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Showing papers on "Wave height published in 1992"


Journal ArticleDOI
TL;DR: In this article, a simple numerical algorithm is utilized to test the wave-by-wave approach to modeling random wave transformation caused by shoaling, breaking and reforming across nearshore profiles of arbitrary shape.

78 citations


Journal ArticleDOI
TL;DR: In this paper, a single dimensionless parameter is developed that predicts the occurrence of storm or normal profiles by rearranging the results of large-scale wave tank tests of monochromatic waves breaking on sandy beaches.
Abstract: Using the results of large‐scale wave tank tests of monochromatic waves breaking on sandy beaches, Larson and Kraus have shown that storm (barred) and normal (nonbarred) equilibrium beach profiles can be segregated in terms of two‐dimensionless parameters, which involve wave and sediment characteristics. Here, by rearranging their results, a single dimensionless parameter is developed that predicts the occurrence of storm or normal profiles. The profile parameter (P=gH02/(w3T)) uses deep‐water wave characteristics to distinguish the two profile types. Using shallow‐water data the shallow‐water Dean number, Hb/(wT) can serve the same purpose. Further, a Froude number representation of the sediment fall velocity, w2/(gH0), is shown to be an important parameter for equilibrium profiles.

67 citations


Journal ArticleDOI
TL;DR: In this paper, a simple linear relationship between backscattered power and wind speed is derived, which is in close agreement with the algorithm recently proposed by Witter and Chelton for wind speeds above 3 m s−1.
Abstract: An assessment is made of the significant wave height and wind speed measurements obtained by the Geosat radar altimeter. In comparison with buoy data, it is found that Geosat underestimated the significant wave height by 13% throughout the range of measurements. An attempt to compare the wave measurements made by Seasat and Geosat reveals problems with both data sets. For the Geosat wind speed measurements, it is found that the smoothed-Brown algorithm, usually employed to convert backscattered power to wind speed, does not give good results in comparison with buoy measurements. A simple linear relationship between backscattered power and wind speed is derived, which is in close agreement with the algorithm recently proposed by Witter and Chelton for wind speeds above 3 m s−1. The implications of these results for deriving wind and wave climatologies from altimeter data are discussed.

65 citations


Journal Article
TL;DR: In this paper, the influence of shoreline orientation, sheltering by adjacent headlands, slope and width of the low tide terrace, and human modification on beach processes and responses was analyzed.
Abstract: Data for eight low-energy meso-tidal sand beaches in developed communities on Raritan Bay and Delaware Bay estuaries in New Jersey. U.S.A., are compared to identify the influence of shoreline orientation, sheltering by adjacent headlands, slope and width of the low tide terrace, and human modification on beach processes and responses. Data on these controls, derived from charts and air photos, are used to explain statistically significant similarities and differences in wind and wave characteristics and beach mobility derived from field investigations. Wind conditions were similar on both bays, but processes and responses differed between sites. Shoreline orientation affects the degree to which refracted ocean waves alter the incident wave field, and sites farther from the ocean may have more conspicuous ocean wave influences than sites closer to the ocean. Site specific differences in the width and slope of the low tide terrace have pronounced effects on wave height and mobility of the upper foreshore. Sheltering by natural headlands appears to be less effective than human controls. Compartmentalization of 8 beach by structures can increase or decrease beach mobility, depending on position relative to the ends of a longshore drift compartment. Localized human impacts can have conspicuous effects on low-energy estuarine beaches that undergo limited profile change under natural conditions.

60 citations


Journal ArticleDOI
TL;DR: In this article, an extensive data set of observed rip currents and associated wave parameters collected on Narrabeen Beach, Australia, is re-examined to determine how rip current spacing is related to incident wave conditions.

54 citations


Journal ArticleDOI
TL;DR: In this article, a procedure for generating simulated time sequences of wave height, period, and direction data at specific locations is described, where a finite length wave record is used to compute a matrix of coefficient multipliers, which are used to generate arbitrarily long-time sequences of simulated wave data, preserving the primary statistical properties of the finite data set.
Abstract: This paper describes a procedure for generating simulated time sequences of wave height, period, and direction data at specific locations. The technique uses a finite length wave record to compute a matrix of coefficient multipliers, which are used to generate arbitrarily long time sequences of simulated wave data, preserving the primary statistical properties of the finite data set. The procedure was developed for simulating time series from the Wave Information Study (WIS) data base, a 20‐year hindcast of wave height, period, and direction provided at three‐hour intervals for locations along United States coasts and the Great Lakes. Application of the methodology is demonstrated in this paper through comparisons of simulated data with hindcast data corresponding to a Gulf of Mexico WIS station near the entrance to Mobile Bay, Alabama. Analysis of the results indicate that the simulated time series does exhibit the primary statistical properties of the WIS data, including winter and summer seasonal patte...

40 citations



Journal ArticleDOI
TL;DR: In this article, the concept of the equivalent uniform current was introduced, which is defined as the uniform current which produces the same wavelength as the actual depth-varying current for a particular observed wave period, wave height and water depth.

37 citations


Journal ArticleDOI
TL;DR: In this article, a semi-empirical method is developed which predicts the wave height shoaling up to the break point on laboratory and natural beaches, which is enhanced with empirical curves for the wave shape, obtained from field measurements of wave height through the break points and the surf zone made on an ocean beach in southern Australia from 1987 to 1989.

34 citations


Book
01 Dec 1992
TL;DR: In this paper, both regular and irregular waves were used to move sand with a mean diameter of 0.18 mm placed on the seaward side of a simulated vertical seawall.
Abstract: : Laboratory experiments consisting of 22 tests were conducted in the 6-ft-wide wave flume at the US Army Engineer Coastal Engineering Research Center (CERC) to evaluate methods for estimating wave-induced scour depth (Sl) at vertical seawalls. Existing scour prediction methods range from rule-of-thumb estimates to semi-empirically derived equations. In the study, both regular and irregular waves were used to move sand with a mean diameter of 0.18 mm placed on the seaward side of a simulated vertical seawall. In the initial part of the study, 18 cases were run using irregular waves with various water depths, seawall locations relative to still-water level (swl), wave heights, and wave periods. All of the bottom profiles generated by the 18 irregular wave tests in the study supported a rule-of-thumb method, which states that maximum scour depth will be less than or equal to the incident unbroken deepwater wave height Ho, or S/Ho less than or equal to 1. When additional data from other studies (which used regular waves exclusively) were considered, the rule of thumb did not hold for all cases. To examine the effects of regular versus irregular waves in movable-bed laboratory studies, four additional test cases were run using regular waves having comparable water depths, wave heights, wave periods, and seawall locations relative to swl to four of the irregular wave test cases. In each of the four regular wave cases, scour depth exceeded scour depths associated with comparable irregular wave tests. On the average, scour depth increased by approximately 15 percent with regular water conditions.

33 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the relationship between damage at the rear of a berm breakwater and the crest height, wave height and wave steepness and found that enlarging the berm height at the crest was effective with regard to stability.

Journal ArticleDOI
TL;DR: In this paper, the relative energy in each wave train, the closeness of the frequency peaks, and the total wave energy were varied over 12 cases in a wave flume.
Abstract: Shoaling and decay of irregular wave trains with two distinct frequency peaks are simulated in a wave flume. The relative energy in each wave train, the closeness of the frequency peaks, and the total wave energy were varied over 12 cases. Wave-gauge measurements across the 1:30 plane slope in the flume show that linear superposition of single-peaked wave trains or lumping all energy into the dominant wave train are not satisfactory representations of multiple wave trains. The measurements also show that the wave train with the low-frequency peak dominates in the surf zone. Waves with the low-frequency peak appear unaffected by the second wave train, but the high-frequency wave train decays faster in the presence of the low-frequency waves. The variation of wave height through shoaling and breaking depends on the relative amount of energy in each of the wave trains and the closeness of the peak frequencies.

Journal ArticleDOI
TL;DR: In this paper, a simulation methodology is introduced to retain the essential features of the theoretical background in Gaussian random noise but to avoid further compromising assumptions in the interpretation of wave height and period in the amplitude domain.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the characteristics of the second decay process on a natural exposed dissipative beach, including its magnitude and dual dependence on local mean water depth and distance from the breaker line.

Journal ArticleDOI
TL;DR: In this article, the authors compared the 1984 version of the Shore Protection Manual (SPM) with three other wave prediction methods including the one used in 1977 and earlier versions of the SPM.

Book ChapterDOI
01 Jan 1992
TL;DR: In this article, the energy dissipation mechanism due to wave breaking is modelled and the dissipation term is included in an elliptic, extended mild-slope equation, which makes it possible to handle relatively rapid undulations in water depth.
Abstract: The energy dissipation mechanism due to wave breaking is modelled. The dissipation term is included in an elliptic, extended mild-slope equation, developed recently by the author [9]. An extension makes it possible to handle relatively rapid undulations in water depth. The resemblance between breaking waves and hydraulic jump is used to model the energy losses due to breaking. Three various types of wave trains are considered. Results of comparison with experimental data are also presented.

Journal ArticleDOI
TL;DR: In this paper, the effects of wave height on wave-fluid particle kinematics were investigated using laser Doppler anemometry and compared to Stokes third-order theory.
Abstract: Results of recent research on experimental investigation of wave-fluid particle kinematics just prior to breaking using laser Doppler anemometry are presented. Extreme transient waves, similar to those found in hurricane Camille, and an "equivalent" regular wave, often used for design purposes, are generated and their kinematics measured. The kinematics of transient waves of smaller height are also measured to evaluate the effect of wave height, and these data are compared to Stokes third-order theory. Due to particular asymmetries not present in the large regular symmetric wave, the transient wave kinematics under the crest are shown to be much more severe above the still water level and somewhat less severe below. The stretching method used for the simulated transient wave underestimates the horizontal velocities in the crest and overestimates them below the still water level. These comparisons suggest that it would be worthwhile to further investigate the use of extreme waves as more realistic design waves and to develop a wave theory that accounts for the effect of the asymmetries.

01 Jan 1992
TL;DR: In this paper, the authors investigated water wave-induced fluidization of cohesive soil beds composed of a 50/50 (by weight) mixture of a commercial plume and a kaolinite in a laboratory flume.
Abstract: The mechanism by which fluid mud is formed by water wave motion over coastal and estuarine cohesive soil beds is of evident interest in understanding and interpreting the microfabric of flow-deposited fine sediments in shallow waters, and hence the erodibility of muddy beds due to hydrodynamic forcing. This study investigated water wave-induced fluidization of cohesive soil beds composed of a 50/50 (by weight) mixture of a commercial attapulgite and a kaolinite in a laboratory flume. Temporal and spatial changes of the effective stress were measured during the course of wave action, and from these changes the bed fluidization rate was calculated. A previously developed hydrodynamic wave-mud interaction model of the two-layered water-mud system was employed to study the nature and the degree of wave dissipation, in terms of energy dissipation rate, during the bed fluidization process. By evaluating the mud rheological properties separately, a mud viscosity model was developed, which was then used in conjunction with the wave-mud interaction model to obtain an effective sheared thickness of the bed resulting from wave action. This thickness, considered to be a representative of the fluidized mud thickness, was compared with the latter obtained from pressure measurements. Also, through this wave-mud model the relationship between the rate of fluidization and the rate of wave energy dissipation during fluidization was examined. In general, for a given wave frequency, a larger wave fluidized the bed at a faster rate and to a greater depth than a smaller one. Furthermore, increased bed consolidation time decreased the rate of fluidization due to increased mud rigidity. The rate of bed fluidization was typically greater at the beginning of wave action and decreased with time. Eventually this rate approached zero, while in some cases the wave energy dissipation rate approached a constant value, which increased with wave height. As the fluidization rate approached zero, there appeared to occur an equilibrium value of the bed elevation, and hence a fluid mud thickness, for a given wave condition. During the fluidization process the bed apparently lost its structural integrity by loss of the effective stress through a build-up of the excess pore water pressure. After wave action ceased, the bed structure exhibited recovery by dissipation of the excess pore water pressure. Further studies will be required in which the hydrodynamic model must be improved via a more realistic description of mud rheology and relaxation of the shallow water assumption, and better pressure data must be obtained than in the present study. Nevertheless, this investigation has been instructive in demonstrating relationships between the degree of mud fluidization, wave energy dissipation and bed consolidation time, and thus offers insight into an important mechanism by which coastal and estuarine muds are eroded by wave action. (Document has125 pages.)

Journal ArticleDOI
TL;DR: In this paper, a computer simulation model was designed to predict the selective shore-normal sorting of grain sizes in the nearshore environment, using linear theory up to the break point and a breaker decay model in the surf zone.
Abstract: This paper describes a computer simulation model which is designed to predict the selective shore-normal sorting of grain sizes in the nearshore environment. The model simulates wave shoaling, wave height attenuation due to frictional losses and breaking, using linear theory up to the break point and a breaker decay model in the surf zone. Peak horizontal orbital velocities at the bed are calculated from Stokes second-order wave theory. The peak onshore and offshore velocities are used with the threshold expression of Komar and Miller (1975) to generate a spatial pattern of size variation of threshold grain diameter along a profile normal to the shore from deep water to the swash zone. The predicted grain size is used in an hydraulic interpretation of grain size distribution on the intertidal profile, based on the hydrodynamic variations over a tidal cycle on a macrotidal beach. The model is successful in predicting the broad pattern of increasing grain size in the onshore direction which has been observed in nature. Comparisons between measured and predicted grain size distributions indicate that the predictions of the model are better than those of previous models, but the model is more successful at predicting sediment size distributions than at predicting mean sizes on a beach profile.

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the storm that disrupted the meeting between President Gorbachev and President Bush in Malta between 2 and 3 December 1989, using two European Centre for Medium Range Weather Forecasts (ECMWF) atmospheric numerical models and an advanced wave model (WAM).
Abstract: The storm that disrupted the meeting between President Gorbachev and President Bush in Malta between 2 and 3 December 1989 is analyzed. The meteorological situation that caused the storm was simulated with two European Centre for Medium Range Weather Forecasts (ECMWF) atmospheric numerical models—a global model (resolution T106) and a limited-area model (resolution T333)—and its effect on the sea was simulated with an advanced wave model (WAM). Verification of the wind and wave forecast shows that to obtain a realistic forecast of wave height and distribution it is necessary to increase the horizontal resolution of the model, whose grid size must be no more than 40 km.

Journal ArticleDOI
TL;DR: In this paper, the authors carried out model tests to estimate directional wave spectra from only a set of simultaneous records of ship motions, and the results were compared with the ones estimated from the observing data in an array of wave height sensors.
Abstract: In this paper, the authors carried out model tests to estimate directional wave spectra from only a set of simultaneous records of ship motions. Based on the assumption of linearity between the waves and the ship motions, many studies which estimate the wave power spectra by using only data of ship motions have been done. However, there are few results for estimation of directional wave spectra based on only information of ship motions. The estimating calculation in this paper consists of three steps. The first step is a calculation of cross spectra of ship motions by a stochastic approach using a multidimensional auto regressive model. The second one is a theoretical calculation of frequency response functions of the ship from the waves by New Strip Method. And, the last one is an estimation of directional wave spectra by using Bayesian Model. In order to discuss the quantitative accuracy of this method, some results were compared with the ones estimated from the observing data in an array of wave height sensors. Successful agreement between measured and estimated directional wave spectra was obtained. And the power spectra which were obtained by integration of the estimated directional wave spectra also agreed quantitatively with the measured ones.

Journal ArticleDOI
TL;DR: The kinematics of an irregular wave are characteristically different from that of a regular wave with similar wave height and frequency in two respects as mentioned in this paper, and the irregular wave induces larger parti...
Abstract: The kinematics of an irregular wave is characteristically different from that of a regular wave with similar wave height and frequency in two respects. First, an irregular wave induces larger parti...

Journal ArticleDOI
TL;DR: In this paper, the velocities and Eulerian acceleration were measured close to the wave surfaces (5 mm) using a very rapid response laser Doppler anemometer.
Abstract: Measurements of both the velocities and Eulerian accelerations have been made in the crests of waves at their breaking point. Measurement close to the wave surfaces (5 mm) has been made possible by the use of a very rapid response laser Doppler anemometer. The results have enabled critical comparisons to be made with mathematical wave models used in offshore design. At low levels within the waves, there is agreement between the theories, and the predictions are conservative. However, in the high crest most models seriously underpredict the kinematics. Validation of the models based on previously available results is shown to be limited in scope. This experiment was conducted in a wave flume using monochromatic waves shoaling on a flat bed and on slopes of 1:50, 1:30, and 1:15. Breaking wave heights were about 0.1 m, surface tension effects were negligible, and breaking occurred over a range of nondimensional depth (d'=d/gT2) from 0.004 to 0.035.

Journal Article
TL;DR: In this article, the authors compared simultaneous observations made by two observers over a four month period and determined confidence limits about estimates of wave heights ranging from 1 to 4 meters and periods ranging from 5 to 20 seconds.
Abstract: Records of littoral environment parameters such as wave height, period, and direction are essential to nearshore process studies. The most detailed studies require an elaborate and expensive array of current meters and wave gauges, which allow high resolution spectral analysis of wave and current variability. Studies concerned with low frequency variability or relatively large stretches of coastline may not be able to afford or even need high resolution spectral analyses. Incident wave parameters of study sites that lack offshore wave gauges can be characterized with data collected by human observers from the shoreline (SMITH and WAGNER, 1991). However, without documentation of observational accuracy, human observations provide only a relative comparison of daily littoral environment conditions. These observations become more useful to researchers when confidence limits can be assigned to the data, allowing their applicability to specific projects to be evaluated. This study compares simultaneous observations made by two observers over a four month period. The study period comprised enough observations to determine confidence limits about estimates of wave heights ranging from 1 to 4 meters and periods ranging from 5 to 20 seconds. These statistics broaden the range of previous statistical comparisons. As in previous studies (SCHNElDER and WEGGEL, 1980; PERLlN, 1984), observers tend to overestimate the period of short period waves, underestimate the period of long period waves, and underestimate wave height as incident wave height increases.

Journal ArticleDOI
TL;DR: In this paper, the effects of bottom friction on the estimation of breaking-wave heights, breaking locations, and breaking angles, determined by using the RCPWAVE model, were examined.
Abstract: The effects of bottom friction on the estimation of breaking-wave heights, breaking locations, and breaking angles, determined by using the RCPWAVE model, were examined. We used direct and a wave-ray approaches to simulate the effects of energy loss caused by bottom friction. The direct approach required knowing the wave friction coefficient prior to the calculation, and it did not given promising results. The way-ray approach is simple and effective; thus, it is used in this study. Three types of bottom roughness (i.e., grain size, ripple, and movable bed) were considered in the calculation of bottom friction. The numerical experiments showed that bottom friction is important when there is a 2- to 5-km-wide shallow beach. Bottom friction reduces the breaking-wave height 30-50%. It also changes the breaking points. The computer codes for the wave-ray approach are portable, and they can be incorporated with any other wave transformation model to give more realistic results.

01 Jan 1992
TL;DR: In this article, a laboratory experiment was undertaken to physically model the wave and current forcing as they pertain to the overwash process, and the experimental results demonstrate that the water surface gradient is the mechanism for transporting large quantities of sand on to and over barrier islands.
Abstract: With the rapid growth and development of barrier islands, understanding the long-term stability of these islands is an integral part of future coastal planning. The overwash process is the largest influence on the long-term stability of these islands and thus a corresponding understanding is of major importance. A laboratory experiment was undertaken to physically model the wave and current forcing as they pertain to the overwash process. The physical model was subjected to various storm conditions common to the occurrence of the overwash. Combinations of wave height, wave period, and overwash depth were tested in an attempt to isolate the significant parameters. Water surface gradients were also applied to observe their influence on the overwash process. Wave height, current, and bed profile measurements were taken at different locations throughout the tank. In addition, wave height transformation modeling and mean current prediction were performed and compared to the laboratory results in an attempt to model the overwash process through computer simulations. The experimental results demonstrate that the water surface gradient is the mechanism for transporting large quantities of sand on to and over barrier islands. In addition, two other conclusions were drawn about the overwash process: 1) the overwash depth plays an important role in determining the overwash velocity and hence the amount of sand deposited on the barrier island. 2) There seems to exist a correlation between the strength of the return flow and bar formation. It was also determined that modeling the wave height transformation during the overwash process is possible if the model is expressly written for the overwash process and not for nonoverwashing cases. The method utilized to predict the mean currents during overwash was not able to predict their strength but was able to substantiate the correlation between return flow and bar formation. As a result of overwash, the increased shoreward mass transport and reduced return flow in the water column are able to initiate and sustain a shoreward sediment transport. Finally, it was concluded that in all likelihood only "significant" overwash events affect the longterm stability of the barrier islands.

Journal ArticleDOI
TL;DR: In this paper, a parametric analysis of the wind generated wave spectrum is presented to determine if a sea is locally developed from the knowledge of the significant wave height, peak spectral period and nominal wind speed.

Book ChapterDOI
01 Jan 1992
TL;DR: In this paper, the authors describe the application of a range of computer models to describe the seasonal variation of seabed bathymetry in the vicinity of Chukpyon Harbour, which is situated on the east coast of Korea.
Abstract: The present paper describes the application of a range of computer models to describe the seasonal variation of seabed bathymetry in the vicinity of Chukpyon Harbour, which is situated on the east coast of Korea. The coastal conditions at the harbour site are dominated by waves and wave-induced currents. Consequently, wave-period-average models were used to predict waves and wave-induced-currents for three wave conditions for two wave directions. A new three-dimensional wave-period-average sediment model was then used to describe particular patterns of seabed change, which were, in turn, combined to predict seasonal changes. Use was made of a variety of field data on waves, currents, and sediment transport rates to set up and calibrate the model. Comparison of model results with field data confirmed the presence of residual sediment movement towards the harbour entrance and the location of shoal zones near the west groyne and east breakwater. The model was subsequently used to study new additions to the existing structures to control nearshore siltation.

Journal ArticleDOI
TL;DR: In this paper, a three-dimensional model for dynamic response analysis of jacket-type offshore platforms under random sea waves is established and the mean-square responses are obtained by Gauss-Legendre numerical integration.

Book ChapterDOI
01 Jan 1992
TL;DR: In this paper, the authors present an attempt to supplement the usual approach based on monochromatic waves or standard spectral simulations with an analysis of measured time series of waves, which is also of paramount importance when evaluating the boundary conditions for the computation of coastal circulation.
Abstract: The effect of mean mass transport on the surface of the sea due to wave movement and known as “Stokes Drift” plays an important role in forecasting the movement of floating pollutants and is also of paramount importance when evaluating the boundary conditions for the computation of coastal circulation; this paper presents an attempt to supplement the usual approach based on monochromatic waves or standard spectral simulations with an analysis of measured time series of waves.