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Showing papers on "Wave height published in 2006"


Journal ArticleDOI
TL;DR: In this paper, an empirical parameterization for extreme runup, defined by the 2% exceedence value, has been developed for use on natural beaches over a wide range of conditions.

1,058 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the use of a digital photographic method for the quantification of marsh vegetation density and then investigated the relative roles played by hydrodynamic controls and vegetation density/type in causing the attenuation of incident waves over a macro-tidal saltmarsh.
Abstract: The degree to which incident wind waves are attenuated over intertidal surfaces is critical to the development of coastal wetlands, which are, amongst other processes, affected by the delivery, erosion, and/or resuspension of sediment due to wave action. Knowledge on wave attenuation over saltmarsh surfaces is also essential for accurate assessments of their natural sea-defence value to be made and incorporated into sea defence and management schemes. The aim of this paper is to evaluate the use of a digital photographic method for the quantification of marsh vegetation density and then to investigate the relative roles played by hydrodynamic controls and vegetation density/type in causing the attenuation of incident waves over a macro-tidal saltmarsh. Results show that a significant statistical relationship exists between the density of vegetation measured in side-on photographs and the dry biomass of the photographed vegetation determined through direct harvesting. The potential of the digital photographic method for the spatial and temporal comparison of marsh surface vegetation biomass, density, and canopy structure is highlighted and the method was applied to assess spatial and seasonal differences in vegetation density and their effect on wave attenuation at three locations on a macro-tidal saltmarsh on Dengie Peninsula, Essex, UK. In this environmental setting, vegetation density/type did not have a significant direct effect on wave attenuation but modified the process of wave transformation under different hydrodynamic conditions. At the two locations, characterised by a relatively tall canopy (15–26 cm) with biomass values of 430–500 g m −2 , dominated by Spartina spp. (>70% of total dry biomass), relative incident wave height (wave height/water depth) is identified as a statistically significant dominant positive control on wave attenuation up to a threshold value of 0.55, beyond which wave attenuation showed no significant further increase. At the third location, characterised by only slightly less biomass (398 g m −2 ) but a shorter (6 cm) canopy of the annual Salicornia spp., no significant relationship existed between wave attenuation and relative wave height. Seasonally (between September and December) significant temporal increase/decrease in vegetation density occurred in one of the Spartina canopies and in the Salicornia canopy, respectively, and led to an expected (but not statistically significant) increase/decrease in wave attenuation. The wider implications of these findings in the context of form–process interactions on saltmarshes and their effect on marsh evolution are also discussed.

290 citations


Journal ArticleDOI
TL;DR: The morphological response of intertidal bars to changing wave conditions is largely forced: bars build up and migrate onshore under calm waves, and are flattened and may migrate offshore during storms as mentioned in this paper.

196 citations


Journal ArticleDOI
TL;DR: In this paper, three sources of long-term wind and wave data are available in the Mediterranean Sea: numerical models, satellites and buoys, and they make use of the overall information to obtain calibrated decadal time series at a large number of points, distributed at 0.5° intervals.

128 citations


Journal ArticleDOI
TL;DR: In this paper, the authors observed morphological change and swash sediment loads, concurrent with measurements of water level, waves and currents, during a spring-to-spring tidal cycle on a steep macrotidal gravel beach in southwest England.

123 citations


Journal ArticleDOI
TL;DR: In this paper, a wave model of the NE Atlantic Model tests were carried out, using synthetic wind fields, varying the strength of the prevailing westerly winds and the frequency and intensity of storms, the location of storm tracks and the storm propagation speed.
Abstract: Wave height in the North Atlantic has been observed to increase over the last quarter-century, based on monthly-mean data derived from observations Empirical models have linked a large part of this increase in wave height with the North Atlantic Oscillation Wave models provide a tool to study impacts of various climate change scenarios and investigate physical explanations of statistical results In this case we use a wave model of the NE Atlantic Model tests were carried out, using synthetic wind fields, varying the strength of the prevailing westerly winds and the frequency and intensity of storms, the location of storm tracks and the storm propagation speed The strength of the westerly winds is most effective at increasing mean and maximum monthly wave height The frequency, intensity, track and speed of storms have little effect on the mean wave height but intensity, track and speed significantly affect maximum wave height

100 citations


Journal ArticleDOI
TL;DR: In this article, a set of empirical formulations are derived that describe important wave properties in shallow water as functions of commonly used parameters such as wave height, wave period, local water depth and local bed slope.

93 citations


Journal Article
TL;DR: In this article, the authors analyzed one of the longest contemporary wave measurements in the northern Baltic Sea, performed at Almagrundet 1978-2003, and found that significant wave height varies from 0.5 m in May-July to 1.3-1.4 m in December-January.

85 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the hydrodynamic characteristics of a pile-supported vertical wall breakwater, the upper part of which is a vertical wall, and the lower part consisting of an array of vertical piles.
Abstract: This paper describes the hydrodynamic characteristics of a pile-supported vertical wall breakwater, the upper part of which is a vertical wall, and the lower part consisting of an array of vertical piles. For regular waves, using the eigenfunction expansion method, a numerical model has been developed that can compute wave transmission, reflection, and run-up, and wave force acting on the breakwater. For irregular waves, the regular wave model is repeatedly used for each frequency component of the irregular wave spectrum. The wave period is determined according to the frequency of the component wave, while the root-mean-squared wave height is used for all the component waves to compute the energy dissipation between piles. To examine the validity of the developed models, large-scale laboratory experiments have been conducted for pile-supported vertical wall breakwaters with a constant spacing between piles but various drafts of the upper vertical wall. Comparisons between measurement and prediction show that the numerical model adequately reproduces most of the important features of the experimental results for both regular and irregular waves. The pile-supported vertical wall breakwater always gives smaller transmission and larger reflection than a curtain wall breakwater with the same draft as that of the upper wall, or a pile breakwater with the same porosity as that of the lower part, of the pile-supported vertical wall breakwater.

60 citations


Journal ArticleDOI
TL;DR: In this article, the authors used an historic record of hourly wind conditions, a depth profile and two rigorously tested oceanographic models, hindcast spatially on a typical subtidal coral reef platform (maximum horizontal displacement, velocity and acceleration per wave cycle).
Abstract: To live successfully in wave-swept habitats, plants and animals must be able to survive, consume resources, and reproduce in the presence of incessant, variable and often unpredictable levels of water motion at a range of scales. However, there is a relatively poor understanding of water motion in natural habitats at the scales necessary to determine its potential physiological and ecological consequences. Using an historic record of hourly wind conditions, a depth profile and two rigorously tested oceanographic models, 37-years of hourly wave driven water motion were hindcast spatially on a typical subtidal coral reef platform (maximum horizontal displacement, velocity and acceleration per wave cycle). For larger waves, those likely to constitute ecological disturbances, around 95% of the wave’s height that is lost over the whole reef occurs within the first 50 m of the crest. The field-validated model of spatiotemporal variation in water motion provided a framework for quantitatively predicting several physiological and ecological effects of wave motion, such as nutrient and gas fluxes and mortality rates from hydrodynamic disturbances. It also suggested a sharp ecological transition between a crest habitat in which disturbance-mediated coexistence mechanisms are important, and a flat habitat in which they are much less important.

60 citations


Journal ArticleDOI
TL;DR: Three reasons for freak wave generation due to interaction of wave with spatially non-uniform current are considered in this article, which are as follows: wave energy amplification due to wave-current interaction, wave height amplification around caustic due to refraction wave in nonuniform currents, nonlinear wave interaction in shallow water due to their intersection described by the Kadomtsev-Petviashvili equation.
Abstract: Three reasons for freak wave generation due to interaction of wave with spatially non-uniform current are considered in the paper. They are as follows: wave energy amplification due to wave-current interaction; wave height amplification around caustic due to refraction wave in non-uniform current; non-linear wave interaction in shallow water due to their intersection described by the Kadomtsev–Petviashvili equation. These mechanisms can generate a large wave amplification producing a dangerous natural phenomenon.

Journal ArticleDOI
TL;DR: In this article, the authors present an assessment of an operational wave model (Wavewatch III) focusing upon the model sensitivity to wind-forcing products, including the NCEP/NCAR reanalysis and three other products that assimilate various satellite wind measurements having high spatial resolution.

Journal ArticleDOI
TL;DR: In this paper, a massive earthquake with magnitude 9.3 occurred on December 26, 2004 off the northern Sumatra generated huge tsunami waves affected many coastal countries in the Indian Ocean.
Abstract: [1] A massive earthquake with magnitude 9.3 occurred on December 26, 2004 off the northern Sumatra generated huge tsunami waves affected many coastal countries in the Indian Ocean. A number of field surveys have been performed after this tsunami event; in particular, several surveys in the south/east coast of India, Andaman and Nicobar Islands, Sri Lanka, Sumatra, Malaysia, and Thailand have been organized by the Korean Society of Coastal and Ocean Engineers from January to August 2005. Spatial distribution of the tsunami runup is used to analyze the distribution function of the wave heights on different coasts. Theoretical interpretation of this distribution is associated with random coastal bathymetry and coastline led to the log-normal functions. Observed data also are in a very good agreement with log-normal distribution confirming the important role of the variable ocean bathymetry in the formation of the irregular wave height distribution along the coasts.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the average wave height of the 50 highest waves reaching a rubble-mound breakwater in its useful life can describe the effect of the wave height on the history of the damage caused by the wave climate during the structure's usable life.

Proceedings Article
01 Jan 2006
TL;DR: A method to simulate ocean surfaces away from the coast, with correct statistical wave height and direction distributions, by using classical oceanographic parametric wave spectra, which fit real world measurements, without depending on them.
Abstract: We present a method to simulate ocean surfaces away from the coast, with correct statistical wave height and direction distributions. By using classical oceanographic parametric wave spectra, our results fit real world measurements, without depending on them. Since wave spectra are independent of the ocean model, Gerstner parametric equations and Fourier transform method can be used with them. Moreover, since they are simple to use and need very few parameters, they allow easy production of ocean surface animations usable in movies and games. We explain how to accurately sample them, to achieve oceanic waves in deep water according to given wind parameters, in a realistic way. 1

Journal ArticleDOI
TL;DR: In this paper, high frequency measurements of water depth, current velocity and suspended sediment concentration were used to investigate sediment transport processes in the swash zones of a dissipative beach and a steeper (intermediate) beach.

Journal ArticleDOI
TL;DR: In this paper, the phase coupling between wind speed and wave height over a certain range of frequencies and the range is different from one segment to another due to the non-stationary feature of the time series.

Journal ArticleDOI
TL;DR: The need for the combination of seismic data with real-time wave height information for an effective prediction of tsunami impact is emphasized in this article, where a preliminary, but comprehensive study of arrival times, wave heights and run-up values at a number of locations and tide gage stations throughout the Indian Ocean seaboard is presented.
Abstract: The need for the combination of seismic data with real-time wave height information for an effective prediction of tsunami impact is emphasized in the paper. A preliminary, but comprehensive study of arrival times, wave heights and run-up values at a number of locations and tide gage stations throughout the Indian Ocean seaboard is presented. Open ocean wave height data from satellite observations are analyzed and used in the reconstruction of a tsunami source mechanism for the December 26, 2004 event. The reconstructed source is then used to numerically estimate tsunami impact along the Indian Ocean seaboard, including wave height, and arrival times at 12 tide gage stations, and inundation at 3 locations on the coast of India. The December 2004, as well as the March 28, 2005 tsunamis are investigated and their differences in terms of tsunami generation are analyzed and presented as a clear example of the need for both, seismic and real-time tsunami data for a reliable tsunami warning system in the Indian Ocean.

Journal ArticleDOI
TL;DR: In this article, an eddy viscosity model for wave and current is proposed in order to close the equations of wave motion or of current motion in a combined flow, respectively, and equations of mud transport are derived based on the visco-elastic properties of mud.

Journal ArticleDOI
TL;DR: In this article, a linear stability model of the surf and shoaling zones is used to examine which type of pattern, transverse or crescentic bar, is likely to form under different wave conditions.
Abstract: [1] We present an investigation into the growth of nearshore, rhythmic patterns. A comprehensive linear stability model of the surf and shoaling zones is used to examine which type of pattern, transverse or crescentic bar, is likely to form under different wave conditions. In contrast to earlier studies we examine normal and near-normal incidence on a plane beach. In doing so we reproduce results of earlier, more restricted studies and thereby identify the physical mechanisms leading to the growth of different patterns. This paper also focuses on the role of random wave height distribution compared with regular waves and identifies conditions likely to lead to pattern growth. To this end, an amended wave height dissipation function is presented, which allows us to move between random and regular regimes. It is found that a sharply defined surf breakpoint leads to larger growth rates and crescentic-bar-type features. In contrast, a large spread in breaking gives rise to transverse bar patterns with reduced growth rates. Transverse bar alongshore spacing is typically about 1/4 to 1/2 the width of the surf zone, while crescentic bar spacing is larger, up to twice this width. It is also shown that pattern types are influenced by the wave height to depth ratio in the surf zone. This indicates that sites with substantial inner surf zone wave energy and thus greater energy available to move sediment will give rise to transverse bar patterns. A new, propagating mode is identified in such cases, which exists for normal wave incidence. Finally, the role of wave shoaling and wave refraction, either on the bed or on the currents is examined. Crescentic bars seem to be a very robust feature as they stem from the model even if those three effects are ignored. Thus the only essential feedback for their formation is the coupling between depth-controlled breaking and the evolving bathymetry. In contrast, transverse bar formation is very sensitive to wave refraction being enhanced by refraction over the bed and weakened by refraction over the current.

Journal ArticleDOI
TL;DR: In this paper, a joint probability distribution for the significant wave height, the relative speed, and the ship heading relative to the wave direction is given, showing that for higher waves the crews avoid sailing in following sea, and as expected the speed is decreased in higher waves.
Abstract: The analysis of almost 25000 observation of the wave height from ships in the North Atlantic shows that the encountered wave height distribution is significantly lower than the distribution provided by the classification societies for structural assessment. The joint probability distribution for the significant wave height, the relative speed, and the ship heading relative to the wave direction is given. This distribution shows that for higher waves the crews avoid sailing in following sea, and as expected the speed is decreased in higher waves. There is, however, still a relatively high probability that the ship will maintain the service speed even in relatively severe sea. The distribution derived could be used to incorporate the effect of weather routing in a long term analysis of the wave loads on a ship.

Journal ArticleDOI
TL;DR: In this article, the authors summarized the theoretical and practical needs for cellular automata (CA)-type models in coastal simulation, and described early steps in the development of a CA-based model for estuarine sedimentation.
Abstract: The paper summarizes the theoretical and practical needs for cellular automata (CA)-type models in coastal simulation, and describes early steps in the development of a CA-based model for estuarine sedimentation It describes the key approaches and formulae used for tidal, wave and sediment processes in a prototype integrated cellular model for coastal simulation designed to simulate estuary sedimentary responses during the tidal cycle in the short-term and climate driven changes in sea-level in the long-term Results of simple model testing for both one-dimensional and two-dimensional models, and a preliminary parameterization for the Blackwater Estuary, UK, are shown These reveal a good degree of success in using a CA-type model for water and sediment transport as a function of water level and wave height, but tidal current vectors are not effectively simulated in the approach used The research confirms that a CA-type model for the estuarine sediment system is feasible, with a real prospect for coupling to existing catchment and nearshore beach/cliff models to produce integrated coastal simulators of sediment response to climate, sea-level change and human actions

Journal ArticleDOI
TL;DR: In this article, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data, and the method of extreme statistical analysis in handling the extreme events like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods of 30-50 years for the cost effective construction of coastal structures.
Abstract: Long term wave climate of both extreme wave and operational wave height is essential for planning and designing coastal structures. Since the field wave data for the waters around Korean peninsula is not enough to provide reliable wave statistics, the wave climate information has been generated by means of long-term wave hindcasting using available meteorological data. Basic data base of hindcasted wave parameters such as significant wave height, peak period and direction has been established continuously for the period of 25 years starting from 1979 and for major 106 typhoons for the past 53 years since 1951 for each grid point of the North East Asia Regional Seas with grid size of 18 km. Wind field reanalyzed by European Center for Midrange Weather Forecasts (ECMWF) was used for the simulation of waves for the extratropical storms, while wind field calculated by typhoon wind model with typhoon parameters carefully analyzed using most of the available data was used for the simulation of typhoon waves. Design wave heights for the return period of 10, 20, 30, 50 and 100 years for 16 directions at each grid point have been estimated by means of extreme wave analysis using the wave simulation data. As in conventional methodsi of design criteria estimation, it is assumed that the climate is stationary and the statistics and extreme analysis using the long-term hindcasting data are used in the statistical prediction for the future. The method of extreme statistical analysis in handling the extreme events like typhoon Maemi in 2003 was evaluated for more stable results of design wave height estimation for the return periods of 30–50 years for the cost effective construction of coastal structures.

Book ChapterDOI
01 Jan 2006
TL;DR: In this article, the authors present several modified nonlinear Schrodinger (MNLS) equations as candidates for simplified phase-resolving models, followed by an introduction to some essential elements of stochastic analysis.
Abstract: There has been much interest in freak or rogue waves in recent years, especially after the Draupner “New Year Wave” that occurred in the central North Sea on January 1st 1995. From the beginning there have been two main research directions, deterministic and statistical. The deterministic approach has concentrated on focusing mechanisms and modulational instabilities, these are explained in Chap. 3 and some examples are also given in Chap. 4. A problem with many of these deterministic theories is that they require initial conditions that are just as unlikely as the freak wave itself, or they require idealized instabilities such as Benjamin-Feir instability to act over unrealistically long distances or times. For this reason the deterministic theories alone are not very useful for understanding how exceptional the freak waves are. On the other hand, a purely statistical approach based on data analysis is difficult due to the unusual character of these waves. Recently a third research direction has proved promising, stochastic analysis based on Monte-Carlo simulations with phase-resolving deterministic models. This approach accounts for all possible mechanisms for generating freak waves, within a sea state that is hopefully as realistic as possible. This chapter presents several different modified nonlinear Schrodinger (MNLS) equations as candidates for simplified phase-resolving models, followed by an introduction to some essential elements of stochastic analysis. The material is aimed at readers with some background in nonlinear wave modeling, but little background in stochastic modeling. Despite their simplicity, the MNLS equations capture remarkably non-trivial physics of the sea surface such as the establishment of a quasi-stationary spectrum with ω−4 power law for the high-frequency tail, and nonlinear probability distributions for extreme waves. In the end we will suggest how often one should expect a “New Year Wave” within the sea state in which it occurred.

01 Nov 2006
TL;DR: In the UK, the largest waves in UK waters are found on the Atlantic boundaries where waves can propagate over large fetches from the ocean, and in autumn and especially winter when strong winds are more intense and persistent as discussed by the authors.
Abstract: Waves and storm-force winds are a significant feature of UK waters and at the coast, particularly in autumn and winter. Waves are forced by the wind, but there is not a simple relationship between local wind speed and wave height. Waves grow and propagate over time, so that waves require sufficient “duration” of the forcing wind and sufficient sea room for the wind to act on the sea surface and the waves to propagate, called “fetch”, to grow to a maximum height. In cases where one of these is insufficient, waves are durationlimited or fetch-limited to a smaller height and period. Thus, the largest waves in UK waters are found on the Atlantic boundaries where waves can propagate over large fetches from the ocean, and in autumn and especially winter when strong winds are more intense and persistent. Many factors affect the height of waves in UK waters, but for the Atlantic margin the persistence and strength of westerly winds are particularly important (Wolf and Woolf, 2006), as well as the intensity and frequency of storms (‘storminess’). Waves are affected by currents and water depth and locally by coastal geometry and man-made structures. Waves decrease in height in shallow water due to energy dissipation by bottom friction and wave breaking; this reduction at a particular site may diminish if sea level rises, unless the coastal morphology, in areas of mobile sediment, can adapt at a similar rate.

01 Jan 2006
TL;DR: In this paper, the authors extended earlier work by Soulsby and Smallman (1986) and Soulsby (1987) to give calculation methods which are simple enough to be written in a single cell of a spreadsheet, for ease of use in practical applications using spreadsheet methods.
Abstract: Many coastal problems require the calculation of wave-generated oscillatory (orbital) velocities at the sea-bed for applications such as sediment mobility, transport and suspension, bed protection measures, and forces on structures. This is most commonly performed by using linear wave theory to transform the wave height and period to the orbital velocity in a given water depth as described by e.g. Sleath (1984). Only nonbreaking waves are considered in this report. The use of linear wave theory to obtain orbital velocities is justified by the experimental work of Kirkgoz (1986), who found that linear theory gave reasonable agreement with observed orbital velocities under wave crests over his entire range of parameter settings, even at the transformation point of plunging breakers where higher-order theories might be expected to give significantly better results. The velocity under wave troughs was significantly smaller than the predicted linear-theory value. Depending on the complexity of the problem, either a regular (monochromatic) wave or irregular (spectral) waves may be considered. However, the expression for the orbital velocity amplitude cannot be written explicitly in terms of depth, wave height and period, so indirect methods must be used. This report extends earlier work by Soulsby and Smallman (1986) and Soulsby (1987) to give calculation methods which are simple enough to be written in a single cell of a spreadsheet, for ease of use in practical applications using spreadsheet methods. It is less accurate than some methods, but is adequate to give at least a reasonable estimate for many desk-study applications. Despite enormous increases in computer speed and power since 1986, it is still often a limitation when using fine grids, long-term simulations, multiple sensitivity tests, or stochastic simulations in present day studies. Efficiency of repeated computations is thus still a desirable goal, especially when wave orbital velocities need to be calculated at every grid point and every time-step of a numerical model. The simple methods may therefore sometimes be preferred to more accurate methods even in numerical models.

Journal Article
TL;DR: In this paper, the seasonal characteristics and temporal variations of ocean wave in Chinese offshore waters are analyzed using the TOPEX satellite altimeter data observed from December 1992 to March 2005, and it is shown from the analysis results that the average wave height in winter is the greatest, and the high wave areas in winter are located in the Taiwan Strait, the northern South China Sea, the sea area southeast of Indo-China Peninsula and the sea areas outside of the Luzon Strait.
Abstract: In this paper,the TOPEX satellite altimeter data observed from December 1992 to March 2005 are used to analyze the seasonal characteristics and temporal variations of ocean wave in the Chinese offshore waters.It is shown from the analysis results that the average wave height in winter is the greatest,and the high wave areas in winter are located in the Taiwan Strait,the northern South China Sea,the sea area southeast of Indo-China Peninsula and the sea area outside of the Luzon Strait;the average wave height in summer is the smallest;and spring and autumn are transitional seasons.It is shown from the study results that the annual variation of ocean wave in the high wave area in winter is the main temporal variation characteristics,the intraseasonal variation is another important feature,and the interannual variations of average wave height with a 5 year period are well consistent with the ENSO event.

Journal ArticleDOI
TL;DR: In this article, the effect of wave climate also in the definition of shape parameter has been investigated by integrating wave energy dissipation rate per unit volume at the surf zone, which leads to theoretical definition of equilibrium beach profiles involving the effects of both the grain size and the wave climate parameters.

Journal ArticleDOI
TL;DR: A wave hindcast for the New Zealand region was used in conjunction with wavebuoy data to evaluate extreme significant wave height at multiple sites around New Zealand, for the first time as mentioned in this paper.
Abstract: A recently implemented wave hindcast for the New Zealand region was used in conjunction with wave‐buoy data to evaluate extreme significant wave height at multiple sites around New Zealand, for the first time. Hindcast storm wave heights were under‐predicted compared with wave‐buoy measurements at three inshore sites, and a method for scaling the hindcast data to improve the comparison of predicted extreme wave heights was explored. Different statistical methods for predicting extreme wave heights were also compared. Offshore, extreme wave heights displayed a north‐south and an east‐west gradient that is in keeping with the mean wave climate, with larger waves in the south and in the west. However, the variation of extreme wave heights between sites was less than the mean wave climate would suggest, because mid‐latitude depressions generate comparatively large waves on the generally more sheltered northeast coast. At the most energetic site to the southwest of the South Island, a 1 in 100‐year re...

Journal ArticleDOI
TL;DR: In this paper, the effects of various groin parameters (length, head length and opening) and wave parameters (wave height, wave period and wave angle) on the accretion of the area protected by T-shape groins are studied in a physical model.