Coastal Engineering 1968

Waves were recorded for nine years at Camp Pendleton, California, and the results of an analysis of records over two years are presented in this paper.

This paper gives details of the wave studies associated with the reconstruction of Benghazi Harbour, from the early forecasts, the installation of a recording instrument, its failures and repairs, to forecasts based on more recent techniques and subsequent analysis and presentation of results of records taken from 1961 to 1965. Conclusions have been drawn and some suggestions for future consideration have been given.

The paper deals with comparative measurements of irregular model waves by a pressure type wave gauge and a continuous wire wave gauge. For the depth and wave conditions used in the study it is concluded that the height of individual waves obtained by a pressure type gauge and using the first order wave theory may be in considerable error, while wave height distributions and wave spectra are fairly good estimated.

Wind-wave characteristics were recorded in the laboratory for the primary purposes of (a) analysis of the probability distribution of wave height and wave period with wind speed, water depth, and fetch length as major parameters, and (b) comparison of the test results with existing theory and empirical formulae.

An important aspect of this study was to test the validity of the Tucker and Draper method (Draper, 1966) for the presentation of ocean wave data as applicable to wave-data analysis for simulated wind waves. It was interesting to note that some corrections were necessary when the method proposed by Draper at the 10th Coastal Engineering Conference was used for analyzing waves generated in the laboratory. Approximately a positive 20% correction was necessary for this study in which the wave spectra distribution is of very narrow range, the wave width parameter ε$=\sqrt{1-{({\text{T}}_{\text{c}}/{\text{T}}_{\text{z}})}^2}$ varles from 0.25 to 0.50, where T_c and T_z represent crest wave period ana zero-crossing wave period, respectively. However, only a negative 5% correction was necessary when the method was used to analyze sea waves (ε = 0 73 to 0 76) measured off the shoreline near Look Laboratory Therefore, it was concluded that the Tucker and Draper Method is quite feasible for engineering purposes in analyzing wind-waves having a spectral width parameter of 0.60 to 0.75.

The experimental data were compared with those wave heights predicted by the Darbyshire formulas (Francis, 1959) developed for ocean waves. A significant correction factor was necessary for laboratory waves produced by low-speed winds.

The "fetch graph" was prepared and compared with those developed theoretically by Hino (1966) and empirically by Ijima and Tang (1966) at the 10th Conference on Coastal Engineering, Tokyo, Japan Comparison was also made with the previous empirical formulae by Bretschneider (1951, 1957), Sverdrup and Munk (1947), and Wilson (1961,1962). The experimental results compared well with the Hino theory for both wave heights and wave periods, and fairly well with Bretschneider's fetch graph for wave heights The difference in the comparison of wave data with other investigators is illustrated in this paper.

It is recommended that further study be made with emphasis on (a) theoretical and experimental studies of wind-wave characteristics on pre-existing waves, particularly moving storms, (b) wave-energy spectra involving stochastic characteristics and extreme values of wind waves.

An investigation of the air velocity profile above progressive, mechanically-generated waves was made in the wind and wave facility at Stanford University. The influence of propagating waves on the mean velocity profile was sought especially.

Both the instantaneous and mean velocity profiles were obtained with the use of high response total head and static pressure probes, in conjunction with a wave height gage. Experimental evidence is presented which suggests that the air velocity field responds to the wave motion.

The dependence of the mean velocity profile on wave frequency was investigated experimentally over mechanically-generated waves having a constant amplitude. Also, the dependence of the mean velocity profile on wave amplitude was investigated over mechanically-generated waves with a specified frequency.

The theoretical results suggest that the wave influence is threefold. The first is due to the fact that a velocity-measuring instrument continuously shifts streamlines when measuring the air velocity above a perturbed water surface. The second is due to the wave-induced perturbation in the air velocity. The third is due to the interaction between the two effects just described. The results contribute towards explaining the lack of consistency in the existing data.

Experimental data on pressure distribution over a sinusoidal wavy boundary with a fixed and a moving condition, measured in a water tunnel, are presented for a number of flow – velocities. The model with the moving boundary condition is related to the situation prevailing in the steady state flow picture of a small amplitude wind-generated gravity wave in – which the water flow represents the air flow in nature, while the "fixed in space" moving wavy boundary corresponds to the nearly constant water particle velocity at the surface of the wave.

The results show that the normal stress distribution – over a moving boundary differs from that over a fixed one by a phase-lag with respect to the wave shape, which varies with the ratio of flow velocity to the boundary velocity (wave celerity), as predicted by the recent theories of Miles and Benjamin.

These results provide an explanation for the energy – transfer from wind to wave due to normal stresses and show that those experiments performed on fixed boundary models can not be associated with the phenomena of water wave generation.

A series of experiments were performed to determine the velocity fieLd and other characteristics of large amplitude shalLow water waves. The experimental results were compared with the predictions of a variety of wave theories incLudmg those commonly used in engineering practice. While no theory was found exceptionally accurate, the cnoidal wave theory of Keulegan and Patterson appears most adequate for the range of wavelengths and water depths studied.

Is is very difficult for engineers to deal with the cnoidal wave theory for practical application, since this theory contains the Jacobian elliptic functions, their modulus k, and the complete elliptic integrals of the first and second kinds, K and E respectively.

This paper firstly proposes formulae for various wave characteristics of new waves named "hyperbolic waves", which are derived from the cnoidal wave theory under the condition that k = 1 and E = 1 but K is not infinite and are a function of $\text{T}\sqrt{g/\text{h}}$ and H/h, so that cnoidal waves can be approximately expressed as hyperbolic waves by primary functions only, in which T is the wave period, h the water depth and H the wave height.

Secondly, as an application of the hyperbolic wave theory, the present paper deals with wave shoaling, that is, changes in the wave height, the wave crest height above still water level, and the wave velocity, when the waves proceed into shallow water from deep water.

Experiments were conducted to determine the various effects on the shoaling, breaking and run-up of solitary waves resulting from the bottom configuration. An initial set of experiments investigated the effect of the initial bottom slope on the breaking and run-up of a wave on a second, higher slope. A second set of experiments considered the effect of a continental shelf configuration on the transmissibility of waves in the shoreward direction, and the decomposition of the waves due to the shallower water depth on the continental shelf. It was found that, in order to make predictions at or near the shoreline for waves generated in deep water, it is necessary to consider the total configuration of the bottom leading to the shoreline.

This paper summarises some recent work on lone gravity waves on still water in channels of arbitrary constant cross-section. Theoretical results have been obtained for both straight and curved channels. Some experimental work has been performed in straight trapezoidal channels and shows reasonable agreement with theory. For straight channels some details of the second approximation are given, and the cases where the approximation breaks down are indicated. For curved channels it is found that the effect of channel curvature is more pronounced when the cross-sectional shape of the channel is not symmetric with respect to its centre-line.

Reflection and transmission phenomena were investigated in a laboratorychannel for transitions of linearly varying depth and/or width terminating in channels of reduced cross-section. Upstream wave characteristics were varied from deep to shallow water waves by changing wave frequencies, amplitudes and channel depths over a wide spectrum of conditions. Experimental values were corrected to correspond to transmission in an endless channel. The reflection and transmission coefficients are given as functions of the pertinent dimensionless parameters such as: group velocity ratio, channel depth ratio and wave steepness. Associated wave energies were also evaluated.

Wind waves in a lake have been observed to reflect from a barrier and to travel upwind for considerable distances. A model has been devised which provides a means of predicting the decay of these waves as a function of wind speed and direction with respect to the barrier. Two floating bridges across a deep lake have formed a convenient, full-scale test basin for the formation and observation of the reflected waves under a range of wind speeds and directions. Wave characteristics have been measured to a limited extent by photographic means, a portable wave probe and visually to provide seme verification of the results computed from the model. The measured and the predicted wave heights and the zones influenced by the waves were found to be in general qualitative agreement.

This paper deals with the mass transport in the boundary layers developed on smooth and horizontal bottoms by standing waves in shallow water. In a theoretical approach, the basic equations of laminar boundary layers are applied to solving the oscillatory motion in the boundary layers caused by the standing waves. The mass transport velocities are derived on the basis of solutions of the second approximation which describe the flow velocity near the bottom, and the effects of convective terms involved in the basic equations are investigated.

Experimental measurements in standing waves of mass transport velocity in the bottom boundary layer were carried out using dye-streak and solid-particle methods. The experimental data are compared with the theoretical prediction.

By considering separately the two termsof the Sommerfeld solution of wave diffraction behind a semi-infinite breakwater, the influence of the wave reflection from the structure can be evaluated The diffraction coefficient at any point can be obtained from a graph or table for full, partial or no reflection by the simple addition of two coefficients From the similarity of the energy-spreading process to the dam-burst problem, it was found that wave heights decreased consistently along the near circular crests for all distances from the breakwater tip For a workable range of incident angle and distance from the breakwater, wave heights could be defined by this arc distance from the shadow line expressed in wave lengths These relationships have been verified experimentally for all but the smallest incident angle in proximity to the breakwater This can be likened to the dam model in which the dam is moving too slowly to permit normal spreading.

The several theoretical solutions for the breakwater gap, when graphed on the same basis, are shown to be very similar, diverging only for small incident angles New parameters are provided which greatly simplify the presentation of information The scatter of past experimental data precludes the verification of this theory and indicates the need for further tests

Theoretical considerations of "beach "behavior are often hampered "by a lack of systematically obtained data sets which reflect the beach environment. For specific studies, lack of time and money often prevent the collection of such data sets. Thus, any opportunity for the collection of such data, on a routine basis, should be fully exploited¹

In 19679 the U S Army Corps of Engineers and the State of California initiated a cooperative program to collect empirical data at selected locations along the California coast. The objective was to establish a reservoir of repetitive, systematic observations, by qualified personnel, with the hope of securing a better understanding of the physical characteristics of the California shore and the littoral processes occurring there.

Once a sufficient volume of data has been collected, analysis of the data will begin with the aim of determining meaningful correlations between the various recorded parameters.

The number of distinct observations and sites dictated standardized observational procedures and recording methods amenable to automatic processing Observational methods and a recording form were designed to provide a base of comparison and an efficient means of processing the expected large volume of data Investigation of various methods of recording data led to the design of a suitable optical scanning form. This form, completed in the field by individual observers, can automatically be converted to punched cards for further processing Experience in collecting similar data in connection with other studies of the Coastal Engineering Research Center influenced the selection of comparatively inexpensive instruments for data collection.

Approximately 50 observation sites, extending from the Oregon-California boundary to the United States-Mexican border are presently contributing data. These sites represent a wide variety of shore types, beach sediments, geographic orientations, and morphology It is anticipated that future expansion of this program will include sites other than those directly controlled by State agencies and will allow a more detailed description of the California shore Although not presently programmed, the extension of this study to other coastal areas of the United States where little or no information is presently available would be desirable, and could provide the necessary background for more comprehensive description of the overall behavior of the littoral zone.

Simultaneous field measurements of the energy flux of breaking waves and the resulting longshore transport of sand in the surf zone have been made along three beaches and for a variety of wave conditions. The measurements indicate that the longshore transport rate of sand is directly proportional to the longshore component of wave power.

The use of fluorescent coated sand In tracing the sand movement along beaches and around Inlets is an important tool in the field of Coastal Engineering. As a part of an extensive beach erosion study along the shore of West Palm Beach, Florida, four areas were subjected to such a "tracer study." Each area represented a particular beach configuration either with or without erosion protective structures. In this paper the procedure and results for one area is described.

As a second application of sand tracers, the results of a study concerned with the sand migration in and around South Lake Worth Inlet is discussed.

Tests were run at Fernandina Beach, Florida, using fluorescent tracers and bed load traps with automatic doors and hydraulic lift to determine the thickness of the bed load transport layer on the bottom ("bottom creep") (ref.l). Four special bed load traps with hydraulic remote controlled doors were installed on an ab. 800 ft. long pier. Fig. 1. Tracers of various colours were dumped at various distances from the pier. Two types of bottom profiles, Fig. 2, "berm profile" and Fig. 3, "bar-profile" were tested. As an example Fig. 4 shows test arrangement and wave action for test No. 17 (berm profile). Longshore wave power for this particular test was 1,5 Watts per ft of wave (one Watt is ab. 0,1 kg m/sec or ab. 0,0014- Horse Power), H_l/3 was o,45 m, T_l/3 was 4-5 sec.

The distribution of bed-load sand transport normal to the beach has been measured in a series of field experiments conducted in the surf zone at Fernandina Beach, Florida. Simultaneous measurements were made of the waves and water particle motion at various locations in the surf zone. The energy flux of the waves was resolved Into Its longshore component from the measured directional and energy spectra. It Is found that the bed-load transport is related to the depth of water and longshore energy flux. Insight into the mechanics of sediment transport is obtained by comparing the wave and water particle motion energy spectra, which give a direct measure of the kinetic and potential energy, at various locations in the surf zone.

A 60-day field study was conducted on a selected natural beach in which the beach profile was measured daily and the waves incident upon the profile were recorded continuously. Beach and wave parameters derived from the field data were empirically combined to yield: (a) quantitative relationships between the change in the profile and the average deep-water wave steepness and wave power over a lunar day (24.8 hours) given the profile at the beginning of the period, (b) equilibrium profiles for different values of wave steepness, (c) an empirical relationship between wave steepness and wave power which agrees well with theory, and (d) rates at which the beach profile approached equilibrium for given initial conditions of non-equilibrium. Using the relationship developed between beach change and wave steepness, hmdcasts were made of the day-to-day sand elevation at a selected location near the middle of the profile and were found to agree fairly well with the observed sand level.

Collective movements of sediment occur in the form of sand waves in the nearshore zone and affect beach topography to a significant extent. Bar-type sand waves move only in the onshore direction and account for various accretive profiles on the subaerial beach. When the beach is eroded, these sand waves are simply disintegrated on the subaerial beach, instead of migrating back in the form of sand waves. These characteristics of bar-type sand waves help explain dynamic behavior of beach profiles with respect to profile configuration, sediment storage, and beach width. Cusp-type sand waves are considered to be a product of interaction between longshore currents and an erodible bed. Their presence causes variability in beach profiles along the shore between those containing a prominent bar and those without a bar. Migration of these sand waves may well produce pulsational transfer of material along the shore.

The shape sorting of pebbles in the swash zone was studied in an effort to determine the effect of the amount of foreshore infiltration per wave on the swash zone energy balance. Measurements were made of pebbles collected from the swash limit and from the step of selected sandy beaches. The pebbles were sampled on occasions when, and at locations where, the conditions of breaker height, breaker approach angle and foreshore slope fell within predetermined limits. The wave period and the foreshore infiltration rate varied among the beaches and were measured. The results of these measurements indicate that the mean shape of swash limit pebbles, and presumably, therefore, the swash zone energy balance depends upon the amount of foreshore infiltration per wave. This finding leads to the conclusion that in the study of the dynamics of the swash zone the effect of wave period and the effect of foreshore permeability must be considered together.

Getting a drift buoy into and over the surf zone in rough weather has always been a problem. A cheap, cold-propellant rocket launcher using either compressed air from aqua-lung bottles or liquid carbon dioxide is admirably suited for hurling drift bottles to ranges of over 1,000 feet. This launcher weighs less than one hundred pounds and can be easily transported to places of difficult access such as cliffed or reefy coasts. The float package can be modified to include mid-depth drogues if that is desired. An example of work done by a single field operator illustrates the versatility of this technique.

Naval Mark II flares are useful for current tracing because they are easily obtained and can be set in arrays from aircraft. As they burn, however, they change their freeboard and are therefore more subject to wind drift than when they are lower in the water. Mark II flares were calibrated for wind drift with results given.

A wind velocity profile between 5/8 inches and 5 inches above the water surface was obtained from floating arrays of flares with the results given.

By oscillation of an array of turbulence-generating grids in still water, the turbulent fluid velocity field in shoaling waves near the bottom is simulated in a laboratory channel. Solid particles with fall velocities varying between 1 and 40 mm/sec are introduced into the test volume from above. Multiple-image photography using ultraviolet lighting techniques and a suitably placed mirror allow recording of the gram trajectories as functions of time and three space dimensions simultaneously. The Lagrangian intensities of turbulence and diffusion coefficients are then directly measured from the photographic data. The scale times, scale lengths, and the frequencies of the power spectra modes can then be calculated. Properties of the fluid turbulence are inferred from the quasi-neutral particles. The analysis, which is restricted to the component of diffusion in the hori2ontal direction normal to the grid motion, shows that the turbulent velocity distributions of both fluid and heavy particles are Gaussian, and that their standard deviations (intensities of turbulence) increase regularly with increasing grid Reynolds numbers (grid speeds). Diffusion coefficients likewise generally increase with increasing grid Reynolds numbers. Diffusivities of the heavy particles relative to the fluid are a function of both particle fall velocity and the structure of the fluid turbulence itself.

The characteristics of oscillatory boundary layer flow have been treated with keen interest during the last decade from the various aspects. Among the previous results the theoretical treatment by K. Kajiura must be the most important and fruitful one to advance in our knowledge on the present phenomena. On the other hand the senior author has had a real interest in the behaviour of sediment particles due to oscillatory fluid motion, and has conducted his systematic investigations on the sediment movement in nearshore area.

The aim of this paper is to introduce some results of the recent investigations conducted at the Coastal Engineering Laboratory, University of Tokyo, with the intention of investigating the applicability of Kajiura's theory to the oscillatory flow in the vicinity of bottom with sand ripples.

In order to accomplish the above purpose, the authors applied the hydrogen bubble technique to measure accurately as much as possible the time history of velocity distribution especially in the very thin layer above the bottom boundary associated with the progressive waves. The above measuring technique was verified to be enormously powerful even in the case of unsteady flow. The bottom conditions tested in the present investigation were of 1) hydrodynamically smooth bottom, and 2) rough bottom with artificial ripples. The pictures of hydrogen bubble lines released successively from a fine platinum wire were taken by using a 16mm cinecamera specially equiped, and were analyzed flame by flame to take the digitalized data of horizontal velocity of fluid. The data were analyzed in Fourier series and the first mode of the series was only taken to compare with the numerical curves obtained through the Kajiura's theory. The horizontal velocity amplitude and its phase, the eddy viscosity and the shear stress at each elevation above bottom were calculated by using not only the experimental data of present investigation, but also the laboratory data obtained by I. G. Jonsson.

The agreement between the analysed data and the theoretical curves is basically consistant; this fact verifies the usefulness of the Kajiura's theory. Even though, there are some questions in the theoretical treatment which are arising out of the present investigations. The accumulation of more accurate data is basically requested to clarify these problems. Lastly the comparative study on eddy viscosity averaged over wave cycles in the neighbourhood of sand ripples was established by using the laboratory data of suspended sediment concentration.

Experimental results are presented from which it is now possible to predict the threshold of movement of shingle.

A mathematical theory will be given about the phenomena, which occur if on a coastal area groynes are constructed.

The paper describes tests carried out in a wave basin to study the effect of groynes on a beach that was stable for a particular wave climate and a given supply of littoral material. The main conclusion was that on the part of the beach between H.W. and L.W. level the groynes produced no build up. The only build-up that occurred took place seaward of the impermeable groynes. Permeable groynes had little effect either inshore or offshore.

Results of an experimental study of the hydraulic behaviour of groyne systems, a very widespread coast erosion protection structure,are described. The characteristics of the evolution of beach stretches between groynes under the action of waves with different obliquity,heights and periods are defined. The results obtained are intended for design of systems of functional groynes which secure an adequate partition of the beach in satisfactory hydraulic conditions, and also meeting use requirements, notably from the architectural and recreation standpoints. Additionally the author briefly discusses longsh-ore drift and presents some experimental conclusions on the relations between longshore drift and the characteristics of the waves.

This paper introduces the terminal erosion problem which usually occurs down drift of coast protection works, an important aspect of coast protection which is often overlooked.

To provide the background to this problem, the formation, replenishment and function of a natural shingle beach is discussed in relation to coast protection. The value of groynes in stabilising the foreshore, the use of artificial beach replenishment, and the effect on the long shore regime following the introduction of a sea wall, are discussed in outline with typical examples.

Terminal erosion is described in more detail, with reference to its cause, and illustrated by examples taken around the coast of the British Isles. Suggestions are made for the investigation of the terminal problem, design considerations are discussed, and terminal groynes and various types of terminal works described. Particular reference is made to the permeable type of terminal section.

Finally the paper is illustrated by examples of terminal works which have been constructed at two sites in this country. The foreshore conditions and exposure are described, together with the details of the sea wall and groynes, and the details of the terminal works at each site.

The paper describes tests carried out in the laboratory and in the field in an attempt to discover whether a field of artificial seaweed placed offshore can promote an onshore transport of bed material and hence a build-up of beach levels. Tests in a wave tank showed that beach levels could be built up in this way – the effect of the seaweed being to increase the net drift of bed water in the direction of wave propagation i.e. towards the shore. The field trials were not as conclusive as was hoped, but nevertheless some build-up of beach levels did take place at a time when erosion of the beach due to many storms might have been anticipated.

A simple hydrodynamic model is proposed to represent the effect of artificial seaweed on gravity waves. The model predicts increased wave attenuation and increased shoreward mass-transport consistent with the experimental results.

This paper presents the results of two-dimensional model experiments conducted in order to clarify the basic characteristics and to find out some preventive measures against scouring around coastal structures. The applicability of these results to the field are discussed on the basis of some results of field investigations.

The results of two-dimensional experiments presented herein show that the characteristics of waves just in front of structures and their reflection by structures are most important factors of scouring. The results of field investigations, however, indicate that in addition to those two factors, the currents caused due to waves around structures play important roles in scouring.

When caisson-type breakwaters or wharves are built in areas exposed to severe wave attack, adequate precautions must be taken to ensure that all parts of the foundations are protected from erosion The joint between abutting caissons is a particularly vulnerable location

This paper describes patterns of erosion which may be expected at joints between caissons resting on sand or gravel foundations for a number of joint configurations The results are based on model studies Criteria are given for estimating scouring velocities through joints and sizes of particles moved Suggestions are made for minimizing the risk of erosion An example of erosion under a prototype structure is given

The theory for the transmission and reflection of the waves at the closely spaced pile breakwater has been developed by the use of shallow water wave theory of small amplitude. Experiment on the hydraulic characteristics of the breakwater has been performed in a two dimensional wave flume. The agreement between the theory and the experiment is pretty good with respect to the coefficients of transmission and reflection of waves, and also to the shoreward velocity of the jet discharged from a space between any two adjacent piles.

Experiment was also made on the local scouring at the foot of the clocely spaced pile breakwater. The maximrai scouring depth at the foot of the breakwater relates closely to the ratio of the velocity of the jet to the mean fall velocity of bed material. The relation between the maximum scouring depth and the power of the jet is discussed.

Many previous studies were confined to problem of beach erosion due to waves breaking on the structure. The investigation reported here involved regular non-breaking, shallow water waves progressing toward a seawall. An analytical solution was developed and compared with laboratory-scale experiments.

The works described in this paper are part of a large Coast Protection scheme recently completed at Clacton-on- Sea, Essex, England. The paper is in two parts, the first describing cliff drainage and the second dealing with beach distribution.

The method of drainage departs from the usual one of surface rubble drains and comprises a system of auger bored vertical and inclined drains. This method of drainage does not depend on the slope of the cliff face, its most important feature being that it makes it possible to dram the water away from within the cliffs.

The second section describes the effect of large impermeable groynes on beach distribution as experienced at Clacton and the remedial works carried out, including tipping of imported material to improve the beach levels, and the results achieved.

Both sections of the paper refer to the specific problems encountered on the Clacton frontage and the methods adopted to deal with them. The solutions found could be applied to other frontages but thorough investigations would be necessary beforehand due to the very varying nature between one frontage and another.

The concept "wave base" (or "surf base"), i.e. the maximum depth below mean sea level at which shoaling waves will effectively erode the ocean bottom leading to the recession of a shoreline, is discussed. Also, past and present opinions as to the magnitude of wave base in general and specifically in the area near Santa Cruz, California, and the variables controlling this phenomenon are presented. Then, an account of the author's successful and unsuccessful attempts to determine average rates of cliff retreat in the study area is presented along with the specific cliff recession rates obtained. These compare favorably with the recession rates measured by the U. S. Army Corps of Engineers for nearby areas of similar geology and topography and with rates determined for similar coastal areas in various parts of the world. A brief discussion of the spectrum of cliff recession rates found in areas of varying geology and wave climate is also presented.

The accepted history of sea level since the last glacial maximum,particularly during the last 7,000 years, is reviewed as well as pertinent information on the geology, topography and wave climate of the study area.

It is then shown that average recession rates estimated by relating extrapolated bedrock profiles of the lowest marine terraces with the accepted history of the latest sea level rise compare favorably with the recently measured recession rates. However, a conflict exists between the present wave-cut terrace profiles, the accepted history of sea level and the accepted value of wave base.

Experiments are underway along the coast of North Carolina using sand fences and dune grasses to create and stabilize a barrier dune line parallel to and behind the existing beaches of low lying barrier islands. Several miles of experimental sections have been established, and their effectiveness in trapping wind-blown sand has been analyzed. Results to date (1968) show that sand fences and dune grasses will trap wind-blown sand and create a barrier dune. A vigorous, rapidly-growing strip of American beachgrass, 90 feet wide, will trap and retain all of the sand being transported by the wind in the area. Thus, a stabilized dune can be "grown" in the area using American beachgrass.

Sand fences have been shown to be effective sand traps and can be used where satisfactory plants are not available or where it may not be feasible to await the establishment of vegetation. Two methods of using sand fences to create large dunes have been investigated; both are workable.

The use of fabrics as sand fences has been investigated; their effectiveness varies with the porosity of the fabric.

The paper describes the application of a novel method of protecting parts of the sand dunes at Pendine, S.W. Wales. These dunes are subject to erosion under conditions when high tides are combined with south-westerly gales.

A series of random rock-fill mounds were sited 20 feet away from the toe of the dunes in certain areas where structures erected on the dune crest were liable to damage through erosion at the toe of the dunes. The object of the mounds is to trap wind-borne sand in the area enclosed between the mounds and the dunes, and also to check wind-driven waves before they can reach the dune face.

Over seven years the mounds and sand traps have operated in accordance with their design concept. Not only have the traps filled with sand but further sand accretion has occurred on the protected dunes, resulting in a flatter slope and a strong growth of self-sown pioneer vegetation on the protected face and on the sand trap surface.

Experimental investigations on the depositional behavior of suspensions of fine cohesive sediments in turbulent flows have been conducted in a special laboratory apparatus. This apparatus consists essentially of an annular channel containing the water-sediment mixture, and an annular ring positioned within the channel and in contact with the water surface. A turbulent shear flow is generated by a simultaneous rotation of the channel and ring in opposite directions at the proper relative speeds to minimize secondary currents in the bottom of the channel, so that the sediment deposits uniformly.

The difficulties inherent in the direct determination of loads on off-shore structures which are exposed simultaneously to wind and waves make it desirable to model each situation in the laboratory It is shown here that scaling of the loads and the waves is possible by using waves which are generated by blowing air over the surface of a laboratory channel, and by choosing a model material with an appropriate modulus of elasticity Wind-generated waves such as those measured in the wind water tunnel of Colorado State University have a dimensionless spectrum (Hidy and Plate (1965)) that is identical in shape to that found off the coast of Florida under hurricane conditions (Collins (1966)) Furthermore, it has been shown that hydro-elastic modeling is quite feasible (LeMehaute (1966)) These two results are combined to give modeling criteria for off-shore structures if direct wind forces are disregarded.

The general purpose of the author's research undertaken in the "Laboratoxre National d'Hydraulique" was to study wave action on rubble-mound breakwaters with regular (periodic) waves on the one hand and irregular (random) wind generated waves on the other, and to compare the effects of these two types of waves by use of the storm duration t. With a first series of periodic waves experiments we have obtained the destruction of the breakwater's cover-layer for different storm durations t, by varying H and T. The mass of armor units remained constant. The angle of the slope, according to the seaward equilibrium profile could be considered as constant.

For the destruction cases we obtained a risk criterion:

which provides the storm duration t, knowing H, T and v.

Then for a second series of random wxnd generated waves experiments we eliminated t and found that the constant periodic wave height (H_dest) is equal to the "significant wave height" (H_1/3) for the random waves. This is an experimental demonstration of the justifiable use of H_1/3 as ""project wave height".

Experimental data are given to aid in the selection of the wave height for the design of a rubble mound breakwater as a function of the type and duration of the wave storm, and the allowed percentage of damage in the armour layers.

In these experiments the model breakwater was subjected to the attack of periodic waves of height and in number according with the known statistical distribution for actual swells.

Some noteworthy differences were found In the effects of different duration storms.

Observation of the destruction process of the breakwater with double layer of armour rocks, showed that the filter layers uncovering occurred always for armour damage percentages above 5% and thus this last value is suggested as the maximum permissible in case of a storm of very high recurrence period.

The purpose of this paper is to present the results of a four-year study of the stability of a prototype breakwater armor layer composed of 28-ton concrete quadripods The study was conducted by measuring the incident wave height and the quadripod movements during this period. The ultimate goal of this study is the verification of empirical breakwater design equations.

There are a number of specially shaped concrete armour units in use today. The Stabit is one of them and was first developed in 1961 for use on the reconstruction of breakwaters at Benghazi Harbour, Libya. This paper describes the development of Stabits and gives the technical details relating to their use. The subjects covered include full scale and model tests, stability coefficients, wave run-up, coverage, placing patterns, moulds, casting, handling and placing.

This paper is a sequence to two papers, (1) and (2), previously read at Coastal Engineering Conferences. They presented a mathematical model for estimating displacements, velocities and accelerations in a downrushmg wave on a rubble mound breakwater slope. Verification by photographic recording of displacements involved some uncertainties. In the present paper are reported measurements of velocities, which gave much more definite data. The correlation with velocities calculated from the model is shown to be good.

An experiment was carried out on the overtopping of mechanically generated irregular waves over veitical walls. The experimental discharge was almost in agreement with the expected discharge which had been calculated with the wave height histogram and the data of regular wave overtopping based on the principle of linear summation. The expected values of overtopping discharge were calculated for various laboratory data, which had been represented in a unified form of non-dimensional quantities. The calculation has yielded two diagrams of expected overtopping discharge, one for the sea wall of vertical wall type and the othei for the sea wall covered with artificial concrete blocks.

The behaviour of wind-generated waves on impermeable slopes of 1:2, 1:4 and 1:10 was investigated in a 40 ft long laboratory wind-wave flume. Apparatus for measuring instantaneous values of the run-up was devised. Wind velocities of up to 44 ft/sec were applied, producing wave heights of up to 2.5 in.

Distributions were obtained for the wave and run-up characteristics. The empirical results were compared with theoretical statistical relationships. A comparison was made with the run-ups in paddle-wave experiments.

The relationship between the waves and their run-ups was further investigated by a comparison of simultaneous recordings, using the methods of spectral analysis.

Previous investigations carried out "by the Delft Hydraulics laboratory have shown the necessity of applying irregular waves in studies on wave run-up. The installation of a wave generator driven "by hydraulic actuators has created the possibility of producing irregular waves with arbitrary wave spectra.

Investigations performed with this type of wave generator show the influence of the shape of the energy spectrum on the wave run-up on smooth straight slopes of 1:4 and 1:6. The results are compared with run-up figures derived from experiments with wind generated waves and with monochromatic waves.

This paper deals with wave forces from short crested waves as compared with two dimensional waves. The investigation comprised measurements of wind wave forces on fixed pontoons in a model, and a comparison of wave crest characteristics of wind waves xn model and prototype. The model tests showed that the wave crests have a marked xnfluence on the wave forces. The investxgatxon of model and prototype wave data showed that the crest characterxstxcs of the model waves compared well wxth that of prototype sea.

The determination of wave forces on piles is for an important part based upon data obtained with regular laboratory waves. Non-linearities in the mechanism that underlies these forces may lead to deviations when applying the data to predict forces exerted by irregular waves.

Experiments have been performed with irregular waves to investigate wave forces, more particularly to study the influence of the energy density spectrum of the waves.

Within the range of conditions in the experiments, the wave motion is sufficiently characterized by its energy and the frequency (or wave period) at which the energy density is maximum to determine the probability distribution of wave forces.

This paper describes an experimental investigation of shock pressures against breakwaters caused by breaking waves. The study only considers shocks of a compressive type, which occur if the wave front is formed in such a way that an air cushion is entrapped between the wave and the wall. In this case the compression and expansion of the air cushion plays an important role in the pressure variation.

Only waves preceded by non-breaking waves were used. For different combinations of bottom geometry and water depth the occurrence of shock pressures of different magnitudes was studied varying the wave height and the wave period. For some interesting combinations of bottom geometry and wave dimensions a series of tests were made to investigate the distribution over the wall of shock pressure and of shock impulse. The results, presented in diagrams and tables, have been commented on and analysed with special respect to the chosen test procedure.

The effects of nuclear explosions on a pier have been investigated to study the interaction phenomena between the blast loading, induced surface waves, the beach geometry, and the depth of coastal region for purpose of damage assessment and protective design of a coastal structure.

For the theoretical analysis, the diffraction pattern predicted by Whitham's theory was used. The characteristic solution for shock diffraction showed the shock front shapes, shock-shock shapes, and flow rays in the pier and beach geometry. A pier model was tested in a six foot diameter horizontal shock tube under four different test situations simulating pier on a beach with water, pier on a dry beach in a Mach reflection region, pier in deep water, and a pier on a dry beach in a region of regular reflection. The model was subjected to various shock overpressures in each of the four test situations.

Transient pressure distribution on the pier was investigated and comparison between the characteristic solution and the test results was made.

This paper sets down basic information on the behaviour of bubble breakwaters, drawn from analytical and experimental studies carried out by the author and others in recent years. Design formulae are given for surface velocity and thickness of the horizontal current produced by a bubble curtain, and for the quantity of free air required to suppress waves of known length and height. The effect of an intermittent air supply is examined. It is concluded that the quantity of air required is astronomical and the practical difficulties immense.

The pattern of vertical velocities induced by an orifice discharging air into water can be represented by Gaussian distribution curves with a linear spread in the vertical except for the regions near the orifice and close to the free surface. An analytical treatment considering the momentum-flux increase due to the buoyancy of the air together with experimental information about the spread of the velocity profiles and the mean rising speed of the air bubble stream, which has been obtained from velocity and density measurements over a wide range of conditions, leads to a complete description of the flow field. The ratio of the water volume flux to the air discharge rate, which has been proposed as an efficiency criterion, is now at hand as a function of depth and air supply for both single orifices and rows. The experimental evidence supports the analysis well and suggests that extrapolation to larger water depths and air supplies should be permissible, which would allow approximate predictions of the volume flux for any air-bubble system.

Experimental results axe presented for a laboratory study of the effectiveness of hydraulic breakwaters in dissipating deep water waves. Test data are reported for a range of wave steepnesses for wave length: water depth ratios ranging from 0.375 to 1.343.

It is shown that the effectiveness of hydraulic breakwaters depends upon the steepness of the incident wave and upon the ratio of the momentum of the opposing surface current created by the breakwater to the momentum of the incident waves. Results also are compared with the theoretical predictions of Taylor which are appropriate to deep water waves.

Data are presented in a form allowing the determination of hydraulic breakwater manifold discharge characteristics in order to achieve specified attenuation for a particular incident wave. It is concluded that while the hydraulic breakwater is better adapted to deep water waves than to shallow water waves upon which prior studies of the device have concentrated, it is generally inefficient for most practical cases because of excess power requirements. Some possible field applications are indicated.

The general objective of this investigation is to determine the wave damping characteristics of model floating breakwaters designed to reduce incident wave heights by processes of wave reflection, wave interference, forced instability of incident waves and turbulence action. Of most interest is the attempt to determine the method and the extent to which the requirement of large mass may be usefully replaced by large moment of inertia of mass in the development of floating breakwaters. Experiments are conducted in a two-dimensional wave channel. Reflection coefficients, transmission coefficients, breakwater motions and mooring forces are determined by experiments. It is found that the range of effectiveness in wave attenuation of floating breakwaters depends on several factors including breakwater design, incident wave properties, depth of water and the motion characteristics of the structures, it is remarkable that the 'A' Frame Breakwater exemplifies that the range of effectiveness of a floating breakwater can be increased by a large increase of its radius of gyration involving only a slight increase of its mass. The mooring forces are of reasonable magnitude. Experimental measurements and observations indicate that the 'A' Frame Breakwater is stable throughout the range of model tests.

Observation of the effect of towed rafts of pulpwood on lake and ocean waves led to a systematic investigation at model scale. An empirical equation compatible with wave theory was devised and lines representing this equation together with points representing experimental results are shown for different conditions. An example of the application of the equation to prototype wave action is given. Four box booms with porous fronts, arranged in series, were substituted for the model pulpwood gam and proved to be effective in damping waves.

The breakwater proposed for a yacht harbour on the Sussex coast of England comprises a solid base up to the level of low water and a cellular structure, having a perforated front wall and solid backwall, above low water level.

A model of the breakwater (scale 1:48) was tested in a flume at the Hydraulics Research Station, Wallmgford, and measurements were made of wave reflections and wave forces.

For comparison force measurements were also made on a solid faced breakwater. The reflection tests were carried out with waves of normal incidence and at 45° to the breakwater for waves (prototype) in the range h to 15 seconds and up to 15 ft. in height. The results are presented in graphical form and a simplified analysis Is put forward to explain them.

The force measurements were made for 7 and 10 second waves (prototype) up to 22 ft. in height. The results are presented as a non-dimensional plot with envelope curves of maximum force.

The results are also given of stability tests on a rock mound against the solid base of the breakwater.

Model tests on a perforated breakwater system were carried out to evaluate effectiveness in different states of sea. Force measurements were made in three long-crested irregular wave systems and, by spectral analysis, the full-scale statistical characteristics of force were obtained. The effect of perforating the back wall was studied to determine the extent of further reduction of force on the structure. An interior perforated wall was also added for force reduction but was not as effective as the perforated back wall. The system was mounted on piles and imbedded in sand for a quasi-quantitative study of scouring in regular waves. In this case, the elevation of the breakwater walls above the sandy bottom was varied. Both the perforations and the elevation contributed to significant reduction in observed scour. The end result of these experiments is to provide information on the kind of improved performance that might be expected as each variation is introduced which, in turn provides input to design for particular applications.

The behaviour of thin and rectangular solid submerged breakwaters is re-examined. Dean's theory is found to be correct for a thin barrier in infinitely deep water. An empirical and theoretical relationship for the reflection coefficient of a thin breakwater across the wave number spectrum is proposed. Rectangular solid breakwaters have a maximum reflection when the incident wave has the same period as a standing wave on top of the breakwater and with a wave length equal to the crest width. A submerged permeable breakwater for depths of submergence greater than 5% of the total depth transmits less wave energy than the solid over a certain frequency range. The minimum is transmitted when the criterion above for solid breakwaters is also met. Both permeable and solid rectangular breakwaters cause a substantial loss in wave energy and at least 501 of the incident energy is lost to turbulence. A substantial proportion, 30 to 601 of the energy transmitted is transferred to higher frequencies than the incident wave.

This paper summarizes the world-wide effectiveness of marine-fender systems A design criteria is recommended as a result of an extensive research and development program executed at the U S Naval Civil Engineering Laboratory, Port Hueneme, California, under the sponsorship of Naval Facilities Engineering Command

Pertinent information includes analytical treatment and experimental investigation of the effects of berthing impact on the design of berthing structures, definition, function, and types of fender systems, advantages and disadvantages of various fender systems, cost-effectiveness and design procedures for different marine environment and exposure conditions. The energy absorption characteristics, berthing velocity, and virtual mass of ship are discussed in detail Energy capacity requirements for marine fender systems are illustrated in both graph and monograph forms. This paper is intended to provide guidelines to coastal engineers who may be involved in design of fender systems for waterfront and offshore structures.

A new floating fender devise designed to absorb berthing energies of ships against piers or harbor structures is described The principles governing the design and operation of the Hi-Dro Cushion Camel are reviewed The materials used in construction and the results of testing on the prototype are also explained and illustrated. Cost data and other information are given to permit evaluation and economic comparison with other systems. The Hi-Dro Cushion Camel consists of rectangularly arranged thin-walled plastic cylinders grouped in clusters in a sandwich between two structural diaphragms The cylinders are submerged in water and are completely enclosed except for an air vent hole and pressure regulating orifice The orifice controls the pressure build up and water release as the tube walls are pushed together at varying velocities. The ability of the device to adapt to variations in vessel displacement, pier flexibility and berthing velocities, is also discussed

Frost action and biological attack are not important causes of damage to concrete in coast protection works in the British Isles and no cases of alkali-aggregate reaction have been positively identified. Chemical attack is usually confined to structures containing concrete of indifferent quality. Damage to exposed concrete structures due to abrasion by wave driven shingle is, however, extensive at many sites in the United Kingdom and gives rise to a considerable maintenance problem. A series of experimental panels was laid in the apron of a sea wall at Fleetwood in 1961 in order to compare the performance of different concrete mixes when exposed to attack by the sea. Some provisional conclusions have been drawn from a study of the results of this experiment, and a survey of coast defence works in England and Wales has provided additional information. Suggestions are made for further research into factors affecting the durability of concrete in coast protection works.

This paper is a brief reveiw of the publications on the field studies carried out in Japanese coasts. Japan has many projects of coastal works in relation with the development of industrial area, the protection of coastal land from disaster and some other purposes. Before the execution of these projects, the agencies in charge of them make field investigations for their necessary items. The results of investigations in detail are reported in their official publications and sometimes the abstracts of them are reported at the annual meeting of coastal engineering held by the Japan Society of Civil Engineers. As the official publications of the governmental organizations are distributed in strictly limited circles, they are not well known by scientists and engineers outside these organizations. The author intended to collect some of these official reports and selected some additional reports on field study from the proceedings of annual meetings of coastal engineering, and tried to make a classification of the contents and to give a brief review of them.

Estero Punta Banda on the Pacific Coast of Baja California was to be improved and stabilized as a small boat harbor by the construction of twin jetties. The throat area-tidal prism relationship at this entrance agreed with that of other inlets on sandy coasts in equilibrium. This throat area was retained in the jetty spacing. The major question to be resolved was whether to retain the entrance in its present position at the north end of the lagoon or to cut a new entrance at the south end. The former position was chosen.

A summary is given of the results of training sixteen rivers in an endeavour to increase bar depths for navigation. The bars are of simple crescent formation fed by littoral drift.

Whilst the training works have improved conditions for navigation they have not resulted in any appreciable increase in bar depths.

Despite the complex mechanisms involved in bar formation a consistent simple correlation is found to exist between channel and bar depths. This correlation seems to apply to all rivers and inlets with simple bar systems and extends over a range from a bar depth of two feet to 60 feet. The correlation holds for rivers elsewhere and with varying climates of exposure.

About 7 years ago, the Department of Public Works of Canada requested the assistance of the National Research Council to devise a means of reducing sediment deposition in the entrance to a small harbour at Dmgwall, Nova Scotia. Siltation of this harbour entrance, which opens to the Atlantic, was so severe that on occasions it was completely blocked by sand at low tides.

The desired objective was to devise a layout of structures which would maintain an entrance depth of 12 feet at low tide. Model studies were carried out and a breakwater configuration was evolved which appeared to have some "self-dredging" characteristics. The recommended structures were built in 1962 and to date have been successful in maintaining minimum depths of 5 feet at low tide which is adequate for the fishing fleet using the harbour. While falling somewhat short of the original objective this performance has been very satisfactory when compared with the conditions which existed before construction.

Similar installations have since been built at two other locations in Nova Scotia Which are on the Gulf of St. Lawrence. Indications so far are that similarly satisfactory results have been obtained.

This paper describes the installations, makes some tentative suggestions concerning the mechanisms involved in their operation and provides data on their performance.

The coast of Great Britain has many interesting examples of the interaction between tidal estuaries of rivers and the littoral drift of the coast. These have been described with historical detail mainly by geographers (ref.l). Two cases coming to the author's firm for action have interest for coastal engineers. For the River Spey in the Moray Firth of Scotland, a famous and vigorous river, unusual works have been undertaken with success. For Dawlish Warren, a sand spit in the Exe Estuary of Devon in South West England, a scheme of works is being prepared which has novelty in regard to British practices.

The paper outlines a proposal to barrage the Bristol channel between Cardiff and Weston-supermare. The benefits from energy generation and to road communications are assessed in detail and in monetary terms. Benefits to navigation and drainage are discussed but not assessed. The effect of the barrage on tidal range, siltation and sediment movement is considered and a suggestion, previously made by others, for a larger international airport on land reclaimed from the enclosed area, is developed.

Cost estimates for the proposal are made and it is shown that the benefit/cost ratio is greater than unity even when only energy and traffic are considered.

Petroleum port site selection is examined in the broad context of the total transportation system from production to consumption area. Basic systems engineering approaches are applied to the problem to formulate a mathematical model which permits all transportation system variables, including capital and operating costs, to be put in quantitative form. An example of the computer solution is given, along with a discussion of the principal calculations involved. Unit transportation cost is selected as the measure of effectiveness of candidate systems. The port site associated with the system yielding the lowest unit transportation cost for the entire range of throughputs is selected.

During the last two decades considerable progress has been made in analyzing the diffusion process in estuaries. Unfortunately, certain difficulties (e g prediction of diffusion coefficients) still prevent common application of the diffusion method An old technique, related to the diffusion concept, can however, frequently give useful information regarding constituent mixing and transport velocities in natural estuaries.

The diffusion phenomena due to the tidal current and the longshore current inside and outside a harbor are studied in a hydraulic model experiment, for which the Kashima Harbor area is used as the prototype. The tidal current, the longshore current and the effect of density are taken into account, but the direct effects of wind and waves are not considered.

A model of Kashima Harbor, with horizontal and vertical scales of 1/500 and 1/63 respectively, was constructed, and a semidiurnal tide generated by an automatically controlled pneumatic tide generator and longshore current by a water circulating system were provided for it. The water level at 4 stations and current pattern were measured. The diffusion of dyed water from instantaneous point sources and a continuous point source was investigated by the photographic method and dye concentration analysis.

A study involving the determination of the bed shear stress and thence shear velocity in the Narrows of the River Mersey (a well mixed tidal estuary) is described. The two dimensional equation of motion is examined and it is concluded that in order to determine the energy slope (S) (and thence the shear stress and shear velocity) it is essential to evaluate density, inertia and kinetic energy terms as well as surface slopes. Although the density term is much smaller than the other terms it is important at periods of low slack-water.

Measurements of the various terms are described and attention is drawn to the difficulties arising m the case of the surface slopes. Comparison is then made between the values of the shear velocity as predicted from the energy slope and those obtained using velocity traverses throughout the depth and with measurements of velocity at three fixed positions near to the bed. Finally consideration is given to the relationship between the cross-sectional mean velocity ($\overline{\overline{\text{U}}}$) the depth-mean velocity ($\overline{\text{U}}$) and velocity at 3ft. above the bed (U₃) and the shear velocity obtained from the energy slope. It is concluded that there is good linear correlation of each of these velocities ($\overline{\overline{\text{U}}}$, $\overline{\text{U}}$ and U₃) with the shear velocity throughout the tidal cycle except for the period around low slack-water.

Waste water may due to buoyancy effects spread horizontally on top of the recipient. The spreading is chiefly determined by the buoyancy flux and to a large extent unaffected by dilution and diffusion. This phenomenon is of great practical importance for larger outfalls of waste or cooling water in coastal regions.

The St. Lawrence River is a major waterway connecting the Port of Montreal to the Atlantic Ocean. As is the case with so many natural rivers, extensive dredging has been necessary to provide adequate navigation conditions. About 100 years ago the Ship Channel of the St. Lawrence River was at several places only 10 ft deep and 150 ft wide; presently it has a minimum depth of 35 ft and a minimum width of 800 ft. However, further improvements are necessary, to meet present and future navigation requirements.

The Hydraulics Section of the National Research Council is studying improvement schemes by means of a hydraulic and a mathematical model of the St. Lawrence River from Montreal to Father Point, a distance of about 350 miles. The hydraulic model has been built to a horizontal scale of 1:2000 and a vertical scale of 1-120. The mathematical study uses a finite-difference approach, employing both explicit and implicit computational schemes.

This paper describes the two studies and deals briefly with the merits of operating a mathematical and hydraulic model simultaneously.

The selective withdrawal characteristics of bottom water intake placed on the sea bed for the condenser cooling system of steam power station are presented and several design methods are proposed The results of field observations are also shown.

In the present report, a few factors of great importance in the determination of the degree of recirculation of cooling water for power station are chosen for theoretical analysis

First, the problem of flow and thermal diffusion in the sea caused by outfall of warmed cooling water is considered. Numerical solution of the equation of thermal diffusion with a complete set of Eulerian equations in which the values of the eddy coefficient of diffusion and viscosity depend upon the relation to the velocity shear and vertical density gradient is presented The Boussinesq approximation LS used throughout The mechanism of development of upwelling phenomenon is discussed from the numerical experiment taking into account of the interaction between the flow and the thermal distribution. From the result of field survey, the occurrence of the return flow in the bottom layer of the coastal region is confirmed The numerical solutions give a good representation of all features of flow and thermal profiles.

Next, study on cold water intake from bottom layer is presented The numerical experiment of the stratified fluid with a continuous density gradient flowing into the submerged intake is conducted to gain additional insight into the mechanism of density flow in the field of the continuously stratified fluid. The results lead to the conclusion that the flow in the field of the continuous distribution of density differs from that for a two-layer system.

Model tests were conducted at the University of California, Berkeley, on six ship models to determine the heights of the waves produced by ships. Measurements were made at various distances from the sailing line with the models moving at various speeds in various water depths. The results of the tests are presented in graphical form, as prototype values.

Models of two types of vessels were towed at various speeds in water of uniform depth. On one side of the sailing line the ship waves were allowed to move over beaches of various slopes. The wave heights were measured and compared at two points equidistant from the sailing line-patterns were determined by photographs.

The importance of knowledge of squat and expected underkeel clearance for ships passing a fairway is essential to the navigational safety and the economy of a harbour.

In order to check the squat of ships in the fairway to the port of Luleå a photographic measuring method has been evolved and used in measurements on three different ships. Determining of squat is made by levelling the position of vessels in relation to water level at the berth before sailing and en route at measuring points along the fairway.

The accuracy of measurements was determined by observations on reference staffs. The order of standard deviation is 1/2 inch, at 2,400 feet distance. Observations indicate squat ranging from 1 foot 5 inches at speeds of 9 knots to 2 inches at 3$\frac{1}{2}$ knots.

The measured squat corresponds rather good to tneoretically calculated values according to Woltiger and Shell/Sogreah.

The measuring method used has reduced the field work. The greatest advantage is that adequate values of squat will be directly recorded with only a few corrections including irregular factors such as turbulent flow, hull deformations and variable channel sections.

A condition is however sheltered water and possioilities of solid foundation for instrument arrangement.

A complete theoretical analysis of the behaviour of resonators built into the breakwaters of a harbour entrance would be extremely difficult. This paper describes an approximate development for extreme values of resonator geometry and shows how a combination of these cases explains certain observed phenomena for intermediate shapes.

The paper also describes comprehensive laboratory tests on resonators and draws attention to certain significant discrepancies from present design practice. In particular, the paper indicates the extent to which optimum resonator geometry depends upon the harbour entrance width and demonstrates that such resonators can be designed to prevent any penetration of waves into harbours, without restricting shipping.

Some dynamical aspects of the surge motions of small boats moored asymmetrically with elastic non-linear restraints are discussed herein. In connection with the theoretical analysis of mooring dynamics, experiments were conducted to determine the periods of the free oscillations of a 26-ft boat moored in various ways in a floating slip. These results are in reasonable agreement with those predicted theoretically. An analytical study of the mooring dynamics of seven small boats indicated that the periods of free oscillation were less than about 10 sec., hence, for these boats the important wave periods for forced oscillations would be in the range of those of storm waves.

A I 20,000 scale model was built of the island of Oahu and neighboring topography. The model was undistorted and rotatable so that an incoming tsunami from any direction could be easily incorporated by turning the 12' x 12' model to face the wave generator from the desired angle. The wave basin was 30' wide and 40' long; with a I-10 wave absorbing beach situated at the opposite end from the wave generator. The waves were modeled to a vertical scale of I:2000.

The model was supplemented by a small-scale (1-247,500) model, also undistorted, in a transparent 6' x 12' ripple tank. This model represented the eight principal islands of the island chain and their surrounding topography.

Nature data of runup height for four different tsunamis around Oahu show a strong local amplification effect, varying more with respect to fixed positions around the Island (prominent features, points, bays, reefs, etc.) rather than with respect to variations in deep sea direction.

A less pronounced local effect was obtained in the model tests and direct point-to-point correlation of model and nature data was not very meaningful beyond a general trend agreement. The orientation effect was similar on the model as in prototype.