bluuebunny/crossref_metadata_2025 huggingface dataset:
NUMERICAL SIMULATION OF TSUNAMIS ORIGINATING IN THE PERU-CHILE TRENCH
Authors: Garcia A.W. , Butler H.L.
Published: June 2019

The U. S. Army Corps of Engineers has as an objective of its research and development program the determination of better harbor design criteria for tsunami protection. A previous report (Houston, et. al., 1975b) addressed the subject of tsunami vulnerability of the Pacific Coast of the continental United States to tsunamis originating in the Aleutian Trench. That report determined the variation in tsunami amplitude as a function of coastal distance due to a standard uplift source at different locations in the Aleutian Trench. The present report is a continuation of that study and addresses the subject of tsunami vulnerability along the same stretch of coast to tsunamis originating in the Peru-Chile Trench. In addition, modifications to the numerical code used in the previous report allowed the simulation of the Chile tsunami of May 22, 1960.
3-D HYDRAULIC MODEL OF WAVES GENERATED BY DISPLACEMENTS
Authors: Liu Shin-Lin , Wiegel R.L.
Published: June 2019

Measurements were made of the water waves generated by the horizontal motion of submerged plungers. The results obtained in a three-dimensional hydraulic model experiment, using a plunger 0.5 ft. wide and 0.25 ft. high, were compared with both the experimental results and theory for the two dimensional case. It was found that at a given location the ratio of the elevation above the still water level (SWL) of the first wave (the largest wave of the group for the range of variables tested) to the displacement of the plunger (HgA) was found to be dependent upon the Froude Number Npa (based upon the average plunger speed and the water depth) and upon the ratio of the height of the plunger to the water depth (D/d). For a constant value of 9, H3/A increased with increasing Npav,, and D/d. A few additional tests were made using a plunger 2.0 ft. wide and 0.25 ft. high. The results show that Ho/A depends also upon the ratio of water depth to the width of the plunger (d/W).
FIELD INVESTIGATION OF SEDIMENT TRANSPORT PATTERN IN A CLOSED SYSTEM
Authors: Sunamura Tsuguo , Horikawa Kiyoshi
Published: June 2019

In order to elucidate the transport pattern of sediment in a closed system, a pocket beach was chosen and investigated from various aspects. This investigation included the following studies: (1) bathymetric survey by an echo sounder, (2) survey of submarine geology using an acoustic probe, (3) observation of nearshore current systems using floats, (4) documentation of the transport pattern of suspended sediment by aerial photographs, (5) examination of depositional environments of bottom and beach material by sieve analysis, (6) inference of long-term alongshore sediment transport pattern from the grain size properties of beach sand, and measurement of short-term trends by use of fluorescent sand, and (7) examination of long-term shoreline change using old and recent maps.
BEACH PROFILES AT TORREY PINES, CALIFORNIA
Authors: Aubrey David G. , Inman Douglas L. , Nordstrom Charles E.
Published: June 2019

Beach profiles have been measured at Torrey Pines Beach, California for four years and correlated with tides and accurate spectral estimates of the incident wave field. Characteristic equilibrium beach profiles persist for time spans of up to at least two weeks in response to periods of uniform incident waves. These changes in the beach profiles are primarily due to on-offshore sediment transport which can be related to variations in wave characteristics and tidal phase. The most rapid readjustment of the beach profile occurs during high wave energy conditions coincident with spring tides. Alternatively, the highest berm building is associated with moderate to low waves that coincide with spring tides.
EXPERIMENTAL VERIFICATION OF GROYNE THEORY
Authors: Hulsbergen C.H. , Bakker C.H. , Van Bochove G.
Published: June 2019

In order to check the results of Bakker's theory [jj , £2] concerning the influence of groynes on a sandy beach, a comparison is made with experimental results obtained in model tests performed in the Delft Hydraulics Laboratory [3] , and in the Laboratorio Nacional de Engenharia Civil, Portugal [V] . The theory gives the bathymetric development in terms of a set of two schematized contour lines, representing the onshore and offshore parts of the model where longshore sand transport occurs. As input in the theory the characteristics of the undisturbed sand transport should be known, i.e. without groynes. This is achieved by computing the longshore sand transport according to Bijker's method [jf] and the transverse sand transport according to Swart's method [jQ > starting from the hydraulic conditions as measured in the model without groynes. In order to make a comparison with the theoretical lines, the bathymetric development as measured in the model with groynes is also schematized to a set of two contour lines. In some cases the result is quite good, whereas in other conditions the theory does not even show the right trend; see [7] for details. Possible causes are discussed, and shortcomings of the model as well as of the theory are mentioned.
COMPREHENSIVE MONITORING OF A BEACH RESTORATION PROJECT
Authors: Shemdin O.H. , Brooks H.K. , Ceylanli Z. , Harrell S.L.
Published: June 2019

This paper outlines the results obtained from monitoring the Beach Nourishment Project at Jupiter Island, Florida. Jupiter Island is a 16 mile long barrier island on the east coast of Florida. Five miles of the beach were nourished in two stages in 1973 and 1974. A total of 3.4 million cubic yards of sand were dredged from an offshore borrow area and placed on the beach. The monitoring program included: seasonal hydrographic surveys of beach and offshore profile to 3000 feet offshore; climatological monitoring of wind, waves, tides and currents over a oneyear period; tracer and dye studies; and sand sampling and coring at selected beach and offshore locations. The results indicate that beach restoration has a groin effect in the sense of producing favorable changes in littoral drift due to shore alignment changes. A net accretion updrift of the restored area occurs. The results demonstrate the importance of the offshore profile in accounting for the total sedimentary balance. Shoreline recession coupled by a build up in the offshore profile may reflect accretion rather than erosion. Finally, the results show that the littoral drift formula using the wave climate as input provides inadequate prediction estimates for erosion or deposition following construction of a beach restoration project.
PROPOSED "IMPROVEMENT" OF KAIMU BEACH, HAWAII
Authors: Cox Doak C. , Gerritsen Frans , Lee Theodore T.
Published: June 2019

Proposals to "improve" a pocket beach at Kaimu, Hawaii have been under active consideration for a decade. The beach, which is famous for its jet black color has been receding for at least a century. The plans proposed have called for its enlargement, and most of them for its protection by an offshore breakwater. Advantages of a larger beach area, and of the improvement of swimming conditions if the breakwater were constructed, are undeniable. Loss of surfing sites would, however, have resulted from the adoption of any of the plans involving breakwater. Other disadvantages associated with some of the plans proposed would have included alteration of beach color, other visual impacts, and threats to archaeological sites from the quarrying of breakwater stone. Sand-loss estimates and breakwater construction criteria dependent on them were based on probably erroneous interpretations of historical evidence. Possible alternative sites for the provision of the swimming opportunity were not investigated. Serious question was raised whether the project would result in overall improvement. However, recent coastal subsidence has rendered all of the plans obsolete and the question is probably moot.
CHANGES OP SEA BED DUE TO DETACHED BEEAKWATEES
Authors: Toyoshima Osamu
Published: June 2019

Since most of the coast lines of Japanese Islands are faced on the open sea and are always attacked by severe waves, beach erosion is one of serious problems in the coastal engineering field. Although Japan has all types of coastal land-forms except the glacial shoreline, remarkable recessions of coast line have been observed at sea cliffs and sandy beaches. The recession of sea cliffs has been found at several districts in Japan since old times. But, beach erosion has become increasingly severe since the early 1950's. The main causes of beach erosion are the reduction in sediment supply from rivers and the interception of the longshore paths of sediment. The former is caused by the river improvement works and by the construction of dams and debris barriers or Sabo works. The later is caused by the coastal structures, such as jetties, groins, breakwaters, and flood-control outlets. In addition a new type of beach erosion has been observed at the coast where coast protection works such as seawalls and bulkheads exist. The beach erosion defence works are being executed at more than 300 sites in Japan. Considerable number of the works were commenced in the 1960's.
EFFECT OF WAVES ON SAND TRANSPORT BY CURRENTS
Authors: Owen Michael W. , Thorn Michael F.C.
Published: June 2019

The effect of waves on the transport of sand in suspension by currents can be especially important in the outer regions of estuaries and tidal inlets. Two series of field experiments are therefore being carried out to investigate the transport of sand under the combined action of waves and currents. In the first series of tests, measurements were taken from a specially constructed tower located just off the Maplin Sands in the outer Thames Estuary, England, (Fig.l). The tower stands in about 1.5m of water at lowest tide levels, and the mean spring tidal range is about 4.5m. Average tidal velocities are about 0.6m/s, with peak values up to about 0.9m/s. The tower has a completely open structure (Fig.2) below the water line, with the exception of the four corner piles penetrating the sea bed, and a vertical trackway which stops approximately lm above bed level. A series of instruments were fixed to a trolley which could be winched up and down the trackway, thus allowing measurements at any height above bed level. The annual wave climate at a waverider buoy position some 900m from the tower is summarised in Fig.3: Fig.3a shows the percentage occurrence of different wave heights, and it can be seen that the tower is at a fairly sheltered site, with less than 2 per cent of the waves exceeding lm in significant height. Fig.3b shows the percentage occurrence of given wave periods which, as one would expect, are correspondingly short, with less than 2 per cent exceeding 4.5s mean-zero crossing period. The second series of field tests are presently being carried out at the seaward end of Boscombe Pier, located in Poole Bay, England, (Fig.4). Water depths at this site are about 2.5m at low tide, with a mean spring tidal range of about 1.7m. Maximum tidal velocities are only about 0.3m/s, although during prolonged storms the tidal currents are enhanced by strong wind-induced currents. This site is significantly more exposed than Maplin, which was the reason for the choice of this second location. Annual wave statistics are not available for Boscombe Pier itself, but a waverider buoy some 3000m from the pier (Fig.4) has been operated by the University of Southampton for several years, and Fig.5 shows the percentage occurrence of given wave heights for the year 1977. Some 17 per cent of waves were greater than lm significant height, and 2 per cent greater than 2m. Fig.6 shows the percentage occurrence of given wave periods: 5 second waves are the most common, but with periods of longer than 10 seconds being recorded. Despite initial appearances, Fig.7, Boscombe Pier is a relatively open structure below the water line, with only vertical columns 0.4 x 0.4m, spaced at 5.5m centres. As at Maplin, a vertical trackway is provided, and an instrument trolley can be winched up and down.
STORM INDUCED PERIODICITIES OF SUSPENDED SAND MOVEMENT
Authors: Leonard Jay E. , Brenninkmeyer Benno M.
Published: June 2019

An array of electronic sensors was installed on Nauset Light Beach, Cape Cod, Massachusetts, U.S.A., in order to provide a description of the sediment movement during storm conditions. These sensors included two sediment concentration indicators (almometers) which monitor sediment movement as a function of elevation and time, one bidirectional electromagnetic current meter, and a resistive wave staff. Prior field studies performed during "normal" conditions have indicated that surf-zone suspended sediment movement is a low-frequency phenomenon, with the relatively high-frequency component (normal wave period) contributing little to the amount of total sediment transported. Development of a computational technique based upon discrete Fourier analysis and digital filtering called Spectrally Filtered Integration (SFI) provides the calculation and filtering of true units of sediment change in grams-per-liter. Moreover, the SFI technique eliminates the possibility spurious sediment information created by the presence of air bubbles in the water column. Generally, higher-frequency sediment movement is more common during storm conditions than during normal non-storm conditions. This movement is controlled not by the prevailing wave and swell periods, but by a longer period which may be due to water interactions below the surface.
MORPHOLOGIC EFFECTS OF WESTERLAND BEACH NOURISHMENT 1972
Authors: Wenzel Dieter
Published: June 2019

In 1972, a "beach nourishment scheme was to delay the steady coast erosion near Westerland (Germany). Morphologic investigations state the development of the fill and its effects to adjacent beaches, and yield recommendations for another nourishment scheme in 1! The morphologic analyses are related to two different profile areas. They show that the effects of the nourishment were quite confined in space and time- Particularly the island base and the bar remained unaffected by the fill. The analysis becomes more instructive and perhaps easier by the use of special means, such as the differential morphometric characteristic and the mean profile depth instead of mass computations or mass balances. The standard mean depth in the morphologic system of the investigation area is found to be NN-^,1 m.
SUSPENSION AND TRANSPORTATION OF FLUID MUD BY SOLITARY-LIKE WAVES
Authors: Wells John T. , Coleman James M. , Wiseman Wm. J.
Published: June 2019

The suspension and transportation of fluid muds in the nearshore zone by shallow-water, solitary-like waves has been investigated along the coast of Surinam, South America. Accumulations of fluid mud which front the coast at a spacing of 30-60 km affect incoming swell by changing the wave profile from sinusoidal to solitary-like and by preventing wave breaking except for occasional spilling. Simultaneous time-series measurements of wave height and period, fluid-mud density, and tide elevation, along with results of suspended-sediment measurements, indicate that in cases when the bulk density is less than 1.20 g/cm and where water depths are less than 5 m fluid mud is suspended from the bottom in two frequency modes: wave-by-wave suspension (-10 sec) and tide related suspension (-12.4 hr) . Surface-water suspensate concentrations exceed 3.4 x 10 mg/1 as up to 0.5 m of fluid mud is periodically removed from the bottom. High concentrations of suspended fluid mud, together with solitary-like waves from the northeast throughout the year, can lead to extraordinarily high sediment transport volumes. Calculations based on solitary wave theory and on data obtained from this ft ^ study indicate that 15-65 x 10 m of mud can move along shore each year without involving breaking waves, the concept of radiation stress and a nearshore circulation cell, or bed-load transport. These values are 10 to 100 times greater than typical transport rates along sandy coasts.
HYDRODYNAMICS AND SEDIMENT TRANSPORT IN A SALT MARSH TIDAL CHANNEL
Authors: Ward Larry G.
Published: June 2019

Processes and sediment transport were investigated in a salt marsh drainage system at Kiawah Island, South Carolina. A general survey of the tidal current was done in the major tidal channel (Bass Creek) for a 10 tidal cycle period in August, 1977. Detailed determinations of current velocity, discharge, and suspended load were conducted during 15 tidal cycles in March, 1977 and again during 8 tidal cycles in July- August, 1977. For each of these periods, mass budget for the total suspended load were computed. The tidal currents have a pronounced time velocity asymmetry with the maximum current velocity occurring nearer high slack water and the peak ebb velocity being 20 - 30% stronger than the flood. Suspended load transport is significantly affected by the time velocity asymmetry. Peak current occurring nearer high slack water causes a net displacement of suspended material in an ebb or seaward direction under normal conditions. This process is enhanced by the stronger ebb currents. Mass budgets reflect the ebb dominance of the system showing a net export of combustible (organic) material during the March sampling period and a net export of both noncombustible (inorganic) and combustible material during the July-August period. Also important to suspended load transport in marsh systems are stressed meteorological conditions. High winds or heavy rains increase suspended load concentration and can cause significant import or export of fine-grained material.
TIDAL SEDIMENTATION IN GROS-CACOUNA HARBOR
Authors: Drapeau Georges , Fortin Guy
Published: June 2019

The harbor of Gros-Cacouna on the South shore of the St. Lawrence Estuary has been silting at the rate of 31 cm/yr. since it was dredged at the depth of 14 meters in 1968. Measurements of temperature, salinity, turbidity, current speed and direction were carried out as well as bottom sampling and reflection seismic profiling. A model of suspended sediment transport combines the tidal volumes and the current profiles at the harbor entrance. During a period of high turbidity (Spring) in the St.Lawrence Estuary, 54.2 tons of suspended sediments entered the harbor during the flood phase, while 41.1 tons were carried out during the ebb phase of a semi-diurnal tide, leaving 13.1 tons of sediments in the harbor. The transfer coefficient is 0.24 indicating that one quarter of the suspended sediment load settles in the harbor during one tidal cycle. In September, the turbidity is low in the Estuary and the suspended sediment budget in the harbor is 4 times smaller but the ratio of deposited sediments versus the total quantity of sediments transported in suspension is the same.
ROSSLYN BAY BREAKWATER; QUEENSLAND, AUSTRALIA
Authors: Foster D.N. , McGrath B.L. , Bremner W.
Published: June 2019

The Queensland Harbours and Marine Department is charged with the responsibility of providing small craft facilities throughout the State. In 1964, the Department engaged a firm of consulting engineers, Blain, Bremner and Williams Pty. Ltd. to prepare a preliminary report on possible boat harbour sites between Yeppoon and Port Alma on the Central Queensland Coast. Five sites were evaluated according to the following criteria:- (i) Degree of protection afforded (ii) Tidal access (iii) Degree of maintenance dredging anticipated (iv) Capital cost necessary to establish the harbour and the ability to construct the harbour in stages (v) Availability of foreshore area for development (vi) Accessibility by road transport and to established amenities (vii) Availability of suitable quarry material The recommendation that the most suitable site would be at Rosslyn Bay (Figures 1 & 2) was accepted and approval to commence construction was obtained. A 105m rubble mound rock breakwater was constructed in 1968. The breakwater was extended to 210m in 1970 and was further extended to 300m in 1972. In 1976 tropical cyclone 'David' extensively damaged the breakwater and harbour facilities. Subsequently the breakwater has been redesigned following model studies and reconstruction was completed in May 1978. This paper discusses damage to the breakwater from wave and surge action, model studies and repair of the breakwater.
LOADINGS ON RUBBLE-MOUND BREAKWATERS DUE TO EARTHQUAKES
Authors: Wang H. , Yang C.Y. , Lamison C. , Chen S.S.
Published: June 2019

It might reasonably be asked, why study the reaction of a rubblemound breakwater to earthquake loadings? After all, it is essentially a pile of rubble before an earthquake and is probably only a lower or otherwise deformed pile of rubble afterwards. Repairs are simply a matter of adding more stones. Even if damage occurred, the breakwater might still offer partial protection. This is precisely why, to date, breakwaters are mainly designed for wave loadings. There is practically no documented literature'^-' concerning breakwater design for earthquake loading! However, the oceans are now being tapped as possible locations for industrial installations such as offshore deep water ports, refineries, and power plants. Such facilities must be adequately protected since failures might result in heavy financial losses and cause severe environmental repercussions. Therefore, breakwaters which might be used for this protection can no longer be treated as structures whose failure would only be of secondary consequence. It is thus reasonable to ask whether breakwaters to serve these purposes should also be designed against earthquake loading, since even partial failures might not be acceptable. If they should, then what type of design problems can one expect to encounter and how should one handle them? The present work is aimed at exploring these problems through laboratory experiments. At present, there is no existing breakwater that has been designed on the basis of earthquake loading. Likewise, observations of breakwaters after continuous earthquakes are also scarce. Okamoto'2' reports crumbling of riprap, uneven settlement and loosening or tilting of the upper parts of Japanese breakwaters that have undergone earthquakes. After the large Kanto earthquake of 1927, for instance, breakwaters at the ports of Yokosuka and Yokohama approximately 50 kilometers from the epicenter developed irregularities over their entire lengths. In no cases, however, did any of the breakwaters topple or overturn. During the great Alaska earthquake of 1964, breakwaters at Kodiak City and Seldovia, Kenai Peninsula were badly damaged. The damage to the Kodiak City breakwaters was well documented'3'with photographs and surveys taken after the earthquake. The damage was attributed to both earthquake motion and the tsunamis which swept the area.
POLOS PACKING DENSITY AND EFFECT OF RELATIVE BLOCK DENSITY
Authors: Zwamborn J.A.
Published: June 2019

Accuracy and compatibility of measuring and testing techniques are discussed briefly and a plea is made for standardization to avoid, as far as possible, deviations in test results of different laboratories. One of the main causes of these differences is inconsistency in Dolos packing densities and corresponding layer thicknesses or shape factors. In an attempt to alleviate this problem three placing densities, namely 'light', 'mean' and 'dense' have been defined and their physical properties determined. Flume tests with regular waves, and Dolos armour units at these packing densities, showed very little difference in stability and, considering practical limitations during construction, it is suggested that the 'mean' packing density be used for a 'first design', followed by proper model tests. The results of tests with model Dolosse using three different unit densities were inconclusive and further tests using a wider range of densities are underway.
IMPACT WAVE FORCES ON VERTICAL AND HORIZONTAL PLATE
Authors: Massel S.R. , Oleszkiewicz M. , Trapp W.
Published: June 2019

The hydrodynamic impact problem is a very difficult problem because the physics of what actually happens during the instant of impact are not understood. Despite of fact that a large number of references exist on the subject, many questions are left unanswered. The object of this research is to investigate the problems of hydrodynamic impact associated with the water waves impacting on the vertical and horizontal plates..Of particular interest are the impact forces, their relation to the incident wave parameters and scale effect problems.
WAVE PRESSURES ON SLIT-TYPE BREAKWATERS
Authors: Nagai Shoshichiro , Kakuno Shohachi
Published: June 2019

For severe storm waves with periods of 7.0 sec to 14.0 sec and heights of 6.3 m to 9.0 m, it was proved that the resultants of the maximum simultaneous pressures exerted by breaking waves on the slit-type breakwaters with the optimum relative chamber width of 1/L = 0.05 to 0.07 were in most cases less than 70 per cent of those exerted on the conventional composite-type breakwaters.
WAVE FORCES INDUCED BY IRREGULAR WAVES ON A VERTICAL CIRCULAR CYLINDER
Authors: Ishida Hajime , Iwagaki Yuichi
Published: June 2019

In order to examine the irregular wave forces on a small diameter cylinder, laboratory experiments have been conducted on water particle velocities and wave forces with various kinds of irregular waves. As the results, it is indicated that the time variation and the spectral distribution of wave forces can be calculated adequately from the water level variations by using the methods proposed by Reid1' and Borgman2' respectively. Moreover, with respect to the irregular wave forces on a large diameter cylinder, a new calculation method was shown by means of applying Reid's linear filters1' to MacCamy and Fuchs's diffraction theory.
LOADING AND RESPONSE OF CYLINDERS IN WAVES
Authors: Bullock G.N. , Stansby P.K. , Warren J.G.
Published: June 2019

The nature of the wave-induced flow around a circular cylinder is to a large extent determined by the ratio of water-particle orbit size to cylinder diameter, characterized in regular waves by the Keulegan- Carpenter number KC (see Appendix II for definitions]. When D/L > 0.2 wave scattering effects are negligible and it is conventional to describe the fluid loading in terms of drag and inertia forces in-line with the direction of wave propagation plus a transverse 'lift' force. The idealised two-dimensional situation of a cylinder normal to planar sinusoidal flow has been investigated in U-tubes by Sarpkaya (10, 11). As KC advances above 2 vorticity starts to be shed and produces forces in addition to the inertia force which would result from the undisturbed fluid acceleration. The vortex-induced forces become more important as KC increases. Defining the drag force as the component of the in-line force in phase with the fluid velocity and the inertia force as the component in phase with the acceleration, it is found that the drag, inertia and lift can have comparable magnitudes when KC is between 8 and 25. This paper is concerned with the corresponding regime in waves. In the idealised situation vortex shedding is almost perfectly correlated along the length of the cylinder but generally this will not be the case in waves. Here the degree of vortex coherence will influence the vortex-induced forces particularly the lift which is strongly dependent on history effects. Although the forces on fixed vertical cylinders have been measured, little is known about the loading on cylinders in general orientation in either unidirectional waves or planar flows. Real seas are further complicated by being random and multidirectional with the possibility of superimposed currents. The interaction of cylinder vibration with vortex shedding can be highly non-linear in currents, e.g see (12), but again little is known about what happens in waves. Although scale influences the magnitude of forces when vortex shedding is important, small-scale experiments can qualitatively represent full-scale flows. Thus, the interrelation between the various parameters which influence wave loading may be studied in the relatively controlled environment of a laboratory channel. Furthermore, analysis techniques which have been justified on the model scale can then be applied with greater confidence to full-scale situations.
NATURAL WAVE TRAINS: DESCRIPTION AND REPRODUCTION
Authors: Lundgren H. , Sand S.E.
Published: June 2019

In many applications there is a great need for a correct description of the natural, irregular three-dimensional sea and its reproduction in physical and numerical models. Because of the tremendous difficulties inherent in the nonlinearities, the science of coastal engineering is still very far from this ultimate goal. Indeed, the scope of this paper is comparatively very modest: To describe and reproduce natural, irregular two-dimensional waves, i.e. waves propagating in one direction in a flume. In addition, this scope is fulfilled only by assuming linear superposition of Fourier terms. As opposed to the usual spectral description, the deterministic description presented here does not eliminate the phase information in the wave train recorded. Because of the nonlinearities, however, the linear deterministic description invariably degenerates with the distance travelled by the waves. It appears though from the present paper that the degeneration is fairly slow even for rather steep waves.
WAVELENGTH, WAVE VELOCITY AND SHOALING CHARACTERISTICS OF RANDOM WAVES
Authors: Kimura Akira , Iwagaki Yuichi
Published: June 2019

Fundamental properties of random waves determined by the zero-upcross method are discussed. Firstly, the wave length and the wave velocity are treated. Experiments are carried out with some supplemental definitions such as the spatial zero-up-cross method in a laboratory wave tank. Average values of K (= a ratio of measured wave length to theoretical one L /L , ) and R (= a ratio of measured wave velocity to e th J theoretical one C /C , ) are very close to unity though data are considerably scattered. But the relations between L
ON LONG-TERM STATISTICS FOR OCEAN AND COASTAL WAVES
Authors: Ochi Michel K.
Published: June 2019

This paper discusses the statistical properties of long-term ocean and coastal waves derived from analysis of available data. It was found from the results of the analysis that the statistical properties of wave height and period obey the bi-variate log-normal probability law. The method to determine the confidence domain for a specified confidence coefficient is presented so that reliable information in severe seas where data are always sparse can be obtained from a contingency table. Estimation of the extreme significant wave height expected in the long-term is also discussed.
ANALYSES OF HINGED WAVEMAKERS FOR RANDOM WAVES
Authors: Hudspeth Robert T. , Jones Douglas F. , Nath John H.
Published: June 2019

The theoretical dimensionless frequency response functions for the wavemaker stroke spectrum, Qs(iu), and for the wavemaker dynamic pressure moment spectrum, Q^{m), were verified experimentally in the Oregon State University-Wave Research Facility (OSU-WRF) from random waves which were simulated from two types of two-parameter theoretical design wave spectra. The random motions of the wavemaker were first digitally simulated by a unique inverse stacked FFT algorithm which were then used to drive the wavemaker through digital-to-analog converters (DAC). The dimensionless frequency response function for the hydrodynamic pressure moment spectrum was not measured directly but was computed from the dynamic covariance equations for a hinged wavemaker of variable-draft by linear combinations of related dimensionless frequency response functions and cross-spectral estimates. The measured estimates were found to agree reasonably well with the analytical approximations, and these measured stochastic hydrodynamic pressure moment estimates on a hinged wavemaker of variable draft are believed to be unique.
EXCITATION OF LOW FREQUENCY TRAPPED WAVES
Authors: King Robert , Smith Ronald
Published: June 2019

Weak nonlinear interactions in water of non-constant depth between an incident wave, a side-band incident wave and a relatively low frequency trapped wave are shown to lead to the generation of the trapped wave. Three situations are considered in detail: edge waves in a wide rectangular basin, progressive edge waves on a straight beach, and standing waves in a narrow wave tank.
SPILLING BREAKERS, BORES, AND HYDRAULIC JUMPS
Authors: Peregrine D.H. , Svendsen I.A.
Published: June 2019

On gently sloping beaches, almost all water waves break. After the initial breaking the water motion usually appears quite chaotic. However, for a moderate time, for example two or three times the descent time of the "plunge" in a plunging breaker, the flow can be relatively well organised despite the superficial view which is largely of spray and bubbles. If waves continue to break the breaking motion, or "white water" soon becomes fully turbulent and the mean motions become quasisteady. A reasonable definition of a quasi-steady wave is one which changes little during the time a water particle takes to pass through it. We exclude water particles which may become trapped in a surface roller and surf along with the wave. At this stage in its development a wave on a beach may be described as a spilling breaker or as a bore. In fact, there is a range of these waves from those with a little white water at the crest to examples where the whole front of the wave is fully turbulent. In investigating the properties of such waves it is desirable to start by looking at the whole range of related motions. The most obvious extension is to the hydraulic jump; since, in the simplest view, it is equivalent to a bore but in a frame of reference moving with the wave. It is also an example where the mean flow is steady rather than quasisteady.
ENERGY LOSS AND SET-UP DUE TO BREAKING OF RANDOM WAVES
Authors: Battjes J.A. , Janssen J.P.F.M.
Published: June 2019

A description is given of a model developed for the prediction of the dissipation of energy in random waves breaking on a beach. The dissipation rate per breaking wave is estimated from that in a bore of corresponding height, while the probability of occurrence of breaking waves is estimated on the basis of a wave height distribution with an upper cut-off which in shallow water is determined mainly by the local depth. A comparison with measurements of wave height decay and set-up, on a plane beach and on a beach with a bar-trough profile, indicates that the model is capable of predicting qualitatively and quantitatively all the main features of the data.
WIND-GENERATED WAVE DIFFRACTION BY BREAKWATER GAP
Authors: Raissi Hooshang , Wiegel R.L.
Published: June 2019

A number of hydraulic laboratory experiments were made of the diffraction of wind-generated waves by a breakwater gap. The directional spectra of the incident wave was used together with the water wave diffraction theory of Penny and Price for a breakwater gap to predict the energy spectra of the diffracted waves. The difference between the predicted values of the energy spectral density and the measured values demonstrated the limits of using the above techniques. It is likely that this is due to the inadequacy of the diffraction theory of Penny and Price for a breakwater gap for certain ranges of B/L.
RIP CURRENT SPACING AS AN EIGENVALUE
Authors: Iwata Noriyuki
Published: June 2019

Mass, momentum and wave action conservation laws, including the radiation stress, are used to obtain a rip current spacing as an eigenvalue. A coastal region is divided into two parts: offshore region and surf zone separated by a breaker line. Only the case of normal incidence of the waves is considered. From the matching conditions of the two horizontal velocity components at the breaker line, we can obtain rip current spacing as a function of a nondimensional parameter characterizing the surf zone, for an arbitrary value of a parameter indicating the strength of horizontal mixing.
STORM SURGE PREDICTION IN TIDAL RIVERS: A NEW CONCEPTION
Authors: Siefert Winfried
Published: June 2019

The heights of extreme storm surges in the North Sea rise up to U or 5 m above mean high tide. Warning services are established along the coast, mainly based on empirical connections between weather and tide data. A lot of wrong announcements are given especially for places up the tidal rivers. This can become disasterous for a lot of modern, highly sensitive harbour facilities. Thus storm surges are the famous plagues of the southern North Sea coast. Moreover, the "ten plagues of Germany" occurred during the last 16 years. So recently a new conception for storm surge prediction in tidal rivers was developed - with the result of a lot of new understandings of tidal dynamics in rivers (SIEFERT, 1968). We investigated about 130 storm surges, hindcasting all of them and forecasting about 20 of them, and analysed their behaviour in tidal rivers. Now we are able to forecast the upstream heights and even the shape of the surge curve in the Elbe with an accuracy of ± 2 dm, ' 6 hours in advance.
WAVE CLIMATE STUDY In THE REGION OF THE EAST FRISIAN ISLANDS AND COAST
Authors: Niemeyer Hanz Dieter
Published: June 2019

The East Frisian Islands and Coast - located at the southern border of the North-Sea - are significantly characterized by a chain of off-shore islands which are separated from the mainland by wide spread tidal flats (FIG.1). Between the islands there are small and deep tidal inlets with strong currents, through which the tidal volume covering the flats is streaming in and out, with a tidal range of about 2,5 m.
A NEW APPROACH FOR TIDAL COMPUTATIONS
Authors: Le Provost C.
Published: June 2019

During the twenty last years, tidal modelling has been intensively developed. Following the growth of engineering needs in coastal areas, more and more accurate models have been established, and this constant research of better accuracy in the representation of real phenomena bring*us to very expansive models. One way of reducing these costs is to use variable grids in space, in order to concentrate refined meshes in areas of interest. But the finite difference schemes are not well adapted to this kind of procedure : this is why several attempts have been made recently to use finite element technics : C. TAYLOR and J.M. DAVIS in 1975 DO , C.A. BREBBIA and P.W. PARTRIDGE in 1976 D 3 , --- But these applications are not easy. During the same period, since 1975, more complex tentative have been made using Fourier transform of the equations, previously to any kind of numerical integration : tides are effectively quasi periodic phenomena, and their spectra are well known. Two important points arise in doing this : - time variable is eliminated from the hyperbolic problem of propagation, transformed into a set of elliptic problems. - for each elliptic problem, a variational formulation is available. It becomes thus possible to look at the various components of the real tides, and to use finite element technic to integrate numerically these problems in real basins. In this way, B.M.JAMART and D.F. WINTER have used recently a purely numerical procedure based upon the Fast Fourier Transform to carry their tidal computations in fjords, cf.fjsj, while A. ASKAR and A.S. CAKMAK introduced a perturbation technic to handle the non linearities, very important in such problems, cf. [j J . We have followed a similar approach to study the complete spectrum of the tides in shallow water areas for the european seas : North Sea and English Channel, cf.£9j . The aim of this paper is to illustrate the main ideas of our method applied on an academic one-dimensional problem.
COASTAL PROCESSES AT OREGON INLET, NORTH CAROLINA
Authors: Jarrett James T.
Published: June 2019

Coastal processes In the vicinity of Oregon Inlet, North Carolina were studied in connection with the design of a dual jetty system for that inlet. Oregon Inlet is the northernmost breach through the "Outer Banks" of North Carolina and is situated approximately 40 miles (64 km) north of Cape Hatteras and 90 miles (145 km) south of the ocean entrance to Chesapeake Bay, see Fig. 1. The improvements planned for this inlet are part of an overall plan of development directed at enhancing the fisheries industry of North Carolina through the provision of a modern fisheries center at the village of Wanchese, located on Roanoke Island, see Fig. 1. The general layout of the proposed jetty system is shown on Fig. 2. Certain aspects of this design will be referred to later in this paper. In addition to their structural and functional aspects, a major part of the design of the jetties concerns the structure-shore interaction and means whereby adverse shore processes will be prevented in operating the project. Obviously, the construction of jetties or any other type of littoral barrier at an inlet would disrupt the normal movement of and processes associated with longshore sediment transport. Therefore, artificial means of moving littoral materials around a stabilized inlet must be employed to assure that the adjacent beaches are maintained in at least the same state existing prior to any navigation related improvements. The need for a reliable sand bypassing method at Oregon Inlet is accentuated by the fact that the inlet is bounded on the north by the Cape Hatteras National Seashore and on the south by the Pea Island Wildlife Refuge, both of which are Federally owned beach areas managed for the purpose of preserving the natural quality of the Outer Banks environment. The design of a sand bypassing system must be based on a knowledge of the existing shore and inlet processes, particularly as they relate to the rate and directional distribution of longshore sediment transport. When the existing conditions are known, it is possible to estimate the sediment transport rates with the structures in place and, thus, predict the amount and direction in which material will have to be bypassed. This paper describes the approach taken to evaluate the existing and future longshore sediment transport in the vicinity of Oregon Inlet and briefly discusses the proposed bypassing system for the stabilized inlet.
NUMERICAL MODEL INVESTIGATION OF SELECTED TIDAL INLET-BAY SYSTEM CHARACTERISTICS
Authors: Seelig William N. , Sorensen Robert M.
Published: June 2019

A spatially integrated one-dimensional numerical model of inlet bay hydraulics has been combined with a simple sediment transport model to investigate selected tidal inlet-bay system characteristics. A parametric study has been performed using the models to determine the effect of various factors on the net direction and order of magnitude of inlet channel flow and sediment transport. Factors considered include astronomical tide type, storm surge height and duration, variation in bay surface area, time-dependent channel friction factor, and the addition of a second inlet connecting the bay and sea.
THE USE OF IMAGING RADAR IN STUDYING OCEAN WAVES
Authors: Mattie M.G. , Harris D. Lee
Published: June 2019

Imaging radar can be used to provide information about the two dimensional character of the wave field. This is especially important near shore where the effects of refraction and shoaling interfere with the simple interpretation of a directional spectrum based on records from a network of gages. Imaging radar has the advantages of providing full two-dimensional information of the type provided by aerial photography and of being available continuously, including night time and during storms. Imaging radar, of course, also has some disadvantages when compared to other data gathering systems. Specifically, the imaging radar does not provide a measure of wave height. It does not provide as much resolution as aerial photography and the shorter waves of interest may be missed. The most important disadvantage is that short ripples are essential to the detection of long waves, hence swell is not detected outside the breaker zone when the wind is calm or the high frequency waves are inhibited by oil slicks. Several characteristics of the radar images of waves, as compared to aerial photography, are illustrated in Figure 1. Note the similarity of the wave patterns in the radar image and the aerial photograph. The image does not show any features of the land. The location of the radar is shown on the aerial photography by an "X". Ijima et al (1964) and Wright (1965) appear to have been among the first to report the use of radar for imaging ocean waves. Oudshoorn (1960), Wills and Beaumont (1971), Evmenov et al (1973) and others have published photographs of a radar scope showing waves. This report differs from earlier papers on this topic by providing a discussion of practical procedures for overcoming some o£ the more mundane technical difficulties associated with routine data collection.
RIP CURRENTS AND THEIR CAUSES
Authors: Dalrymple Robert A.
Published: June 2019

"The outworn dogmas of science seem to be particularly concentrated in the discussions of the ocean in geology books". Beginning with this controversial statement, F. P. Shepard in 1936 tried to lay to rest the concept of the undertow, which had been debated in the pages of Science for over a decade. At the same time, he introduced the term, rip current, to describe the rapidly seaward-flowing currents, which were well-known to lifeguards at that time, as these currents were responsible for carrying swimmers offshore at frightening speeds. Subsequent studies by Shepard and his colleagues (Shepard, Emery and LaFond, 1941; Shepard and Inman, 1950a, 1950b) showed that rip currents (1) are caused by longshore variations in incident wave height, (2) are often periodic in both time and in the longshore direction and (3) increase in velocity with increasing wave height. The major reason put forth to explain the variation in wave height was the convergence or divergence of wave rays over offshore bottom topography (such as submarine canyons) or the forced wave height variability caused by coastal structures, such as jetties. McKenzie (1958) and Cooke (1970) in their studies corroborated the findings of the Scripps Institution of Oceanography researchers and also pointed out the persistence of rip currents (once high energy waves in a storm had caused rip channels to be cut into the bottom) after the storm had abated. In fact it appears that on coastlines which are affected by major storms which build offshore bars, that the nearshore circulation may be dominated by the storm-1-induced bottom topography for long afterwards. The researchers up to the late 1960's who attempted to theoretically model rip currents knew the importance of longshore wave height variability and the wave-induced set-up in the formation of rip currents, but it was not until Longuet-Higgins and Stewart (e.g., 1964) codified the wave momentum flux tensor that great strides were made in providing models for rip currents. This paper is intended to categorize and review the more recent theories for rip current generation and to discuss a simple model for rip currents on barred coastlines.
WIND-GENERATED LONGSHORE CURRENTS
Authors: Nummedal Dag , Finley Robert J.
Published: June 2019

This paper evaluates, through the use of a stepwise multiple regression procedure, whether parameters descriptive of the surf-zone wave field adequately explain the variability in longshore current velocities, or if the inclusion of additional physical environmental parameters could significantly improve the ability to predict such currents. The data set consists of 250 LEO - observations, collected on a seasonal basis over one year, at Debidue Island beach, South Carolina. A regression analysis was performed both on linear combinations of all measured wave parameters, and on nonlinear parameter combinations proposed in various semiempirical predictive equations. Invariably, in all the regression analyses, the longshore component of the wind velocity proved to be the independent variable explaining most of the observed variance in the current velocity. Therefore, the statistical data analysis presented in this paper strongly suggests that wind stress can be a most significant factor in surf-zone current generation.