bluuebunny/crossref_metadata_2025 huggingface dataset:
THB INFLUENCE OF WAVES OH CURRENT PROFILES
Authors: Coffey Felicity C. , Nielsen Peter
Published: June 2019

A simple model is presented for steady current profiles in the presence of waves. The current reduction and apparent roughness increase caused by the waves are shown to depend mainly on one dimensionless parameter u*/u"*, i.e. the ratio between the friction velocity amplitude due to the waves and the time averaged friction velocity. The model recognises the need to apply different eddy viscosities to different flow components. Also, the thickness of the wave influenced layer near the bed is comceptually separated from the vertical scale of the wave boundary layer.
THE DYNAMICS OF OSCILLATING SHEETFLOW
Authors: Bakker W.T. , Van Kesteren W.G.M.
Published: June 2019

Two mathematical models for the simulation of the dynamics of sheetflow are presented, an analytical and a numerical one. In the analytical model the theory of Bagnold (1954) is implemented: a constant ratio between shear stress and normal stresses is assumed. In the numerical model the motion of each layer of grains is considered separately; each layer exists of a rigid rectangular structure of spherical grains. Grain- grain interaction between the successive layers occurs in two ways: on one hand viscous interaction forces, comparable with squeezing forces in lubrication problems and on the other hand direct contact with elastic response when the distance between the grains becomes less than .01 of the grain diameter. When the relative motion of adjacent layers results into compression or dilatation, a resistant force analogous to the Darcy law is assumed.The numerical model has been combined with the turbulent boundary layer model of Bakker and v. Kesteren (1984). Results of computations are compared with measurements of Bagnold (1954) and Horikawa et al (1982). The analytical model predicted the concentration in the sheet flow layer and the intrusion depth rather well, where the numerical model gave reasonable results with respect to the velocity pattern above the sheetflow layer. It is concluded, that up to now the more sophisticated assumptions of the numerical model do not lead as yet to higher accuracy with respect to the intrusion depth of the sheet flow, probably because the separation between sheet flow and the turbulent boundary layer above has been assumed too smooth.
TOWARD A SIMPLE MODEL OF THE WAVE BREAKING TRANSITION REGION IN SURF ZONES
Authors: Basco David R. , Yamashita Takao
Published: June 2019

Breaking waves undergo a transition from oscillatory, irrotational motion, to highly rotational (turbulent) motion with some particle translation. On plane or monotonically decreasing beach profiles, this physically takes place in such a way that the mean water level remains essentially constant within the transition region. Further shoreward a rapid set-up takes place within the inner, bore-like region. The new surf zone model of Svendsen (1984) begins at this transition point and the new wave there contains a trapped volume of water within the surface roller moving with the wave speed. This paper describes a simple model over the transition zone designed to match the Svendsen (1984) model at the end of the transition region. It uses a simple, linear growth model for the surface roller area development and semi-empirical model for the variation of the wave shape factor. Breaking wave type can vary from spilling through plunging as given by a surf similarity parameter. The model calculates the wave height decrease and width of the transition region for all breaker types on plane or monotonically depth decreasing beaches.
TIME AND BED AVERAGED CONCENTRATIONS UNDER WAVES
Authors: Bosman Jan J. , Steetzel Henk J.
Published: June 2019

Four types of sediment concentration under waves are discussed: (a) instantaneous, local, (b) time-averaged, local, (c) instantaneous, bed-averaged and (d) time and bed averaged. The first three mentioned are either hard to interpret or difficult to obtain experimentally. The time and bed averaged concentration is discussed in particular, both its interpretation and its measurement. Two features are discussed: the vertical concentration distribution and the bottom concentration.
SIMULATION OF SANDFILL BUILDING STAGES WITH NUMERICAL FLOW MODELS
Authors: Bosselaar G.J. , Thabet R.A.H. , Van Roermund A.J.G.M. , Bijlsma L.
Published: June 2019

The paper describes the application of two dimensional vertically integrated models (WAQUA system) , the results being used for the calculation of sandlosses during sandfill closure operations. Investigations with test models, physical scale models as well as numerical models, are presented to prove that the WAQUA system is not only suitable for large scale applications, but also for the simulation of detailed flow patterns.
BEACH DEVELOPMENT BETWEEN HEADLAND BREAKWATERS IN A LOW WAVE ENERGY ENVIRONMENT, PASIR RIS, SINGAPORE
Authors: Chew S.Y. , Ho S.K. , Wong P.P. , Leong Y.Y.
Published: June 2019

One of the function of the offshore breakwater is to protect the coast from wave action. By dissipating the wave energy along its entire length, the breakwater causes sediments in its lee to deposit and a shore salient is formed. If the offshore breakwater are placed in a series along a coast with a gentle offshore slope and a substantial littoral drift tombolo will form behind the breakwaters between which bays will be sculptured by waves to form stable shapes (1). These attached breakwater would thus form a series of artificial headlands. In nature, beaches between headlands are influenced by the position of the headlands. Where the headlands are closely spaced and a limited sediment supply exists, small pockets beaches are formed. Where the headlands are far apart and an adequate sediment supply exists, long and wide beaches are formed. Generally, between these two extremes most beaches between natural headlands take a shape that is related to the predominant wave approach; on the downcoast sector is a long and straight beach, while on the upcoast end is curbed beach. Silvester (2) in his model study established a relationship between the logarithmic spiral constant ( °^ ) and the angle of predominant wave approach ( & ). A quasi-permanent shape was reached when waves broke simultaneously around the model bay. As it is difficult to measure the curve sector in nature, Silvester and Ho (3) suggested the use of an indentation ratio to relate the bay's shape to wave approach.
OFFSHORE SAND WAVES
Authors: Deigaard Rolf , Fredsow Jorgen
Published: June 2019

A theoretical model for the equilibrium dimensions of offshore sand waves is presented. The model is an adaptation of the dune model by Fredsoe (1982) to the marine environment, making use of the physical analogies between offshore sand waves and river dunes. The predicted sand wave heights and lengths conform well with the observations of sand wave formation reported in the literature. One of the results from the model is that for a given wave climate sand waves will only be formed under a certain range of mean current velocities. This range becomes narrower for increasing wave height or decreasing water depth and grain size.
VIRGINIA BEACH SAND SIZE AS BASIS FOR DESIGN OF ON-SHORE DREDGED MATERIAL DISPOSA
Authors: Galvin Cyril , Holton James W. , Vann Ronald G.
Published: June 2019

Analyses of sand samples collected along and across the Atlantic Ocean shore of Virginia Beach, Virginia, suggest that sand placed on the shore should have a minimum median diameter of 0.20 mm to efficiently benefit the beach. Size analyses and shoreline change data show that the existing long-term beach replenishment by mechanical bypassing across Rudee Inlet and by truck-hauled sand from land sources is effective and necessary to maintain the shore along the commercial segment of Virginia Beach. The data also indicate that the northern segment of Virginia Beach shore, occupying more than half the distance between Rudee Inlet and Fort Story, is gaining sand. About two million cubic meters of sand to be dredged from the Atlantic Ocean Channel offshore of Virginia Beach will be suitable for placement on the beach.
TIME SCALE FOR MODELING BEACH CHANGE
Authors: Ito Masahiro , Tsuchiya Yoshito
Published: June 2019

A time scale in the similarity of beach change between model and prototype in transitional beach processes from an initial even slope to an equilibrium is developed using a series of small- and large-scale experiments in which the experimental conditions were set up with the scale-model relationship by the authors (1984). The time scale is obtained empirically as a function of experimental scale. Applied the proposed time scale and the scale-model relationship to model experiments, similarity of morphological beach change such as shoreline change and relative breaker point was well reproduced within the allowable range of experimental error. A semi-theoretical time scale is obtained from the continuity equation, the sediment transport rate, and the scale-model relationship of equilibrium beach profile in two-dimensional beach change. The relation between experimental and semi-theoretical time scale is discussed.
LENGTHS OF RUNS OF JUST BREAKING AND BROKEN WAVES IN IRREGULAR WAVE TRAIN ON GENTLE SLOPES
Authors: Iwata Koichiro , Itoh Shunji
Published: June 2019

This paper is aimed to investigate theoretically and experimentally the variations of the probability distribution and mean values of the run length and total run length of just breaking and broken waves in an irregular wave train on gentle slopes. The theoretical model developed here is shown to be valid for evaluating the lengths of runs of just and broken waves from deep water up to the shoreline.
TRANSFORMATION OF RANDOM BREAKING WAVES ON SURF BEAT
Authors: Dally William R. , Dean Robert G.
Published: June 2019

Based on a previous study by the authors of regular breaking waves in the surf zone, a model for random wave transformation across the nearshore region is developed. The results of a laboratory investigation of the effect of a steady opposing current on the wave decay process are presented and a proposed governing equation verified. Surf beat effects on wave transformation are then included in the model by representing the long wave as a temporally and spatiallyvarying current and mean water level. The concept of an equivalent water depth, which contains the effect of the current, is introduced and then included in a stochastic form in the random wave model. Surf beat is found to noticeably increase the decay of the root mean square wave height, especially in the inner surf where the beat is strongest. Comparison of the models to two field data sets show very good agreement for Hotta and Mizuguchi (1980), but rather poor for Thornton and Guza (1983). Possible explanations for the unexpected behavior of the second data set, pertaining to filtering, are discussed. Finally, a possible explanation for the dependence of random wave decay on deepwater steepness, noted by Battjes and Stive (1985), is presented.
EVALUATION OF INCIDENT WAVE ENERGY IN FLUME TEST
Authors: Kit Eliezer , Gottlieb Oded , Rosen Dov S.
Published: June 2019

A two dimensional model study, carried out for a structure in a flume using irregular waves, presents the problem of determining the relationship between the total incident wave energy attacking the structure and its response to that attack (displacements, forces, etc.) in various sea states, The total incident wave energy can be evaluated indirectly only, because the wave energy measured in the flume contains an extent of residual wave energy in addition to that generated by the wave machine. This residual energy consists of the re-reflected wave energy from the paddle of the wave machine, assuming the existence of quasi-stationary wave conditions in the flume. A method originally presented by Gravesen et al. (1974), was applied in this study to evaluate the total incident wave energy. In view of the results obtained by this method, a physically more sound refinement is proposed for the evaluation of the total incident wave energy (and characteristic wave height). Results of model tests were analyzed by the CAMERI refinement and compared with the Gravesen method and with a cross-spectral least squares method, separating incident and reflected wave spectra from wave spectra measured in the flume, Good agreement was found between the results obtained employing the CAMERI refinement and the cross-spectral least squares method, Advantages and drawbacks of these methods are indicated,
TURBIDITY - SEDIMENTATION IN CLOSED-END CHANNELS
Authors: Lin Chung-Po , Lott Jonathon W. , Mehta Ashish J.
Published: June 2019

In order to investigate the mechanism by which turbidity currents cause sedimentation in closed-end channels such as pier slips or residential canals, a laboratory investigation using fine-grained sediments was carried out. Two similar flume systems were used, each consisting of a main channel carrying sediment-laden flow and an orthogonally placed closed-end channel with a gate at the entrance. Characteristics of the turbidity current and sediment deposition in the closed-end channel were investigated following gate opening. Behavioral similarities between turbidity current and non-settling gravity currents were observed. Several properties, e.g. suspension concentration, showed exponential-type decay with distance. The ratio of sediment settling velocity to the densimetric velocity was found to be a useful parameter for comparing different test results. A relationship for estimating the sediment influx through the entrance is presented.
CLOSURE OF TIDAL CHANNEL IN LAND RECLAMATION
Authors: Liu Chin-I , Shang Ruey-Shyong
Published: June 2019

The land reclamation of Lunwei subdistrict A in the development of Changhua Industrial Estate Project was commenced in May 1980. Fill sand was dredged by suction dredgers from borrow area and placed in the south and central parts of this subdistrict. Bamboo fence was used as sand retaining structure. In November, a new tidal channel occurred between two fill sand islands and across the head of seawall, it caused the increase of materials and the difficulty of construction of the seawall. Closure of the tidal channel was completed by constructed a sand embankment dike with low cost materials such as; bamboo piles, bamboo mattress and sand bags.
Complete Proceedings - Single PDF Download
Authors: Edge Billy L.
Published: June 2019

This book contains over 200 papers presented at the 20th International Conference on Coastal Engineering. The book is divided into five parts: theoretical and observed wave characteristics; coastal processes and sediment transport; coastal structures and related problems; coastal, estuarine and environmental problems; and ship motions. Reports include the effects of wind, storms, and currents. Erosion, sedimentation and beach nourishment are covered. The papers approach these topics with theoretical studies, case reports, models, and field studies.
NONLINEAR DIFFRACTION BY A VERTICAL CYLINDER
Authors: Kriebel David L.
Published: June 2019

A theoretical solution is developed for the interaction of second-order Stokes waves with a large vertical circular cylinder in water of finite depth. The solution is obtained in terms of the velocity potential such that any kinematic or dynamic quantity of interest may be derived, consistent to the second perturbation order. In this study, the second-order wave field around the cylinder is determined, showing the modification of the incident Stokes waves by wave-wave and wave-structure interactions, both in the reflection-dominated up-wave region and in the diffraction-dominated down-wave region. The theory is then compared to experimental data for wave runup and rundown amplitudes on the cylinder as well as for wave crest and trough envelopes in the up-wave and down-wave regions.
IMPROVED LONGSHORE SAND TRANSPORT EVALUATION
Authors: Arcilla A.S. , Vidaor A. , Pous J.
Published: June 2019

In this paper an improved bulk formulation for the longshore sediment transport rate is presented. It is based on a simplified hydrodynamic analysis of surf zone flow and supplemented by an exhaustive dimensional analysis. The proposed model includes the effect of the surf zone dynamic state (e.g. variation of longshore sand transport, II, with breaker type) and it is now being used in the one- and twoline shoreline evolution models developed by the Maritime Engineering Laboratory in Barcelona.
BARCELONA'S LITTORAL REGENERATION LOOKING FORWARD TO THE OLIMPIC GAMES. NUMERICAL MODEL
Authors: Valdecantos Vicente Negro , Gutierrez Manuel Quecedo
Published: June 2019

The modern technique of Coastal Engineering has enabled the succesful modification of the environment, the recuperation and the stabilization of those sandy areas which due to human action, were in a process of regression and erosion. This work developes a mathematical and numerical model to adjust and analyze the variations between the dissipative profiles and the reflectives ones. The research also emphasizes the enveloping profile to calculate the stable behaviour of the beach.
WAVE-INDUCED FLOW AND NEARSHORE SUSPENDED SEDIMENT
Authors: Doering J.C. , Bowen A.J.
Published: June 2019

It has been realized for nearly one hundred years that the transport of sediment is related to the characteristics of a wave, in particular its shape. Cornish (1898) noticed that the shoreward velocity associated with a wave crest was more effective at moving coarse sediment than was the seaward velocity associated with the wave trough. Cornish's observation was consistent with the theory of Stokes (1847), which predicts the onshore velocity associated with the wave crest is stronger and of shorter duration than the offshore velocity associated with the wave trough. This horizontal asymmetry of the cross-shore flow, which is a reflection of the wave shape, is known as velocity skewness. It has been suggested that "the existence of the beach depends on small departures from symmetry in the velocity field balancing the tendency for gravity to move material offshore"(Bowen, 1980). Although the concept of velocity skewness has been incorporated into detailed predictors of sediment transport (Bowen, 1980; Bailard and Inman, 1981) it is only one of many facets that needs to be understood in order to make the accurate prediction of sediment transport realizable. A comprehension of sediment transport is hampered by both an incomplete knowledge of the hydrodynamics and a lack of instrumentation to directly measure instantaneous sediment concentration and the accurate prediction of sediment transport is probably the most enigmatic problem in coastal engineering. Occasionally, suspended sediment concentration has been inferred from in situ pumps and hand-held tubes, but these methods lack the temporal and spatial resolution necessary to elucidate the details of the interaction between the waveinduced flow and the sediment. Recently, a miniature optical backscatter sensor (MOBS), which provides a time series of suspended sediment concentration at a "point", was developed by Downing et al. (1981). During a recent field experiment a vertical array of 5 of these optical backscatter sensors and a colocated flow meter was deployed close to the sea bed. These colocated measurements provide a unique opportunity to investigate the response of near-bed suspended sediment concentration to the wave-induced flow.
WAVE-INDUCED BREAKOUT OF HALF-BURIED MARINE PIPES
Authors: Foda Mostafa A. , Law Adrian W.K. , Chang Jo Y.H.
Published: June 2019

An experimental study is conducted in order to identify the major physical processes leading to the breakout of half-buried submarine pipelines from the seafloor under ocean wave action. Both the hydrodynamic loading on the exposed surface of the pipe, as well as the resulting displacement history of the pipe, were recorded and analyzed in order to identify the critical pipe-soil-wave conditions for the detachment of the pipe from the seabed. The paper also examines the balance of the pipe under the combined lift and drag loading from the water wave. An experimental breakout force-time power law is obtained and compared to available theoretical breakout models.
CHARACTERISTICS OF DIFFUSION AND AERATION DUE TO WAVE ACTION NEAR PERMEABLE BREAKWATERS
Authors: Murakami Hitoshi , Hosoi Yoshihiko
Published: June 2019

This paper deals with the effect of wave action on the water purification near a permeable breakwater. When determining standards for water purification, three indexes are usually taken into account: the diffusion coefficient, the concentration reflection ratio and the reaeration coefficient. In our study, the values of the diffusion coefficients Kx near -12 2 the breakwater ranged from about 10 cm /sec to 7x10cm /sec. The effect of aeration caused by setting up a permeable breakwater was limited to within a distance of only one wave length at either side of the breakwater. As a result, values of the reaeration coefficients were then estimated to be in the order of 10 - 10 /sec.
PERCHED BEACH PROFILE RESPONSE TO WAVE ACTION
Authors: Sorensen R.M. , Beil N.J.
Published: June 2019

Wave tank experiments were conducted to investigate the response of a perched beach profile to storm wave attack. Irregular waves having a JONSWAP spectrum were used for all of the test runs. Beach profile erosion was measured initially for a 1:20 slope nourished profile without a toe structure in place. This established base test profiles for comparison with subsequent erosion profiles with a toe structure or sill in place. The subsequent tests with a sill were conducted with the sill placed at a range of depths along the nourished profile slope. Each of the test conditions was subjected to erosive wave attack for 42 hours with periodic interruptions for measurement of resulting beach profiles. Test results are presented and interpreted to evaluate the effect of the sill structure on beach profile response and the effectiveness of the structure in retaining the beach. Scaling of the results to prototype conditions is also discussed.
EFFECTS OF A VERTICAL SEAWALL ON PROFILE RESPONSE
Authors: Barnett Michael R. , Wang Hsiang
Published: June 2019

An attempt is made to determine beach profile response due to the presence of a vertical seawall placed in various cross-shore positions, and to examine the differences between natural beaches and seawall-backed beaches in response to normally incident wave attack. The investigation was mainly restricted to two-dimensional profile response under erosive wave conditions, with beach recovery response monitored to a limited extent. Spatial and temporal profile response was investigated by examining time-series profile configuration, volumetric changes, sediment transport patterns, and quasiequilibrium profile configuration. Additionally, dominant profile features such as the break point and reflection bars (as well as scour at the toe of the seawall-backed profiles) were observed and quantified.
REPRODUCTION MODELS OF BEACH CHANGE BY STORM WAVES
Authors: Ito Masahiro , Tsuchiya Yoshito
Published: June 2019

This paper presents a technique to reproduce, by a twodimensional moveable-bed model, beach change due to the timedependent storm waves which are generated by the passage of an atmospheric depression. In the model test, scaling conditions for sand grain-size, vertical and horizontal lengths, and wave height and period characteristics were established by applying the authors' scale-model relationship which was reported; and wave duration time also was decided. A method of employing regular waves in the model to represent irregular waves in the field is proposed. From the results, it was shown that the model can reproduce well the beach change in the field using the regular waves having the mean wave properties in the irregular waves.
LITTORAL DRIFT MODEL FOR NATURAL ENVIRONMENTS
Authors: Deigaard Rolf , Fredsoe Jorgen , Hedegaard Ida Broker , Zyserman Julio A. , Andersen Ole Holst
Published: June 2019

The littoral drift model developed at DHI and ISVA, see Deigaard et al. (1986b) has been extended to include the effects of the irregularity of the waves, of a coastal current and a wind acting on the surf zone. Further, a mathematical model to simulate the near-shore current pattern along a barred coast with rip channels has been developed. The influence on the littoral drift of the irregularity of waves, wind, coastal current, and rip channels is discussed. It is concluded that irregularity of waves and presence of rip channels must be considered while coastal current and wind action are of minor importance.
SUSPENDED SEDIMENT CONCENTRATION IN THE SURF ZONE
Authors: Ifuku Makoto , Kakinuma Tadao
Published: June 2019

The water particle velocity,the pressure fluctuation and suspended sediment concentration near the bottom were measured in the surf zone. Data were obtained on the mean sediment concentration, phase lag between onshore velocity and suspended sediment concentration. The near-bottom velocity distributions under finite amplitude waves were calculated on the basis of the turbulent boundary layer theory by using timeindependent/ dependent eddy viscosities and Prandtl mixing length theory. The concentrations at reference level were estimated from the Kalkanis' theory using the velocity value at the top of a sand particle and the distributions of suspended sediment concentration were calculated on the basis of the turbulent diffusion theory by using time-independent/ dependent diffusion coefficients. The computed mean values of the suspended sediment concentration agree with those observed by Noda, the authors and Nielsen and those measured by Deigaard et al.. The computed phase lag agrees well with observed by the authors.
A QUASI-3D MATHEMATICAL MODEL OF COASTAL MORPHOLOGY
Authors: De Vriend H.J. , Ribberink J.S.
Published: June 2019

A semi-analytical model of 3D nearshore currents and sediment transport is presented. It describes the tidal motion, the waves, the surfzone currents and the sediment transport in complex coastal areas. The results of a first application, to a well-documented case at the Dutch coast, indicate the potential and the shortcomings of the model. The latter are analysed and suggestions for improvement are given.
ABOUT THE INFLUENCE OF EROSION VOLUME ON CROSS-SHORE SEDIMENT MOVEMENT AT PROTOTYPE SCALE
Authors: Uliczka K. , Dette H.H.
Published: June 2019

In order to estimate erosion of sand beaches attacked by storm surges, experiments at prototype scale are necessary, since small scale models do not reproduce physical processes in the surf zone. The present study describes the influence of erosion volume on crossshore sediment movement during the development of beach profile. The discussion includes parameters which affect the erosion volume and the accuracy of assessment.
SAND RIPPLE GEOMETRY AND SAND TRANSPORT MECHANISM DUE TO IRREGULAR OSCILLATORY FLOWS
Authors: Sato Shinji , Horikawa Kiyoshi
Published: June 2019

This paper describes characteristics of sand ripples and sand transport mechanism in regular and irregular oscillatory flows on the basis of detailed laboratory measurements. A set of empirical relations were proposed to evaluate the sand ripple geometry as well as the onset of the sheet flow transport. The applicability of the proposed relationships to the irregular wave conditions with prototype scales was confirmed with existing field data.
THE DYNAMIC RESPONSE OF SHINGLE BEACHES TO RANDOM WAVES
Authors: Powell K.A.
Published: June 2019

An extensive laboratory investigation into the behaviour of shingle beaches has been undertaken using a large random wave flume. The study utilised a lightweight material scaled to reproduce the correct permeability of the beach, and the correct threshold and relative magnitude of the onshore/offshore movement. Results are presented describing both the wave reflection characteristics of the beach and the probabilistic distribution of wave run-up crests on the foreshore. Where possible the laboratory results are validated against field data.
ESTIMATES OP GROSS-SHORE BEDLOAD AND BED CHANGES
Authors: Pruszak Zbigniew , Zeidler Ryszard B.
Published: June 2019

Four series of tracer studies employing radioisotopic sand, tracked remotely from land, were carried out at the IBW PAN's coastal research station at Lubiatowo. Incipient motion of single grains with velocity Vcr1 has agreed with Komar and Miller's (1974) formula, and has been 5...8 times smaller than voro, the threshold velocity of water inducing bulk motion_of sediment. The ratio of average nearbed water velocity, v, to_the effective speed of tracer sand, in the inshore zone, va, is estimated about 100...1,000. The cross-shore sediment transport rates measured are ten times smaller than those predicted by Pruszak's (1987) energetics formula, the discrepancy being due to the real field phenomena of mixing and overburdening in a thick bed layer. Our wave flume and wave tank studies with movable bed point to the importance of initial slope in shore evolution. The laboratory findings on bed variability are extended by our 1987 field data obtained with an ultrasonic setup. Intensive cyclic depth changes are acoorapanied by varying transport rates computed from continuity equation.
SECULAR CHANGE IN TIDAL FLAT HEIGHTS
Authors: Siefert Winfried
Published: June 2019

The German North Sea Coast is relatively short (370 km); its shape is extremely irregular with estuaries, extended tidal flats, partly protected by sandy islands with deep tidal gullies between them (Fig. 1). In order to gain more detailed information and sufficient knowledge about the variety and variations in this region, the German Coastal Engineering Board (KFKI, Kuratorium fur Forschung im Kusteningenieurwesen) has initiated a high-level and extensive programme, "MORAN", "Morphological Analysis Klorth-Sea-Coast". The purpose and the first ideas of the programme were presented by Siefert and Barthel (1981). Investigations are still under way. It is of high interest whether the mean height of the tidal flats will rise, if the green house effect results in an acceleration of the mean sea level rise. In that case coastal protection in areas behind tidal flats will have to be changed completely, as then wave energy will no longer be dissipated in front of the coastline and will attack the dikes heavily .
PHYSICAL MODELLING OF BEACH EROSION AND LITTORAL DRIFT
Authors: Sayao Otavio J. , Nairn Robert B.
Published: June 2019

A new procedure for physical modelling of beach sedimentary processes is presented. It is shown that the modelling requirements proposed by Dean (1985) are necessary but not sufficient for dynamic similarity. Quantification of scale effects due to slope and relative grain size scaling conditions enables extrapolation of the physical model results to prototype situations. Selected examples of the application of the proposed model design are also given.
A MODEL FOR BREACH GROWTH IN A DIKE-BURST
Authors: Visser Paul J.
Published: June 2019

A mathematical model for sand-dike breach erosion is presented. The heart of the model is a modified Bagnold (1963) energetics-based sand transport conception combined with a simplified Galappatti and Vreugdenhil (1985) pick up mechanism for the suspended load. The model has been tested to three laboratory experiments. The agreement between model predictions and experimental results is surprisingly good. Prototype calculations are presented for the 73 m high sand-dike of a proposed pumped-storage plant in the Netherlands.
SHORELINE AT JETTY DUE TO CYCLIC AND RANDOM WAVES
Authors: Walton Todd L. , Liu Philip L.F. , Hands Edward B.
Published: June 2019

This paper examines the effects of random and deterministic cycling of wave direction on the updrift beach planform adjacent to a jetty. Results provided using a simplified numerical model cast in dimensionless form indicate the importance of the time series of wave direction in determining design jetty length for a given net sediment transport. Continuous cycling of - wave direction leads to the expected analytical solution. Simplications in the numerical model used restrict the applications to small wave angles, no diffraction, no reflection of waves off structure, no refraction, and no sand bypassing at jetty. The concept can be extended to more sophisticated numerical models.
PREDICTION OF 3-D BEACH CHANGES ON THE FUJI COAST
Authors: Ohishi H. , Uda T. , Murakami Y. , Watanabe M.
Published: June 2019

The temporal and spatial beach changes on the Fuji Coast are elucidated through this study, and the 1i t toral transport rate on the downdrift coast of Tagonoura Port is evaluated. In particular, it is concluded that a large amount of sediment eroded from the downdrift beach of Tagonoura Port is carried away toward a zone deeper than 20m. The second aim of this study is to devel op a numerical model whi ch can predict three-dimensional beach changes. For this purpose, a model in which the vertical distribution of littoral transport is taken in to account and the effect of the wave-dissipating breakwaters on the beach changes can be evaluated is developed.
THE THEORICAL TEMPORAL STRUCTURE OF THE LONGSHORE CURRENTS
Authors: Aguilar Jose , Diez Jose Javier
Published: June 2019

For a better Knowledge of the causes about the littoral solid transport is essential to experience advances in the littoral hydrodynamic. In this field the longshore currents are may be who play the most important role due to the intensity, the distribution and the relative duration of them, causing the movement of the solid particles due to the suspension of them and the friction in bottom. The first theorical formulation about the longshore currents were established by Bowen (1969), Longet-Higgins (1970) and Thornton (1970). Previously another works trated an aproximation about the problem, obtaining a little precise results basing his works in simplest formulations, it shows in Sonu et alt. (1966).
NUMERICAL MODEL OF BREAKWATER WAVE FLOWS
Authors: Thompson Alex C.
Published: June 2019

A mathematical model of flow on a sloping breakwater face is described and results of calculations compared with some experimental results to show how the model can be calibrated. Flow above the surface of the slope is represented by the shallow water wave equations solved by a finite difference method. Flow within the breakwater is calculated by one of two methods. A solution of the linear seepage flow equations, again using finite differences or a simplified model of inflow can be used. Experimental results for runup and reflection coefficient are from tests performed at HRL Wallingford.
STATISTICAL ANALYSIS OF DETACHED BREAKWATERS IN JAPAN
Authors: Uda Takaaki
Published: June 2019

Construction of detached breakwaters is one of the main countermeasures against beach erosion in Japan. The number of breakwaters has been rapidly increasing, with about 2500 constructed as of the end of 1981. This study aims at the investigation of the effect and stability of detached breakwaters along Japan's coasts on the basis of survey of 1552 breakwaters constructed by the Ministry of Construction. The existing conditions of the dimensions of the detached breakwaters are statistically analyzed; the optimal dimensions for sand deposition behind a breakwater are proposed, and the critical conditions for advance of the shoreline facing an opening of breakwaters are investigated. Furthermore, the relations between the scattering rate of concrete blocks and various conditions such as bottom slope, the depth at the breakwater, the offshore distance of the breakwater and the weight of the blocks are studied. It is concluded that, in order to prevent scattering, the weight of the blocks should be at least 1.5 times heavier than that calculated from the Hudson formula.
DESIGN ASPECTS OF BLOCK REVETMENTS
Authors: Pilarczyk K.W.
Published: June 2019

The increasing shortage and costs of natural materials in certain geographical areas has resulted in recent years, inter alia, in the rapid development of artificial (concrete) block revetments. In general, two main types of revetments can be distinguished: permeable (stone pitching, placed relatively open block-mats) and (relatively-) impermeable (closed blocks, concrete slabs). Regarding the shape and/or placing technique a distinction can be made between: a) free (mostly rectangular-) blocks and b) interlocking blocks of different design (tongue-and-groove connection, ship- lap, cabling, blocks connected to geotextile by pins etc.). In all these cases the type of sublayer (permeable/impermeable) and the grade of permeability of the toplayer are very important factors in the stability of these revetments. The design also needs to be made (executed) and maintained. Both aspects must therefore already be taken along within the stadium of designing. At the moment there is a large variety of types of revetment-blocks and other defence systems (i.e. block-mats), see Fig. 1. Until recently no objective design-criteria were available for most types/systems of blocks. The choice (type and size) of the revetments built sofar is only based on experience and on personal points of view, sometimes supported by small-scale model investigations. In the light of new (stricter) rules regarding the safety of the Dutch dikes, as they have been drawn up by the Delta-Commission, the need for proper design-criteria for the revetments of dikes has evidently grown. Because of the complexity of the problem no simply, generally valid mathematical model for the stability of the revetment are available yet. For restricted areas of application however, fairly reliable criteria (often supported by large-scale tests) have been developed in the Netherlands not only for the kind of revetment, but also for conditions of loads. This new approach is discussed in (Klein Breteler, 1988). This paper presents a short state-of-the-art review of existing knowledge on the designing of different types of revetments and, where ever possible, the available stability criteria are mentioned. There is also given some comparison of the different types of revetments with their advantages and disadvantages and suggestions regarding their practical application.
STABILITY AND STRUCTURAL BEHAVIOUR OF STRENGTH IMPROVED DOLOSSE
Authors: Zwamborn J.A. , Scholtz D.J.P. , Claassens H.
Published: June 2019

Stability model tests and prototype breakage tests were done to provide data for the optimum design of dolos breakwater armouring. Stability tests with irregular waves were done with dolosse with waist ratios of 0,33, 0,36, 0,38, 0,40 and 0,43 and breakwater slopes of 1:1,33, 1:1,5 and 1:2. All model dolosse had a mass of about 80 gr and were placed at a 'normal' density, 0 = 1,00. The results showed that regular waves with H g = 1,1 H must be used to get similar damage. Also, a significant reduction in stability is evident for dolosse with larger waist-to-height ratios and for the shorter period waves (Figures 4 and 5), Some 50 9 t dolosse, without reinforcing and with different types of simple rail reinforcing, were tested for breakage behaviour, using a specially developed cushioning device to closely represent breakwater conditions. The results showed that unreinforced dolosse can withstand falls up to 1,5 m, without breakage and X or double-V rail reinforced units about double this height. The results of these tests, together with specific model tests, were used to design an effective protection for the Table Bay main breakwater. The tests indicated the use of 25 t dolosse (minimum) but, because of the shallow waterdepth, the toe dolosse of the repair slope were reinforced (double-V rail reinforcing), stabilized by 75 mm steel chains, and bitumen grout will be placed to reduce their movements.
LARGE VERIFICATION TESTS ON ROCK SLOPE STABILITY
Authors: Van der Meer J.W. , Pilarczyk K.W.
Published: June 2019

A number of large scale tests on stability of rock slopes and gravel beaches is described and compared with small scale test results. The following topics are treated: the stability of a rock armour layer, the profile formation of a berm breakwater, the profile formation of gravel beaches, including ripple formation, and reflection and overtopping on rock slopes. The general conclusion is that scale effects could not be found.
ANALYSIS OF 42-TON DOLOS MOTIONS AT CRESCENT CITY
Authors: Kendall Thomas R.
Published: June 2019

Photogrammetry has been applied to make precise measurements of post-construction displacements of 38.2-metric ton (42-ton) dolosse on the outer breakwater at Crescent City, California. Data from two storm seasons are currently available from this monitoring program which was initiated in November 1986 and which is expected to continue at least through the next three winters. Supplemented by conventional land surveys, wave measurements, aerial inspections, and side scan sonar underwater imagery, observations from the photogrammetric monitoring have led to several preliminary conclusions regarding regions of relatively large dolos movement, dolos nesting, the dependency on breakwater slope of uprush or drawdown dominated armor unit movement, and the relative importance of armor unit movement and boundary conditions in dolos breakage. This paper describes the methods used for, and results obtained from, this monitoring effort along with the application of these results to a Corps study (Howell, 1988) Whose objective is to develop structural design criteria for the dolos concrete armor unit.
WIDE-ANGLE WATER WAVE MODELS USING FOURIER METHOD
Authors: Dalrymple Robert A. , Suh Kyung Duck
Published: June 2019

Two Fourier models for the propagation of surface waves are reported, which are theoretically valid for angles of propagation up to ±90° with respect to normal incidence. This is a great improvement in comparison with the present parabolic models. The first model is based on the assumption of straight and parallel depth contours, and the second one is the extension to the case of irregular bathymetry.
FULL-SCALE WAVE ATTACK OF UNIFORMLY SLOPING SEA DYKES
Authors: Fuhrboter Alfred , Sparboom Uwe
Published: June 2019

Shock pressure phenomena due to breaking waves acting on sloping faces of sea dykes are focussed in this paper. The probability approach is pointed out and maximum shock pressure estimations are given for smooth and impermeable dyke slopes 1:4 and 1:6. An extension of the results to steeper and flatter slopes is proposed. Results of full-scale stability tests on concrete block slope revetments are also reported in this paper. For various structural solutions with granular and geotextile filter layers stability numbers are recommended. Initial block lifting is explained physically by pressure measurements. The full-scale experiments were carried out in the new research facility LARGE WAVE CHANNEL of the universities in Hannover and Braunschweig (Federal Republic of Germany).
WAVE TRANSMISSION THROUGH A DOUBLE-ROW PILE BREAKWATER
Authors: Herbich John B. , Douglas Barry
Published: June 2019

Several previous investigators have conducted experiments leading to expressions for predicting the transformation of waves passing through closely-spaced pile or large cylinder breakwaters. The present study extends the earlier experiments which used a single row of piles instead of a double row of piles forming a breakwater. The experiments using the double-pile breakwater were performed in the same facility as the experiments conducted on a single-pile breakwater and employed the same method of analysis for a more meaningful comparison. The experiments consisted of allowing waves to pass through a pile array and measuring the incident and transmitted wave heights. The variables were: depth, period, diameter, monochromatic and random waves. The experimental matrix was three water depths, four wave periods, two pile diameters, two gap dimensions between piles and four random wave spectra: Darbyshire, I.T.T.C., Pierson- Moskowitz and JONSWAP, two pile diameters and two gap dimensions between piles. The two-row breakwater had less wave transmission than the single-row breakwater, as expected. For a gap to a pile diameter ratio, or b/D = 0.2 (where b = gap spacing, D - pile diameter), the wave transmission was reduced by 15 percent, as compared with a single-row breakwater; for a gap ratio of b/D - 0.1, the wave transmission was reduced by 5 to 10 percent.
CEOHYDRAULIC INVESTIGATIONS OF RUBBLE MOUND BREAKWATERS
Authors: Burger W. , Oumeraci H. , Partenscky H.W.
Published: June 2019

Due to the increase of ship sizes in recent decades a number of harbours and terminals have been built in deeper waters. Accordingly, the structures which have to provide protection against wave action become higher, too. In most cases, these protective structures are of the rubble mound type. Under such conditions the flow induced by waves within the breakwater and the related geotechnical behaviour of the rubble mound fill become more significant fcr the overall stability and should be considered in the design. In addition, it is known that the scales usually adopted in hydraulic models (1:30 to 1:60) for investigating the stability of large rubble mound breakwaters generally lead to scale effects with respect to the flow field inside the breakwater. This means that small-scale model tests are not appropriate for investigating the internal flow patterns or for evaluating the pore pressure field induced by the incident waves in,the core material. because of the uncontrolled conditions in the prototype, and since the actual permeability of the prototype rubble mound fill cannot be predicted (segregation, settlement, variation in grading, etc.), the use of large-scale physical models seems to be the most promising method for basic investigations of this kind. Moreover, the results of such largescale model tests may be used to validate the usual smaller scale models and to calibrate numerical models. Therefore, it is one of the objectives of our research programme on rubble mound breakwaters, which started in 1987, to concentrate on the evaluation of the wave-induced flow and pore pressure distribution within the breakwater.
EXPERIMENTAL STUDY OF IMMERSED PLATES USED AS BREAKWATERS
Authors: Drouin Alain , Ouellet Yvon
Published: June 2019

Under certain wave conditions, an immersed plate which is free to move horizontally produces what has already been called the oscillating water wall phenomenon. When this happens, the plate and the volume of fluid located under the plate move back and forth and then behave as a wave reflector. This type of breakwater was studied in a wave flume with monochromatic and irregular wave trains. Tests have provided a better understanding of the influence of certain parameters that define a plate and the hydraulic conditions under which the plate is used. Results show some interesting efficiencies and also transfert of the energy to harmonic frequencies.
WAVE UPLIFT FORCES ON PLATFORMS WITH ENERGY ABSORBERS
Authors: Lee Jiin-Jen , Lai C.P.
Published: June 2019

Interaction of large amplitude wave with platforms or docks in a variable depth medium has been studied theoretically and numerically. The underside of the platform is equipped with energy absorbing linear spring in order to study the energy absorbing effect for reducing the uplift forces on the platform or dock. The flow is assumed to be inviscid, irrotational without current. Laplace equation with full non-linear free surface equations are solved by isoparametric mapping technique. A Galerkin finite element model is used to model the transformed equations. The adaptive line SOR (Successive-Over-Relaxation) technique is used. The results indicate that uplift wave forces on platforms or docks can be significantly reduced by very soft springs. Wave profile history confirms the manifested mechanism of energy absorption. The results also indicate that larger uplift forces are easier to be damped out by the prescribed energy absorbing mechanism than the smaller uplift forces.
WAVE-INDUCED SHOCK PRESSURES UNDER REAL SEA STATE CONDITIONS
Authors: Grune Joachim
Published: June 2019

This paper deals with a study on shock pressures, which occur on sloping seadykes and revetments due to breaking waves. Results from field measurements are presented with respect to peak pressure values as well as to characteristics of pressure-time histories.