bluuebunny/crossref_metadata_2025 huggingface dataset:
A SIMILARITY MODEL IN THE SURF ZONE
Authors: Wang Hsiang , Yang Wei-Chong
Published: June 2019

In fluid mechanics, a powerful tool known as the similarity model has been applied successfully to describe velocity and pressure fields in steady boundary layer flows, jet flows and wake flows. These flows, with the exception of a few laminar cases, are quite complex and are usually not amenable to theoretical analysis. The similarity analysis offers an alternative and often provides useful engineering information on the mean flow characteristics. The present work explores the possibility of applying the similarity concept to describe the flow field of breaking waves in the surf zone. Before presenting the similarity solution, a non-dimensional surf zone parameter is examined. This parameter, in addition to its many implications of characterizing surf zone properties, is pertinent to defining the region of validity of the similarity solutions. Solutions on mean flow characteristics are then established based upon a similarity hypothesis which states that the profiles of flow properties such as velocity and wave form preserve geometrical similarity downstream from the source of the disturbance and, therefore, can be defined by a few local characteristic parameters. Conditions required to preserve similarity are examined. Finally, laboratory results from a number of studies (Flick, 1978; Svendsen et al., 1978; Sakai and Iwagaki, 1978) and those from the authors are used to test the validity of the proposed model.
PREDICTION OF THE SEVEREST SIGNIFICANT WAVE HEIGHT
Authors: Ochi Michel K. , Whalin Joseph E.
Published: June 2019

This paper presents a method to statistically estimate the severest sea state (significant wave height) from the observed data. For the estimation of extreme significant wave height, a precise representation of the data by a certain probability function is highly desirable. Since we do not have any specific technique to meet this requirement, this situation seriously affects the reliability of the current method of predicting the severest sea condition. The author's method is to express asymptotically the cumulative distribution of the significant wave height as a combination of an exponential and power of the significant wave height. The parameters involved are determined numerically by a nonlinear minimization procedure. The method is applied to available significant wave height data measured in the North Sea, the Canadian coast, and the U.S. coast. The results of the analysis show that the data are well represented by the proposed method over the entire range of the cumulative distribution.
PREDICTION OF DOMINANT WAVE PROPERTIES AHEAD OF HURRICANES
Authors: Shemdin Omar H.
Published: June 2019

A method is proposed for predicting properties of dominant waves in the forward region of hurricanes where the waves are found to propagate predominantly in the direction of hurricane forward travel. An extended fetch concept is used in which each wave component is exposed to the action of wind over a fetch length that is determined by wave group speed, hurricane forward speed, and location with respect to eye. Maximum extended fetches are found to the right of the eye (with respect to direction of hurricane travel) in the northern hemisphere. The method correctly predicts dominant wave frequencies and significant wave heights. The prediction method utilizes recently developed concepts in wave generation and energy transfer among wave spectral components; the predicted values are compared favorably with observations.
LONG PERIOD DISTURBANCES DUE TO WAVE GROUPS
Authors: Bowers E.C.
Published: June 2019

Measurements of long period disturbances associated with wave groups are compared with theoretical predictions. The experiments were carried out in a wave flume with an absorbing beach at one end. Tests were carried out using both regular wave groups (made up of two wave frequencies so that groups occur at a single beat frequency) and a random sea. The theoretical predictions are based on a Stokes expansion of the basic wave equations up to second order. The results are consistent with having three components in the long period disturbance at wave group periods. The first is set-down beneath wave groups, a disturbance that is tied to the wave groups travelling towards the beach. The second is a surf beat, a free long wave propagating back from the beach that is generated by reflection of the set-down from the beach. The third component is a secondary wave, a free long wave propagating towards the beach, that is generated by the wave-maker when it is only programmed to produce the primary wave system without its associated set-down beneath wave groups. The experimental results show that this third component can be minimised for both regular wave groups and a random sea by adding an appropriate long period movement of the wave-maker. Also, results are presented that indicate that long cycles of truly random waves, lasting many hours in model terms, are required to obtain reliable estimates of the effect of wave grouping on marine structures.
RAY CURVATURE AND REFRACTION OF WAVE PACKETS
Authors: Breeding J. Ernest
Published: June 2019

Directional wave data obtained simultaneously at two measurement sites is used to confirm the constancy, and therefore the validity, of Snell's laws for wave packets. It is found that the wave packets refract according to Snell's law with the geometric group velocity whereas the wavelets within a packet refract according to Snell's law with phase velocity. An expression for the ray curvature of a wave packet is derived which is suitable for use in wave prediction programs. The ray curvature of the wave packet is found to vanish if the packet direction becomes either perpendicular or parallel to the wave speed contours, assuming the wavelet direction is not parallel to the contours. This means that as a hydron (wave packet) moves into shoaling water refraction tends eventually to turn the hydron so that it is directed either perpendicular or parallel to the shoreline. The first case is similar to monochromatic waves. For parallel water depth contours, it is the result for hydrons which begin in deep water if the angle of incidence is between 0° and 74.8° with respect to the contour normal. However, for deep water angles of incidence equal to or greater than 74.8° the hydrons are turned and move parallel to shore in water of intermediate depth. The packet ray curvature approaches infinity as the wavelet direction, but not the hydron direction, becomes parallel to the wave speed contours. The result is total reflection of the waves. Total reflection occurs if a hydron is moving into deeper water and its initial direction exceeds a critical angle. At the reflection point the hydron direction becomes perpendicular to the water depth contours. Further, the hydron velocity goes to zero, which is consistent with a particle concept. As in quantum mechanics, the wave-particle duality is encountered.
TSUNAMIS ALONG WEST COAST OF LUZON, PHILIPPINES
Authors: Wiegel R.L.
Published: June 2019

A detailed engineering study was made by Ebasco Services, Inc., (1977), for a proposed nuclear power plant in the Napot Point region of Bataan, between the entrance to Manila Bay and Subic Bay, Republic of the Philippines (about 14°- 37-12'N, 120°- 18-3/4'E), Figure 1. As a part of the oceanographic portion of this work, a study was made by the writer of the characteristics of tsunamis that had occurred in the region, and the statistics of occurrence (Wiegel, 1976). The study of tsunamis has been updated to the present time (May, 1980). The location of the site is such that the large tsunamis generated in some areas of the Pacific Ocean (such as off the coasts of Chile, Alaska, Japan and Kamchatka) are not likely to reach Napot Point with any appreciable amplitude (see, for example, Wiegel, 1976). There is good evidence that this is the case. Owing to the relative stability from the standpoint of earthquakes (aseismic) of Borneo, the Malaya Peninsula, most of Indochina and the intervening China Sea (Gutenberg and Richter, 1949, pp. 82 and 93), there is probably little, if any, chance of tsunamis being generated in this region; this appears to be a fact (Berninghausen, 1969). The great eruption of Krakatoa and the tsunami generated by it was not noticed on tide gages at either Singapore or Hong Kong, so that it would be reasonable that it would not have been detected at Manila (Wharton, 1888). Also, the large tsunamis that have been generated in the Sulu Sea and the Celebes Sea do not seem to reach the site with any appreciable amplitude. Thus, the tsunamis of importance to the site are those which will be generated in the local seas off the west coast of Luzon. In order to establish this fact, information is presented on a number of tsunamis generated in other regions, especially those generated in the seas off the west coast of the Philippine Islands.
TSUNAMI PRONE FRICTION FACTORS FROM WIND MEASUREMENTS
Authors: Bretschneider Charles L.
Published: June 2019

The long wave equations, used for tsunami run-up and flood wave calculations, have an unknown friction term. As an alternative to hydraulically determined friction factors, an adjustable three-level anemometer staff system is used for making wind profile measurements over typical Hawaii terrain. Results from measurements taken during trade wind conditions are given for three types of terrain: (1) golf course, (2) large flat knoll covered with 2 to 2 1/2 feet tall grass thin to medium dense, and (3) a large rock farm covered with several layers of stone 2 1/2 to 3 feet or more in diameter. Average values of Manning's "n" determined approximately from the von Karman friction length, n = .06 z ' vary from 0.028 over the golf course, 0.046 over the grass knoll, and 0.051 over the rock farm. The top level anemometer for both systems is at elevation 10.6 meters (35.8 feet) and the remaining anemometers are equally spaced on the log scale, with the bottom level anemometer at 1.3 meters (4.28 feet) above the support base. We are presently repeating the experiments using an adjustable five-level anemometer staff system. It is pointed out that the results obtained from wind experiments have not yet been correlated with hydraulic experiments, and it is known that the friction factor decreases with increase in the Froude number, given by F = V//gR, where V is the mean velocity over the vertical distance of the hydraulic radius, R. The question seems to be, what is the equivalent hydraulic radius for the adiabatic atmosphere that would give the same friction factor for the same roughness for the von Karman velocity profile in hydraulic experiments? The wind experiments do show that there is a tendency for the friction factor to decrease with increase of mean wind speed. It would be of scientific interest to determine an equivalent hydraulic radius for wind profile experiments, making it possible to correlate the data with hydraulic experiments. This needs further investigation.
RUN-UP OF TSUNAMIS BY LINEAR AND NONLINEAR THEORIES
Authors: Goto Chiaki , Shuto Nobuo
Published: June 2019

Linear and nonlinear sets of equations of long waves in the Lagrangian description are solved numerically to obtain run-up heights. Numerical results are compared -with theoretical ones in case of simple topographies and the agreement is quite satisfactory. As a practical application, the computation is carried out for the Okkirai Bay in Japan. The computed run-up neighs agree fairly well with the recorded ones.
A NUMERICAL MODEL OF STORM WAVES IN SHALLOW WATER
Authors: Hauguel A.
Published: June 2019

For studying storm waves in coastal areas, usual waves theories are no more valid. The presented enoidal theory allows the modelling of these problems. Furthermore, thanks to its non-linear properties, it makes possible the simulation of many phenomena usually neglected. A numerical model using this theory has been developped. it has been tested against analytical results and certain properties of non-linear waves experimentaly observed. Finaly, the practical problems raised by the utilisation of this model for harbour agitation computations, have been solved.
CORRECT REPRODUCTION OF GROUP-INDUCED LONG WAVES
Authors: Hansen N.E. Ottesen , Sand Stig E. , Lundgren H. , Sorensen Torben , Gravesen H.
Published: June 2019

In nature short period storm waves generate longer waves with periods corresponding to the wave group periods. The long waves are generally referred to as the wave set-down of water level. The set-down term is of second order in the height of the short waves. With first order reproduction of natural storm waves in the laboratory, the setdown bound to the wave groups is not reproduced. As a result, various free waves are generated, propagate towards the model and reflect from the boundaries. These so-called parasitic waves cause an exaggeration of long wave phenomena, such as harbour resonance and slow drift oscillations of moored ships. The parasitic waves can be eliminated by means of compensating free waves imposed on the system by second-order paddle motion reproducing the natural set-down. The control signal for this motion has been calculated and checked by testing. The agreement between calculated and measured results is found to be good. Further, an alternative method for reducing the parasitic wave problem is presented. Utilizing the shoaling properties of the various waves, the influence of parasitic waves can be diminished by generating the waves in somewhat deeper water before they propagate into the shallower model area.
AN ELECTROMAGNETIC ANALOGY FOR LONG WATER WAVES
Authors: Jackson G.W. , Wilkinson D.L.
Published: June 2019

Seiching must be considered when designing mooring, berthing or navigational facilities in semi enclosed basins and harbours. The considerable oscillatory currents which may be generated along nodal lines of a seiche can result in serious surging of a vessel moored in such areas. Hydraulic modelling of the long gravity waves which form the seiche poses particular problems for the hydraulic modeller. In the prototype situation, a balance is achieved between the long wave energy entering a basin, the energy dissipation within the basin, and the wave energy which is radiated back into the ocean. The presence of the wave generator in the model may result in much of the radiated energy being reflected back into the basin, thereby distorting the seiche observed in the model. The relatively low Reynolds numbers present in the model leads to exaggerated frlctional damping of the waves and possible suppression of certain resonant modes. Scaling of long wave amplitudes in resonance' situations cannot be determined from simple Froude laws but must be based on equivalent dissipation rates in the model and the prototype (Ippen, 1966). Alternative methods of physically reproducing long wave behaviour have been studied, such- as acoustic modelling (Nakamura, 1977). However, these models also have their limitations and are largely confined to constant depth situations. It Is suggested that electromagnetic radiation in the microwave range may be used to model long gravity waves and that this method has many advantages over the various techniques which have previously been used. It can be rigorously shown that the laws which govern the propagation, reflection and dissipation of electromagnetic radiation (Maxwell's equations) are identical to the linearised equations describing the motion of long gravity waves, (Jackson and McKee, 1980). The linear wave equation gives an accurate description of long wave oscillation in basins as the wave length is of the same order as the basin dimensions and non-linear effects do not have time to develop.
INTERACTIONS OF WAVES WITH SUBMARINE TRENCHES
Authors: Lee Jiin-Jen , Ayer Robert M. , Chiang Wen-Li
Published: June 2019

An analysis is presented for the propagation of water waves past a submarine trench of irregular shape. Two dimensional, linearized potential flow is assumed. The fluid domain is divided into two regions along the mouth of the trench. Solutions in each region are expressed in terms of the unknown normal derivative of the potential function along this common boundary with the final solution obtained by matching. Reflection and transmission coefficients are found for various submarine geometries. The accuracy of the technique employed is demonstrated by comparing with previously published results for a rectangular trench. In addition, results from limited laboratory experiments were included for comparison. The result shows that for a particular flow configuration, there exists an infinite number of discrete wave frequencies at which waves are completely transmitted.
AN INVESTIGATION OF WAVE SHELTERING BY ISLANDS
Authors: Hsiao S.V. , Vesecky J.F. , Shemdin O.H.
Published: June 2019

The West Coast Experiment, a meso-scale oceanographic experiment, was conducted from February to April, 1977, off the coast of Southern California. The wave data measured by an air-borne synthetic aperture radar (SAR) and a shore-based high frequency (HF) radar on March 25, 1977, are used to study the sheltering effect of islands on waves propagating towards shore. The comparisons between wave directional spectra offshore, in the vicinity of islands, and nearshore show that islands play a significant role in determining the near shore wave climate. The data show clearly the "shadow" and "window" effects. An investigation of waves coming out of the "shadow" region indicates that nonlinear wave-wave energy transfer is the likely mechanism responsible for producing such waves.
THE DISSIPATION OF WAVE ENERGY BY TURBULENCE
Authors: Kuang-ming Yu
Published: June 2019

This paper first gives a brief review of the existing research works on the laws governing the dissipation of rave energy by turbulence. Starting from the general theory of turbulent motion and the writer's suggestion in regard to the mixing length of water particles in two-dimensional flow and making use of the principle of dimensional analysis and the trochidal rave theory, a formula has been derived to compute the mean dissipation per unit time and per unit horizontal area of wave energy due to turbulence. The formula takes the horizontal and vertical gradients of both the horizontal and vertical velocity fields into consideration. Coefficient in the formula has been determined through laboratory experiments.
SOFT DESIGNS FOR COASTAL PROTECTION AT SEABROOK ISLAND, S.C.
Authors: Hayes Miles O. , Kana Timothy W. , Barwis John H.
Published: June 2019

To gain a better understanding of the cycles of shoreline changes on Seabrook Island, South Carolina and advise a private developer on how to deal with localized erosion problems, a detailed field survey and historical study were completed. The data base included historical charts dating from 1661, vertical aerial photographs from 1939, field surveys of beach profiles and nearshore bathymetry over a sixmonth period, and sediment cores through the entire Holocene section. Seabrook Island, less than 6 km in length, is bounded by tidal inlets with extensive seaward shoals. With a 2 m tidal range for the area, changing exposure and orientation of the shoals over time has had a profound effect on the adjacent shoreline of Seabrook Island. Historical evidence points to the importance of offshore shoals which act as natural breakwaters and sediment storage systems. At various times in recent history, these shoals have supplied sediment to Seabrook beaches by means of bypassing mechanisms around tidal inlets. On the other hand, migration of shoals has allowed excess wave energy to strike portions of the shore causing local erosion. Along a portion of the shoreline, short-term erosion is jeopardizing the development. Based on the present study, a set of "soft" engineering designs was proposed which attempt to manipulate offshore sand bodies in a way that will be beneficial to the development and preserve the inherent beauty of the shoreline. Remedial measures recommended for the developer included dredging new inlet channels and construction of a breakwater in the position of a former protective shoal.
INSHORE-NEARSHORE MORPHODYNAMICS - A PREDICTIVE MODEL
Authors: Chappell John
Published: June 2019

The two-dimensional topography, developed on a sandy sea bed between surf base and the breaker zone, is computed using (i) sediment gain or loss per unit bed area = zero, (ii) simple models of sediment drift in terms of, firstly, simplified saltation under Stokesian waves, and secondly, frictional wave work on the sea bed, (iii) the drift tendency in direction of wave propogation being offset of the local sea bed gradient. An input contour line at surf base is assumed, across which the input wave train is propogated. Using standard wave refraction combined with (i) to (iii), above, an equilibrium topography is generated by iteration. Inshore of the breaker line, longshore currents generated by radiation stress are combined with the gradient effect to balance sediment drift, producing bar - trough topography.
WAVE SHOALING CALCULATED FROM COKELET'S THEORY
Authors: Sakai T. , Battjes J.A.
Published: June 2019

Cokelet's numerical non-linear theory for progressive, periodic gravity waves is applied to the two-dimensional shoaling of finite amplitude waves on a beach up to breaking. The shoaling curves so obtained are compared with existing shoaling curves calculated from different finite amplitude wave theories, and with existing experimental data. It was found that the shoaling curves calculated from Cokelet's theory predict higher wave height ratios than other curves. The agreement between the present curves and the experimental results is good except near the breakpoint, where the wave height of the present curves is larger than the experimental wave height.
BREAKER TYPE AND PHASE SHIFTS ON NATURAL BEACHES
Authors: Cowell Peter J.
Published: June 2019

The kinematics of incipient breakers were measured on various complex natural beaches. Water velocities were found to consistently lag behind the wave crest. This phase shift appears to be partly inherent in shoaling waves and partly a result of partial wave reflection. Phase shifts vary from 5 degrees through to quadrature. This variation probably depends to a large extent upon beach reflectivity and distance of the break point from the shoreline. Phase shifting also varies vertically beneath the wave crests from uniform distributions to those in which maximum shifts occur near the bed. There is a strong relationship between the nature of phase shifting, the morphodynamic condition and the breaker type. Surging waves were associated with large, and vertically uniform phase shifts. Waves towards the plunging and spilling end of the breaker type continuum occurred where phase shifts were significantly larger at lower depths than near the surface.
THE DYNAMIC SWEPT PRISM
Authors: Chapman David M. , Smith A.W.
Published: June 2019

In the course of an intensive study of beach and inshore morphodynamics associated with a nourishment project on the Lower Gold Coast, Australia (Chapman, 1978), approximately 400 profile lines were surveyed from backshore to the point of zero change in the nearshore zone, to a high degree of accuracy (Chapman & Smith, 1977). Analysis of this data base has led, inter alia, to the development of the concept of the dynamic swept prism, since the maximum and minimum ordinates on a shore-normal profile line, over a specified time period, form the vertices of an irregular polygon which may be regarded as the cross-section of the prism of sand which is worked over by waves during that time period. Representative prism cross-sections from the Lower Gold Coast are displayed in Figure 1 . The important limits of the swept prism, viz., the landward and seaward extremities and the lower surface, are probabilistically, not deterministically defined. Prism cross sections a -:- illustrated are not isotropic with respect to the probability of disturbance by waves. Isolines of probability may be conceptually defined, with the zone of maximum probability of disturbance corresponding to that zone which is re-worked during the tidal cycle (cf. Duncan, 1964).
A LABORATORY STUDY OF OFFSHORE TRANSPORT OF SEDIMENT AND A MODEL FOR ERODING BEACHES
Authors: Sunamura Tsuguo
Published: June 2019

A two-dimensional laboratory investigation of sediment transport, induced by shallow-water waves, showed that the sediment motion over suspension-dominant asymmetric ripples is closely related to the development of eroding beaches. High-speed motion picture analysis revealed that vortices, formed over this type of ripple, play a crucial role in transporting the sediment to the offshore region. A relation for net offshore sediment flux was formulated for sand 0.02 cm in diameter. A simple model for eroding beaches was proposed and its validity was checked by using two existing data sets for 0.02-cm sand beaches; the model could predict fairly well profile and shoreline changes in the early stages.
AN APPROACH TO UNDERSTANDING COASTAL PROCESSES
Authors: Gordon A.D. , Lord D.B.
Published: June 2019

The approach adopted in N.S.W. for investigating coastal processes leading to development of a numero-descriptive model for management purposes is outlined. The technique involves the formation of a regional coastal model and its adaptation to site specific cases. This site specific conceptual model is then tested and modified on the basis of theoretical calculation and field data collection. Two specific case histories are outlined.
LONGSHORE WATER AND SEDIMENT MOVEMENT
Authors: Swart D.H. , Fleming C.A.
Published: June 2019

The mean sediment transport rate obtained by using six known longshore transport formulae3 for which the input variables are determined consistently3 is used as best estimate of the transport. A good comparison is obtained when this package deal approach is compared with a prototype situation where the transport rates are inferred from quarterly bathymetric surveys over two years. The accuracy of the input variables is reviewed theoretically and the results are used to perform a sensitivity analysis.
ZETA BAYS, POCKET BEACHES AND HEADLAND CONTROL
Authors: Silvester R. , Tsuchiya Y. , Shibano Y.
Published: June 2019

The now familiar equilibrium shape of bay sculptured by waves between headlands can indicate to man the direction he could follow in stabilizing shorelines. The characteristics of these crenulate or zeta shapes are known and can be applied in design or defining limits of erosion. Some natural settings are discussed which introduce difficulties in identifying the correct bay shapes for applying these tools. The application of headland control to specific cases of instability is presented. The final requirement is emphasised of aiding Nature to protect the coastline by the formation of the offshore bar and its subsequent return to the beach without concurrent downcoast drift. The method currently receiving widespread support of placing offshore breakwaters in close proximity to each other is discounted as a viable protective alternative.
BEACHES: PROFILES, PROCESSES AND PERMEABILITY
Authors: Gourlay Michael R.
Published: June 2019

Equilibrium beach profiles have been investigated in the laboratory for two beach materials, 0.22 mm marine sand and 1.55 mm crushed coal. Analysis of the results confirms that the dimensionless fall velocity H0/Tw is an important parameter influencing both surf zone hydraulics and the form of the resulting equilibrium profile. Beach permeability also significantly influences the hydraulics within the beach face and it has been found that both H0/Tw and the parameter wf/w, the ratio of the fluidizing velocity to the fall velocity, influence the form of the equilibrium profiles of permeable beaches.
SEDIMENT DISPERSAL ON THE N.S.W. CONTINENTAL SHELF
Authors: Boyd Ron
Published: June 2019

This paper presents a semi-empirical model for describing sediment dispersal on the central New South Wales (N.S.W.) continental shelf. Results from a program of field experiments identify wind speed and direction, wave height and frequency distribution of near-bottom currents as being the dominant factors influencing near-bottom current asymmetry on this shelf. A combination of theoretical prediction and field experiment has been used to define the seaward limits for onshore/offshore sediment exchange and the modes of sediment transport operating within this active zone.
WAVE FORCING OF BEACH GROUNDWATER
Authors: Waddell Evans
Published: June 2019

A field project was conducted to measure swash and surf characteristics and related processes on a beach with a high tide range and very low slope. Variables measured were beach waterlevels in the surf and swash zones, beach groundwater levels, and on-offshore and alongshore currents. A variety of deployment patterns and instrument combinations were used. Results show a nonlinear transfer of wave energy from high to low frequencies. This appears to have occurred because finite amplitude waves and bores caused an onshore mass flux which produced an increased local waterlevel. Periodically, this impounded water was released. Groundwater records indicate that low frequency waterlevel oscillations on the beach face were the dominant forcing function for oscillations of the beach watertable. A model is generated which adequately predicts some of the response characteristics of the groundwater table.
LONGSHORE TRANSPORT EVALUATIONS AT A DETACHED BREAKWATER
Authors: Bruno R.O. , Dean R.G. , Gable C.G.
Published: June 2019

A field experiment was conducted by the Coastal Engineering Research Center (CERC) to develop correlations between wave characteristics and longshore sediment transport. The waves were measured by two near-bottom mounted pressure transducers and the average longshore sediment transport rates were determined from sequential volumetric surveys behind an offshore breakwater which was regarded as a total trap. The data analyzed herein encompass a period of nine months during which a total accumulation of 675,000 m3 occurred as documented by eight surveys. Spectral analyses of the wave data were conducted and yielded one direction per frequency. The correlations include immersed weight sediment transport rate, I, versus (1) longshore component of wave energy flux at breaking, P&Sf and (2) the onshore flux of the longshore component of wave-induced momentum, S ,,. The most widely used correlation constant, K, in the relationship I = KPjig is 0,77. The best-fit values found from the data were K = 0.65 and 0.92 for linear and log best-fits, respectively, as based on the p£s values directed toward the trap. The corresponding values of KA (dimensional) relating I and Sxv are 4.98 m/s and 6.37 m/s, respectively. One feature of this type of trap is the potential for overtrapping if the waves are directed nearly normal to shore.
MIGRATION OF LONGSHORE BARS
Authors: Dette Hans H.
Published: June 2019

It is known that nearshore areas occupied by longshore bars constitute a zone of active migration of bottom deposit due to agitation by breaking waves and wave-induced on-/offshore currents and longshore currents. So far there is still a lack Of actual data from the field itself concerning the magnitude and variability of single parameters involved in the stability and migration of longshore bar features. This paper summarizes data collected from a comprehensive field study in the years from 1976 to 1979 when grain size distributions were obtained from a narrow grid of core samples and repeated soundings and continuous measurements of waves and wave-induced currents were carried out. With regard to the characteristics of different longshore bar feature relationships e. g. in between bottom gradients and mean grain sizes are analyzed. Furthermore distinct types of topographic response within the submarine belt occupied by longshore bars depending upon the variable intensity and position of breaking waves and the resulting magnitude and variability of wave-induced currents are pointed out and presented for discussion as a contribution towards a general understanding of longshore bar characteristics and changes.
DESIGN OF ENCLOSED HARBORS TO REDUCE SEDIMENTATION
Authors: Everts Craig H.
Published: June 2019

Sedimentation may be an important problem when quantities of suspended material are carried into an enclosed harbor on a flooding tide. In order to forecast future maintenance costs, two methods for predicting the sedimentation rate prior to harbor construction are proposed: 1) a sedimentation tank to be placed at the proposed harbor site, and 2) a mathematical model which uses sediment and hydraulic data collected at the harbor site. Certain considerations in the design phase of a project may effect a reduction in harbor sedimentation. If feasible, the harbor may be sited in a region where suspended sediment concentrations are low and sediment sizes (settling velocities) are small. Proximity to river sediment sources may be a factor. Conversely, a harbor site in a clear-water river adjacent to a sediment-laden estuary may be desirable if bedload transport during freshets would not be a problem. Settlement of suspended material may occur in the channel which connects an enclosed harbor basin with navigable waters. This material may subsequently be resuspended and carried into the basin thereby increasing the sedimentation rate. To reduce that rate the channel should be designed as short as possible. A sill in the channel may also be used to reduce initial excavation costs and the sedimentation rate. Flotation for vessels in the basin will be provided at all times, but movement into and out of the harbor will be reduced to times of higher water. In high latitude areas where harbor use is limited to periods when ice cover is absent, the sedimentation rate may be reduced using a channel closure structure during non-use periods. Winter sedimentation rates can be predicted using the mathematical model for summer conditions, and when ice thickness is known.
SAND TRANSPORT UNDER THE ACTION OF WIND
Authors: Zanke Ulrich
Published: June 2019

Field investigations on sand-transport by wind were carried out at German North-Sea coast. A special trap was constructed, which allows to measure bed load and suspended load separated. In addition wind speed was measured up to 10 m over the bottom. The results of the field investigations were used to calibrate a transport-equation for sandtransport by wind.
A NUMERICAL MODEL FOR DUNE DYNAMICS
Authors: Sundermann J. , Vollmers H.-J. , Puls W.
Published: June 2019

A numerical sediment transport model is formulated that serves especially for the simulation of bedform mechanics. The model is based on the idea that sediment transport is determined by the erosion rate and the path length of bed material. Formulas for the erosion rate and the path length are derived from physical considerations and from measurements; they depend mainly on the local values of the shear velocity and the mean flow velocity near the bed. The behaviour of detached sediment is simulated by a Monte Carlo procedure, which is based on the mean flow velocities and the eddy viscosity. All flow properties that are needed for the sediment transport model are computed by a numerical flow model that includes two turbulence equations. Results of the flow model and the sediment transport model are compared with measured data.
ESTUftRINE RESPONSE TO DREDGING IN THE TWEED RIVER, AUSTRALIA
Authors: Druery Bruce M.
Published: June 2019

Between mid 1974 and mid 1975,760,000 m3 of sand was dredged from the bed of the Tweed River for the purpose of nourishing cyclone damaged beaches of the Gold Coast (Queensland). A comprehensive field data programme was established in 1976 to record the changes in the hydraulic processes of the Tweed River brought about by the dredging. The field measurements demonstrated that the dredged area was being infilled with sediments of both marine and estuarine origin. The dredging increased tidal ranges throughout the lower estuary, the effect being more pronounced at low water. Sediment bedload rates were estimated from detailed measurements of bedforms and used to calibrate a sediment transport formula. The formula was used in conjunction with a 1 Dim. numerical model of tidal hydraulics to simulate estuarine shoal dynamics by means of a simple sediment routing technique. The results showed that the dredging had altered the tidal hydrodynamics so as to enhance the ebb transport of sediment towards the dredged hole. In the long term it was found that the sediment transport switched to a weak net upstream movement of sediment. The detailed hydraulic mechanisms involved are discussed. The study demonstrates that the impact of dredging can be minimised by location upstream of the entrance plug of marine sand.
NOOSA BEACH RESTORATION SCHEME
Authors: Lloyd R.J.
Published: June 2019

A significiant beach restoration scheme has been implemented at the coastal resort of Noosa in South-East Queensland. The scheme which cost $1,400,000 involved sand nourishment, dune stabilisation works and the relocation of the entrance to the Noosa River using sand pumping techniques. The effect of the scheme has been to greatly improve the quality of the main surfing beach at Noosa as a recreational facility and to provide much needed protection to a canal estate development which had been constructed within the Noosa River estuary close to the river entrance. The successful implementation of this scheme also demonstrates that practical solutions to beach erosion problems are available and that sand pumping techniques may be used to economic advantage where relocation or closure of a river entrance is required and where local conditions and analysis indicate that such techniques can be applied. Photograph 1 shows the completed restoration scheme.
BEACH NOURISHMENT AS A MANAGEMENT TECHNIQUE
Authors: Chapman David M.
Published: June 2019

Beach nourishment is considered an environmentally safe management technique, since an unsuccessful nourishment project would simply result in the redistribution of borrow material by wave action into environments more in keeping with a state of equilibrium. No permanent modifications of the beach and nearshore environment need result, and since no permanent structures are required for beach nourishment, the management commitment allows rapid project abortion if necessary. Beach nourishment monitoring has usually been concerned with evaluating changes in the extent of subaerial beach and/or retention of fill volume. These parameters are important, but it is also necessary to consider the way in which nourishment sand is taken up by the beach system since relationships between volume change, change in extent of subaerial beach, and changes in beach morphology are complex. This paper is concerned with evaluating beach nourishment on the Gold Coast (Figure 1), Australia's major resort, where 2.A million cubic metres of fill were applied in the largest beach nourishment project attempted in this country at the time of writing. Methodology, reported in Chapman & Smith (1977) and Chapman (1978a) included repetitive profile survey from backshore to point of zero change in inshore zone (over 4.00 profiles) using highly accurate techniques, and use of 38 tonnes of tracer, which was injected into the dredge line at a controlled rate.
Complete Proceedings - Single PDF Download
Authors: Edge Billy L.
Published: June 2019

One hundred eighty-six papers presented at the seventeenth coastal engineering conference are included in these three volumes. There are four parts: 1) Theoretical and observed wave characteristics, 2) coastal sediment problems, 3) coastal structures and related problems, and 4) coastal, estuarine and environmental problems. Part one explores recent advances in wave theories, orbital velocities in irregular waves, and laboratory generation of long waves. Subjects in the second part include sediment flux through reef-lagoon systems, sediment dispersal, natural beaches, and dune dynamics. Part three examines coastal pipelines, seawalls, marinas and breakwaters, and part four explores estuarine modeling, tidal channels, mooring forces induced by passing ships, and port planning. The conference was sponsored by the ASCE Coastal Engineering Research Council, the ASCE Waterway, Port, Coastal and Ocean Division, and the Australian Institution of Engineers.
ANALOGOUS DISPERSION PROPERTIES OF SURF ZONE AND ELECTROMAGNETIC WAVES
Authors: Busching Fritz
Published: June 2019

Resonant interaction processes in the surf zone are marked by an anomalous dispersion property (dc/df > 0) as it is well known from resonance absorption processes of electromagnetic waves in dielectrics.
MODELING LONGSHORE CURRENTS FOR FIELD SITUATIONS
Authors: Vemulakonda Seetharama R. , Houston James R. , Butler H. Lee
Published: June 2019

There is a growing need for generalized numerical models for longshore currents and nearshore circulation that solve the complete equations of motion, are flexible in the formulations chosen for various terms, and can be applied to field situations at a reasonable cost. The development and application of one such model is described in this paper. The model was first tested by comparing its results to known analytic solutions and experimental data. There was good agreement. It was next applied to a field situation near Oregon Inlet, North Carolina. The results appeared to be reasonable and the computational costs were modest.
SHORE-PARALLEL FLOWS IN A BARRED NEARSHORE
Authors: Greenwood Brian , Sherman Douglas J.
Published: June 2019

A field experiment to measure the horizontal and vertical structure of shore-parallel, nearshore currents was conducted at Wendake Beach, Georgian Bay, Canada, in 1980. Waves and currents were measured with continuous resistance wire wave staffs and bi-directional, electromagnetic current meters, respectively. Substantial variations from theoretical horizontal velocity profiles were found as an influence of small amplitude nearshore bars. Data smoothing resulted in a Longuet- Higgins type mixing parameter estimate of P=0.18. Vertical velocity profiles analysis suggests that an estimate of mean, surf zone roughness length is of the order of lxl0-3m.
FORCES INDUCED BY BREAKERS ON PILES
Authors: Wiegel Robert L.
Published: June 2019

This paper consists of three parts. The first part presents a method for analyzing the forces exerted by breaking waves on a cirular pile. The force consists of two components, a slowly varying force and a much larger but very short duration quasi-impact force (probably of the order of 1/100 of a second). The second part is concerned with breaker characteristics, with emphasis being given to the few field data that have been measured. The third part consists of a presentation of some available data on surf zone bottom profile variations with time. Information on all three of these parts is needed for the proper design of a pile supported structure in the surf zone. If the bottom along the site of a proposed pier is sand, an estimate of the variability with time of the profile must be made. The effect of bottom depth and configuration on the height of waves moving shoreward, and the effect of this, in turn, on the wave loading is important in the calculations of wave-induced moments about the bottom. The ability of the structure to withstand these horizontal loads depends in part upon the depth of penetration of the piles. If the bottom varies with time, then calculations of wave characteristics and wave-induced loads on the piles should be made for appropriate bottom configurations.
REPAIR TO A DOLOS ARMOURED BREAKWATER
Authors: Glodowski C.W. , Lajoie D.L. , Ropars Y.
Published: June 2019

In recent international experience several breakwaters armoured with concrete units have failed shortly after or during construction of the structure. Although investigators have not necessarily agreed on the causes of these failures, it has been generally implied that there is a relationship to breakwater construction in deep water with large units and severe wave conditions (4,9). However, the damaged sections of the dolos armoured breakwater that is the subject of the paper, are in water depths of 6 to 8m with depth limited wave conditions. The original design parameters for selecting the dolos weight appear to have been reasonably accurate by current estimates. The recent hydraulic model tests indicate that the breaking wave conditions and overtopping of the breakwater have combined with the breakage of dolosse in the resulting failure. The recommended repair work which was the primary objective of the study, consisted of armouring the crest of the damaged section with large stone (20t) and leaving the damaged front layer of dolos below low water level. It was judged that the further use of concrete dolosse was not economically justifiable and that there did not exist a satisfactory procedure to design dolos armour within the scope of the study.
ZEEBRUGGE'S MAIN BREAKWATERS
Authors: Van Damme L.V.
Published: June 2019

The design scheme of the Zeebrugge Outer Harbour, Belgium, consists mainly of two breakwaters protruding into the sea as far as 1,750 m beyond the existing mole or 3.000 m out from the coastline. The west outer breakwater is 4,450 m long, the east breakwater runs 4,300 m out from the seafront. The east outer harbour will accommodate terminals for liquid bulk products such as LNG. The west outer harbour will provide space to install two harbour bassins to suit general cargo, hazardous cargo, container and ferry traffic. In the paper emphasis is put on the environmental design conditions (wave height, wave period, water depth), the development of preliminary designs and the final design. Some design features such as dimensions, wave breaking carpet, armour units, workable limits in respect to rock grade, etc ... are discussed. By developing the design the rubble-mound breakwater has been judged to be the only viable alternative versus the caisson type breakwater, taking into account costs, technical risks, construction problems and flexibility under changing environmental conditions. The main feature of the breakwaters is that a huge concrete parapet will have been avoided. A so called flat semi-cube armour unit has been developed. The main advantage lies in the substantial economic benefit whilst maintaining the same stability performance as a concrete cube armour unit.
PROTOTYPE TESTS ON RIPRAP UNDER RANDOM WAVE ATTACK
Authors: Pitt J.D. , Ackers P.
Published: June 2019

This paper describes the performance of test panels of riprap on an offshore island in the Wash estuary, UK, for the first 2h years after their construction, by which time all but one had failed. It outlines the methods used in obtaining and analysing data on stone size, wind, tides and waves. The techniques used in surveying the test panels for damage and the reduction of the survey data to yield quantitative estimates of damage are described. Comparisons are made between the damage to the riprap panels and what might have been estimated using laboratory data. Results do not support any scale effect causing riprap sized on laboratory data to be larger than necessary, and this conclusion is supported by the outcome of model tests carried out retrospectively by the Hydraulics Research Station (now HRS Ltd) at Wallingford, UK. Slope protection is sensitive not only to wave height and stone size but also to construction methods and, bearing in mind possible departures from the desired specification, a cautious approach to the design of riprap protection is advisable.