bluuebunny/crossref_metadata_2025 huggingface dataset:
RESPONSE OF SEADYKES DUE TO WAVE IMPACTS
Authors: Fuhrboter A. , Dette H.H. , Grune J.
Published: June 2019

Damages on seadykes and revetments are mainly caused by wave impacts due to breaking waves. These impact forces act on small areas for a very short time and cause crater-like formations, when the forces are transmitted instantaneously to the side-walls of cracks in the cover of dykes or through joints into and below revetments. In this paper the results of investigations on impact forces are presented. A comparison of field data and laboratory data proves considerable differences, which must be explained mainly by the different air entrapment for prototype and small-scale conditions in the breaking waves. Both the data from field and small-scale model emphasize, that the slope of the dyke or revetment is responsible at first for frequency and magnitude of the impact forces. Furthermore the effect of impact forces is demonstrated by the results of investigations on the stability of stone revetments with joints.
CHARACTERISTIC WAVE PERIOD
Authors: Manohar M. , Mobarek I.E. , El Sharaky N.A.
Published: June 2019

The wave period estimates obtained from different procedures are not consistent unlike statistical distribution analysis of wave heights. Thus not one definition of wave period is satisfactory for engineering analysis of coastal processes. There are at least 10 different measures of wave periods including the zero up-crossing period, the average wave period, significant height period and peak of the energy density spectrum period. For Lhe analysis of periods, 20 min. records were obtained from offshore pressure recorders. Summer and winter records were analysed separately. In the analysis, zero up-crossing period and average period were taken as reference periods. There were significant differences between the wave periods and they were found to depend also on the spectral width parameter. Finally comparison was made between the energy flux obtained under the spectral diagrams and energy flux obtained using various wave periods and heights. Study shows that if the total energy flux is desired, then the most appropriate values to be used are the root mean square wave height and period corresponding to that wave height. Use of significant wave height, along with zero up-crossing period gives higher values.
WAVE OVERTOPPIMG EQUATION
Authors: Weggel J. Richard
Published: June 2019

In the early 1950's the Corps of Engineers' Jacksonville District initiated a series of laboratory tests to investigate the overtopping of proposed levee sections for Lake Okeechobee, Florida. For economic reasons, the alternative to build levees with crest elevations that were at times below the limit of wave runup was investigated and the quantities of water carried over the structures for various freeboard allowances, structure slopes and wave conditions determined. The initial tests were conducted at the Waterways Experiment Station (WES) in Vieksburg, Mississippi for the Jacksonville District at what was taken to be a 1 to 30 model scale. Model wave heights varied from 1+.05 cm to 12.2 cm (0.133 to 0.^0 ft). In order to expand the range of test conditions investigated, the Beach Erosion Board, currently the Coastal Engineering Research Center (CERC), commissioned an expanded series of tests that considered the overtopping of riprap faced, curved and stepped seawalls as well as the overtopping of "smooth" slopes. These tests, also conducted at WES, were considered to be at a 1 to 17 scale with model wave heights ranging from 5-36 cm to 21.5 cm (0.176 to O.706 ft). A number of tests were subsequently conducted in CERC's large wave tank to determine the influence scale effects might have on overtopping. These tests are referred to as 1 to 2 1/2 scale tests. The model wave heights investigated ranged from U8.8 cm to 11*0.2 cm. (1.60 to h.6o ft).
FINITE ELEMENT MODEL FOR ESTUARIES WITH INTER-TIDAL FLATS
Authors: Herrling Bruno
Published: June 2019

This paper deals with finite element formulations for the numerical computation of two-dimensional incompressible long period shallow water waves. The described mathematical model is used to reproduce the dynamic situation occurring at the tidal propagation in estuaries. Areas which fall dry and wet again within a tidal cycle - so called inter-tidal flats - are taken into account.
RESONANT INTERACTIONS FOR WAVES BREAKING.ON A BEACH
Authors: Guza Robert T. , Bowen Anthony J.
Published: June 2019

A laboratory and theoretical study of the transition from strongly reflected surging to dissipative plunging breakers on a relatively steep plane beach (1:8) has revealed the following: (1) The run-up and offshore variation of sea surface elevation of surging waves are well predicted by linear theory. (2) The fluctuating part of the run-up (related to the amplitude of the reflected incident wave) reaches a maximum value; a further increase in incident progressive wave energy results in increased dissipation. (3) Subharmonic edge waves (the growing instabilities of surging waves) are driven primarily by the swash motion, which does not increase with increasing incident breaking wave height. However, the turbulence accompanying incident wave breaking, and the effective eddy viscosity, rapidly increases with increasing breaker height. As a result, subharmonic resonances do not occur with spilling or steep plunging waves; very strong viscous effects suppress the nonlinear instabilities. (4) edge waves generated by a surging incident wave can be suppressed by superimposing an additional breaking wave of different frequency on the incident wave field. Thus, any excited edge waves are likely to have length scales at least the order of a surf zone width.
ENCLOSING SCHEME FOR BATHING-BEACH DEVELOPMENT
Authors: Tauman Joseph
Published: June 2019

This paper refers to bathing beaches. It presents a method for beach design which provides both coastal protection and protection for the bathing public. Reasons are pointed out as to why the open sea foreshores are, in many cases, not suitable for recreation. The method uses an enclosing submerged breakwater coupled with short groins to provide a bathing beach with a safe swimming area and a controlled sand plaza. Economical in execution and maintenance, the method can be used for sandy or rocky coasts.
RADAR OBSERVATIONS OF HURRICANE WAVE DIRECTIONS
Authors: King D.B. , Shemdin O.H.
Published: June 2019

This paper presents an analysis of data collected in a hurricane wave research program. The data were collected with a synthetic aperture radar (SAR) during five aircraft flights into hurricanes in August and September, 1976. These data are the first collected on the directional distributions of waves throughout the region of active generation. The wave patterns in all of the storms are similar and show a marked radially asymmetry. The dominant waves propagate ahead of the storm in a broad arc that has an apparent center in a region of confused sea to the right and rear of the hurricane eye. The asymmetry in the wave patterns is attributed to the forward motion of the storms. The wave directions throughout the storms do not show a sensitive dependence on the forward speed of the storms or on their maximum wavespeeds. However, there is an increase in peak wavelength with increasing windspeed and forward velocity.
PROBLEMS OF DESIGN AND CONSTRUCTION OF AN OFFSHORE SEAWATER INTAKE
Authors: Standish-White D.W. , Zwamborn J.A.
Published: June 2019

A seawater intake had to be constructed for a diamond mine on the coast of Namibia just north of Oranjemund. The solution adopted consisted of a piled jetty with a dolos island on its seaward end protecting the pump chamber which was built of closely spaced concrete piles. The paper briefly describes the various problems encountered during the construction of the intake, including : limited penetration of the piles leading to the failure of the first jetty, serious slump of the initial dolos island, breakages of dolosse due to excessive movements during storms, considerable wear of the vertical spindle pumps due to sand and surging. Also described are the engineering solutions which had to be found at very short notice for immediate application.
NON-BREAKING AND BREAKING WAVE LOADS ON A COOLING WATER OUTFALL
Authors: Mogridge G.R. , Jamieson W.W.
Published: June 2019

Cooling water from a power generating station in Eastern Canada is pumped to an outfall and distributed into the ocean through discharge ports in the sidewalls of a diffuser cap. The cap is essentially a shell-type structure consisting of a submerged circular cylinder 26.5 ft in diameter and 14 ft high. It is located in 25 ft of water at low water level and 54 ft at high water level. Horizontal forces, vertical forces and overturning moments exerted by waves on a 1:36 scale model of the diffuser cap were measured with and without cooling water discharging from the outfall. Tests were run with regular and irregular waves producing both non-breaking and breaking wave loads on the diffuser cap. The overturning moments measured on the diffuser cap were up to 150 percent greater than those on a solid submerged cylinder sealed to the seabed. Unlike sealed cylinders, all of the wave loads measured on the relatively open structure reached maximum values at approximately the same time. The largest wave loads were measured on the diffuser structure when it was subjected to spilling breakers at low water level. For a given wave height, the spilling breakers caused wave loads up to 100 percent greater than those due to non-breaking waves.
AN INCLINED-PLATE WAVE GENERATOR
Authors: Raichlen Frederick , Lee Jiin-Jen
Published: June 2019

A numerical method for determining the characteristics of waves generated by a hinged inclined-plate wave generator operating in a constant depth channel is discussed. The analysis is in reasonably good agreement with experimental results. The results indicate the sloping generator operating under certain conditions is completely inefficient, i.e., for a given stroke and depth-to-wave-length ratio, very small waves are produced; for other wave periods for the same conditions significantly larger waves are generated.
FIELD STUDY OF BREAKING WAVE CHARACTERISTICS
Authors: Weishar Lee L. , Byrne Robert J.
Published: June 2019

This study focuses upon four elements of breaking wave behavior: 1) Relative breaking depth criteria 2) Breaking wave classification 3) Evaluation of the plunge distance 4) Breaking wave height prediction The data set is 116 waves filmed at Virginia Beach, Va., on the Atlantic U.S. coast. The cine-photographic observation technique permitted the viewer to freeze the free surface profile at successive time steps as the waves passed an upright plane grid placed perpendicular to the beach. The results indicate that: 1) While the average value of %/d^ - 0.78, there was a significant difference between plunging and nonplunging waves. 2) Neither the breaker classification of Galvin nor that of Battjes successfully discriminated between plunging and spilling breakers. 3) The distance travelled by the foreface of a plunging wave was found to be underestimated by the free fall trajectory model advanced by Galvin. The field observations show the weakness to be in the plunge time arising from neglect of the vertical velocity component. 4) The breaking wave height prediction formulation advanced by Komar and Gaughan adequately predicts the breaking wave height within the constraints of calculating deep water wave characteristics, neglecting wave refraction and frictional effects. The combined data set covers the breaker wave height between laboratory scale observations to greater than 3 m.
COASTAL FLOOD SIMULATION IN STRETCHED COORDINATES
Authors: Butler H. Lee
Published: June 2019

Coastal flooding in developed areas can be catastrophic. As an essential element in coastal water level prediction, a two-dimensional numerical model of long period wave behavior is presented. The time dependency is treated implicitly for cost-effective simulation of coastal flooding from hurricane surges or other hydrodynamic phenomena such as extratropical storm surges, tides, tsunamis, etc. An important feature of the model is use of a coordinate transformation in the form of a piecewise exponential stretch. Such a technique permits simulation of a complex landscape by locally increasing grid resolution and/or aligning coordinates along physical boundaries. The model is applied to Galveston Bay, Texas, for storm surge and coastal flooding from Hurricane Carla 1961. Verification for the Galveston area was accomplished by using physical model data from simulations of free gravity waves (tide and design surge). Subsequent hindcasting of Carla produced good agreement between observed and computed surges with a mean absolute error of 0.18 m for peak elevations.
A NEW METHOD FOR THE REPRESENTATION OF SEDIMENTARY SEQUENCES IN COASTAL REGIONS
Authors: Streif Hansjorg
Published: June 2019

Coastal lowlands usually consist of a body of unconsolidated sediments of up to 30 m thickness which have been deposited under the influence of a rising sea level during the past 10,000 years. These lowlands increasingly are acquiring importance for industrial plants, harbour construction, pipelines, and for the exploration of mineral resources. Consequently a basis for planning is required which will permit an economic exploitation of the coastal zone. Geological mapping at scale of 1 : 25 000, which has been going on in Germany for more than 100 years, is of fundamental importance for this. Especially the newest type of geologic maps - the sequence map - offers the possibility of classifying and representing (BARCKHAUSEN, PREUSS & STREIF 1977) the costal deposits in a way that is well suited for technical and scientific purposes. Its range of application covers tidal flat areas, marshes and coastal bogs, as they occur for example in the coastal zone of the southern North Sea. Combined with a documentation system of the field data and the techniques of automatic data processing this type of map offers new aspects which by far exceed the possibilities of conventional geological mapping.
LONGSHORE SEDIMENT TRANSPORT DATA: A REVIEW
Authors: Gree Matthew N. , Madsen Ole Secher
Published: June 2019

Siltation rates anticipated at harbor entrances, in navigation channels and at inlet structures as well as possible adverse effects caused by these and other coastal engineering constructions are often assessed based on considerations of longshore sediment transport rates. The ability to predict the longshore sediment transport rate is consequently of considerable importance in many coastal engineering problems. The engineering need for an ability to predict longshore sediment transport rates is evidenced by the fact that the development of empirical relationships preceeded, by decades, any attempts at rigorous analyses of the mechanics of sediment transport processes in the surf zone. A predictive relationship for longshore sediment transport rates, which enjoys considerable popularity in the United States, is the empirical relationship suggested by the U.S. Army (1973), Coastal Engineering Research Center (CERC) in their Shore Protection Manual (SPM-73).
THE GENERATION OF LONG WAVES IN THE LABORATORY
Authors: Goring Derek , Raichlen Frederic
Published: June 2019

It became evident in the experimental aspects of a recent study of the propagation of nonlinear long waves past a step and up a slope that it was important to be able to generate waves which were initially well defined. The investigation dealt with the reflection and transmission of tsunamis past the continental shelf-break, and as such, two simple waves were used to represent certain characteristics of tsunamis: solitary waves and cnoidal waves. (Both of these permanent waves are solutions to the Korteweg-de Vries equation which to a certain order describe the propagation in two dimensions of nonlinear dispersive shallow water waves (see, e.g. Whitham, 1974).) The solitary wave actually can be generated in the laboratory in a simple manner if the wave tank is long enough and wave groups trailing the main wave are unimportant to the study. An example of the resulting waves obtained in the laboratory using a crude generation, procedure is demonstrated by the oscillograph record presented in Figure 1. Six traces are shown: the one at the bottom of the figure describes the time-displacement history of a vertical bulkhead wave generator which is moved by a hydraulic-servo system, the other five are the time variations of the water surface obtained using resistance wave gages spaced at the indicated number of depths downstream from the generator. (In the example presented, the depth of water was 10 cm and the wave plate was moved linearly with time a distance of 10.33 cm in 0.8 sec.) The wave generated and first shown 10 depths downstream appears to qonsist of a large wave followed by a series of oscillatory waves (termed the tail). As would be expected, as the waves propagate, due to the frequency content and the amplitude of the waves, the system separates into a leading wave followed some distance behind by the tail. The lead wave has the characteristic shape of a solitary wave. However, if the oscillatory tail is unacceptable for the type of experiments being conducted, and if it cannot be eliminated or the method of elimination is unacceptable, then a means of generation must be sought which eliminates the trailing waves initially.
BEACH EROSION-ACCRETION AT TWO TIME SCALES
Authors: Thom B.G. , Bowman C.M.
Published: June 2019

Erosion and accretion on the beachface have been studied at two time scales on the central and south coast of New South Wales, Australia. This research aims at providing a temporal perspective to contemporary problems of beach erosion in areas where the historic map record of changes in shoreline position is poor. Field work has been concentrated at two localities Moruya (lat. 35° 53'S long. 150°09'E) and Newcastle Bight (lat. 32°48'S long. 151°55'E)(Fig. 1).
CRITERION FOR STABILITY OF SHORELINE PLANFORM
Authors: Wang John D. , Le Mehaute Bernard
Published: June 2019

The problem of beach planform stability has been known for a long time: When does a small perturbation on a straight beach tend to grow with time and when does it tend to be flattened out? The interest in this problem arises from evidence of instabilities occurring in nature, but perhaps more importantly it is a problem that must be taken into account when formulating models for beach evolution and erosion. Existing mathematical models describing shoreline changes assume that the beach planform is stable and in equilibrium. It is therefore important to establish the range of wave conditions for which instabilities could occur, thereby invalidating such models. In the present case our interest is specifically directed towards determining conditions for which a model for shoreline evolution is intangible because of development of local instability. Grijm (1960) gave an approximate mathematical analysis indicating that at the point where the longshore sediment transport Q as a function of wave angle is maximum the shoreline must either be straight or form a cusp. Under his assumption that Q is proportional to sin 2a the maximum occurs for a = 45°. Le Mehaute and Soldate (1977) summarizes other studies that essentially arrive at the same results, viz. when the deep water wave angle is greater than 45° the shoreline is unstable. This result did not seem to be substantiated by field or laboratory observations. In this study of shoreline planform we first derive a criterion for instability of straight beaches. Then assuming that longshore sediment transport is proportional to the alongshore wave energy flux component at the point of breaking we determine the range of deep water wave characteristics and beach slopes which would cause unstable situations to occur. We consider only the longshore transport and exclude effects of on-offshore transport.
BLOWN SAND ON BEACHES
Authors: Kubota Susumu , Horikawa Kiyoshi , Hotta Shintaro
Published: June 2019

The blown sand transport rate and the vertical and shore-normal distributions of the wind speed were measured simultaneously on a windy beach. The sand transport rate was measured with conventional total quantity-type traps and with a large trap in the form of a trench. The vertical distribution of the wind speed was measured using an ultrasonic anemometer array consisting of six meters. The distribution of wind speed at a height of 1 m in a section normal to the shoreline was measured with five ultrasonic anemometers. A logarithmic law for the vertical distribution of the wind speed was satisfied, and the wind speed in the section normal to the shoreline was almost constant. The Kawamura and Bagnold formulae were found to predict well the sand transport rate. The trench trap and conventional traps gave empirical coefficients of 1.5 and 1.0, respectively, for the sand transport rate averaged over a section normal to the shoreline. The lower value determined with the conventional traps (1.0) is attributed to their inefficiency compared with the trench trap. In order to obtain data at high shear velocities, a wind tunnel experiment was carried out. This experiment showed that both the Kawamura and Bagnold formulae were valid in the range between 60 to 300 cm/s in the wind shear velocity. The empirical coefficient in the laboratory experiments was 1.0: the difference between the field result with the trench trap and the wind tunnel experiment is attributed to the fluctuations in natural wind.
SEDIMENT TRANSPORT AND BEACH TRANSFORMATION
Authors: Shibayama Tomoya , Horikawa Kiyoshi
Published: June 2019

Laboratory and field investigations were performed in order to formulate a predictive model of two-dimensional beach profile change. The observed transport was classified into six types, and transport formulas were deduced for each type based on a microscale description of sediment movement caused by wave action. A numerical model of two-dimensional beach transformation was then developed. Beach profile changes calculated with the model were then compared with the laboratory results. The model was found to give reasonable results except in the vicinity of the wave plunging point. The sediment transport calculation is based on a sinusoidal velocity profile. The model appeares to give good results as long as the wave motion can be reasonably approximated by linear wave theory.
NUMERICAL MODEL FOR DUNE EROSION DUE TO WAVE UPRUSH
Authors: Fisher J.S. , Overton M.F.
Published: June 2019

The objective of the work presented herein is to quantitize dune erosion as a function of the awash mechanics. In order to achieve this aim, a numerical model is developed which solves the one dimensional continuity and momentum equations for depth and velocity of the swash at the face of the dune. These parameters are then used as input to the dune erosion model which predicts the e::tent of toe retreat of the dune as a function of time. Since the model is formulated in real time, both short and long term events may be simulated. This is particularly important in terms of understanding the short term event in which the dune and beach face do not achieve an equilibrium profile.
DUCK82 - A COASTAL STORM PROCESSES EXPERIMENT
Authors: Mason Curtis , Sallenger Asbury H. , Holman Robert A. , Birkemeier William A.
Published: June 2019

In recent years, several field experiments have been conducted to define nearshore processes and sediment transport patterns under "normal" wave and wind conditions. Large arrays of wave and current measuring sensors, combined with bathymetric surveys, have provided preliminary evidence of complex relationships between forcing processes and sediment response. To date, however, lack of both rugged instrumentation and a means to survey nearshore areas during high wave conditions have precluded measurements of storm-related nearshore processes. To document the response of a typical East Coast site to extratropical storms (northeasters), a cooperative experiment known as DUCK- 82, was conducted in October, 1982 at the Field Research Facility (FRF) of the U. S. Army Engineer Waterways Experiment Station, Coastal Engineering Research Center, Vicksburg, Miss. Participating in the experiment were investigators from the FRF, the 0. S. Geological Survey, Oregon State University, and the University of Washington. Newly developed sensors and equipment were deployed which, for the first time, allowed a comprehensive analysis of the processes affecting the magnitude and time scale of short-term nearshore response.
OSCILLATORY BOUNDARY LAYER FLOW OVER RIPPLED BEDS
Authors: Sato Shinji , Mimura Nobuo , Watanabe Akira
Published: June 2019

Characteristics of the oscillatory boundary layer flow above rippled beds were investigated through experiments and numerical calculations. Experiments were conducted in an oscillatory flow tunnel. Velocities above symmetric and asymmetric ripples were measured with split-hot-film sensors under conditions of both sinusoidal and asymmetric oscillations. The stress field in the boundary layer was evaluated based on the distributions of the measured velocity and Reynolds stress. Relations between vortex formation and turbulence were examined, and effects of the asymmetry of oscillatory main flow and of ripple form on the velocity field were discussed. Numerical calculations were carried out by integrating the Navier-Stokes equations with an implicit finite difference scheme. Formation of a lee vortex above ripples was simulated in the calculations. The bottom shear stress and the energy dissipation rate were estimated based on the results of the experiments and calculations.
LOW-PROFILE BARRIER ISLAND OVERWASH AND BREACHING IN THE GULF OF MEXICO
Authors: Penland Shea , Suter John R.
Published: June 2019

An analysis of 17 tropical cyclone impacts along barrier islands in the Gulf of Mexico has led to the following conclusions: 1) tropical cyclones are the primary mechanism of barrier island overwash and breaching, 2) landward-directed and seaward-directed overwash flow can breach barrier islands, 3) storm track orientation to the shoreline controls the direction of barrier island breaching, 4) shore-normal and right-oblique hurricane impacts breach barrier islands by landward-directed overwash flow, and 5) left-oblique hurricane impacts breach barrier islands by seaward-directed overwash flow.
STABILITY OF RUBBLE MOUND SLOPES UNDER RANDOM WAVE ATTACK
Authors: Van der Meer J.W. , Pilarczyk K.W.
Published: June 2019

The objective of the present research project is to give new practical design formulae for rubble mound slopes under random wave attack. The study is based upon a series of model tests. More than two hundred tests have been performed in order to vary systematically all the relevant variables. The main shortcomings in Hudson-type formulae have been solved as a result of the present series of investigations. Stability formulae are given which include the influence of wave period, number of waves, armour grading, spectrum shape, groupiness of waves and the permeability of the core.
VERIFICATION OF KIMURA's THEORY FOR WAVE GROUP STATISTICS
Authors: Battjes J.A. , Van Vledder G.Ph.
Published: June 2019

North Sea wave records, obtained in conditions of active wave generation, have been analyzed with respect to the distribution of the length of wave groups. The results are compared to a theory by Kimura, in its original form as well as with the addition of a new spectral wave groupiness parameter, based on the theory of Gaussian processes. The results lend support to the validity of Kimura's theory, this in turn implies further evidence that the phenomenon of wave groups in sea waves can by and large be explained, both qualitatively and quantitatively, in terms of the linear, random phase model for the wave motion, even in conditions of active wave generation.
WAVE GROUP ANATOMY OF OCEAN WAVE SPECTRA
Authors: Thompson Warren C. , Nelson Arthur R. , Sedivy Dean G.
Published: June 2019

This paper inquires into the questions of how wave groups are related to the wave spectrum, and how they differ in sea versus swell. Some results are presented in the form of a wave group model for sea spectra and for swell spectra. The models were developed from statistical analysis of a large number of wave records and apply to deep water only.
SWASH ON A NATURAL BEACH
Authors: Mizuguchi Masaur
Published: June 2019

A field measurement was conducted in order to clarify the swash motion on a natural beach. It is found on this particular beach, which had a rather steep foreshore slope, that cross spectra calculated between the surface elevations, onshore velocities and the swash agree very well with those given by linear long two-dimensional standing wave theory in the lower frequency region than a certain value. This finding together with the observed f~ (f; frequency) high frequency saturation in swash spectra encourages a partial reflection model to describe the fluid motion in the inner surf zone, including the swash. The model developed shows a good agreement with the observed results, in which being employed an analogy to regular waves for the criticality of wave reflection. This model makes it possible to predict the swash spectrum for a given incident wave spectra and a given beach profile, as far as wave breaking takes place on a foreshore slope.
A MODEL FOR BREAKER DECAY ON BEACHES
Authors: Dally William R. , Dean Robert G. , Dalrymple Robert A.
Published: June 2019

Based on the observation that a shallow water breaking wave propagating over a region of uniform depth will reform and stabilize after some distance, an intuitive expression for the rate of energy dissipation is developed. Using linear wave theory and the energy balance equation, analytical solutions for monochromatic waves breaking on a flat shelf, plane slope, and "equilibrium" beach profile are presented and compared to laboratory data from Horikawa and Kuo (1966) with favorable results. Set-down/up in the mean water level, bottom friction losses, and bottom profiles of arbitrary shape are then introduced and the equations solved numerically. The model is calibrated and verified to laboratory data with very good results for wave decay for a wide range of beach slopes and incident conditions, but not so favorable for set-up. A test run on a prototype scale profile containing two bar and trough systems demonstrates the model's ability to describe the shoaling, breaking, and wave reformation process commonly observed in nature. Bottom friction is found to play a negligible role in wave decay in the surf zone when compared to shoaling and breaking.
A FINITE ELEMENT MODEL FOR WIND WAVE DIFFRACTION
Authors: Skovgaard Ove , Berhrendt Lars , Jonsson Ivar G.
Published: June 2019

The applicability of a hybrid finite element model for the calculation of combined diffraction-refraction of small time-harmonic water waves is demonstrated. The model is valid for arbitrary water depths and wave lengths, i.e. it is based on intermediate depth theory (IDT). The model includes arbitrarily varying partial reflection along the boundaries. Superposition of waves (to simulate a spectrum approach) with different incident directions is demonstrated, and CPU-times and core memory requirements are given. The model is verified and documented with respect to sensitivity of the model parameters in detailed tables, using the classical Homma island on a parabolic shoal. The wave period is here chosen in such a way that a small number of elements (larger than 500 and less than 2,000) is enough to get an accurate solution. For a new simple, but realistic harbour geometry many detailed and accurate graphical results are given. The wave period (T = 9 sec.) is here chosen so that it is representative for natural wind waves, and the size of the harbour is selected, so that the model gets a fairly large number of elements (of the order 10,000).
CURRENT DEPTH REFRACTION OF REGULAR WAVES
Authors: Jonsson Ivar G. , Christoffersen John B.
Published: June 2019

The complete set of equations for the refraction of small surface gravity waves on large-scale currents over a gradually varying sea bed is derived and presented. Wave lengths, direction of propagation and wave heights are all determined along the so-called wave rays as solutions to ordinary, first-order differential equations. Dissipation due to bed friction in the combined current wave motion is included. The ray tracing method is used in an example. A method for the calculation of current depth refraction of weakly non-linear waves is proposed.
FRICTION IN HURRICANE-INDUCED SURGES
Authors: Wang Shang-Yih , Christensen B.A.
Published: June 2019

With the increasing development of coastal areas, it is necessary to have a sound method for predicting hurricane-induced flooding in these areas, especially for studies such as the coastal construction set-back line, flood insurance rate-making and county land use planning. The objective of this study is to develop the capability of describing the friction factor in coastal areas for improved representation in numerical models of storm surges. Five types of areas are considered: A, ocean bottom with bed forms and some vegetation; B, mangrove fringes and areas; C, forested areas and cypress swamps; D, grassy areas and saltwater marshes; and E, developed residential and commercial areas. The friction factors, which incorporate both the bottom friction coefficient and drag coefficient due to the submerged parts of obstructions were verified by conducting laboratory experiments for mangrove and developed areas, using the typical distribution found in each of these coastal areas. The formulas of the friction factor for the ocean bottom, forested areas and grassy areas are determined by adopting results from previous investigations and discussed with the results of the current study.
NEAR-SURFACE ORBITAL VELOCITIES IN IRREGULAR WAVES
Authors: Daemrich K.-F. , Gotschenberg A.
Published: June 2019

The paper deals with measurements of horizontal orbital velocities near the surface of mechanically generated waves in a wave flume. Due to the characteristics of most velocity probes, it is difficult or impossible to measure with a fixed probe in the area above the lowest trough. As the probe is not submerged continuously, failures or uncertainties in the measurements may occur. To overcome these limitations, a movable frame for the velocity probe was designed, which can be moved vertically up and down with the surface elevation by a disc rotor servo motor, controlled by a wave gauge. By that continuously velocities up to 3 cm below the surface could be measured. Theoretical velocities have been calculated for comparison with different simulation methods for irregular waves, based on linear wave theory.
FIELD MEASUREMENTS OF DUNE EROSION
Authors: Fisher J.S. , Overton M.F. , Chisholm T.
Published: June 2019

A series of field experiments was made to evaluate the use of a laboratory derived relationship between the force in the wave uprush and the erosion of beach dunes. Measurements of the swash velocity and height at the dune face were used to compute a specific force parameter. This force term was correlated with the specific erosion of the dune. A linear relationship similar to that found in the laboratory was determined with a R squared value of .87.
AN EXPERIMENTAL STUDY OF HARBOUR RESONANCE PHENOMENA
Authors: Martinez F.M. , Naverac V.S.
Published: June 2019

An extensive series of experiments has been carried out at the laboratory in order to study rectangular harbour oscillation excited by incident long waves. Attention is focused on the effect of head loss entrance on resonant response attenuation. A "gross" quadratic hydraulic head loss coefficient is defined and information about it, resulting from tests, is provided. Experimental conditions used in this piece of work seem to be realistic under suitable scaling for Northern Spain harbours.
ABOUT THE ENERGY DISSIPATION OVER BARRED BEACH
Authors: Oelerich Johannes , Dette Hans-Henning
Published: June 2019

Since wave energy dissipation in the surf zone is a stochastic process closed mathematical formulations cannot be expected. The dissipation was computed using several analytical and/or empirical approaches and compared with prototype measurements in the Big Wave Flume (GWK) in Hannover as well as with field measurements from the west coast, of the Island of Sylt/North Sea. Generally good agreements were found for moderate energy dissipation conditions (spilling-breaker), whereas in the case of plunging breakers, however, the fitting is not solved satisfactory.
THE BEACH OF VINAROZ. ITS ORIGIN, EVOLUTION AND FUTURE
Authors: Peris Jose Serra , Gonzalez Jose Javier Diez
Published: June 2019

The great physiografical unity named "Ovalo Valenciano" is outstanding in Western Mediterraneum. The Oval is limited by River Ebro, in the North, and Cape San Antonio in the South. On its Northern, margined by River Cenia, in the north, and Tombolo of Peiiiscola in the South, is the subunity called Peniscola and there stand the beach of Vinaroz, extending itself from the harbour of Vinaroz to river Cervol mouth.
NUMERICAL MODELING OF WAVE DEFORMATION WITH A CURRENT
Authors: Ohnaka Susumu , Watanabe Akira , Isobe Mashiko
Published: June 2019

A numerical computation method for a wave field coexisting with a current is presented to study wave-current interaction on a slowly varying bottom topography. Derivation is given for a new set of time-dependent mildslope equations extended to a wave and current coexisting field, which can deal with wave deformation due to combined refraction, diffraction, reflection and breaking as well as to wave-current interaction. Discussion is made on the numerical computation schemes, boundary conditions and breaking conditions. Some examples of the numerical computations are shown for wave and current coexisting fields.
LONGSHORE CURRENT FORCING AT A BARRED BEACH
Authors: Whitford D.J. , Thornton E.B.
Published: June 2019

The FRF site is located along a 100-km unbroken stretch of barrier island formation known as North Carolina's "Outer Banks." There are no littoral barriers to perturbate incoming wave trains along the entire reach of shoreline. The site has a tidal range of 0.5 to 2.0 m and regular offshore bathymetry.
NONLINEAR EFFECTS ON FOCUSSED WATER WAVES
Authors: Peregrine D.H. , Skyner D. , Stiassnie M. , Dodd N.
Published: June 2019

A brief account is given of theory and experiments for water wave focussing. The theory uses weakly nonlinear wave modulation theory, that is the nonlinear Schrodinger equation, summarises earlier theoretical papers and augments them with numerical results. Experiments were performed to compare with theory. The limited comparison shown here indicates that the theory gives satisfactory results even for waves close to breaking. Both the numerical and experimental results indicate the importance of linear diffraction when waves are focussed. The relevance of diffraction is easily assessed, and is likely to dominate in many coastal examples of weak focussing.
SPECTRAL WAVE ATTENUATION BY BOTTOM FRICTION: EXPERIMENTS
Authors: Madsen Ole Secher , Rosengaus Moises Michel
Published: June 2019

This paper presents a summary of carefully conducted laboratory experiments on sediment response and resulting wave attenuation for waves, periodic as well as simulating a wave spectrum, propagating over an 18-m-long bottom section covered by a 10-cm-thick layer of 0.2-mm-diameter quartz sand. The results for wave-generated bedform geometry as well as the equivalent Nikuradse roughness are obtained. The results show that the sediment response to the agitation of a wave spectrum may be approximately described by the sediment response to an equivalent periodic wave having the same root-mean-square near-bottom orbital velocity and excursion amplitude as the spectral wave. This equivalent wave, defined by the near-bottom characteristics of the spectral wave, is identical to that derived by Madsen et al. (1988) in the context of dissipation within the wave boundary layer. Although limited by the range of experimental conditions achieved in this study, the results obtained here and in the companion paper suggest a predictive methodology for the evaluation of spectral wave attenuation from knowledge of sediment and wave characteristics.
WAVE GROUP ANALYSIS BY THE HILBERT TRANSFORM
Authors: Hudspeth Robert T. , Medina Josep R.
Published: June 2019

A methodology based on linear theory is presented for analyzing wave groups from a random sea representation in the complex plane. A wave height function [H(t)], a local frequency function, [0(t)] , and an orbital velocity function [V(t)] are defined from the Hilbert transform of the sea surface elevation. Envelopes computed by the Hilbert transform are compared with the SIWEH. A three axes representation of the mean lengths of runs of waves is employed to compare the lengths of runs computed by the discrete wave method with runs computed by the Hilbert transform method.
PROBABILITY OF WAVE BREAKING IN THREE-DIMENSIONAL SEAS
Authors: Mather D. , Snook M.W.G. , Greated C.A. , Easson W.J. , Bryden I.G.
Published: June 2019

Current guidance notes for the design of offshore or coastal structures to withstand breaking waves are based on the behaviour of long-crested, monochromatic waves. It has been acknowledged for some time that although useful for first approximations and in some cases conservative load estimation, the adoption of long-crested wave theories and design principles for a short-crested sea environment may be inappropriate. Halliwell & Machen (1981) have shown that in shallow water, isolated breaking waves under short-crested conditions can occur with greater elevations and hence potentially greater destructive power than existing design codes predict*. Similarly work by Easson & Greated (1981)) has highlighted deficiencies in wave theories to predict particle velocities and accelerations within waves by direct non-contact measurement of these properties, the implications being that such theories may significantly underestimate the total wave loading encountered under breaking waves. These observations call into question our ability to predict accurately and so design to withstand wave breaking effects in short-crested environments. This paper reviews some of the present approaches to the prediction of wave breaking or whitecapping occurrences and compares data.
A NEW PARAMETER FOR WAVE BREAKING WITH OPPOSING CURRENT ON SLOPING SEA BED
Authors: Sakai Shigeki , Hirayama Ken-ichi , Saeki Hiroshi
Published: June 2019

Opposing currents affect the wave breaking processes. The condition of wave breaking caused by opposing currents in deep water is described by the ratio of the wave celerity to the velocity of the opposing current(Yu(1952)). For the wave breaking caused by the opposing currents in shallow water on a flat bed, the equation given by Miche(1951) for the breaking criteria without current remains available (Iwagaki et al.(1980)). However, it is the breaking of shoaling wave in the presence of opposing current on a uniform slope, which is of concern in this paper. Sakai et al.(1981) showed that the wave breaking affected by opposing currents on a sloping sea bed is characterized by a normalized unit width discharge q*, as well as an incident wave steepness Ho/Lo and a slope of sea bed S, where q* is defined as q*= q/g2T3; q: a unit width discharge, g; the gravitational acceleration, T: a wave period. They proposed diagrams for the breaker height and the breaking depth as a function of these three parameters. The breaker index curves in their diagrams show the relationships between the breaker height (or the breaking depth) and q* for waves with particular values of Ho/Lo and S, and it is much more convenient to give a general expression for the breaker indices for arbitrary conditions of q*, Ho/Lo and S. The purpose of this study is to formulate the effects of these parameters on wave breaking, based on the results of systematic experiments performed by the authors, and to derive an empirical and simplified expression for the breaker height and depth in the presence of opposing currents.
SURF BEAT GENERATION ON A MILD-SLOPE BEACH
Authors: Schaffer Hemming A. , Svendsen Ib A.
Published: June 2019

Two dimensional generation of surf beats by incident wave groups is examined theoretically. An inhomogeneous wave equation describes the amplitude of the surf beat wave. The forcing function is the modulation of the radiation stress. The short waves are amplitude modulated both outside and inside the surf zone causing the long wave generation to continue right to the shore line. Resonant generation as shallow water is approached is included. The analytical solution is evaluated numerically and shows a highly complicated amplitude variation of the surf beat depending on the parameters of the problem.
SOLITARY WAVE TRANSMISSION THROUGH POROUS BREAKWATERS
Authors: Vidal C. , Losada M.A. , Medina R. , Rubio J.
Published: June 2019

A semi-empirical theory is formulated to predict wave reflection and transmission at a porous breakwater of rectangular cross section for normally incident solitary waves. The solution is based on the linearized form of the governing equations and on equivalent linearization of the friction loss in the porous structure. Experimental results of transmission coefficients are presented for a large range of incident wave amplitudes, with several gravel sizes, water depths and breakwater geometries. Experimental and theoretical results are compared and evaluated; the comparison shows satisfactory agreement for the transmission coefficient.
NON-UNIFORM SUSPENDED SEDIMENTS UNDER WAVES
Authors: Armanini Aronne , Ruol Piero
Published: June 2019

An original mathematical formulation for suspended sediments in a two-dimensional wave boundary layer is presented. The model accounts for non-immediate adaptation of sediments to the hydrodinamic conditions, and allows to include the effect of sorting of the different diameters considered. The mathematical model is numerically solved through a finite difference scheme. It is suitable that results compare favourably with experimental data by Staub et alii.
ENVIRONMENTAL CONTROLS ON LITTORAL SAND TRANSPORT
Authors: Komar Paul D.
Published: June 2019

Quantities of sand transported along beaches are generally related to the "longshore component of wave power", F^, through the proportionality is = KF£ where l8 is the immersed-weight sand transport rate and K is a dimensionless proportionality factor. A more-generally applicable relationship is that of Bagnold, ls = K'(ECn)bvL/um where (ECn)b is the energy flux or total power of the breaking waves, y^ is the longshore current, um is the mean orbital velocity under the waves, and K' is another dimensionless coefficient. It is apparent that sediment transport rates on beaches should depend on environmental factors such as the grain diameter or settling velocity, and possibly on factors such as the beach slope or wave steepness. However, examinations of such dependencies for K and K' within the field data are hampered by problems with large random scatter within any one data set, and by systematic differences between separate studies which have employed diverse measurement techniques. Examinations of the field data for K and K' variations indicate that meaningful dependencies on sediment grain diameters and other factors cannot be established with confidence in the sand-size range. Limited data available from gravel beaches support the expected decreases in K and K' with increasing grain sizes. These data are too few in numbers to establish firm trends, but do suggest that future investigations to establish dependencies on environmental factors would be most profitably undertaken on gravel beaches. The measurements collected in recent years from sand beaches suggest revisions in average K and K' coefficients to be used in transport evaluations, but such revisions must be coordinated such that K/K' = 2.7 so as to maintain agreement with the longshore current data.