Coastal Engineering 1970

This paper describes the need for, and the factors involved in, the establishment of a Wave Climate Study, illustrated with particular reference to the Canadian Wave Climate Study

Wave recording on a national basis in South Africa commenced in 1967, when an "Ocean Wave Research" project was initiated, aimed at obtaining reliable data on sea conditions around the shorelines of the Republic and South West Africa and to improve on wave prediction techniques

Various instruments are being used in this programme Some of the problems encountered in practice with these instruments and the agreement between the results obtained using various wave recorders simultaneously at the same station are discussed An indication of the volume of wave data so far obtained and the methods of analysing them are included

Manual analysis of strip-chart records from a conventional wave sensor at Monterey, California was found to yield a linear frequency shift associated with each arriving swell tram, from which the origin time and travel distance of the swell could be computed The use of surface weather maps allows identification of the source, and thereby yields an accurate determination of the deep-water arrival direction of the swell for use on the local coast The wave records are analyzed for the frequency of the individual waves composing wave groups, f_g, consistency of the results obtained indicates that f_g is equivalent to the frequency of maximum energy density f_max, obtained by spectral analysis Five swell sets studied were found to originate in North Pacific storms advancing toward Monterey The seas in the fetch were fully arisen at the time of computed swell origin, and the surface to geostrophic wind ratio was 0 83 The dominant swell emerged from the fetch at a time when its group velocity equalled the velocity of the fetch toward Monterey

A very general model is presented for the probability distribution function for wave heights in storms with time-varying intensities Some of the possible choices for functions in the model are listed and discussed Techniques for determining the "equivalent rectangular storm" corresponding to a given historically recorded storm are developed The final model formula expresses the probabilities for a random number of random length storms each with random intensities

With a view to establish sea wave data processing procedures to be applied to records obtained at the Portuguese coast, a detailed study is made of different choices of certain parameters used in one-dimensional spectral analysis of a pressure wave gauge record Statistics computed by the selected spectral procedure are then compared with results of a Tucker-Draper analysis of the same record Finally a hindcast of sea conditions for the date and place of the record is made by different methods and comparisons with previous results are presented

Data obtained from two surface profile wave gages and two pressure wave gages at the Steel Pier in Atlantic City, New Jersey, are used to check the consistency of the analysis variables obtained from a given set of records by several commonly used analysis procedures

All estimates of the characteristic height tested are found to be correlated better than 86 The estimates of characteristic period are not so satisfactory and in some cases are below 25 Consideration of several proposed definitions of the characteristic period indicates that they are based more on convenience in data processing than on application of the derived data Consideration of the use of wave data in engineering design shows that no one definition of the period can be satisfactory for all applications The best definition of the characteristic wave period for a given engineering problem can be specified only when the dynamic aspects of the problem have been identified

Simultaneous records from two pressure gages located at different depths, a step-resistance relay gage, and a continuous-wire staff gage have been collected at Atlantic City, N J

Spectra and cross-spectra are computed using the Fast Fourier Transform Algorithm (FFT) method proposed by Cooley and Tukey Individual harmonics of the pressure energy spectra are compensated for pressure attenuation according to classical theory Results indicate better agreement is obtained between the wave height and the spectra computed from the compensated pressure gages and those computed from the continuous-wire staff gage than between the two surface gages

Values of coherences are near 98 in the energy-containing part of the spectrum, and are always larger for the pressure-continuous wire staff cases than for the two surface gages which are displaced from each other only 12 feet m the horizontal

The ocean surface may be considered to be composedof many waves traveling at different directions with different frequencies A graphical plot showing the allocation of wave energy to the different component frequencies and directions is the directional spectrum Directional spectrum has many applications in Coastal Engineering Herein an analytical procedure is developed to obtain the directional spectrum from records of an array of wave gages The two methods developed are the "locked phase method" and the "random phase method The locked phase method can be used to obtain the distribution of both phase as well as energy of the waves with respect to frequency and direction and is a deterministic approach The random phase analysis, on the other hand, is more suitable for wind waves in the ocean and yields just the distribution of energy alone as in most other procedures of spectrum analysis The procedures programmed for computers are checked using simulated data and laboratory data Wave records of the Pacific Ocean obtained off Point Mugu, California, on a 5-gage array were analyzed using the method developed and examples of the directional spectra obtained are presented

In shoaling water on sloping beach, waves break by hydraulic instability due to the finiteness of water depth, so that frequency spectra of waves in surf zone must have any limiting form similar to the equilibrium spectrum given by Phillips(1958) In this paper, authors have derived an equilibrium form of spectra for surf waves from the limiting wave condition at constant water depth by Miche(1944) and from breaking wave experiments on sloped bottom by Iversen(1952) The results are compared with surf wave spectra obtained from field observations by means of stereo-type wave meter devised by the authors(1968).

By means of this spectrum and by deep water wave spectra for various wind conditions, significant wave heights and optimum periods of limiting waves in surf zone are calculated

Examinatxon of the significant heights of zero-crossing waves in the Elbe Estuary has yielded two noteworthy results: 1 In the deeper water of the estuary, the value of the quotient relating the significant and the mean wave heights is larger than on the bordering tidal flat. 2. The value of this function is dependent on the height of the waves; on the tidal flat this dependency is considerably more sensative than in deeper water. With increasing wave height the value of significant wave height divided by mean height becomes smaller

The propagation direction of waves moving onto the tidal flat is contingent upon the position of intertidal channels Such channels sharply reduce the possible propagation directions The waves nearly always move up-channel regardless of the wind direction

It is possible to derive special wave period and wave height distributions representing the conditions in very shallow water

The seas in front of China coast such as Yellow Sea, East China Sea and Taiwan Straits are all located on continental shelf. In consequence, waves approaching these coasts are generated in shallow water area in comparsion with wave length. The authors has developed tangible calculation procedures for evaluating the wave features in such areas in stationary or moving fetches (l). However, the basical formulas of calculation are derived from experimental data of Bretschneider and Thijsse. In order to investigate the generating process of shallow water wind waves and obtain more detailed informations for correcting calculation criteria, a series of experiments have been performed at a wind tunnel of 75 meters in length. Various investigations on the relationships between waves and wind as well as water depth ar4 to be submitted in this paper.

In addition, the situation of wind wave coexistance with regular wave is studied from experiments, because it resembles the superposition of refracted and local wind waves on the western coast of Taiwan.

The applicability of the general Wave Forecasting procedures like the SMB and the PNJ methods, to the Indian coasts is studied. The study consisted in analysing the bynoptic charts to obtain the necessary wind characteristics. The computed wind characteristics were used in the above Forecasting methods to yield significant wave heights These were compared with the wave characteristics as recorded by a sub-surface pressure type recorder after suitable modifications to account for the attenuation of wave pressure with depth.

The predicted wave heights compare well with the recorded wave heights and the SMB method predicts wave heights better for the case studied.

Laboratory studies m a wind wave flume were carried out to investigate the macro-scale turbulence associated with wind waves and white cap conditions Velocity fluctuations m water were measured with a hot film anemometer and parametric correlations between wind waves and turbulence characteristics were established Measured data were recorded m analog form, digitized and stored on magnetic tape Auto – covanance functions and power spectral density functions were then obtained for all sample records

Results showed that the depth of the penetration of the macro-scale turbulence increased rapidly with wind speed but the rate of penetration diminished at the higher wind speeds This rate of macro-turbulence penetration was found to vary inversely with wave height and wave steepness Most turbulent fluctuations having frequencies equal to or higher than the frequency of the ambient surface waves were confined to the zone of macro-turbulence penetration although some disturbances such as vortex rings and other turbulence associated with white cap wave conditions occasionally penetrated to greater depths It was found that the energy dissipation increased with wave height and that almost all wave energy dissipation was concentrated near the water surface

Measurements of shear stress under the effect of a sea hreeze were made by simultaneous wind and temperature profiles over a shore near Fort Walton Beach, Florida It was found that the sea breeze In the surface boundary layer is in the atmospheric free-convection, regime The measured shear stress coefficient is in conformity with that obtained by other investigators by the sea surface tilt method under the unstable condition For coastal applications, the result is found to be more reliable than those assumed coefficients obtained under neutral stability for this localized coastal wind system

Wave-height attenuation measurements were made in two identical flumes of different widths and the results used to separate bottom energy losses from sidewall energy losses These energylosses, in the form of rates of energy dissipation, were then compared with their theoretical values as calculated by solving the linearized Prandtl boundary layer equations and evaluating the Rayleigh dissipation function Using these results, an adjusted formula for the wave-height attenuation modulus was determined

The wave-induced longshore current variation across the surf zone is described for a simplified model The basic assumptions are that the conditions are steady, the bottom contours are straight and parallel but allow for an arbitrary bottom profile, the waves are adequately described by linear theory, and that spilling breakers exist across the surf zone Conservation equations of mass, momentum, and energy, separated into the steady and unsteady components, are used to describe second order-wave-induced phenomena of shoaling waves approaching at an angle to the beach An expression for the longshore current is developed, based on the alongshore component of excess momentum flux due to the presence of unsteady wave motion Wave set-down and set-up have been included in the formulation Emphasis in the analysis is placed on formulating usable predictive equations for engineering practice Comparison with experimental results from the laboratory and field show that if the assumed conditions are approximately fulfilled, the predicted results compare quite favorably

This paper firstly describes two methods to measure vertical distribution and time variation of horizontal water particle velocity induced "by surface waves in a wave tank These two methods consist of tracing hydrogen bubbles and using hot film anemometers, respectively

Secondly, the experimental results by the two methods are presented with the theoretical curves derived from the small amplitude wave theory, Stokes wave theory of 3rd order, and the hyperbolic wave theory as an approximate expression of the cnoidal wave theory

Finally, based on the comparison of the experimental data with the theoretical curves, the applicability of the finite amplitude wave theories, which has been studied for the wave profile, wave velocity, wave length and wave crest height, is discussed from view point of the water particle velocity

A single-ended, cylindrical hot-film sensor and a directionvane transducer are studied as instruments for measuring flow fields in laboratory waves Errors in the hot-film measurements are discussed in terms of sensor voltage and water temperature drifts, and directional sensitivity The response of the direction-vane transducer is discussed in terms of the parameter b/r, which is the ratio of the vane chord length to the radius of curvature of the measured orbital flow

The instruments are tested in a laboratory wave system, using stationary and traversing measuring techniques The velocity measurements so obtained are compared to those obtained by a photographic technique, to determine instrument error The flow speed comparisons indicate that the maximum hot-film error in flow speed measurements is between ± 5 and ±10 inches/sec for the range 1 to 11 inches/sec tested The flow direction comparisons indicate that the direction vane response is subject to errors larger than 5° for fo/r>0 1

The study was carried out under the sponsorship of the Coastal Engineering Research Center at the Massachusetts Institute of Technology and is reported in full detail in the M.I T. Hydrodynamics Laboratory Report No 118

This work focuses on the shoaling of large water waves with particular application to storm-generated waves and tsunamis The specific objective is the exact simulation on a digital computer of finite-amplitude waves advancing on a beach of constant slope

The study is based on the simulation technique called SUMMAC (the Stanford-University-Modified Marker-And-Cell Method) The flow field is represented by a rectangular mesh of cells and by a line of hypothetical particles which defines the free surface Based on the Navier-Stokes equations, finite-difference equations were derived so that the entire flow configuration could be advanced through a finite increment of time The pressure and velocity components are used directly as the dependent variables Through extensive analyses and numerical experiments, this scheme was found to be computationally stable if the cell size and the time increment are properly selected

As a specific example, the dynamics of a solitary wave passing from a zone of constant depth onto a sloping beach were simulated Primary attention was focused on the details of the water particle motions and the changes in the amplitude and shape of the wave as it climbed the slope The computed results are compared with the experiments with good agreement

The bottom bed slope plays a vn tal role m the shoaling and breaking of periodic waves. This study aims at the understanding of the effect of steep sDopes (range steeper than 110) on the breaking point and the breaker trajectory and the point of impact. This range of slope is often met with in. the near-shore structures. Analytical investigations and model studies are outlined. The influence of slope on each of the significant breaker parameters is discussed.

Waves of large amplitude on a gentle slope may form spilling breakers which propagate shoreward and are slowly transformed In addition, there occurs a modification of the mean water level termed wave setup An analytical description based upon consideration of momentum flux has been developed which predicts this wave setup and the decay history of breaking wave height The results have been compared with experiments and found quite satisfactory

The effect of wave setup on breaking wave transformation is particularly important near the shoreline, where setup dominates the vanishing mean depth

Utilizing the hydrodynamic relationships for shoaling and refraction of waves approaching a shoreline over parallel bottom contours a procedure is developed to transform an arbitrary probability density of wave characteristics in deep water into the corresponding breaking characteristics in shallow Water A number of probability distributions for breaking wave characteristics are derived m terms of assumed deep water probability densities of wave heights wave lengths and angles of approach Some probability densities for wave heights at specific locations in the surf zone are computed for a Rayleigh distribution in deep water The probability computations are used to derive the expectation of energy flux and its distribution

A two-dimensional model submerged offshore bar was installed in a Texas A&M Hydrodynamics Laboratory wave tank Monochromatic waves with a range of heights and periods were generated at this bar for three different depths of water over the bar For each wave, water surface time-histories were measured at points before and after the bar and spectral analyses of these measurements were performed

The analysis of each wave record yielded an equivalent wave height which is proportional to the square root of the wave energy per unit surface area The ratio of the reformed to incident equivalent wave height is shown to relate to the ratio of incident wave height to water depth over the bar The predominant periods of the reformed waves are found to be the same as for the incident waves but the presence of energy at higher frequencies is also observed The cause of these higher frequency waves is discussed

A theoretical and experimental study of the initial development of undular bores in two-dimensional, rectangular channels with and without boundary friction was performed Equations similar to those of Boussinesq, but including higher order and wall friction terms are presented and solved numerically by an implicit finite difference method A Pohlhausen-type boundary layer momentum integral method is used to obtain the wall shear stress distribution under a developing long wave from the consideration of the boundary layer underneath it The solution is performed in a quasi-iterative manner proceeding from the friction coefficient calculation for an initially assumed wave profile to the inclusion of this coefficient in the calculation of a new wave profile at an advanced time Comparisons of theoretical and experimental results are given For the initial development of the undular bore with which the present work is concerned, the measurements are found to be m reasonable agreement with the theoretical predictions The effect of the wall shear stress manifests itself mainly in a slight reduction of the wave amplitudes

A digital computer model for diffraction of wind waves behind a breakwater is developed The model combines the hydrodynamic theories and the concept of directional spectra It is designed so that it may be used not only for the study of the wind wave diffraction problem behind breakwaters but also for the investigation of experimental (or field) data analysis procedures of other kinds An extensive study of optimum data length, lag number and gage spacmgs m wave gage arrays is presented

This paper presents some theoretical results of a general study of the interaction between surface gravity waves and a steady current Assuming irrotational flow and a second order Stokes wave motion, the main objects of the paper have been

• To present a simple graphical method for the computation of the wave length m a current field
• To introduce the concept of the mean energy level for a periodic wave motion with a steady current superimposed
• To utilize this for the calculation of the "current-wave set-down" for a two-dimensional motion with a constant discharge over a gently sloping bottom
• To present a complete set of conservation equations for the case considered under point c
• To present graphs and tables for the variation in length and height of wave for the case considered under point c

No experimental results are presented

Results from experiments on the reflective power of smooth and rough impermeable slopes are presented The importance of relative depth to the regular scatter diagram of the function R=R (δo) and the need for an adequate computational wave theory through which no significant alterations are introduced in the determination of reflective power is pointed out Stokes 2nd order corrections are introduced These help find a superior value for the reflexion coefficient and destroy the mentioned regularity of the scatter diagram A regular scattering of experimental points, also of function R=R (δo) , where, however, for constant steepness, reflexion decreases when relative depth increases, is found in rough slope tests In this case, the more inclined is the slope, the greater is the influence of roughness

The purpose of this paper is to make clear the validity and limiting condition for the application of the finite amplitude standing wave theories by the perturbation method In a numerical example, the errors of each order solution of these theories for two non-linear free surface conditions are computed for various kinds of wave characteristics and compared with each other

Some experiments on the wave pressure on a vertical wall by standing waves were carried out and a plot of the limiting condition for the application of these theories is proposed based on the comparison with theoretical curves

In addition, as an example of the application of these theories, the change of characteristics of wave pressure of standing waves accompanying the overtopping wave on a vertical wall is discussed

A higher order theory is presented for symmetrical, non-linear gravity waves As a consequence of the generality employed, the theory includes the full range of possible wave lengths, water depths and wave heights that may be encountered, and brings them into one unified formulation Thus, the theory encompasses both linear and non-linear waves, including Airy waves, Stokes waves, cnoidal waves and the solitary wave

Based on the work of Nekrasov, a complex potential in the form of an infinite series is developed to describe the flow field The potential satisfies the bottom (horizontal) condition as well as the kinematic surface condition exactly Furthermore, the dynamic surface condition is satisfied by numerical calculation of the series coefficients which appear in the complex potential The calculation of these coefficients is accomplished by solving a set of non-linear algebraic equations, with the aid of a Newton-Raphson iteration procedure and matrix inversion

Coefficients of the complex potential have been obtained for a fifth order analysis and preliminary results are presented in tabular form A brief discussion of the characteristics of the waves, including wave speed, wave shape and the height of the highest possible wave follows

A study programme has been initiated to investigate the impulse waves generated by landslides originating entirely above the water surface It may be seen that the characteristics of this wave depend mainly on the slide volume and the Fronde number of the slide upon impact with the water The resulting wave goes through a transition period For the highest wave (usually the first), the wave height becomes stable relatively quickly and decays exponentially during the period of transition, the wave period continues to increase for a long time, the velocity of propagation may be approximated very closely by solitary wave theory

When a wavemaker generates a finite number of waves, it has been found that one of the first and one of the last waves in such a burst is considerably larger than the average A mathematical model, based on the linearized governing equations, is used for the particular problem of the waves generated by a sinusoidally moving piston-type wavemaker starting from rest Theoretical results for the magnitude of the large wave relative to the average agree fairly well with experiments, however, the actual wave height is smaller in the experiments than predicted by theory It is shown, by extending the classical wavemaker theory to second order, that finite amplitude effects do not offer an explanation However, pistons rarely fit the tank dimensions exactly, and an approximate evaluation indicates that the discrepancy between predicted and observed wave heights can be attributed to the effects of leakage around the piston

Dimensional analysis and errors leading to spurious correlation are presented using a number of practical examples

Photographs taken from space provide a new source of data concerning coastal processes By utilizing the high vantage point and broad view orbiting space cameras can record little known large-scale processes at short time intervals Major outflow plumes, fresh-salt water "fronts", turbidity maxima and massive effluents are among the wide range of features displayed It is shown from selected examples how coastal processes can be evaluated from space photography and how the information may be of use for solving certain problems as a supplement to field and other remote sensing data By 1972 satellite photography will be available on a routine basis for many coasts of the world Engineers are urged to consider the potential for improving their information which space photography has to offer

The physiography of Continental Shelves and their major composition of sediment indicate strongly their terrigenous origin and their smoothing by wave action This premise is supported by the geologic time over which waves have existed and the mass-transport velocity in these relatively shallow depths, particularly the net movement within the wave boundary layer at the bed A given wave tram arriving obliquely to the shore can transport material along the coast, both beyond the breaker line and within the surf zone It is shown that for equal over-all discharge in the two zones, the average sediment concentration offshore close to the bed need be reasonably small, indicating that transport near the beach could be a fraction of that from the breakers to the reach of the waves This latter limit is shown to extend at least half way across the Shelf, with possibilities of greater reach when more realistic prototype conditions are introduced into experiments

The thickness and extent of the sediment cover in the Patuxent Estuary has been determined using a high-frequency, high-spatial resolution, shallow penetration, continuous seismic profiling system. From these data, an isopachous map was prepared The isopachous map provides the subbottom information required to determine optimum locations for placing test equipment on the river bottom

Mud filled depressions, acoustically transparent to 12-kHz sound pulses, occur mainly to the north of Half Pone Point, and east of the present channel Based on the identification of first subbottom reflectors, these depressions are as much as 16 feet thick The dominance of the thicker deposits east of the channel and evidence of a submerged terrace indicates that either the channel has migrated to the west, or that the channel of the Patuxent River at this location was larger in the past and has subsequently filled in much of the material in the eastern edge Maximum penetration at the scarp of the submerged terrace was 36 feet beneath the water-sediment interface This study demonstrates the use of seismic profiling techniques for collecting and presenting data required for coastal engineering applications

For observation and interpretation of sedimentological movements an Underwater Television set-up is employed, which is discribed in the following paper The so long achieved results and experiences are exemplified

The purpose of this paper is

The following conclusions are drawn

The formation and behaviour of 'Mud Banks' is a phenomenon peculiar to the Southwest Coast of India. They are unique in their formation as veil as functions. The paper deals with the history of mudbanks, their locations, causes of their formation, the nature of material and their sources. The behaviour of the mudbaaks and their influence on the stability of the coast is also reported. The mudbanks act as storehouses of littoral material. Itis also the initiator of erosion on its downdrift areas. Itis noted that the material stored in the mudbanks must be advantageously utilised in stabilising the shores adjacent to it and for reclamation. Of extreme importance is the recognition that mudbanks are closely associated with the stability of the Southwest Coast of India and is a factor to be reckoned in any programme of coastal development or protection uthis area.

A new electrolytic turbulenoe transducer has been developed in order to measure the turbulent velocity fluctuation superposed on the oscillatory flow velocity The aim of the present paper is firstly to describe the outline of this transducer and secondly to introduce some of the experimental results The main items of the results are, l) the vertical distribution of turbulence intensity averaged over one wave cycle, where the turbulence is induced by ripples which appear on the movable bed of wave flume, and 2) the correlation between the turbulence intensity and the characteristics of sediment particles at the same level such as their fall velocity and sediment concentration

Bi-weekly monitoring of four closely-spaced permanent beach profile stations located on the northeast end of Monomoy Island (Cape Cod) has revealed major variations in the amount of erosion and accretion occurring along this portion of the Massachusetts shoreline During the 27-month monitoring period a close relationship was observed between changes in the beach and offshore portions of the profiles Three distinct types of bars were noted

The large variations in erosion and accretion occurring along the beach at any one time are related to the nonumform distribution of energy within the waves arriving at this section of the coastline This nonunifortuity of wave energy is attributed to refraction of the waves around the irregular bathymetry offshore from Monomoy, and it appears to produce shoreline protuberances of sand which are flanked updrift and downdrift by erosional zones

Wave refraction calculations indicate zones of alternately converging and diverging orthogonals in the wave fronts impinging upon Monomoy Island, with a correlation observed between the zones of converging orthogonals, i e wave energy concentrations, and the areas of the beach presently undergoing the greatest amounts of erosion

The U S Army Corps of Engineers' Coastal Engineering Research Center, in cooperation with the Atomic Energy Commission, initiated a multi-agency program to create a viable radioisotopic sand tracing (RIST) program Other agency participants in this program have been the Los Angeles District, Corps of Engineers, U S Air Force (First Strategic Aerospace Division), U S Navy (Pacific Missile Range), U S Army Mobility Equipment Command, National Aeronautics and Space Administration, and the State of California (Dept of Navigation and Ocean Development) CERC, together with the AEC's Oak Ridge National Laboratory has developed tagging procedures, hardware development, field surveys and data handling techniques that permit collection and analysis of over 12,000 bits of information per hour over a survey track of approximately 18,000 feet Data obtained with the RIST system can be considered as nearly synoptic observations of sediment transport m a single environmental zone or in adjacent beach, surf and offshore zones

Using sand tagged with isotopes of gold, experiments have been carried out at several sites on the California coast Surf, Point Conception area, Point Mugu, and Oceanside Data from the studies carried out in beach areas unmodified by littoral barriers indicate that under a given set of wave conditions the alongshore velocity of sediment transport differs from zone to zone such that transport seaward of peakmg-breaking waves < transport on the beach face < transport in the plunge and surf zone Because of these differences, tracing surveys confined solely to the foreshore or offshore zones produce data only partially indicative of transport in the zone of immediate concern to coastal engineers

Survey equipment for use in tracing sediment tagged with radionuclides has been designed and field tested The system is unique in its ability to operate on the dry beach, m the surf, and in deep water, making it possible to synoptically examine the beach face, surf zone, and off-shore marine environment The ball-shaped radiation detector vehicle is towed behind an amphibious vessel Data are collected on punched tape at a rate of one set of data (position, radiation counts, time) every two seconds Gold-198 and xenon-133 have been used for tagging sand indigenous to the survey area under study Operational characteristics and detection sensitivity are discussed

Data collected during the Radioisotopic Sand Tracer (RIST) field tests are processed through digital computers Data treatment requires computing and plotting the detector position and correcting the corresponding radiation count rates for radioactive decay The field data are recorded on punched paper tape which is then edited and transferred to magnetic tape for input to data reduction programs The navigation data, which are m the form of distances to shore-based microwave responder beacons, are tested for spurious values by comparison with the theoretical maximum travel distances of the survey vehicle between successive fixes The navigation ranges are then converted to rectangular geographical coordinates

Present emphasis is in the development of computer programs to construct a count rate surface from data collected along track lines This technique facilitates machine contouring and enables numerical integration of the count rate surface The ultimate goal is to obtain an estimate of mean direction and volume of littoral transport and a radiation material balance to be used to check the results Several programs required to accomplish these tasks are operating at the Coastal Engineering Research Center (CERC) and the Oak Ridge National Laboratory (ORNL)

Tests were made in CERC's Shore Processes Test Basin witlt wayes approaching the toe of a test beach at a 30-degree angle Beach material was quartz sand with median diameter of 0 22 millimeter which, in most tests, was molded to a 1 on 10 slope before starting a test Long crested waves generated in a constant depth of 2 33 feet traveled over the beach, shoaled and were refracted before breaking near the shoreline The breaking action caused the sand to be transported along the shore in the direction of the longshore component of the wave energy flux Transport rates of 2 to 170 cubic yards per day were measured, with the lower rate within the range of laboratory rates reported by Savage⁽¹⁾ and the higher rate comparable to field rates reported by Watts⁽²⁾ for South Lake Worth Inlet, Florida Analysis includes correlation of the measured rates to the longshore wave energy flux, and in some tests, to the longshore current Transport rates, defined by visual fit curve of the data, are about 3 times the rates indicated by the CERC TR-4 design curve for a longshore energy range of 0 016 to 0 760 millions of foot pounds per foot of shore per day

This work encompasses a study of the littoral regime of a section of the coastline of the city and county of San Francisco, California The study included a complete refraction analyses of all applicable deep water wave directions and periods, the determination of breaker locations, and a computation of alongshore energy and potential littoral transport for seven stations located just offshore along the thirty foot depth contour The waves are refracted from deep water locations to the shoreline using the Stanford Wave Refraction computer program Wave breaking is assumed to take place whenever the computed wave height exceeds 0 78 times the local water depth The effect of limiting the refraction coefficient is explored since the refraction theory, in analogy with its parent theory of geometric optics, fails along caustic curves and predicts unreasonably large values for the refraction coefficient

A sand transfer system that requires no surface impounding area and that can be installed and operated at low cost is proposed The system consists of a hydraulic jet assembly operating from the bottom of a sand crater A jet pump and suction mouth are located at the lowest point of a crater-like depression dredged into the sea floor The crater acts as a gravity-fed sink for sand and other cohesion I ess material, thus serving the dual purpose of a mechanism for collecting sand and a sub-surface impounding area for the accumulation of sand

The title of this paper may sound like a joke Correctly the title ought to be "Determination of Direction of Littoral Drift on the South Coast of Iceland by Geomorphological Approach" In order to check the results of such study based on the movements of river entrances and their geometry the use of an accelerometer buoy to be placed in offshore open waters for collection of wave data combined with the results of meteorological data was discussed Then the volcano Surtsey suddenly emerged from 400 ft depth (Nov 1964) and its huge outpours of volcanic material built up an "offshore pole station", where the shoreline development provided some information which supported conclusions from the shoreline study on the mainland Computation of wave energy input provided further information

The University of Florida has conducted a series of tests to evaluate the effectiveness of beach nourishment from offshore sources by a specially designed drag scraper The field work, over a nine-month study period, included hydrographic surveys, fluorescent sand tracing, and a sand sampling program for two scraper sites at Jupiter Island, Florida

The conclusions provide information as to the effect of the borrow pits and the dredged sand on the beach characteristics, the mechanisms of the filling of the pits, and the efficiency of the drag scraper

Aspects of the Federal beach erosion control project at Virginia Beach, Virginia are described with particular emphasis directed to the sources, characteristics, costs, methods of placement and quantities of material periodically placed on the beach following project inception The beach response to nourishment is analyzed on the basis of yearly survey records compiled from data gathered by the sea-sled direct leveling technique The quantity of annual nourishment material required to maintain present beach dimensions is determined to be approximately 141,000 cubic yards

The construction of an underwater mound of sand for the protection and improvement of Durban's beaches has been recommended on the basis of intensive investigations These investigations included prototype measurements of beach changes as related to recorded sea conditions, basic scaling tests in which these beach changes were reproduced to scale in movable bed models and tests of the proposed underwater mound in models, using different scales in order to eliminate possible scale effects

The test results showed that, provided the shear-settling velocity similarity criterion is satisfied, beach changes can be reproduced in a movable bed model to a reasonable degree of accuracy Optimum dimensions for the cross section of the mound were determined on the basis of the criterion for erosive and non-erosive wave conditions which was derived from the prototype beach profile changes and confirmed by model tests The resulting dimensions are a mound of sand about 4 5 km long, about 1 200 m offshore, reaching to 7 3 m below LWOST, with side slopes of 1 in 25 and a crest width of 61 m

Of the total quantity required (8 000 000 m³ ) some 2 500 000 m³ of sand, available from harbour dredging works in Durban Bay, had been dumped by May, 1970 Model predictions on mound stability and beach improvements were confirmed to a high degree of accuracy by the full scale events

Tests are described m which the effect of artificial seaweed on bed sediment movements due to waves was studied in a model Water velocities near the bed and coal particle velocities on the bed, within the seaweed array, were measured over a range of wave conditions and densities of packing of the seaweed The water velocity measurements were erratic, probably due to additional turbulence caused by the seaweed Coal particle movements on the bed were slowed down in the presence of seaweed

This paper is a continuation of the paper with the same name, presented on the Xlth Conference on Coastal Engineering by the first author [1] , in which a mathematical theory was given about the behaviour of a coast after the construction of a groyne system. Now this paper extends the former paper theoretically and practically.

Results are given of computations with a coastal model in which the coast is schematized to one line (one-line theory) and a model in which the coast is schematized to a beach line and on mshorelme (two-line theory).

The influence of changing wave conditions is investigated.

This paper presents the results of an experimental study on the behaviour of inclined groynes and a short discussion on the optimization of groyne systems It supplements a paper presented at the XI Coastal Engineering Conference (London, 1968) In the present paper both studies are applied to the design of a groyne system looated to the south of the Tagus estuary (near Lisbon)j where a serious erosion has been under way

Laboratory tests are described, in which the effect of impermeable groynes on an eroded beach was studied A beach was allowed to reach equilibrium for a particular wave climate and supply of littoral material The foreshore was then manually eroded, and the beach allowed to return to equilibrium with and without groynes It was found that the presence of groynes increased the rate of accretion but did not significantly build up the inshore beach beyond the stable levels Bed levels seaward of the groynes were increased

Shingle beaches differ from sand beaches mainly in the mode of transport of the material and in the permeability of the beach. The typical beach forms are in consequence different and the typical problems of beach stabilisation require different types of solution.

The mechanism of littoral drift of shingle is controlled predominantly by the action of the breaking wave, on a groyned beach a simple theory is advanced to relate drift to groyne length and spacing.

Longitudinal sorting of shingle sizes is a specially notable sign of a stable beach. Well marked size-sorting transverse to the coastline is a more general characteristic.

Examples of schemes of management are provided for a beach with high littoral drift and a beach which has to te controlled as artificial cells

The accreting shingle beach may in suitable circumstances develop a steep in-shore profile – examplee are given of such.

A comparison of the conditions of similitude for movable bed scale models of rivers and estuaries on one hand, and beaches and shorelines on the other hand, is presented It is demonstrated that despite the fact that the knowledge in sediment transport by wave action is less advanced than in the case of steady current, the conditions of similitude for beaches are less stringent than for rivers In particular, the effect of relative roughness is comparatively unimportant in the case of beaches, while the necessity of similitude of head loss imposes an imperative condition in the case of scale models of rivers An introduction to a natural law of distortion for beaches is presented in analogy with the Lacey condition for rivers

A 1 · 300 vertical, 1 : 100 horizontal scale model of seven miles of coastline, including the major area of the port limits and the inner harbor, was constructed to study combined wave, tide and wind action on transport of sand along the coast.

The effects of three predominant conditions of swell and wind-waves on the state of the ocean front beaches were studied by observing relative changes in shoreline contours. Fluorescentdyed sand tracers were also used in the model. The accumulation and dredging of sand near the harbor entrance was reproduced in the model and various dredging and storage proposals were carried out to scale on the model.

The model study enabled the cause of beach erosion to be attributed to the existence of an offshore shoal produced by the localized dumping of sand dredged from the harbor approaches. This shoal caused selective wave action along the coastline, which was reproduced to scale in the model. It was found that wind and tidal action had a major effect on the redistribution of sand on the beaches as modeled but a minor effect on the permanence of the harbor entrance channel. Apart from the interaction of dredged sand at times being fed to the beaches, the problem of beach erosion could be studied independently of that of harbor silting on the same model. Sand was fed to maintain a state of equilibrium on the southern aooroach beach to the harbor to simulate the littoral sunply.

The northern beach downdrift of the harbor entrance, where the erosion problem existed, was found to be essentially starved of littoral supply, due to maintenance of the harbor entrance by dredging and offshore dunroing.

The requirements of the model study also gave rise to a program of field data collection on the governing environmental factors, which in itself aided considerably to the diagnosis of the causes of the state of unbalance in the shoreline. The model study led to several proposed remedial schemes, certain of which have been adopted since completion of the model study. The model study was conducted by the South African Council for Scientific and Industrial Research, for the South African Railways and the City Council of Durban.

A hydraulic model study was conducted to determine the most feasible means of reducing shoaling into a coastal inlet channel that had been used by loaded Landing Ship Tank (LST) class vessels serving the port of Tan My near Hue, Republic of Vietnam The ultimate objective was to increase the time during which the channel will be open to navigation by improvements in physical configuration

An extensive field data acquisition and analysis program was executed to provide basic information for model prototype correlation This incidentally resulted in the re-evaluation of several empirical formulae being used for prediction of littoral transport and of tidal currents The comprehensive field measurements of shoaling in the channel area also permitted the determination of the scale effects on the quantitative results of sediment deposition in the channel and on the time scale of bottom evolution

The experiments were conducted systematically in three phases The three-dimensional studies for Phase I and II were conducted using a rigid bed, sand or walnut shell covered (1/250 horizontal and 1/50 vertical scale) hydraulic model of a 15 sq mi ocean-estuary land area Periodic long-crested waves tides tide/river induced currents were simulated in the model Phase I covered qualitative evaluation of nine improvement plans, from which a BEST PLAN," an upshore jetty to protect the existing channel, was selected Phase II covered qualitative and quantitative evaluation of four variants of the "BEST PLAN,' from which the most effective and economical variant was determined To insure reliability of quantitative results, comprehensive experiments were conducted using three different sediments (D₅₀ = 0 41 mm and 0 90 mm, γ = 1 35 for two types of ground walnut shells and D₅₀ = 22 mm, γ = 2 65 for sands), and three model scaling criteria (Froude Scaling, "Ideal Velocity" Scaling, and Modified Froude/Ideal Velocity Scaling) Phase HI covered two-dimensional model tests, in a 180 foot flume, of the stability characteristics of the proposed rubble mound type jetty on a movable bed

The major conclusions of this study include (1) the jetty, as postulated in the BEST PLAN,' would reduce annual maintenance dredging requirements by 74 to 84 percent, (2) a systematic three phase model study such as used in this investigation is most feasible (from a time-consumption viewpoint, use of light weight materials such as ground walnut shells may be more economical than use of natural sands as model material), and (3) use of theory alone in predicting a tune scale for bottom evolution should be approached with caution especially where field data are not readily available

This paper is a factual account of studies carried out for the design of a new deep water harbour As so often happens construction work had to be begun before many of the conclusions of the study were available so that alterations to the initial designs had to be made while work progressed The studies comprised tidal and wave recordings and analysis, model studies to determine residual wave conditions at the quays, studies to determine the extent of littoral drift, the effect of the proposed works upon this and possible measures to counter downdrift erosion In addition studies were made of the stability of the adjacent creek channel which had previously been the harbour and a mathematical model study was carried out of the effects on the creek regime of various proposed entrance works including the construction of an entirely new creek entrance channel through the new deep water harbour

The New England Division of the United States Army Corps of Engineers has created and improved many harbors along the New England coast for the benefit of commercial fishing and recreational boating fleets A harbor, to be effective, must provide a protected area for boats and it must have a safe access, that is, a protected and stabilized tidal inlet A coastal inlet has been defined as a waterway connecting a bay, lagoon or similar body of water with a larger body of water The major engineering problems encountered in the development of harbors have involved stabilization of these inlets The problems have been caused by excessive littoral drift resulting from erosion of the shorefront adjacent to the inlets by wave attack Planning, designing, constructing, and modifying these inlets under very dynamic conditions is complex and difficult Each inlet is unique This paper discusses very briefly some of the problems encountered

Offset coastal inlets are common on the coasts of New England and the northern Gulf of Alaska In both areas, the dominant waves approach the shore at an oblique angle, resulting in a strong net littoral drift The most common type of offset on these coasts is a downdnft offset (i e, the downdnft side of the inlet protrudes further seaward than the updnft side) Wave refraction around the ebb-tidal deltas at the inlets is an important process in the formation of the downdnft offsets, inasmuch as it creates a local reversal in drift direction just downdnft of the inlet, and allows sediment to accumulate there Associated with the offset appears to be a segregation of tidal current flow in the inlets, with the ebb flow being more channelized than the flood

The type of inlet offset at any one location can vary through time Studies of the changes at the Hampton Harbor, New Hampshire, inlet from 1776 to the present show two reversals from updnft to downdnft offsets during that interval

The inlet bathymetry was mapped by standard photogrammetric techniques after photographing the bottom directly through the water column The channel bottom is bare beachrock or is floored with bioclastic sands and gravels (S G = 284)

A nine-day time series of observations of current speed and direction, and water temperature and salinity was obtained at two depths at each of eight stations using tripod-mounted, telemetering sensor packages Twelve-to-l8-mmute pulsations in the flow were often observed Spectral analysis of near-surface current speeds shows significant peaks at 2 4, 3 2, 4 3, 6 7, and 12 3 hrs

Evolution of sand ripples and dunes was monitored over a 200-ft distance during one tidal cycle The pattern of growth illustrates the differences m bedform geometry which may be expected to influence friction coefficients Evidence is presented for a bottom jet that is induced by flow over the crests of sand waves

Tracer sand, sorted into two size groups and color-coded for identification, was released on a flood current Sampling of color-coded tracer sand was conducted by divers using strips of grease-coated plastic tape Spatial distribution of tracers in relation to the bedforms, and the importance to gram erosion of a natural mucoid coating, are noted

The reaction of shores adjacent to salient features which interrupt alongshore processes has long been recognized as an important consideration in connection with the investigation of engineering works to be undertaken on shores characterized by a littoral drift regimen Particular emphasis has been placed on the evaluation of shore changes related to major control structures at navigation entrances, however, manmade interruptions of small scope, which initially appear innocuous, can produce costly damage to the adjacent shores located on the downdrlft side of the interruption

The town of Carolina Beach, a seaside resort on the Atlantic Ocean in southeastern North Carolina, is a classic example of an area experiencing inordinate and costly erosion associated with an initially small manmade interruption on the updrift shore In 1952, local boating interests excavated a channel through the updrift barrier beach to connect the Atlantic Ocean and a lagoonal area traversed by the Atlantic Intracoastal Waterway The channel, located 8,000 feet north of the Carolina Beach town limits, soon developed into a small, permanent coastal inlet having a width of approximately 550 feet and a depth of 15 feet In the ensuing 17-year period, 1952-1969, this inlet entrapped over 4 million cubic yards of littoral material, resulting in a concomitant downdrift erosion which progressed southward to the town of Carolina Beach A protective beach fill placed along the town's ocean front in 1965 has suffered considerable erosion damage

This paper develops and quantifies the cause and effect relationships of the problem generally in terms of the alongshore processes and, in so doing, also furnishes basic information in regard to the performance of the largescale artificial beach fill placed along the ocean front of Carolina Beach in 1965

Rio Grande harbour is situated inside the outlet of Lagoa dos Patos (9 910 km2) and Lagoa Mirim (3 770 km2). Most of the rivers in the State of Rio Grande do Sul, that are not tributaries of river Uruguay, flow into the two lagoons and the latter discharge through Canal do Norte into a tideless sea. Flood flows can exceed 20 000 cumecs. The outlet is on a sandy coast with littoral drift in both shoreline directions.

The time history of the outlet can be divided into three periods. Before breakwater construction, the bar was extremely unstable in lay-out, position and controlling depth. The latter ranged from 2.5 to 7 m. From 1911 to 1916 two 4 km long rubble mound breakwaters were built. They deepened the entrance channel to 8 – 10 m but a new bar came about further offshore entailing objectionable navigation conditions in the approach channel. No previous dredging was carried out as the breakwater construction proceeded out to sea, and as result a total of Ik million cubic metres was scoured out between the two breakwaters and discharged offshore to build up the new bar. Some improvement by dredging was not achieved until 1962.

The improvement of the approach channel lay-out as well as deepening the entrance to 14 m below datum are under consideration. Field and model investigations have been designed for this purpose.

A vertical circular cylinder to simulate a pile was installed in the Texas A&M Hydrodynamics Lab two dimensional wave tank along with a built up section containing a horizontal bed of fine sand This was subjected to monochromatic waves of differing characteristics and conditions for mcipi ent motion were observed for each of three sands Also, the magnitude and pattern of ultimate scour and the time interval required to reach this state were measured for six different conditions of wave steepness and relative depth

These results were related to influential parameters, including wave, pile and sediment character istics, and developed by dimensional analysis with consideration of the literature pertaining to past work on the movement of sediment by oscillatory flow Conclusions regarding the critical flow velocity for incipient motion, the effect of the above parameters on incipient motion and ultimate scour depth, the time required tor maximum scour, the significance of eddies generated by the pile, and the catalytic action of the pile in causing the initiation of scour are presented

The above conclusions are also generally discussed in light of the difficulties involved in extend ing the results to prototype conditions

Artificial or natural barriers may be divided into two classes, those from which waves are reflected and those on which waves break In general, any intermediate type that gives a combination of reflection and breaking may set up severe erosive action of the beach m front of barriers When the reflected waves are superimposed on the incident waves a stationary spatial envelope of the combined incident and reflected waves is produced Previous laboratory studies indicated that the crests of the sand bed appear fairly closely under the nodes of the envelope and troughs of the scoured sand bed under the loops of the envelope The predominant scouring pattern had a spacing between crests equal to one-half the wave length

Other studies by Keulegan and Shepard established characteristic parameters for bar and trough depth for laboratory conditions and for several field locations Their studies were compared with beach profiles taken along the Texas Gulf Coast

Relationships between (a) scour depth and sand crest wave length, (b) between trough depth and sand bar depth and between wave characteristics and beach scour were established for selected locations along the Texas Coast

The investigation reported herein covers two aspects of equilibrium beach profiles, namely, (a) the criterion governing their type and (b) their reflection characteristics The problems are first analysed from dimensional considerations and then studied experimentally in laboratory wave flumes using different sizes of quartz, ground walnut shell and ground plastic as movable bed material. Empirical relations between pertinent parameters governing the beach process are given.

Stochastic prediction of beach changes by means of a linear leastsquares transfer function requires a knowledge of power spectra Since most field data are too short to ensure stable analysis, an attempt was made to generate data artifically by a Monte Carlo simulation A beach profile transition model which considers the beach profile as a dynamic system allows beach width, sediment storage, and surface configuration to be determined m successive profiles and simulates beach cycles associated with random waves which are in sufficient agreement with the actual observation The simulated data are amenable to standard stochastic analysis to yield power spectra, cross spectra, coherence functions, and phase lags Comparison of the results with those derived from actual data shows reasonable agreement It appears that the process of beach sediment storage involves a combination of classes of Markov Gaussian random processes, whereas that of beach width resembles a white noise Coupling between these two parameters occurs in the lower frequency range with periodicities longer than about 8 days Moreover, the beach width shows phase advance before sediment storage Although the beach profile transition model requires further refinement, especially m regard to quantitative response to waves of various magnitudes and characteristics, the basic concept of the model is sound and will probably explain beach changes in various types of world coasts

Beach profile observations and sediment sampling were carried out for six months at frequent intervals to study the seasonal changes of the beach. Iht study is helpful in bringing out the qualitative and quantitative changes of the beach under varying wave and tide conditions. Useful information is obtained and presented regarding i) the maximum rate of erosion ii) the total quantity of material eroded iii) the critical wave steepness values which changed from depositing to eroding nature and iv) the sediment characteristics of the beach.

Five bottom surveys over a period of a year were made in the north portion of Bolmas Bay, California Comparisons between successive surveys permitted an evaluation of the areas and depths of scour and fill with the seasons and were correlated with littoral current measurements Data for a 22-year period also were available on the position of the mean high-tide line over a limited length of beach These data showed a cyclic variation of the position of the high-tide line with the season with the most variation from year to year occurring during the spring months

Grain size and heavy mineral analyses of 6 cliff, 12 beach, and 44 marine sediment and rock samples from Bolmas Bay and its surrounding drainage area were done as part of a long term study of sediment transport on the continental shelf off Central California

Sediments in the bay are predominately very fine sands Some samples, particularly adjacent to Duxbury Reef on the west, have a coarse sand to pebble component The primary mode of the marine samples is in the range 088 to 125 mm, whereas, the primary mode for beach material is from 175 to 25 mm The range of median diameters of the marine samples is from 07 to 14 mm The median diameters show a trend of decreasing grain size seaward parallel to the depth contours except opposite the entrance to Bolmas Lagoon where a tongue of relatively coarser material cuts across the depth contours The range of other statistical parameters are (1) sorting coefficient 1 10 to 1 41, (2) skewness 0 83 to 1 18, and (3) kurtosis 0 15 to 0 32

Our sediment studies indicate

In order to establish the mechanics of sand transport in an air or water stream, the mechanics of saltation of sand grains should first be considered In sand storms, most of the saltating sand grains on a granular bed have successively continued the saltation motion In this paper, such a saltation motion is defined as successive saltation A theoretical approach to the saltation of a single sand grain on a fixed granular bed is proposed on the basis of the equations of motion for the saltation and the dynamic characteristics of collision between a saltating sand grain and bed sand grains Some experiments of the successive saltation of a single sand gram on a fixed granular bed were carried out to compare with the theoretical relationships It was verified from the comparison that the theoretical relationships of the height and distance of saltation of a sand gram are in fairly good agreement m substance with the results of experiment

In the recent decade, very wide areas of sea where the depths of water are from several meters to ten meters or more during storms have been reclaimed for industrial firms and port facilities in many places in Japan As the incident wave energy in such cases is very large at the sea-walls, the protection of the reclaimed lands from wave overtopping by the conventional sea-walls of vertical type or composite-slope and-berm type is generally impossible from an economical point of view In Japan a special type of sea-wall, which is of such a type that a rubble-mound covered with specially shaped precast concrete armor blocks is built in front of the sea-wall to absorb most of the incident wave energy, has been constructed to protect the reclaimed lands from wave overtopping Most of the seawalls have been proved satisfactory after passing of typhoons over or near the sea-walls The design of the sea-walls is presented here in by showing the comparisons between the experiments and prototypes during typhoons

This paper is concerned with the study of the breaking wave pressure exerted upon the breakwater of the vertical type. The method of calculation of the wave pressure, named the quasistatical method, is based with the theory of the impact of the water jet en the vertical plane and some new results of the experimental data.

The formulas for the calculation of the pressure distribution of the breaking wave and the surf wave on the vertical wall are given.

Laboratory tests were made on a 6-inch diameter semi-cylindrical tube simulating a prototype concrete structure designed to be placed parallel to the coastline in the surf zone to intercept offshore transport of beach materials and thus preserving the beach The model beach was of fixed bed type with a slope of 1 to 15 The crest elevation of the tube was set at the still water level for most of the test runs and the sloping beach intersected a flat channel bottom at a depth of 20 75"

Through scale-model tests, the forces, moments, and the pressure distributions, including impact pressures, were determined for large diameter piers extending through large-amplitude wave system in which current strengths vary Tests were performed at 1/100 scale, simulating piers of the bridge for the Northumberland Strait Crossing, Canada These piers are partially cylindrical with a base diameter of 100 feet Close to the surface, where the wave action is greatest, they are conical Waves up to 25 feet and current up to 4 knots have been reproduced m the laboratory, according to Froude similitude The tests results fully support the known concept that, when the pier diameter is large in comparison with the wave length, mertial force becomes dominant Generally, the presence of current, either with or against the wave tram, results in a decreasing wave force Semiempirical relations were developed for force predictions that require the experimental determination of a singular coefficient

Experiments with the use of long sand-filled flexible plastic tubes ("Sand sausages") have been carried out for coastal protection purposes at several exposed locations along the Danish coasts since 196T In general the results have been encouraging

Several methods have been used to fill the tubes with sand A simple inexpensive hydraulic method for easy filling of almost impermeable tubes on site has been developed by model and prototype experiments with promising results

As a result of the experiments it seems likely that sand-filled tubes may be used with advantage as temporary structures, 1 e for full-scale pilot investigations and to solve acute problems, or they may be incorporated in more permanent structures

Wave action to breakwater and quay wall by fixed horizontal plates as shown in fig 4 and 5 are studied theoretically and experimentally Transmission and reflection coefficients for breakwater are calculated as shown m Fig 6(a)(b), which suggest that only fixing the water surface by rigid plate is effective to reduce the transmitted waves for appropriate wave conditions Pressure distributions to plates are calculated as shown in Fig 7 and total pressures are in Fig 8 Pressure distributions to norizontal plate and vertical wall of quay wall are shown in Fig 9 and 10, which show that the plate makes the pressure distribution to vertical wall more uniform than the one without plate and also submerged plates of breakwater and quay wall make the pressure distributions smooth

Wave action m case when the region under plates is filled by permeable material are also calculated The results suggest that the void of the material has the effect to elongate the plate and the fluid resistance acts as wave energy absorber

Test data related to the stability of dumped quarry stone riprap under wave action is presented The tests were conducted in the large 635-foot wave tank at the Coastal Engineering Research Center at near prototype scale The data indicate that the stability of the riprap is strongly influenced by the type of breaker The lowest riprap stability is associated with a breaker type intermediate between plunging and surging, sometimes referred to as a collapsing breaker

In this paper experimental data are given to aid in the design of a rubble-mound breakwater The use of armor damage functions is supported rather than the use of the wave height for the no damage condition Damage curves defined experimentally are proposed, for both rocks and tetrapods, for different wave storm durations and for different placing tech niques

A determinant influence of storm duration is found for advanced damage of the armor layers

The experiments with different placing techniques showed that stability coefficients based upon the no damage criteria, do not give a reliable picture of the ultimace strength of a rubble-mound breakwater

Theoretical analysis and experiments are made to clarify the mechanism of reducing the wave energy by the block structures In order to express the hydraulic reistance of three different kinds of blocks, three different models are proposed The hydraulic radius and the porosity of the block structures are essentially important factors m the expression of the hydraulic characteristics of the block structures

It is recommended, from experimental results, to carry out the hydraulic experiments by using blocks heavier than at least 500 gr

Resistance coefficients obtained in the steady and oscillatory flows show almost no difference

Criteria for design of a wave barrier to protect the proposed Honolulu International Airport Reef Runway from breaking waves were developed in wave flume model tests Structures with tribar and quarrystone armor units placed in single and multiple layers, on homogeneous and composite slopes, were subjected to both overtopping and non-overtopping breaking waves Data on wave runup, armor unit stability, quantities of overtopping water, and transmitted wave heights were obtained using a 1 50 bottom slope, which modeled the irregular coral bathymetry seaward of the proposed structure The model to prototype scale ratios ranged from 1 5 to 1 35

Model Tests indicated that the weight of armor units placed below one-third the water depth may be three-fourths that of the units located near the water surface It was noted that the maximum wave runup was 1 8 times the water depth fronting the structure Data were obtained concerning quantities of overtopping water and transmitted wave heights over the low barriers The study augments available criteria for economical design of structures subjected to breaking waves

The concept of multiple use of reservoirs is resulting in the construction of marinas for recreational boating requiring breakwaters that can function for a large range of water levels A typical set of design criteria is an average water depth of 20 to 25 feet, wave lengths from S to 60 feet (wave periods of from 1 to 4 seconds) and wave heights from ½ to 5 feet Calculations based on Bulson's results showed a pneumatic breakwater to be too expensive An extensive literature search revealed that floating structures based upon the concepts of large effective mass or moment of inertia resulting from "entrained" water, or structures which can dissipate energy might be more effective than one of the floating bag types of breakwaters Several new-types of moored floating structures which combined two or more of the concepts mentioned above were tested in a wave tank, and several of the devices appear to have merit in that they were reasonably small compared with the longest design wave length and could reduce the highest design incident wave height to less than one foot, prototype, in the lee of the breakwater

In this paper the resonance of a moored object in wave trains is discussed and demonstrated with the help of some results obtained from model tests with a right angled barge The measured results correspond well with a simple theory which calculates the slowly varying drifting force of regular wave trains.

The added mass and damping coefficients for semi- and fully-submerged twin cylinders in vertical motion are determined as functions of the oscillation frequency, the cylinder spacing ratio, and the cylinder submergence ratio It has been found that resonance may occur in particular combinations of cylinder spacing and oscillation frequency at which the hydrodynamic mertial and damping characteristics deviate from the trend curves for the case of a single cylinder Justification of using the two-dimensional results to calculate motions of threedimensional twin-hull vessels is discussed It is suggested that, by means of strip theory approach, these results can be used to estimate the hydrodynamic forces for catamaran type vessels in pitch and heave motions

The unsteady-state response of a slender body in nonlinear shallowwater wave environment was studied Numerical scheme has been developed which permits rapid calculation of the following, which describe the motion of an arbitrarily shaped body in three degrees of freedom anywhere within such an environment

Sample calculations are given for a typical submersible Results are expressed in generalized parameters, defining the circumstances wherein various displacements, velocities, accelerations, etc , would occur

Coastal Louisiana wetlands are a product of Mississippi River delta building that has occurred over a period of 5,000 years The building process was a gradual one, for riverine and marine processes were very nearly balanced In modern times man's use of the area (flood control, navigation improvement, exploitation of petroleum and other minerals, road building, etc ) has seriously altered the natural balance As a result, overbank flooding has been virtually eliminated and river flow is confined to channels discharging into the outer shelf area Most transported sediment is now deposited in the deep Gulf of Mexico or along the continental shelf Saltwater encroachment in the deltaic estuaries has been detrimental to fauna and flora Even though considerable sediment deposition has resulted from the historic Atchafalaya River diversion and growth of subdeltas, comparative map studies indicate a net land loss rate of 16 5 miles²/year during the last 25 to 30 years Land loss is only one symptom of general environmental deterioration

A dynamic management plan is proposed for better utilization of combined freshwater discharge – dissolved solid and transported sediment input from the Mississippi River Controlled flow into estuaries will reduce salinity encroachment and supply badly needed nutrients Large areas of new marshland and estuarme habitat can be built by controlled subdelta diversion Studies of natural subdeltas indicate that these systems are amenable to environmental management, salinities and sediment deposition may be manipulated to enhance desired conditions

Tidal computations, wave studies, refraction computations, and morphological studies are discussed and practical results are mentioned Theoretical investigations on refraction computations, in particular the accuracy, are dealt with in detail, because difficulties occurred in the practical applications A former study of Morra, based on Kalinske's work on sand transport,has also been discussed in some detail in the section on morphological studies

Sediment pollution can be defined as the increase in sediment concentration, due to artificial infusion of sediment, to a level harmful to fish and plant life

The coastal engineer may be called upon to evaluate the result of an artificial sediment influx in terms of characteristic parameters like concentration and turbidity and to determine eventual deposition areas of the sediment

This paper describes the field investigations carried out to evaluate a case of sediment infusion in one of the estuaries on the U S east coast The sediment was discharged via a pipeline at a rate of approximately 10 lbs/sec Nearly all the released sediment was in the silt range In addition to the results of the field measurements a simple mathematical model is presented, describing the temporal and spatial distribution of the sediment in the resulting sediment plume

A theoretical model is presented to provide an approximation of the water and temperature recirculation in a shallow bay, lake or river, between the outlet and inlet canals of the cooling system for a power plant In particular, a temperature recirculation factor relating the outlet and inlet temperatures is derived

A mathematical model of New Haven Harbor, a shallow embayment with approximately 8 square nautical miles of water surface within boundaries established by Long Island Sound and the mouths of the Quinnipiac, West and Mill Rivers, has been developed. The Harbor has extensive tidal flats and dredged channels which help to produce large lateral variations of velocity and mixing over a tidal cycle.

In order to adequately consider these lateral variations, a two-dimensional model of mixing, dispersion, pollutant reactions, and reaeration is made by linking together 28 segments of the Harbor, using a series of mass-balance equations. Mixing, or dispersion, is a complex function of reversing tidal currents, salinity-induced circulation patterns, fresh-water inflow, and the physical boundaries of the Harbor. Field measurements of salinity, dissolved oxygen, BOD, and tidal and hydraulic factors are used, in conjunction with laboratory studies, to evaluate coefficients and rate constants for the model. The linked system of equations is solved by matrix inversion procedures on a large computer.

After verification, the model was used to predict the effect of treatment levels, outfall locations, and hydrologic parameters on oxygen levels and water quality m the Harbor. An important aspect of the work is that it presents a rational evaluation of estuarine water quality as a function of tidal mixing, outfall location, and the degree of BOD removal by proposed treatment plants, rather than the acceptance of arbitrary treatment standards.

In south central Louisiana non-reactive liquid effluents are introduced into man-made relatively straight prismatic canals which are comparatively narrow and have brackish water To study the flushing pattern of liquid effluents introduced into those canals (or estuaries), a one-dimensional numerical model is considered for a simplified system consisting of a long straight gently sloping reach with a sinusoidal tidal variation at the mouth of the estuary, sinusoidal tidal variation with a phase lag and an attenuated amplitude at the upstream end, a variable inflow hydrograph, and a variable inflow or outflow. For this system, the continuity and momentum equations are solved numerically by an explicit finite difference scheme. The output of the model describes the spatial and temporal variations in flow velocity (also in water depth and discharge) from which the flushing pattern is obtained for a liquid effluent introduced at any time during the tidal cycle at any section along the estuary. The numerical model is applied to Charenton drainage canal in south central Louisiana and good agreement is obtained between the velocities and stage elevations predicted from the model and recorded in the field. An IBM 360/65 computer is utilized.

A drag-sphere water current meter with a 0 to 6 ft/sec range has been developed for velocity measurements of relatively steady flows A two-component strain-gage type force transducer is mounted within a 3 7-inch-diameter perforated drag sphere Drag force measurements are related to the flow velocity around the meter Several drag sphere configurations were tested in selecting the 336-hole pattern

Frequency response data have been recorded and evaluation tests were made with current meters deployed in an estuary Use of these current meters in studies of steady-state fluid processes and sediment responses is feasible They are simple, relatively inexpensive, and well suited to applications where several simultaneous measurements are needed to determine velocity profiles or map flow distributions

Communication Between such coastal resipients of waste water as Days and fjords and the ocean is often through an outlet of small cross section

The combined effects of a topography with transverse ridges and a brackish surface layer creates a rather stagnant body of water. The ridge or stil deflects the tidal currents away from the bottom so that only the upper part of the water column is continually flushed Tne stability of the pycnocline prevents surface-generated turbulence from penetrating downwards, so the turbulence in the deep pool is weak.

A scheme has been proposed to store the nutrients of sewage outfalls behind the sill at Drødak in the Osloflord The storage capability of that flora was estimated for a conservative outfall constituent by means of a one dimensional dispersion equation From the analysis the gains of deep outfalls through diffusors compared with surface outfalls can be estimated for various periods between deep water inflows, which are observed to occur.

The present work describes the derivation of equations which can represent the vertical distribution of sediment in a well mixed tidal estuary The starting point for the analysis is the two dimensional longitudinal equation of motion, including the longitudinal salinity gradient term Equations are given which represent a steady state sediment profile and it is shown that these are similar to the expression used in urn-directional flow e g Rouse's equation

It is argued that the derived equations could be applied to a real estuary, subject to certain restrictions on sediment size and estuary type

An application of the theoretical equations to the Mersey Estuary indicates reasonable agreement between observed and predicted sediment quantities for medium and coarse sand particles Agreement is shown to be worst for fine grained sediments and it is concluded that much better results can be obtained by using the non-steady one dimensional sediment distribution equation in discrete steps throughout the tidal cycle

A laser velocimeter has been used to measure particle velocities in a turbulent suspension in open channel flow.

Both mean and fluctuating velocity components can be determined and the system may also be used to give records of instantaneous fluid velocities.

The paper describes a study of density-currents in locks where there is a net inflow of water into the dock The velocity profiles occurring are different than might be expected by simply superimposing the net flow onto a normal density-current profile The differences are shown to be due to the non-uniform salinity profiles occurring in the docks and a semi-theoretical study is presented which illustrates the importance of this salinity profile

The accretion in the docks is explained by the transport of material into the docks during the levelling period The quantitative agreement between estimates based on measurements during the levelling period and the dredged quantities from the dock are good The locking operation is also shown to be an important factor in certain cases

An attempt to describe the flow of silt into the dock using the one-dimensional diffusion equation has shown that allowance must be made for the pick up of silt off the bed of the lock and the settling of silt (as the velocities drop) if quantitative agreement is to be obtained

From knowledge of wind resistance coefficients measured over the sea, it is possible to compute the shear stress of a wind field on its surface Where a body of water is relatively shallow, such a shear stress will transport water to the downwind end and so create a high water level or surge Graphs are presented for ready application of the relevant formulae to cases of lakes and Continental Shelves The wind fields of either uniform or triangular horizontal distribution in velocity are included, as well as conditions of stationary or moving fetches Surges from seven typhoons travelling towards Hong Kong are computed and compared to actual records

High water associated with a hurricane is an important design parameter in coastal engineering Long range rational predictions can be made on the basis of Gumbel's theory of extremes and Wemelsfelder's theory respectively Fundamentals and underlying assumptions of the two theories are investigated and predictions are made for Breakwater Harbor, Lewes, Delaware, and Atlantic City, New Jersey Gumbel's theory is found satisfactory according to a criterion A crucial point, the ground rule of counting exceedances, is found to be vague in Wemelsfelder's method The ground rule must be made definite in a meaningful prediction

To establish design data, a study was undertaken to determine expected hurricane tide elevations, durations and frequencies of occurrence for events of various magnitudes in the vicinity of a proposed development at Padre Island, Texas A set of synthetic hurricanes with selected sizes, translation speeds, wind fields, and pressure patterns were generated corresponding to various frequencies of occurrence of the CPI Two numerical computer models were developed to determine the offshore surge hydrograph and to route the surge through the bay waters for each synthetic hurricane moving directly over the site

Results included storm tide hydrographs at selected locations near the development Synthetic storms were also routed across the coast at locations north and south of the site and storm hydrographs again computed

Wind and current meter records taken during the passage of a hurricane were subjected to time series analysis Filtering techniques isolated the speed fluctuations in the 10-60 CPH frequency band These turbulent fluctuations proved to follow the Gaussian distribution for both wind and current With the passage of the storm front the turbulence intensity of the wind actually decreased, while, on the other hand, the turbulence intensity of the current rose to extremely large values, even exceeding 27 percent of the mean flow speed

Three phases of the storm were examined separately, and the energy density of the wind varied with the -1 power of the frequency in all phases With respect to the energy density of the current, a -1 power dependency on the frequency was approximated by the first two phases, whereas in the third phase, which was the most intense, the energy density varied approximately as the -0 5 power of the frequency The characteristics of the spectra indicate that there is little direct transfer of energy from the wind to the current in the frequency range studied Energy is passing into the 10-60 CPH band of the current from still lower frequencies

A 12 4 mile beach erosion control and hurricane flood protection project includes Jamaica Bay and the Rockaway Inlet in the southwest corner of Long Island, New York The project would provide 6 1 miles of beach fill and floodwalls along the Atlantic Ocean shore and 6 3 miles of inland structures to tie back to high ground, including a 0 9 mile barrier across the inlet The barrier, with a 300 foot gated opening and a 300 foot ungated opening, would permit suppression of the design hurricane surge so as to eliminate the need of flood protection works within the bay Linear mathematical models were used to determine these openings Because of the limitation of these models to produce adequate data m the bay pertinent to environmental and ecological considerations, three hydraulic models were utilized General conclusions drawn from the hydraulic model test data are that the results of the mathematical models were upheld, a design storm with high peak is critical for determining the height of protection, a design storm with high volume rather than high peak plus rainfall runoff is critical in determining ungated openings and suppression of bay levels, and there is a combination of gated and ungated openings that would meet the flood protection, navigation, environmental and ecological objectives

For the city and harbour of Kochi, including Urado Bay, facing the Pacific Ocean, an experimental study has been carried out on the problem of protection from tsunami disasters, and future harbour planning; that is, dredging, reclamation and construction of breakwaters against tsunamis. A hydraulic model of horizontal scale 1/250 and vertical 1/100 was used according to Froud's similitude. The transformation of the design tsunami in the hay was studied to find the effect of the tsunami breakwaters, dredging and reclamations by use of the model which was able to reproduce the Chilean Tsunami.

A unique laboratory facility to generate waves by impulsive movements of the bottom of a wave tank is described and examples of the wave forms which result are shown An analytical model is presented for the case of rapid bottom movements which describes, in a qualitative way, certain features of the experiments

Marigrams from various field stations for the tsunamis from the Chilean earthquake of I960 and the Alaskan earthquake of 1964 have been analyzed using spectral analysis techniques to determine the harmonic components of these records Comparisons are made between the spectra of the two tsunamis at each of several locations

The head loss at breakwater opening is an important factor for evaluating the effect of breakwaters against tsunami. This paper examines the coefficient of the head loss term in the equation of motion by comparing the results of numerical calculations with the actual record observed in the Port of Ofunato at the time of 1968 tsunami. Numerical calculations are repeated changing the head loss coefficient from zero to 3.0 with the interval of 0,5. The calculated water level variation is quite different from the record if no head loss is taken into consideration. Although the most suitable value of the coefficient is not definitely determined, the value of 1.5, which has been adopted in our previous calculations, seems to be reasonable for practical purpose.

An investigation of tidal waves in schematic estuaries has been carried out simultaneously for hydraulic and hydrodynamic-numerical (HN) models Thereby a far-reaching agreement of results is obtained for geometrically simple shapes. In these cases hydraulic investigations can be replaced equivalently by HN-computations.

Along gently sloping coasts of seas having rotary tidal currents, the symmetry of the rotary current is interrupted where the water is shallow As a result, residual counter currents are formed The dynamics of such a current system are described based on current measurements in the Elbe Estuary (southeastern North Sea) The residual currents of this area result in the movement of bottom sediment and are most likely responsible for a series of similar appearing morphologic features.

A theory is presented for analyzing the wave induced oscillations in an arbitrary shape harbor with constant depth which is connected to the open-sea The solution is formulated as an integral equation which is then approximated by a matrix equation The final solution is obtained by equating, at the harbor entrance the wave amplitude and its normal derivative obtained from the solutions for the regions outside and inside the harbor

The results of experiments conducted using a harbor model of the East and West Basins of Long Beach Harbor (Long Beach, California) are presented and compared to the theory Good agreement has been found between the theory and experiments

An outline is given of methods devised recently "by the author to predict the spectral response of rectangular resonators, and to improve the response of resonators generally A simple small scale acoustic model of the ocean-resonator-harbor configuration was developed and is described The acoustic "ocean" is effectively decoupled from the rest of the system by means of sound absorbent material placed along the "infinite" boundaries, and standard audio-frequency equipment is used The results demonstrate that the open end contraction for rectangular resonators may not differ significantly from the contraction for resonators of similar geometry placed in a semi-infinite (or effectively decoupled) wave channel, at least if the wavelengths are not smaller than the width of the harbor entrance channel

A pair of ducted impeller current meters, one mounted vertically and the other horizontally, were used to measure wave action at San Nicolas Harbor, Peru The horizontal water velocity records are superior to conventional wave records because they measure directly the wave property which induces adverse horizontal ship motion, and provide directional wave data Spectral analysis methods proved well-suited to detailed interpretation of the particle velocity records, while considerable insight into the wave phenomena was gained by simple, rational inspections and interpretations of the records Time-lapse movies of a moored ship, when correlated with simultaneous water particle velocity records, provided an exceptionally clear picture of ship response to wave action, and led to the rather surprising observation that long-period ship motion is not necessarily caused by long-period waves The foregoing ship response was duplicated in hydraulic model tests

A method is proposed to investigate periodic tidal motion in single or multiple basins connected to the ocean by an inlet Non-sinusoidal tidal motion in the ocean and square friction law in the inlet are both considered The method is applied to Boca Raton inlet, Florida The calculated tidal elevation and velocity in the inlet are found to be in reasonable agreement with measured values The bottom shear friction coefficient is defined $${\text{T}}_{\text{to}}=\rho \text{r}\text{u}\left|\text{u}\right|$$ where ρ is the water density, T_to. IS the shear stress, and u is the average velocity in the inlet The results of the study yield r = 0 0039, and predict net transport of sediment into the bay

In this paper are studied the surface oscillations that form in a water tank when a jet emerges from the bottom

The experimental system consisted of a circular water tank with the water intake at the bottom close to its circumference Surface oscillations were recorded for different situations

The experimental results are presented in both dimensional and dimensionless plottings where the oscillations amplitud is related with water depth and jet diameter and velocity

The dimensionless graphs show that the oscillation amplification is, within the variables ranges studied, mostly independent of tank diameter

In conjunction with routine hydrographic surveys at Santa Cruz Harbor, California, bottom elevation discrepancies were observed which were not associated with positional errors It was suspected that these errors were associated with long period wave activity, common at this particular location on the Pacific Coast

The existing practice for obtaining hydrographic soundings is by use of floating craft using either echo sounding techniques or a "lead line " Both of the above techniques utilize the instantaneous water surface at the survey boat as a datum reference Normally the water surface elevation is determined by use of a water level recorder

Based on the analysis of 50 repetitions of a well monumented cross section in Santa Cruz Harbor, it was concluded that long period waves affect the results of hydrographic surveys by slowly varying the datum plane In the case of Santa Cruz Harbor, the maximum error due to this effect would be about ± 1 5 feet

Selection of sites for the diked disposal of 100 million cubic yards of spoil dredged from Baltimore Harbor presented a formidable problem Fifty percent of this spoil will be derived from harbor improvement in the next ten years The remainder will result from maintenance dredging and some private dredging over a 20 to 25 year period

The number of sites available for diked disposal areas, the various methods used for dredging and the fact that the dike material required transportation to site gave rise to a number of variables The decision making process was facilitated by an econometric model

Concentrations of metals such as chromium, cadium, zinc, lead, and copper have been found in the sediments of Chesapeake Bay An investigation as to the mode of their occurrence in the material to be dredged was made to appraise any possibility of toxic concentrations occurring in filter feeders such as oysters for shellfish constitute a sizeable industry in the Chesapeake Bay

Stabilization of the deposited dredged spoil was investigated m order to determine whether the unstable loosely-deposited fine gram material extending over a three to five square mile area could be economically converted to a firm foundation material suitable for industrial parks, harbor terminals or water-oriented parks