Search

A review of the existing research on the interaction between a pipeline and an erodible bed exposed to waves and/or currents is presented. The review covers three topics: scour, liquefaction, and lateral stability of pipelines. The basic mechanism that leads to scour in twodimensional (2D) and three-dimensional (3D) cases is first described, as deduced from small-scale laboratory experiments. The onset of scour from piping and the developing tunnel erosion are among the processes described. The lateral expansion of the scour hole along the pipe is described, also based primarily on small-scale laboratory experiments. The state of the art of the mathematical/numerical modeling of the scour processes is presented. The associated self-burial of the pipe is described and compared to field observations. In addition to scour, liquefaction may also constitute a risk for pipeline stability. The cause of liquefaction and the resulting consequence for pipeline stability in a natural environment are discussed. Finally, the lateral stability of pipelines placed on an erodible bed and exposed to waves is briefly described. [ABSTRACT FROM AUTHOR]

Beach profile evolution is a dynamic phenomenon that often leads to threatening consequences such as severe beach erosion and shoreline retreat. A new comprehensive morphodynamic model is introduced in this study that includes representation of bedload and suspended size-selective sediment transport and cross-shore sediment grain-sorting models. The model is capable of simulating the changes in cross-shore bathymetry and sediment grain size composition observed under laboratory conditions for both erosive- and accretive-type equilibrium beach profiles. The new model is most advantageous for scenarios with poorly sorted sediments or sites with strong cross-shore variability in sediment grain sizes. Information on sediment size composition in the domain and its history is also provided by the new model, which can be useful for engineering, recreational, or biological considerations. [ABSTRACT FROM AUTHOR]

The response of physical models of beach profiles to random breaking waves was studied to investigate size-selective sediment transport and cross-shore profile evolution. Three types of beach profiles with different sediment mixtures were considered and subjected to waves until profiles reached equilibrium. Size-selective sediment transport was evident in the experiments, with the mean sediment size varying up to 20% along the beach profiles. Consistent coarsening and fining of the surface sediment in the experiments revealed size-selective sediment transport governed by cross-shore variations in energy dissipation, affecting important beach profile features such as sandbar structures and offshore and foreshore slopes. The theoretical basis of the transport phenomenon was described by analyzing the relationship between the transport processes and essential wave and hydrodynamic parameters obtained using a new set of numerical models. The results showed that beach profile changes and associated sediment grain sorting are most sensitive to instantaneous total water velocity and local energy flux under propagating waves. [ABSTRACT FROM AUTHOR]

This paper focuses on the optimal location for dumping nourished sand on a barred coastline. This is done by investigating the short-term behavior of the cross-shore redistribution of nourished sediment on a breaker-bar profile in a two-dimensional vertical plane. This is achieved by the use of a complete numerical description of the surf-zone processes with respect to both hydrodynamics and sediment transport. The numerical model is based on the finite-volume approach with a free surface-tracking method, also known as the volume of fluid (VOF), and the sediment transport is calculated applying the Engelund and Fredsøe deterministic concept. The methodology is as follows: a Dean/Bruun equilibrium profile is exposed to regular waves (chosen as and ). These waves will form bars on the Dean/Bruun equilibrium profile, and the wave impact is continued until a quasi-steady behavior of the bars has been obtained, i.e., bars that have stopped growing in height and only migrate slowly offshore. Next, the profile is nourished. The resulting continued morphologic developments are compared with the development of the unnourished (reference) profile. Also, the effect of a net shoreward current over the profile is consider as a means of imposing the net recirculation resulting from longshore nonuniformities or the impact of wind-induced shear stresses. The impact of wave height, irregularity in incident waves, and the size of the sediment grains on the cross-shore distribution of suspended sediment transport rates are described. In addition, all profiles are seen to lose sediment seaward when no net shoreward current is enforced over the outermost breaker bar. Alternative strategies for nourishment are investigated, and it is seen that the shape on the nourishment seaward of the outermost bar can have both destructive and protective impacts on the original shoreward-located cross-shore profile. [ABSTRACT FROM AUTHOR]

This paper introduces the tide data acquisition and processing procedures in the Nationwide Ocean Wave Information Network for Ports and Harbors (NOWPHAS), especially those for global positioning system (GPS) buoys that measure water surface elevations using real-time kinematic GPS technology at water depths of 100-400 m and 10-20 km from the coastline. It then describes specific features of the 2010 Chile tsunami and the 2011 Tohoku tsunami, including foreshock and main shock profiles, which were measured along the Japanese coast by the NOWPHAS equipment. In the main shock of the 2011 Tohoku tsunami, the GPS buoy at a water depth of 204 m off Kamaishi Bay showed that the first wave crest consisted of primary slow and subsequent quick rises, and exceeded 6 m approximately 30 min after the earthquake occurrence. Some geometrically adjacent sets of GPS buoys, coastal wave gauges, and coastal tide gauges revealed the tsunami propagation and amplification near the coast. [ABSTRACT FROM AUTHOR]

Reliable simulation of onshore-offshore sandbar migration under various wave and current conditions has remained a challenging task over the last three decades because wave-undertow interaction in the surf zone has been neglected in the existing numerical models. This paper presents the development of an improved sandbar migration model using a phase- and depth-resolving modeling approach. This new model includes interactions between waves and undertow and an empirical time-dependent turbulent eddy viscosity formulation that accounts for the phase dependency of turbulence on flow velocity and acceleration. The authors demonstrate through extensive model-data comparisons that these enhancements resulted in significant improvements in the predictive capability of the cross-shore sandbar migration beneath moderate and energetic waves. The comparison showed wave-undertow interaction playing a crucial role in cross-shore sediment transport. Waves increased the undertow-induced suspended-load flux during offshore sandbar migration, and a weak undertow suppressed the wave-induced onshore bed-load transport during onshore sandbar migration. The proposed empirical time-dependent turbulent eddy viscosity significantly improved the prediction of onshore-directed bed-load transport during onshore sandbar migration. [ABSTRACT FROM AUTHOR]

A theory on the horizontal spreading of contaminants in the surf zone is described in this paper. The surf zone is viewed as a narrow strip comparable to the characteristic wavelength, in which turbulence caused by wave breaking is strong. Flows inside the surf zone consist of both oscillatory motions and a steady current induced by breaking waves. The wave field in the shoaling zone is modeled by the linear theory for monochromatic waves, and it is assumed that the breaking wave height is proportional to the local depth in the surf zone. The simplest scenario of longshore current on a straight beach of constant slope is considered, for which the longshore current velocity is predicted by a slightly modified version of Longuet-Higgins' original theory developed in the 1970s. On the basis of the estimation that the time scale of horizontal diffusion is much longer than the wave period, the perturbation method of multiple scales is applied to derive the transport equation for the advective diffusion of a solute. The total advection velocity is found to be the sum of the steady current caused by radiation stresses and a contribution from the covariance of fluctuating velocity and concentration, which is the same as the Stokes drift in periodic waves. Numerical predictions for the movement of a solute cloud released, instantaneously or continuously, in a longshore current along a plane beach are examined. The solute is found to drift shoreward in addition to the expected transport along the shore. Computed examples are presented and comparisons with available laboratory experiments are also discussed. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the seabed liquefaction beneath standing waves. Silt (with ) was used in the experiments. Two kinds of measurements were carried out: pore water pressure measurements and water surface elevation measurements. These measurements were synchronized with video recording of the liquefaction process from the side. The ranges of the various quantities in the experiments were wave height , wave period , and water depth . The experiments show that the seabed liquefaction under standing waves, although qualitatively similar, show features different from that caused by progressive waves. The pore water pressure builds up (or accumulated) in the areas around the node and subsequently spreads out toward the antinodes. The experimental results imply that this transport is caused by a diffusion mechanism with a diffusion coefficient equal to the coefficient of consolidation. The experiments further show that the number of waves to cause liquefaction at the nodal section appears to be equal to that experienced in progressive waves for the same wave height. [ABSTRACT FROM AUTHOR]

Landslide-generated impulse waves are considered a severe danger for humans and infrastructure. Design formulas following intensive laboratory research allow for a quick assessment of potential slide-event wave features. Unfortunately, prototype data are rare except for underwater slide deposits often corresponding to the only traces of a past event. If past events could be back-analyzed based on in situ scanned underwater slide deposits, the existing assessment approaches could be supported. Video recordings of 41 slide-generated impulse wave tests in a two-dimensional (2D) wave channel were analyzed regarding the underwater slide dynamics and their final deposition patterns. The underwater slide propagation process is described for three specifically selected tests. Correlation equations are presented for underwater slide front propagation and velocity, which are also useful for numerical modeling purposes. In addition, correlation equations are given for slide deposit features, including length and thickness, allowing for their estimation based on initial slide parameters. [ABSTRACT FROM AUTHOR]

The current study experimentally investigates the wave-induced drift velocity of two-dimensional large floating objects (with , where = longitudinal length of the floating objects, and = wavelength) under the action of regular waves. The focus is on the high-precision measurement of drift behavior and a wider range of parameters than what was previously reported in the literature. Stacked wood pieces with various submergences () were used to simulate the large floating objects on the water surface. An infrared-based motion monitoring system with two high-resolution cameras continuously recorded their motion in regular waves. The results show that the drift velocity increased quickly from the beginning and reached a quasi-steady mean value. The magnitude of the quasi-steady drift velocity increased with ratio of the pitch period to the wave period (), until reaching a maximum when . After that, further increasing the ratio of did not lead to additional significant changes in the drift velocity. Three nondimensional submergences () of 0.0075, 0.022, and 0.036 were examined. The drift velocity typically decreased with larger submergence, which can be attributed to the larger added mass involved in the oscillatory motion. [ABSTRACT FROM AUTHOR]

The road toward a sustainable inland waterway network entails the installation of ecologically sound and technically effective bank protection. Heavy shipping traffic complicates the development of environmentally friendly bank protection on confined, nontidal waterways. Because in such conditions ship waves vary with ship design and operation, with topographic boundaries and locally changing hydraulic conditions, ship wave action is poorly understood. Therefore, a stand-alone field monitoring system was designed that accurately measures the impact on and response of environmentally friendly bank protection, consisting of off-bank timber piling and vegetation (reeds). Subsequently, the instrumentation was re-engineered and extended to a mobile version, enhancing the dynamic measurement possibilities. In this paper, the setup of both measurement systems is described, together with a detailed overview of the selected measurement instrumentation and good installation practices. The added value of these field monitoring systems is illustrated with an example of the monitoring system's data output. [ABSTRACT FROM AUTHOR]

Breakwaters can be broadly classified into overtopping and nonovertopping structures. In the case of a nonovertopping breakwater, either the crest level is designed in consideration with the maximum run-up level or a concrete crown wall is provided at the crest on the ocean side of the breakwater to avoid or minimize overtopping. It is essential to understand the wave-induced dynamic and uplift pressures exerted on the vertical face and base slab of the crown wall to incorporate this information in the design. The recently introduced armor block KOLOS, a modified version of DOLOS, is considered for detailed investigation of its hydrodynamic characteristics. Empirical relations have been proposed for the wave-induced pressures caused by regular waves on the crown wall fronted by KOLOS through a comprehensive experimental program. The overall results, compared with a breakwater fronted by natural rocks, indicate that the KOLOS armor layer offers better wave energy dissipation and results in minimal pressures induced on its crown wall. [ABSTRACT FROM AUTHOR]

A laboratory experiment consisting of five tests was conducted to examine the effects of woody plants on erosion and overwash of high and low dunes. Scarping occurred on the foreslope for three high dune tests and no scarping occurred for two low dune tests. A narrow vegetation zone on a steep backslope of a high dune did not reduce wave overtopping and overwash in comparison with the corresponding bare dune. A wide vegetation covering the high dune reduced foreslope scarping, prevented wave overtopping initially, and reduced sand overwash after the initiation of wave overtopping. A wide vegetation zone covering an entire low dune reduced dune erosion by retarding wave uprush and reducing wave overtopping and overwash. [ABSTRACT FROM AUTHOR]

The current study proposes prediction formulas both for random wave runup and mean overtopping discharge at seawalls constructed on land or in very shallow water. Although several existing formulas for runup and overtopping use the incident wave characteristics at the toes of seawalls, this study adopts the equivalent deepwater wave characteristics and an imaginary seawall slope for easy application of the formulas, especially in relation to seawalls constructed on land. The prediction formulas for overtopping use the predicted runup values. For the wave runup prediction formulas two sets of experimental data are used; i.e., a new set of data and the data obtained in a previous study. For the wave overtopping prediction formulas, the experimental data measured in a previous study are used. Comparisons with measurements show good performances of both new prediction methods. [ABSTRACT FROM AUTHOR]

Profiles of exceptionally large waves before a vertical breakwater were obtained by using a gauge array. These profiles were compared with the profiles obtained using the quasi-determinism (QD) theory. The experiment performed in the field confirmed the QD theory for a wave field that is strongly nonhomogeneous in space. [ABSTRACT FROM AUTHOR]

The channel analysis and design evaluation tool ( CADET) is a numerical program to determine the optimum dredge depth for the offshore portions of entrance channels. A brief description of the theoretical basis and risk assessment in CADET is presented. Validation comparisons between CADET predictions and field measurements of wave-induced vertical motions at Ambrose Channel, New York, are presented. Prototype ship motions were measured with a differential global positioning system in April 1998 along three 488-m-long reaches. Comparisons were made with six ships, three tankers and three containerships, during inbound and outbound transits. In general, the CADET predictions matched the field measurements reasonably well, especially considering the wave heights were relatively small during the measurement period. [ABSTRACT FROM AUTHOR]

In the probabilistic design of a breakwater armor layer, it is often necessary to calculate the damage accumulated over the breakwater's life cycle. In this paper, a comparison is made between existing methods to calculate the cumulative damage to the breakwater armor layer. In the current study, hydraulic experiments are conducted to gauge the damage progression of Tetrapod armor units. When severe damage occurs at the beginning of the breakwater's life cycle, the two methods do not differ significantly, but, in general, the latter predicts a larger cumulative damage than the former. For a Tetrapod armor layer, it is recommended that the average of the two methods be used. [ABSTRACT FROM AUTHOR]

Different types of strengthening systems were introduced to protect the crest and land-side slope of the levees against surge overflow and wave overtopping after Hurricane Katrina. Three levee-strengthening systems, roller-compacted concrete, articulated concrete block, and high-performance turf reinforcement mat, were investigated through full-scale laboratory tests in this study. Hydraulic performances of these three levee-strengthening systems were compared to determine the effect of strengthening systems and to provide the equivalency analysis between surge-only overflow and combined wave and surge overtopping. The findings of this study indicate that the high-performance turf reinforcement mat system has the strongest effect in reducing and smoothing the overtopping discharge and in reducing the flow velocity and wavefront velocity on the land-side slope, whereas roller-compacted concrete has the weakest effect. Equivalency analysis between surge-only overflow and combined wave and surge overtopping reveals that the impact of waves on the overtopping discharge and flow velocity on the land-side slope during combined wave and surge overtopping is negligible when the relative freeboard . The equivalency relationships are proved to be applicable to all three tested strengthening systems and can be used to estimate the hydraulic overtopping parameters on levees under combined wave and surge overtopping conditions strengthened with roller-compacted concrete, articulated concrete block, high-performance turf reinforcement mat, or other strengthening systems. [ABSTRACT FROM AUTHOR]

About 6,300,000 pressure head waves beneath the sea surface were recorded by an array of 26 transducers aligned orthogonally to the coastline of Reggio Calabria, Italy. The data set covered spectra from very narrow unimodal to very broad multimodal and waves from shallow to deep waters. Herein, the quasi-determinism (QD) theory is proven to be very effective in predicting the probability of large-wave heights as well as the period and particle acceleration of these waves both on deep and shallow waters. In addition, the Tayfun model for predicting the probability of large-wave heights is also proven to be highly effective. [ABSTRACT FROM AUTHOR]

The relative contributions of sea-level rise (SLR) and increasing extratropical storminess to the frequency with which waves attack coastal features is assessed with a simple total water level (TWL) model. For the coast of the U.S. Pacific Northwest over the period of wave-buoy observations (approximately 30 years), wave height (and period) increases have had a more significant role in the increased frequency of coastal flooding and erosion than has the rise in sea level. Where tectonic-induced vertical land motions are significant and coastlines are presently emergent relative to the mean sea level, increasing wave heights result in these stretches of coast being possibly submergent relative to the TWL. Although it is uncertain whether wave height increases will continue into the future, it is clear that this process could remain more important than, or at least as important as, SLR for the coming decades, and needs to be taken into account in terms of the increasing exposure of coastal communities and ecosystems to flooding and erosion. [ABSTRACT FROM AUTHOR]

Sea-level rise (SLR) estimates vary broadly, but most estimates predict significant increases in sea levels within the next century. Through the use of validated, coupled wave and hydrodynamic models, this study investigates SLR effects on storm surge and nearshore waves, including variation with coastal landscape type and storm characteristics. Both the wave and hydrodynamic models account for bottom friction based on land-use type, so the modeling procedure accounted for SLR-related changes to land cover, in addition to higher mean sea levels. Simulation of storms with similar meteorological characteristics and track but with landfall in the northeastern and southwestern coastal areas allowed examination of how the coastal features influenced the storm surge and wave response to increased sea levels. The simulation results analyzed here demonstrate that the relationship between storm surge and relative SLR (RSLR) varies between geographic region and storm scenario. The increase in an inundated area is linear in the north, and in the south, the inundated area approaches the northern values for similar storms asymptotically. Nearshore wave results indicate, as expected, that larger water depths created by positive RSLR and amplified surge allow larger waves to propagate into inland areas. For the Texas simulations, it was found that an increase in hurricane wind speeds of 25% is approximately equivalent to a RSLR of 0.5 m in terms of increased area of inundation impact. Because of the complexities of storm-surge dependency on storm strength, track, and local topography, there is no one-size-fits-all response to RSLR descriptive of all locations. Site-specific computer modeling should be used to evaluate the risk facing coastal communities. [ABSTRACT FROM AUTHOR]

Experiments on a large pipeline and a small pipeline in a piggyback configuration under regular and irregular waves are carried out. A comparison of the wave forces on the large pipeline and the small pipeline is made. The nondimensional force coefficients for the drag, inertia, and lift are obtained based on the Morison equation. The effects of the Keulegan-Carpenter (KC) number and the spacing ratio between the two pipelines on the force coefficients for the large pipeline, small pipeline, and piggyback pipeline system are investigated. The experimental results indicate that the variation tendencies of the drag coefficients and inertia coefficients with the KC number or the spacing ratio for the large pipeline, small pipeline, and piggyback pipeline system are similar. The variation tendency of the lift coefficient with the spacing ratio for the large pipeline is opposite to that for the small one. [ABSTRACT FROM AUTHOR]

Extensive knowledge is available on the overtopping behavior of traditional smooth impermeable sea defense structures, such as mildly sloping dikes and vertical walls, both typically featuring a high crest freeboard to reduce wave overtopping. A particular design application emerges in the development of wave energy converters of the overtopping type, where maximization of wave overtopping is required, i.e., smooth impermeable steep sloping structures with low crest freeboards subjected to nonbreaking waves. To date, relatively limited knowledge is available on the overtopping behavior of those structures. In this study, the average overtopping rate obtained from new experiments has been analyzed and compared with existing prediction methods. This study contributes to a better knowledge on the overtopping behavior of the steep low-crested structures, which is positioned in between that of mildly sloping dikes and vertical walls and that of structures with zero crest freeboards and relatively large crest freeboards. The existing prediction methods seem unable to predict the significant effects of the slope angle and small relative crest freeboards on the average overtopping rate accurately. Therefore, a new set of prediction formulas is proposed based on the new experiments combined with existing data from literature. These formulas include wave overtopping at vertical walls subjected to nonimpacting waves and at structures with zero crest freeboard. [ABSTRACT FROM AUTHOR]

The effects of external currents on the longshore current and sediment transport in the surf zone are examined using the cross-shore numerical model CSHORE, which is extended to include the alongshore pressure gradient term in the longshore momentum equation and to allow oblique waves in the swash zone on a beach. The extended CSHORE is compared with five tests conducted in a wave basin with a recirculation system. The cross-shore variations of the longshore current and sediment-transport rate are predicted fairly well for the cases of no and favorable pressure gradients. The cases of adverse and time-varying pressure gradients are computed to extrapolate the experimental results for wider applications. [ABSTRACT FROM AUTHOR]

Vessel-generated waves have the potential to erode the shoreline where there is regular commercial and recreational boat traffic in otherwise low-energy estuarine and fetch-limited environments. Whereas it is well established that vessel-generated waves are capable of resuspending significant quantities of bottom and bank sediment, there are limited field data showing how and when sediment is resuspended by the wake and the direction of net transport. This paper presents the results of an instrumented field study to measure sediment resuspension and transport in response to wakes generated by supercritical pilot boats and subcritical container ships at the mouth of the Savannah River in Georgia. Suspended sediment concentrations increase with the turbulent kinetic energy of the supercritical pilot-boat wake. The amount of sediment resuspended dependent on the available supply of sediment on the upper-foreshore. Whereas sediment is transported landward by the individual waves of the group, net transport is offshore in response to a low-frequency oscillation similar to a second-order group-forced current. In some cases, the direction of net transport is reinforced or reversed depending on the timing of the pilot-boat wake with the seiche forced by a passing container ship. In contrast to the pilot boats, sediment transport by subcritical container ships tends to be landward, but can also be weakly offshore depending on the timing of the wave group with the low-frequency drawdown and surge. [ABSTRACT FROM AUTHOR]

An experiment was conducted in a wave flume to examine the processes of gravel beach profile evolution under irregular waves. Two erosion tests were performed on a steep slope of 1/2 with two different significant wave heights. An accretion test was conducted on a mild slope of 1/5 until its profile became quasi-equilibrium. Another test was initiated with a gravel bar constructed at the toe of the equilibrium profile. The bar migrated onshore and resulted in the seaward shift of the equilibrium profile. Quasi-equilibrium profiles observed after 18 or 36 bursts of 400-s wave action were similar but affected by the differences in the wave height and initial profile. A numerical model developed for damage progression of stone armor layers is shown to predict the profile changes of the two erosion tests. The bed load formula used in the model is adjusted to better predict the onshore bar migration and the accretional change on the mild slope. More extensive comparisons of the numerical model with data will be required before it can be applied to gravel and cobble beaches. [ABSTRACT FROM AUTHOR]

A process is described for computation of bathymetry in and near the surf zone, from spatially varying celerity and breakpoint location data. The procedure involves the use of three submodels: (1) a wave shoaling model (outside of the surf zone); (2) a wave breaking model (defining the offshore boundary of the surf zone); and (3) a wave dissipation model (inside the surf zone). Influence of wave amplitude on the wave dispersion relation and celerity is included. Output includes wave height and water depth throughout the domain. In the application described here, oblique digital video served as the initial data source, although the model could be applied to data derived from other sources. Results are compared with data recorded by in situ sensors and beach profile survey data acquired by traditional means. Results suggest that water depths can be computed within 15% normalized error (equally, less than 0.1 m in biased depth error) for in and near the surf zone characterized by high wave nonlinearity. [ABSTRACT FROM AUTHOR]

The viscous, two-dimensional, free-surface flow induced by the propagation of nonlinear water waves over a rigid rippled bed was simulated numerically. The simulations were based on the numerical solution of the Navier-Stokes equations subject to fully nonlinear free-surface boundary conditions and appropriate bottom, inflow, and outflow boundary conditions. The equations were properly transformed so that the computational domain became time-independent. A hybrid scheme was used for the spatial discretization with finite differences in the streamwise direction and a pseudospectral approximation with Chebyshev polynomials in the vertical direction. A fractional time-step scheme was used for the temporal discretization. Over the rippled bed, the wave boundary layer thickness increased significantly, while vortex shedding at the ripple crest generated alternating circulation regions over the ripple trough. The velocity of the Eulerian drift profile was opposite to the direction of wave propagation far above the ripples, whereas close to the bed, its magnitude was influenced by the ripples up to a height of about six times the ripple height above the ripple crest. The amplitude of the wall shear stress on the ripples increased with increasing ripple steepness, whereas the amplitude of the corresponding friction drag force on a ripple was insensitive to this increase. The amplitude of the form drag force attributable to the dynamic pressure increased with increasing ripple steepness; therefore, the percentage of friction in the total drag force decreased with increasing ripple steepness. The period-averaged drag forces on a ripple were very weak, while the influence of form drag increased with increasing ripple steepness. [ABSTRACT FROM AUTHOR]

During nine small-scale laboratory experiments simulating combined wave overtopping and storm surge overflow on a trapezoidal levee, time series measurements of flow thickness and velocity were acquired at a location on the levee crest and at a location on the landward-side slope. Flow thickness and velocity were combined to estimate time series of the instantaneous discharge. Comparisons of the calculated overtopping discharge time series at the two locations revealed that the time series of instantaneous discharge was the same at both locations with the only difference being a short phase lag. Individual peaks of the discharge time series were examined, and an empirical expression was determined for the root-mean-squared discharge peak. The largest discharge peaks were overestimated by the Rayleigh distribution. For locations on the landward-side slope where the friction slope is approximately the same as the levee slope, it is possible to derive a stream power probability density function based on the overtopping discharge cumulative exceedance probability. The stream power probability density function may be a useful tool for assessing erosion potential of overtopped earthen levees. [ABSTRACT FROM AUTHOR]

To gain a better understanding of the wave forces that led to the failure of numerous causeway-type coastal highway bridges along the U.S. Gulf coast, a series of experiments was conducted on a realistic, 1:5 scale reinforced concrete bridge superstructure. The experimental setup is unique compared to other wave-in-deck studies in that the stiffness of the horizontal support system can be varied to represent different dynamic properties of the bridge system. The bridge specimen is subjected to a wide range of regular and random wave conditions at multiple water levels. In addition to measuring pressures and forces, the experiments measure the dynamic response of the bridge specimen using strain gauges, displacement sensors, and accelerometers. This paper presents the innovative experimental setup, and a preliminary analysis of the data showing the effect of wave height, wave period, and water level, on the forces experienced by the bridge superstructure. [ABSTRACT FROM AUTHOR]

Singularities play a significant role in the characterization of time series. The temporal characteristics of fluctuating significant wave height time series are investigated in this study. The hourly time series from 24 stations located off the west coast of the United States are used for the analysis. The multifractal nature of these time series is unveiled by employing a wavelet-based method. The wavelet transform modulus maxima method is applied to obtain the multifractal spectra (singularity spectrum) of the significant wave height series. The multifractal spectra and their parameters such as peak, min and max Hölder exponents, skewness coefficients, and support lengths are calculated. The peak Hölder exponent ranged from 0.30 to 0.46 throughout the study area. Hölder exponents that are less than 0.5 indicate that the time series exhibits an antipersistent random walk. The spatial variation of parameters is depicted through kriging maps. Different spatial variation patterns can be seen from the maps. It is clear that deep offshore stations have relatively higher Hölder exponents than coastal areas. This change can be related to the wave generation mechanism, by way of physical interpretations. Since the stations located in the deep offshore can receive more swell waves than coastal zones and are open to large-scale storms, they may tend to be more persistent and have greater Hölder exponents. Also, the type of the singularities occurring in deep offshore and in the coastal zones is assessed by considering the wave generating mechanisms. [ABSTRACT FROM AUTHOR]

This case study on the Mississippi River Gulf Outlet earthen berm/spoil bank (EBSB) illustrates a method to quantitatively analyze wave-induced lateral erosion and breaching through the flood side of coastal flood protection levees with grass armor prior to overtopping. Lateral wave-induced erosion was evaluated based on a three-step process: (1) velocity profiles were generated using a general purpose transient dynamic finite element program; (2) resistance to wave-induced erosion as a result of grass cover (turf) on the flood face of the EBSB was estimated and no wave-induced erosion was applied until the grass cover protection failed; and (3) estimated soil erodibility characteristics were used, in combination with the estimated wave-induced flood face velocities, to estimate the magnitude of lateral erosion. This case study identified that soil erodibility characteristics directly impact coastal flood protection levee performance, grass/turf armoring provides erosion protection for a limited duration, and identification and evaluation of pre-overtopping wave-induced erosion is an important failure mode to be considered in order to ensure reliable coastal flood protection. [ABSTRACT FROM AUTHOR]

An approach to estimating sediment transport along the Delaware–Maryland coast is described. Wave information study (second generation model, WISWAVE 2.0) hindcast frequency-direction spectra from 1980 to 1999 are used to generate a radiation stress-conserving angle for bringing offshore waves to breaking to estimate alongshore sediment transport. Using standard values for the coefficients in the United States Army Corps of Engineers’ Coastal Engineering Research Center (CERC) equation yields 20-year mean alongshore sediment transport rates between 470,942 and -517,088 m3/year depending on alongshore location after shoaling waves to shore. Interannual variability is large with SDs between 95,078 and 241,313 m3/year again depending on alongshore location. Alongshore sediment transport rate estimates are commensurate with past studies using WIS data but overpredict the typically cited value of ∼100,000 m3/year near Indian River Inlet, Delaware based on sediment budget data by a factor of 3–4. This overestimation could be compensated for by altering the constant K in the CERC transport equation or slight variations in the shoreline normal. The yearly estimates of the nodal point location where the sediment transport rate reverses direction were just south of the Delaware–Maryland border. The nodal point experienced interannual variability on the order of several thousand meters and is mainly attributed to the interannual variability in wave forcing. It is found that estimating alongshore sediment transport rates from offshore wave data are dependent on proper preservation of the radiation stress (using a radiation stress-conserving wave angle) and accurate determination of the shoreline normal. [ABSTRACT FROM AUTHOR]

A numerical model that combines a random wave transformation and a wave-induced current model was developed in order to predict the wave and current fields around a detached breakwater. The wave field was determined using the EBED model, as reported by Mase in 2001, with a modified energy dissipation term. The surface roller associated with wave breaking was modeled based on a modification of the equations in works by Dally and Brown, and Larson and Kraus, in which the term for the roller energy flux in the alongshore direction was added to the energy balance equation. The nearshore currents and water elevation were determined from the continuity equation together with the depth-averaged momentum equations. The model was validated by three unique high-quality data sets obtained during experiments on detached breakwaters in the large-scale sediment transport facility basin at the Coastal and Hydraulics Laboratory in Vicksburg, Miss. The calculated significant wave height and longshore current were in good agreement with these measurements, whereas the cross-shore current was underestimated because undertow processes were not included in the modeling (depth-averaged equations employed). The calculated wave setup was somewhat overestimated; however, the absolute differences between the calculations and measurements were overall relatively small. [ABSTRACT FROM AUTHOR]

Subaerial landslide generated impulse waves were investigated in a prismatic wave channel based on Froude similitude and granular slide material. The tests included the following seven governing parameters: still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide impact angle, and grain diameter. All governing parameters, except for the grain diameter with a negligible effect, are included in the impulse product parameter P allowing for a simple application. Empirical equations based on 211 experiments for all relevant wave features in practice including the maximum wave height, the maximum wave amplitude with its location and period in the slide impact zone, and both the wave height and amplitude decay and the period increase in the wave propagation zone are a simple function of P. The presented equations were validated with 223 runs resulting in improved goodness of fit. The limitations of the herein derived empirical equations are also highlighted. The wave height and amplitude equations based on a wave channel (2D) agree well with the 1958 Lituya Bay case. [ABSTRACT FROM AUTHOR]

Velocities and sand concentrations measured along 20 transects at the Field Research Facility (FRF) at Duck, North Carolina during October 16–23, 1997 are analyzed to examine the cross-shore and longshore suspended sand transport in the FRF pier depression. The suspended sand volume Vs per unit bottom area remains large outside the surf zone in the depression. The depth-integrated offshore and longshore suspended sand transport rates are shown to be estimated as a, UVs and VVs, respectively, where the empirical parameter a is in the range of 0.1–0.4 in the depression, U is the cross-shore current and V is the longshore current. The offshore suspended sand transport rate at the end of the pier is estimated to be as large as 3.5 m3/h/m at the peak of a storm with an offshore significant wave height of 3.5 m. The sand transported offshore appears to have been supplied by the longshore sand transport toward the pier depression. [ABSTRACT FROM AUTHOR]

An experimental study has been undertaken within the U.K. Coastal Research Facility (CRF), located at HR Wallingford Ltd. Detailed measurements were made to examine the on–off shore spreading of a solute, mostly inside the surf zone, for shore normal waves combined with a longshore current. The results show that the on–off shore mixing is significantly increased by almost 70 times, when compared to current-only conditions. A theoretical advection–dispersion mixing mechanism has been postulated. Using suitable estimates for the turbulent diffusion and on–off shore wave-induced velocity, a theoretical approximation to the overall mixing within the surf zone can be obtained. This theoretical analysis suggests that the on–off shore mixing in the surf zone is proportional to Hb3/2, where Hb is the breaker wave height. It is demonstrated that within the surf zone, the on–off shore mixing is dominated by the effects of the on–off shore velocity. Some previous experimental studies to determine the magnitude of the mixing within the surf zone have been performed. However, the mechanisms responsible for generating the mixing were neither fully investigated nor reported. The previous studies, together with the results obtained from the CRF, are compared to estimates for the theoretical description of mixing developed within this present study. A good agreement exists. [ABSTRACT FROM AUTHOR]

Bridge decks in Escambia Bay were damaged during the storm surge of Hurricane Ivan in 2004. In this study, a numerical wave-load model based on the incompressible Reynolds averaged Navier–Stokes equations and k-[variant_greek_epsilon] equations has been used to investigate dynamic wave forces exerted on the bridge deck. The volume of fluid method is adopted in the model to describe dynamic free surface, which is capable of simulating complex discontinuous free surface during wave breaking and wave-deck interactions. The model was satisfactorily tested against experimental data of uplift wave forces on horizontal plates. The validated model was applied to investigate wave forces acting on the bridge deck in Escambia Bay in the case of Hurricane Ivan. The time history of wave profiles, turbulent velocity fields, and dynamic uplift and horizontal forces acting on the full-scale bridge deck were simulated and analyzed. Results indicate that, during the storm surge event of Hurricane Ivan, the maximum uplifting wave forces were larger than the weight of the simply supported bridge deck, causing direct damage to the deck. Wave forces on three different deck elevations are discussed. Comparisons of numerical modeling results to maximum wave forces obtained from empirical equations are provided as references for coastal hazard assessment and bridge design. [ABSTRACT FROM AUTHOR]

Nonlinear effects for wave groups in bimodal sea states are investigated. The linear free surface displacement is obtained by applying the quasi-determinism theory of the highest waves, with the spectrum given by the superposition of two JONSWAP spectra. Linear groups are modeled as the sum of two groups produced by each unimodal spectrum. Nonlinear effects are given as second-order contribution to the linear free surface displacement. The structure of wave groups is then analyzed for some bimodal spectra. The linear component of wave groups shows a strong variation with respect to the classical structure with unimodal spectra, particularly in mixed seas. It is observed that the nonlinearity gives small contributions for swell dominated seas. For wind dominated sea states, the main nonlinear contribution is given by the wind wave spectral components. For mixed sea states, the interaction among the components of the wind wave spectrum and the components of the swells could give a meaningful contribution to the nonlinear profile. The strongest nonlinear effects occur when the two peaks of the spectrum are close to each other. Finally, the results are validated by means of Monte Carlo simulations of nonlinear sea waves. [ABSTRACT FROM AUTHOR]

The present study is to parameterize the influence of regular progressive waves on the diffusion of a neutrally buoyant turbulent round jet experimentally. The jet, located at the middepth, discharges into the wave field horizontally in the direction against the wave propagation. The particle image velocimetry technique and the laser induced fluorescence technique were used to measure the velocity field and examine the jet cross-sectional profile. Three different wave periods with a range of wave amplitudes in each wave period were tested to investigate the effect of waves on jet diffusion. The wave conditions cover both the shallow water and deep water, whereas the wave slopes range from linear to weakly nonlinear. The results showed that the width of the jet was significantly affected by the waves. The wave dispersion enhanced the jet diffusion, especially for a larger wave slope and a shallower water depth. The results also showed that the wave-to-jet momentum ratio is the most important parameter to characterize the effect of waves to the diffusion of jet. [ABSTRACT FROM AUTHOR]

The present work is a numerical investigation on waves generated by a pressure disturbance moving at constant speed in a channel with a variable cross-channel depth profile. The channel profile, which is uniform in the along-channel direction, has a deep trench located along the centerline of the channel, and shallow banks near the channel walls. Characteristic features upstream and downstream of the moving pressure disturbance are related to the parameters of the pressure disturbance and the cross-channel profile. Our numerical investigation is based on the COULWAVE long wave model. [ABSTRACT FROM AUTHOR]

A comparative assessment of available formulae for the water setup inshore of submerged breakwaters is made on the basis of a wide and varied dataset derived from basin and flume laboratory experiments. Formulae derived from a simplified view which does not account for the horizontal flow circulation provide a large overestimate (up to one order of magnitude) of the smaller setup values. A much better overall approximation of the measured data is obtained through formulae that consider the setup as part of a complete flow description, be it partially or fully accounting for the horizontal flow motion. [ABSTRACT FROM AUTHOR]

Grid point pooling is a commonly used method to account for hurricane track variability in extreme value analysis. This paper presents a simplified mathematical interpretation of grid point pooling. Through logical arguments and numerical experiments, some general guidelines are then developed for a selection of grid points to include in the statistical pool. [ABSTRACT FROM AUTHOR]

This paper reports experimental results of the toe scour of seawall on a steep seabed with slope of 1:5 under the action of breaking waves. The equilibrium toe scour profiles were investigated and the depths of toe scours related to the wave parameters were analyzed. Experimental results indicated that the depth of toe scour increased as the steepness of the incoming wave increased, but decreased with an increase in the water depth at the toe. The breaker types in front of the seawall were investigated. The scour depth due to a plunging breaker is larger than that of a spilling breaker or a nonbreaking wave in front of the seawall. The down-rush flow velocity induced from the wave rundown on the seawall was also investigated in the experiment, and it was found that the scour depth increased as the flow velocity at the toe increased. Empirical formulas of the relative scour depth in terms of the relative toe water depth or surf similarity parameter were obtained based on the experimental results. [ABSTRACT FROM AUTHOR]

Offshore wave setup generated by wave breaking during coastal storms can create significant flow through tidal inlets and increase bay flooding. However, these flow contributions are not always considered when determining coastal flooding risk for engineering studies. This paper describes the wave-driven flow process at tidal inlets and demonstrates its impact on bay flooding on Long Island, New York. Numerical simulations using a coupled hydrodynamic and wave model are presented to show contributions to bay water level by wave-driven flow with respect to those by wind surge. These simulations include two major historical coastal storms and a small nor’easter in 2003, during which the model was validated using field measurements of water level. Finally, an approach is introduced for estimating wave-induced flow contributions to bay flooding as a function of inlet and storm characteristics, including tidal prism and wave conditions. The findings of this study indicate that wave-induced flow contributions make up 15–35% of the total storm surge, where the wave-induced flow contribution increases with increased inlet efficiency. [ABSTRACT FROM AUTHOR]

This investigation deals with the changes in the mean velocity associated with a bichromatic wave train in a steady current. The Eulerian-mean velocity model originally developed for monochromatic waves is applied to the calculation of the mean horizontal velocity for bichromatic waves. Instantaneous two-dimensional velocity components for waves following or opposing a current were measured to examine the turbulent intensities and wave-current Reynolds stress. The experimental data suggest that wave direction is an important factor to change the vertical profile of mean velocity based on the logarithmic law. The predicted shape of the mean velocity shows quantitative agreement in the whole depth with the experimental data for various conditions such as irregular waves. [ABSTRACT FROM AUTHOR]

The semicircular breakwater (SBW) is a composite breakwater consisting of a semicircular caisson resting on a rubble mound. The SBW function as a barrier dissipates the incident wave energy and creates tranquility on its leeside. The dynamic pressures due to random waves exerted on seaside perforated SBWs with 7, 11, and 17% of its exposed surface area with perforations were measured. The measured pressures are compared with experimental results of SBW without perforations. In addition, the forces exerted on the caisson alone are measured. The reflection coefficient, runup characteristics, measured total forces, and dynamic pressures in a dimensionless form are presented as a function of relative water depth. The tests were conducted for surface piercing conditions. The effect of the water depth, perforations, and rubble mound height on the above stated variables are brought out, the details of which are reported in this technical note. [ABSTRACT FROM AUTHOR]

This paper compares the output from four methods used to predict the mean overtopping discharge at the root of the South Breakwater of Póvoa de Varzim Harbour (Portugal): two numerical models AMAZON, based on solving the nonlinear shallow-water equations, and COBRAS-UC, based on the Reynolds averaged Navier–Stokes equations, Pedersen’s empirical formula, and the neural network tool NN_Overtopping. Output from the methods is considered alongside data from two-dimensional (2D) physical model tests. The results show that rather accurate predictions can be obtained with COBRAS-UC. Agreement between the data and the AMAZON output depends principally on the impact of porosity on overtopping: agreement is very good when the impact is limited (for high overtopping discharges) and it worsens as porosity plays a more important role (for small discharges). NN_Overtopping estimates the mean discharges with a degree of accuracy similar to AMAZON. Pedersen’s results are those which deviate more from the data, substantially overpredicting the mean discharges for the conditions analyzed. [ABSTRACT FROM AUTHOR]

The notion of surf similarity in the runup of solitary waves is revisited. We show that the surf similarity parameter for solitary waves may be effectively reduced to the beach slope divided by the offshore wave height to depth ratio. This clarifies its physical interpretation relative to a previous parameterization, which was not given in an explicit form. Good coherency with experimental (breaking) runup data is preserved with this simpler parameter. A recasting of analytical (nonbreaking) runup expressions for sinusoidal and solitary waves additionally shows that they contain identical functional dependence on their respective surf similarity parameters. Important equivalencies in the runup of sinusoidal and solitary waves are thus revealed. [ABSTRACT FROM AUTHOR]

Coastal disasters such as sliding, settlement, and overturning of coastal structures as well as subsidence of reclaimed areas occur due to toe scouring and backfilling sand discharge. In this study, the sand discharge mechanism from a gap under a vertical revetment without wave absorption and foot protection is investigated using hydraulic model experiments and newly developed numerical simulations. In the hydraulic model experiments, sand discharge and sinkholes similar to those observed in the field surveys are reproduced, and it is found that sand discharge is very sensitive to wave steepness and relative gap height. In numerical simulations, a comparison with the experimental data demonstrates the validity of the numerical methods. It is revealed that sand discharge tends to occur with an increase of the maximum seaward velocity just outside the gap under the revetment as well as the maximum volumetric strain inside the most offshore side of the sand inside the gap. [ABSTRACT FROM AUTHOR]