentation in its access channel. Facing the need to accommodate larger fishing vessels, the harbour wishes to increase the navigation depth in front of the harbour entrance while at the same time reducing the sedimentation in the access channel. An innovative scheme is proposed consisting of a combination of new protective breakwaters and an updrift capital dredging of the coastline: while the streamlined breakwaters will increase the bypass of sediment past the harbour mouth by increasing the flow velocity due to contraction, the retreat of the coastal profile will help maintain the required additional water depth needed. The present morphological study shows that the proposed scheme results in an increased equilibrium depth of the bypass bar in front of the harbour without increasing the downdrift erosion, and an improved natural bypass of the littoral drift.

Sabine Bank, a transgressive shoal located 30 km off the Louisiana-Texas border, USA, has been considered as one of the plausible resources for re-nourishment of the adjacent barrier islands and beaches. Little has been reported on the bottom boundary layer dynamics and sediment transport from this shallow coastal environment. A comprehensive field investigation, coupled with numerical modeling, has been implemented. Wave and bottom boundary layer interactions were strongly associated with the passage of cold fronts across the region. Strong southerly/southeasterly wind regimes also contributed to the re-suspension and transport of sediments, even during summer season. Modification in bulk wave parameters due to two mining scenarios were computed using modified bathymetries and the result shows minimum impact from the proposed mining from the shoal crest. Sediment re-suspension intensity (RI) was computed and found to be high over the inner shelf and shoal during severe storms.

Numerical simulations of hydrodynamics and sediment transport were conducted for Sebastian Inlet, FL, using the Coastal Modeling System (CMS). The study is aimed at determining changes in morphology under the existing topography and configuration as compared with two proposed modification scenarios: 1) an extension of the south jetty and 2) dredging of the outer section of the ebb shoal. The analysis time period encompasses short term (storm vents), as well as long term (seasonal). Overall, the predicted morphology changes were in good agreement with measured data. Model calculations of littoral sand transport under the existing configuration indicated an overall sand transport to the south over the long term, as well as reversal approximately 2km south of the inlet. The model also successfully reproduced the variability in littoral transport due to the different storms, especially the reversal in the drift direction.