bluuebunny/crossref_metadata_2025 huggingface dataset:
A COMPARISON BETWEEN MODEL AND PROTOTYPE WAVES IN HARBOURS
Authors: Bjordal Sverre , Torum Alf
Published: June 2019

A common method of estimating the sheltering effects of different breakwater locations and layouts is to carry out physical model wave disturbance tests. Such tests have been carried out in different laboratories throughout the world for many years. But to our knowledge no reports are available in the literature showing comparison between model measurements and field measurements. The trend is that we know more and more on the wave cl imate along our coasts. Hence we have a better basis to make our economical calculations on breakwaters. We therefore also want to operate our models on a more absolute basis rather than on a comparative basis. The trend in recent years has also been to study breakwater locations and layouts in order to minimize mooring forces and ship movements. On this background VHL found a comparison between model test results and field measurements necessary. Full scale measurements of waves were carried out in two harbours by VHL during the winter 1976/77. This paper will present the results of the comparison of the model and the full scale measurements in Berlevag and Vard0 fishing harbours on the open coast of Finnmark in the northern part of Norway (Fig. I) . The model tests, as well as the full scale measurements, have been sponsored by the Norwegian State Harbour Authorities.
COMPARISON OF SHIPBORNE WAVE RECORDER AND WAVERIDER BUOY DATA USED TO GENERATE DESIGN AND OPERATIONAL PLANNING CRITERIA
Authors: Graham C.G. , Verboom G. , Shaw C.J.
Published: June 2019

This paper presents the results of recent investigations at three sites where waves have been monitored simultaneously by two commonly used deep-water wave recorders, over a total period of 16 sensor-years. The study confirms earlier statements that there are relative differences between the wave parameters and statistical values calculated from the measurements of the two instruments. However, the large amount of data has enabled the authors to quantify the results in engineering terms and to assess the implications for extreme value analysis, spectral analysis and wave climate operational planning.
EXPERIMENTAL STUDY OF WIND WAVES GENERATED ON CURRENTS
Authors: Kato Hajime , Tsuruya Hiroichi
Published: June 2019

This paper presents some experimental results of wind waves generated on currents in a wind-wave channel with a water circulation pump system. The waves were measured at fetches less than 27.8 m by using resistance-type wave gauges. Surface velocities as well as velocity profiles in water were also measured elaborately and true frequency wave spectra were obtained from observed apparent spectra which were modified by the doppler effect of current. Significant wave heights Hwj computed from r)2 and peak frequencies of true spectra fprn were examined with emphasis. It was inferred from the variation of true spectra that the most prominent effect of water current is to change the effective fetch length. Then an idea of equivalent fetch length was proposed to express the current effect on the development of total wave energy. By using the equivalent fetch F' in place of the natural fetch it is shown that Hj/3 and fQm measured under various current conditions can be represented by the non-dimensional fetch relations, respectively, which were originally obtained in the case of no current.
VARIABILITY OF LONGSHORE CURRENTS
Authors: Guza R.T. , Thornton E.B.
Published: June 2019

Simultaneous measurements were made of the offshore directional spectra of gravity waves, and longshore currents within the surf zone. The goal was to test theories which suggest a direct relationship between mean longshore currents (V) in the surf zone and offshore values of the off axis component of radiation stress (S ). Seventeen minute - xv averages of both S and V showed considerable temporal xv variation, and little or no tendency to vary together. There was also considerable longshore spatial variability of the 1ongshore"current. Attempts to measure gradients of S in the surf zone failed because of small errors in instrument orientation. The measurements suggest that considerable temporal and spatial averaging will generally be required to obtain a representative picture of longshore currents, even if no rip currents are present, due to the presence of "eddy" motions or long edge waves.
LONGSHORE CURRENTS DUE TO SURF ZONE BARRIER
Authors: Bettess R. , Fleming C.A. , Heinrich J.C. , Zienkiewicz O.C. , Austin D.I.
Published: June 2019

We consider a straight coastline exposed to large regular waves, of typical wave length, 100 m amplitude 1.6 m, and period 12 sec. The radiation stress gradients in the extensive (up to 2 km wide) surf zone cause set up and long-shore currents. Despite these currents, the beach is known to be fairly stable. If now a cooling water intake basin is introduced on the coast, it is required to determine first whether the wave induced currents in the vicinity of the basin will affect the circulation of cooling water and second, whether sediment transport will occur, leading to a dredging requirement for the basin. An extensive programme of physical model testing and numerical studies is being undertaken, in order to answer the above questions, and this paper will survey the progress made to date. At the 15th Coastal Engineering Conference a paper on the application of a mathematical model to the prediction of dredging properties inside a cooling water intake basin was 9 presented by Fleming and Hunt, which described the first stage of this work . - In that paper a sediment transport model was combined interactively with numerical models of wave refraction, wave diffraction, long shore currents and circulation currents. The last of these numerical models was used to evaluate the current patterns due to the interruption of the continuity of the longshore currents, together with the cooling water flows in the vicinity of the basin. In this paper we describe the development of more sophisticated numerical models for the first three stages of the process. An understanding of the process of longshore current and set up creation, depends on the concept of radiation stress, introduced by Longuet-Higgins and Stewart,12'13' ' in a series of papers. A number of workers have since used the radiation stress to determine coastline phenomena, and we now describe a few of the relevant papers, without any attempt at a comprehensive survey. Bowen 5'6 considered a straight coastline with parallel contours, and determined near shore circulation patterns, using a stream function formulation of the shallow water equations, for normally incident waves, with a sinusoidal coastwise variation in wave amplitude. He used a finite difference method to solve for the stream function. Longuet-Higgins10'11 criticized Bowen's use of a constant mixing length (horizontal) viscosity, and introduced a viscosity which varied directly with the distance from the shore, in his one dimensional analytical model for obliquely incident waves. He was able to obtain analytically longshore velocity profiles, which he plotted for a range of viscosities.
OBSERVATION OF NEARSHORE CURRENT AND EDGE WAVES
Authors: Sasaki Tamio O. , Horikawa Kiyoshi
Published: June 2019

Nodal lines normal to the shoreline of infragravity low mode edge waves in the nearshore zone were observed with eleven wave staffs simultaneously with the nearshore current spatial velocity field on a gently sloping beach. About five peaks were found in the energy spectrum and their frequencies agreed well with cut-off mode edge waves [Huntley(1976)]. Based on the above observation, conceptual models of nearshore current patterns for the infragravity domain are proposed and general current patterns for the three domains are discussed by combining the horizontal patterns of Harris(1969) and the vertical patterns of Sasaki et al.(1976).
COMPARISON OF MODEL AND OBSERVED NEARSHORE CIRCULATION
Authors: Allender James H. , Ditmars John D. , Harrison Wyman , Paddock Robert A.
Published: June 2019

Results from a two-dimensional numerical model for nearshore circulation induced by waves and wind are compared with observations made during two storms at a beach on Lake Michigan. Model-input data include bathymetry, offshore wave characteristics, wind histories, and local water-level changes. The predicted locations of the breaker zone are in rough accord with those observed during the storms. Data for comparison with model results consist of wave and current observations across the surf zone, especially those acquired by using a towed, instrumented sled. The comparisons show that the model often predicts peak currents near the breaker zone quite well, but underestimates the decay of wave height and the strength of longshore currents across the surf zone. Wave breaking on the bar-trough beach structure prevalent in this study apparently is not well represented by the model. An improved breaking criterion, treatment of breaking waves as traveling bores, and inclusion of horizontal mixing of momentum might add to better simulation of surf-zone currents.
WIND-INDUCED WATER SURFACE SET-UP AND DRIFT CURRENTS
Authors: Tang Frederick L.W. , Wu Jin , Chang Charles C.C. , Ou Shan-Hwei
Published: June 2019

A systematic experiment to study the wind-induced flow phenomena was conducted in a laboratory tank. The results are related to the wind friction velocity and subsequently scaled for applications at various fetches under different wind velocities. The wind-stress coefficients are found to be well scaled by the Froude number. The bottom friction is measured with an effective shear gauge. The ratios between the bottom stress and the wind stress are obtained. The complete profiles of wind drift current are measured under various wind velocities. A tentative distribution of drift currents in the whole water depth is proposed. The results from the experiment are used to examine the wind-induced flow phenomena in a closed basin.
DRIFT SPEED OF BUOYS IN WAVES
Authors: Nath John H.
Published: June 2019

The drift speed of small floating objects subjected to periodic waves was investigated experimentally. Although data scatter is evident, the results show reasonably good agreement between Stokes third order mass transport drift speed and the drift speed of small surface floats, for the lower wave amplitudes. For the steepest waves there is good agreement between the data and recent developments of Longuet-Higgins. Surprisingly, the objects of deeper draft, such as a small spar-type buoy, drifted faster than the Stokes drift speed in the lower amplitude wave region of the tests. In the steepest waves the deeper buoys drifted a bit slower than the small objects.
EXTREME SEA LEVELS FROM TIDE AND SURGE PROBABILITY
Authors: Pugh D.T. , Vassie J.M.
Published: June 2019

This paper considers a method of deriving the probability of occurrence of extreme sea levels by combining the probability functions of surge and tide. As a result the quantity of data required is less than with traditional methods. The philosophy of the method is discussed and the conditions under which the theory can be applied are examined. Finally the technique is applied to a number of ports in the United Kingdom and the results are compared with known estimates of extreme levels.
ANALYSIS OF MAXIMUM SEA LEVELS IN SOUTHERN ENGLAND
Authors: Graff J. , Blackman D.L.
Published: June 2019

Along the south coast of England, series of observed annual maximum sea levels, ranging from 16 years to 125 years have been analysed for each of 10 ports. The Jenkinson method of analysis was used to compute the frequency of recurrence of extreme levels. For a number of these ports the series of annual maxima are shown to have significant trends of the same order as those for mean sea level. The Jenkinson method can be simply adjusted to cope with maxima having a component linear trend, making it possible to allow for such trends in computing the frequency of recurrence of extreme levels. If a trend in the annual maxima varies throughout the sample of observations it is shown that difficulties arise in using the Jenkinson method to compute acceptable statistics. It is also shown that for certain ports having long series of observed annual maxima it may be necessary to restrict the sample size of observations in order to compute estimates of the recurrence of extreme levels within reasonable return periods.
NUMERICAL STORM SURGE FORECASTING
Authors: Engel Manfred
Published: June 2019

The present state of the development of an operative storm surge prediction system in Germany is described. It is based on numerical models of the atmosphere and the North Sea. First simulations of the storm surge on Jan. 3, 1976 yield the result, that the observed water levels along the North Sea coasts can be recalculated quite well using a meteorological input derived from observations, Whereas the forecasted water levels, using the predicted geostrophic winds of the atmospheric model, are too low since the pressure gradients are too weak. A series of storm surge recalculations with observed and predicted meteorological data shall answer the question, wether parameter fits, applied to the predicted wind stress, lead to satisfying results, suitable for practical applications.
ANALYSIS OF STORM TIDE WAVES
Authors: Barthel Volker
Published: June 2019

First results of a wave investigation program in the Outer Weser (German Bight of the North Sea) point out, that under storm conditions higher waves than computed by the normal prediction methods are possible in the exterior estuary. In the interior estuary higher waves occur mainly as a sort of swell. The influence of bad weather conditions on the probability of runs of waves with H*> H 1/3 is shown in two examples in comparison with a theoretical investigation.
ADJUSTMENT AND VERIFICATION OF THE RANDDELTA II MODEL
Authors: Langerak A. , De Ras M.A.M. , Leendertse J.J.
Published: June 2019

In the mid-1950s the Netherlands government embarked on a massive construction program, called the Delta Plan. Its purpose was to enhance protection from floods caused by the North Sea in the estuaries of the Rhine, Meuse and Scheldt. According to the plan, all connections to the sea were to be closed by dams, except the New Waterway to Rotterdam and the Western Scheldt. In 1974 all dams and dikes were complete except the dam closing off the Eastern Scheldt from the sea. In view of growing opposition to a complete closure, plans were revised in 1976, and instead of the dam, a storm surge barrier will be constructed. This barrier will reduce the tidal range in the Eastern Scheldt and will be closed during storm surges. In support of engineering and environmental studies related to the construction and operation of this barrier, a large numerical model has been developed, which covers the Eastern and Western Scheldt and the adjacent offshore area. The section of the North Sea which is included in the model is about 120 km long and 30 km wide, running from Blankenberghe in Belgium to Scheveningen in the Netherlands (Fig. 1). The bathymetry of the model area varies widely. In general it slopes from the shore to about 25 m at 30 km from the coast. In certain sections of the offshore area, the bottom is relatively flat; in other areas it has offshore bars and the bottom contains underwater sand dunes with a height of several meters. In the estuaries the tidal flow has scoured deep channels. The tidal flats near the North Sea are generally sandy, but the ecologically important tidal marshes located more inland contain much finer material. The flow and the water levels in the region which is modeled are generally tide-induced. However, the influence of meteorological effects is always present and sometimes dominates water movements and water levels (storm surges). The influence of the fresh water discharges is of much less importance; generally their effects can only be noticed in the immediate vicinity of the discharge. The tides in the offshore area of the model are part of the complicated tide system in the North Sea. The semidiurnal tidal wave propagates along the coast in a northeasterly direction. During this propagation the amplitude reduces from about 1.90 m near Blankenberghe to about .85 m near Scheveningen.
ROLE OF 2D AND 3D MODELS IN JONSDAP '76
Authors: Davies A.M.
Published: June 2019

This paper describes how a two-dimensional numerical model of the North Sea was used to determine optimum positions for the deployment of off-shore tide gauges during the JONSDAP '76 oceanographic exercise. A three-dimensional model of the North West European Shelf is also described. Using this model the three-dimensional distribution of the M2 tidal current over the shelf has been computed. This model has also been used to compute the wind induced circulation of the North Sea for the INOUT period of JONSDAP '76.
HYDRODYNAMIC MODELLING OF THE SOUTHERN NORTH SEA
Authors: Prandle David
Published: June 2019

Numerical modelling of rivers, estuaries and shallow seas has attracted increasing interest over the last two decades. The models have developed from one dimensional (ID) applications to tidal propagation and flood routing through two and, finally, three dimensional applications to motions ranging from "pseudo-turbulence" to annual mean residual flows. The present account describes the development, over the last five years, of the modelling studies carried out by the author concerning the hydrodynamics of the southern North Sea and River Thames. The objective is to identify those major points which have emerged that may have a wider significance.
VARIATIONS OF WAVE-ENERGY LEVELS AND COASTAL SEDIMENTATION, EASTERN NICARAGUA
Authors: Owens E.H. , Roberts E.H.
Published: June 2019

High rates of weathering, abundant rainfall, and high discharge rates combine to supply large volumes of sediment to the coastal zone of eastern Nicaragua. This terrigenous sediment is confined to a narrow section of the inner shelf (
AN EVALUATION OF EXTREME WAVE CLIMATE AT KEAHOLE POINT, HAWAII
Authors: Bretschneider Charles L. , Rocheleau Richard E.
Published: June 2019

An evaluation of extreme wave climate was made for Keahole Point, Hawaii. This evaluation was based on three separate sources of wave data and five methods of statistical evaluations. The three sources of data include (1) wave hindcasts data of 10 severe storms between 1947- 1961 by Marine Advisors (1963), (2) wave hindcast data of 11 severe storms between 1947-1965 by U.S. Army Corps of Engineers, Honolulu District, and (3) shipboard wave observations of the U.S. Navy reports. Figure 5 shows SSMO area No. 1 for south and southwest of the islands and SSMO areas Nos. 2 and 3 for north of the islands. The five methods of statistical extrapolations for extreme events include: (1) Gumbel's (1958) first asymptotic distribution, (2) Weibull distribution (1961), and (3,4,&5) semilog, log normal and normal distributions. The three most widely used distribution functions are: (1) Gumbel's (1958), (2) log normal (see Jasper, 1956), and (3) Weibull (1961), given in order as to the author's preference. The statistical extrapolations for Keahole Point, Hawaii, are given in Table 9 and Figure 9. Only Gumbel's (1958) distribution was applied to the north shore as shown in Table 8. Based on Gumbel's distribution function, the results of the wave hindcasts statistics on the average (50 year recurrence interval) indicate that (1) the Marine Advisors (1963) wave hindcasts are about 25 percent higher than the U.S. Army Corps of Engineers wave hindcasts and (2) the U.S. Navy SSMO observations and the U.S. Army Corps of Engineers wave hindcasts are in closest agreement. Shipboard wave observations have always been subjected to questions. However, various authors have correlated instrumentally measured and observed wave observations. A summary of these correlations are given in Table 6. No correction was made to the statistical analysis of the SSMO data.
MORPHOLOGY OF COASTAL BARRIERS, DELAWARE, U.S.A.
Authors: Kraft John C. , John Chacko J. , Maurmeyer Evelyn M.
Published: June 2019

The Atlantic Coast of Delaware consists of four separate but continuous segments including (from north to south): (1) a northward-projecting spit complex (Cape Henlopen); (2) eroding Pleistocene headlands; (3) a linear coastal washover barrier; and (4) an area of migrating inlets with associated modern and relict ebb and flood tidal deltas. Coastal process studies show that continuing coastal erosion is accompanied by longshore transport of sand eroded from headlands, offshore transport to the nearshore marine area, and overwash processes transporting sand landward across the barrier. Studies of the adjacent nearshore marine area show that the barrier and its various geomorphic elements lay at the outer edge of the continental shelf approximately 12,000 years ago, and migrated landward and upward to the present position as the Holocene marine transgression continued. The sequence of coastal sediments of the barrier system consist of (landward to seaward) tidal marsh fringe, lagoonal muds and sands, barrier sands (including washover, dune, and beach deposits), and shallow nearshore sand and gravel. Drill-hole studies provide information on the subsurface configuration of the barrier from which the three-dimensional structure and stratigraphy of coastal sedimentary environmental lithosomes may be defined.
MAINTENANCE OF SANTA CRUZ HARBOR, CALIFORNIA, USA
Authors: Magoon Orville T. , Baer Don C.
Published: June 2019

In planning and operating coastal harbors subjected to shoaling, it is imperative that the characteristics and regime of the sediments which deposit in the harbor entrance be quantified to the maximum extent possible in order that the economic impacts of the channel shoaling and along adjacent shores may be evaluated. This paper presents a brief progress report on the study of a coastal harbor in an area subjected to shoaling. This study represents the input of many engineers and researchers in the United States.
CASE STUDIES OF DELAWARE'S TIDAL INLETS: ROOSEVELT AND INDIAN RIVER INLETS
Authors: Dennis W.A. , Lanan G.A. , Dalrymple R.A.
Published: June 2019

Studies were undertaken to document the past and present characteristics and trends of Delaware's two major tidal inlets, Roosevelt and Indian River Inlets. It was found that both inlet complexes are effective sediment traps causing considerable downdrift erosion. The major mechanism by which sand enters Indian River Inlet is by overtopping the impounded south jetty. At Roosevelt Inlet sediments are readily transported past the severed steel sheet pile jetties. The results of a one-dimensional hydraulic model, as well as field measurements, predict the presence of a mean southerly flow through the canal and bay system which connects these two inlets. This flow is shown to have a substantial effect on the behavior and stability of these entranceways, causing major asymmetries on the depositional patterns at each location. Roosevelt Inlet was found to have a strong tendency to trap sediment within its throat; whereas, Indian River Inlet, on the opposite end of the system, was found to retain large quantities of sand on its developing ebb tidal shoal.
VELOCITY AND STRESS MEASUREMENTS IN A TIDAL INLET
Authors: Huntley David A. , Nummedal Dag
Published: June 2019

Fast-response electromagnetic flowmeters were used in a marginal flood channel of an ebb tidal delta to assess the importance of wave contributions to the flood dominance of these channels. Measurements were made at a single point in the channel in both ebb and flood currents. The oscillatory motion of waves was a very significant feature of the velocity records, and its magnitude was comparable with the mean flow at all stages of the tide. This observation shows that flowmeters capable of responding accurately to wave velocities are needed to obtain accurate values of mean flow. Some earlier measurements made with slow response flowmeters are probably unreliable. Wave contributions to the mean flow were assessed by looking at the correlation between the low frequency (>17.5s) oscillations of the along-channel current and the low frequency envelope of the wave velocities. Surprisingly little correlation was found for any time lag, suggesting that wave effects were not important in the mean tidal currents in the channel studied. However, close to low tide on the ebb, conditions existed which appear to have been favourable for the "wave pump" mechanism suggested by Bruun andViggisson (1973). Significant correlation between the wave envelope and low frequency fluctuations was observed at this time. It is therefore suggested that wave effects can be important to the mean flow in marginal channels with rapidly converging and shoaling mouths which are oriented towards the dominant incident wave direction.
THE EFFECT OF OFFSHORE DREDGING ON COASTLINES
Authors: Price W.A. , Motyka J.M. , Jaffrey L.J.
Published: June 2019

The South of England is well endowed with land deposits of river gravel and sand. Nevertheless, the demand for aggregate and the need to conserve agricultural land have increased to the point where in 1976 sea dredged aggregate was accounting for 11% of the total sand and gravel production. In addition to this annual home consumption of about 12 million tonnes of dredged aggregate a further 3.5 million tonnes was exported to Europe in 1976. Understandably, authorities responsible for coast protection and sea defence view the increase in the removal of marine deposits with concern and a system of licensing by the Crown Estate Commissioners who are responsible for the sea bed from high water to the UK Continental shelf limit has been developed over the years. Dredging by port authorities within their area ofjurisdiction, for navigational purposes, is outside this licensing system. Within the three mile limit local authorities have powers under the Coast Protection Act to regulate dredging. In 1976 a report by an advisory committee to the Department of the Environment1-1^ recommended, among other things, that further studies should be carried out by HRS aimed at reviewing the existing constraints on marine dredging for gravel. In general, the material which is sought for construction purposes is a 60% shingle, 40% sand mixture, but sand is also needed for reclamation fill and for industrial purposes. The areas dredged at present are shown in Figure 1. This paper deals briefly with the licensing procedure and at some length with the involvement of the Hydraulics Research Station in assessing how dredging might affect the coastline. The effect on fisheries, navigation, coastal ecology, and other interests is considered by other organisations. Very little is known of the criteria applied to offshore dredging by other countries, apart from Germany, but with the increased exploitation of the sea bed it is important that information gained by other countries should be used to improve our existing criteria. .
SURF ZONE RESONANCE AND COUPLED MORPHOLOGY
Authors: Chappell John , Wright Lynn Donelson
Published: June 2019

The edge wave hypothesis for periodic inshore morphology and circulation is tested for five beaches and is supported by resulting wave-current spectral and cross-spectral data. Beach types range from a reflective, narrow surf zone, case through various dissipative medium to high energy beaches including some with inshore bar-trough morphology and one broad surf zone troughless one. In all cases beachface reflectivity is moderately high (E < 2.5) and inshore resonance occurs, indicated by strong spectral peaks at lower than incident frequency with wave-current co-peaks being 90°out of phase. Several different edgewave frequency and mode combinations are indicated. The reflective beach shows an n = o subharmonic edgewave (i.e. at half incident wave frequency) which Guza and Davis (1974) predict as the most likely case, viz. the (o,o) triad. The troughless dissipative case shows a (1,0) edgewave triad; the same occurs in some bar-trough dissipative cases but in other cases is supplanted by the (o,o) sub-harmonic wave and/or by a lower subharmonic wave at h, incident frequency. The likelihood of a given edge .waveset appears to be regulated by surf friction, and a change of edge wave set appears likely to explain observed changes of inshore circulation.
BEACH CUSPS AND EDGE WAVES
Authors: Huntley D.A. , Bowen A.J.
Published: June 2019

Beach cusps are very common, concave-seaward cuspate patterns at the shoreline of a beach, which tend to occur with a regular longshore spacing, but which can have a wide range of longshore wavelengths from a few centimeters to several kilometers or more. Edge waves, resonant waves trapped at the shoreline by refraction, have been suggested as the cause of beach cusps but it has proved difficult to establish a definitive link on natural beaches . This paper describes field measurements of nearshore velocities, in all three orthogonal directions, that show the presence of edge wave motion just before the formation of beach cusps of the corresponding wavelength, and thus provides convincing evidence that edge waves are responsible for beach cusps. The magnitude of the observed edge wave oscillatory and drift velocities are found to be large and apparently well able to form cusps of the observed size. The observed edge waves are at the subharmonic of the incident wave frequency and thus are the field equivalent of the laboratory observations of Guza and Inman (1975) and Guza and Bowen (1977). It is not clear, however, whether the developing cusp topography enhanced or suppressed the edge wave motion.
TRACKED VEHICLE FOR CONTINUOUS NEARSHORE PROFILES
Authors: Seymour Richard J. , Higgins Alan L. , Bothman David P.
Published: June 2019

The measurement of nearshore profiles has been the traditional method for evaluating on- and offshore transport of beach sand by waves. The measurement on that portion of the beach face which is dry at low tide presents no particular problems and can be effectively accomplished with conventional rod and level surveying techniques. Once the measurement location moves into the wet part of the foreshore, however, the problems rapidly increase. In general, it requires an extremely dedicated rod man to remain on position in breakers larger than a meter, although measurements in breakers up to 2 meters in height have been accomplished on a nonroutine basis. When waves exceed this height, or when the water depth exceeds the ability of a man to stand and hold the rod, this method must be abandoned. In deeper water, and well outside the surf zone, a boat and fathometer approach is normally employed with considerable loss in vertical and horizontal accuracy. In particular, the vertical resolution is decreased by the uncertainties in knowledge of the instantaneous sea level because of the combination of tides, waves and storm surge. If the tides are large and the waves small, it is possible to achieve an overlap between the boat survey and the shore survey. When the wave height exceeds the ability of the boat to operate, this method also must be abandoned. Although larger boats can operate in larger waves, they are generally also restricted to deeper water. The result of all of the restrictions described above is that profiles can be measured with reasonable accuracy only during periods of low waves. Unfortunately, the episodes of greatest interest are the rapid cutting back of the beach face and the accompanying offshore bar building which occur during times of high waves. The technology to measure the storm waves has been available for many years. The ability to correlate wave parameters with offshore transport rates requires the ability to make accurate profiles from the dry beach through and beyond the breaker line under storm wave conditions. This paper describes a vehicle that was developed to meet this need.
DISTRIBUTION OF SAND TRANSPORT RATE ACROSS A SURF ZONE
Authors: Swaragi Toru , Deguchi Ichiro
Published: June 2019

The distributions of longshore and on-offshore sediment transport rates in a surf zone were measured by an apparatus which was able to separately record both components of the sediment transport rate,, The characteristics of their distributions were discussed from the bottom shear stresses which were measured by the shear meter under the same wave conditions as the laboratory experiment of the sediment transport. The maximum bottom shear stress took place at the depth between the breaking depth of waves and the depth where the velocity of the longshore current showed a maximum. On the other hand, the maximum on-offshore and longshore sediment transport rates occured at the depth slightly shallower than the depth where the maximum bottom shear stress took place. What's more, the longshore sediment transport rates were represented by the longshore current velocity and the bottom shear stress generated by waves and the longshore current. However, the distribution of the on-offshore sediment transport rates showed more complicated profile than that of the longshore sediment transport rates because there were no eminent unidirectional flow in the direction normal to the shore line. Therefore, the on-offshore sediment transport rates could not be formulated by the bottom shear stresses.
SEDIMENT TRANSPORT AND RIPPLES DUB TO WAVES AND CURRENTS
Authors: Pruszak Zbigniew , Zeidler Ryszard B.
Published: June 2019

Water velocities and shear stresses have been determined for a laminar boundary layer of a progressive wave travelling over a regular series of ripples. The Lavrentiev variational method was used to transform conformally the water area with ripples into a strip with flat bottom, while the Lin approach permitted solution of the boundary layer equation. The theoretical prediction of the bed friction was verified experimentally with a new mechanical apparatus. By coupling the theoretical shear stress at the rippled bed with laboratory data for ripple parameters one can expose the friction conditions that control the growth and decay of ripples. If waves develop higher values of shear stress, the rippled bed becomes gradually washed out. Eor known shear stresses, basing on the Erijlink-Bijker formula one can compute sediment transport rates. In the respective diagram, a curve of s.t. rate versus bottom friction consists of two branches. The stages of the growth and decay of ripples are reflected in the lower and upper branches of the curve. For identical ripple height there are two values of s.t. rate , for two different wave intensities, likely to differ by as much as 25 per cent. Three-dimensional ripples have been analyzed with regard to bed friction and compared with two-dimensional conditions.
SEDIMENTATION IN CHANNELS AND TRENCHES
Authors: Bijker E.W.
Published: June 2019

In this paper the siltation in approach channels and trenches due to cross currents and waves is discussed. It is in this respect not necessary that the current crosses the channel at a right angle. When the current crosses the channel obliquely simply a greater distance over which the water flows over the greater depth is introduced. Deviations in the flow pattern - see figure 1 - due to the channel are neglected. When the flow pattern is known, either from measurements in nature or in model this effect can easily be introduced. The influence of the waves is introduced through the introduction of an increased bed shear and subsequently higher diffusion coefficient (see Bijker, 1971, [3]).
SEDIMENTATION IN DREDGED NAVIGATION CHANNELS
Authors: Mikkelsen Lars , Mortensen Preben , Sorensen Torben
Published: June 2019

The feasibility of a harbour project, which involves dredging of an access channel, may to a large extent depend on the future maintenance dredging in the channel. It is therefore important to be able to calculate sedimentation in dredged channels with sufficient accuracy. In 1974 and 1975 the Danish Hydraulic Institute (DHI) carried out a study of the most feasible access channel to Warri Port situated in the Western Niger Delta, Nigeria. Two alternative entrances were studied and in conclusion it was recommended to improve the existing access channel through Escravos Entrance.
SOME ASPECTS OF COASTAL ENGINEERING RESEARCH WORKS IN CHINA
Authors: Kai Yen
Published: June 2019

China has a long coastline. Only for the continental part of China, the length of coastline amounts to 18,000 km and, when including the coastline of more than 6,400 islands, an overall length of more than 32,000 km may be counted. As far as the geographical features are concerned, China is characterized by the prevalence of plateau in the west, such as plateau of Tibet and Sinkiang regions and plateau of Yunnan and Kweichow provinces. There are nearly a hundred rivers, the most prominent of which are: the Yangtze River, the Yellow River, the Pearl River etc., flowing from west to east into the Pacific, and carrying about 2,000 million tons of sediment each year to the sea. As a result, silty coasts prevail in the vicinity of estuaries while sandy coasts emerge from a distance away. Generally speaking, the depth of coastal waters is comparatively small, especially along the silty coasts, where the beach profile presents a very gentle slope, varying from 1/50 to 1/500, and in some extreme cases even to 1/2000. Hence the maintenance of water depth in coastal harbours and estuaries has become one of salient problems of coastal engineering in our country.
SIMULTANEOUS WAVE AND CURRENT FORCES ON A PIPELINE
Authors: Knoll David A. , Herbich John B.
Published: June 2019

The hydrodynamic loads on an offshore pipeline resting on the ocean bottom are a function of parameters associated with waves and currents acting near the pipeline. There have been many studies conducted to develop the criteria needed to estimate the hydrodynamic loads imposed by waves and currents. Many of these studies have investigated the effect of these phenomena individually, but to date only limited research has been directed towards evaluating the combined effect. In general, the investigations of the interaction of waves and currents and their effect on the fluid force have been directed toward vertical piles1'2'3'1*'5 and structures in a random wave field with a current present;6'7'8'9 however, the fluid force of waves in the presence of currents on pipelines has not been directly addressed. The purpose of this research was to investigate the interaction of waves and currents and its relationship to the forces on submerged pipelines. A model pipeline in a wave-flume was used to obtain experimental values which were compared to values predicted by the Morison equation in conjunction with the superposition of the waves and a current. The Morison equation10 was used to evaluate the forces on a horizontal cylinder resting on the bottom. The two major input parameters required by this equation are (1) the water particle kinematics of velocity and acceleration; and (2) the coefficients of drag and inertia. The testing program investigated the drag forces developed by the combined waves and a current. The inertia forces were assumed small when compared to the drag forces since a relatively small diameter cylinder was used in the experiments, thus the accelerations were small.
WAVE-INDUCED SEEPAGE EFFECTS ON A VERTICAL CYLINDER
Authors: Durand Thomas J.P. , Monkmeyer Peter L.
Published: June 2019

This study deals with the seepage effects experienced by a large, vertical, circular cylinder resting on a submerged bed of sand when planar water waves interact with it. Potential theory is used to describe the seepage flow field. The sea bottom pressure condition is determined from the water field velocity potential derived by MacCamy and Fuchs (1954) in the case of planar waves diffracted by a large impervious cylinder. Consideration is also given to cylinders with a thin circular base whose diameter exceeds that of the cylinder itself. The problem formulation as well as the initiation of the analysis apply to the general case of a bed of sand with finite depth. For the case of infinite depth of the porous medium, theoretical solutions for the seepage pressure are obtained in the form of infinite integrals. Theoretical solutions for the pressure along the cylinder circular base are then derived, leading by integration to closed form expressions for the wave-induced seepage uplift force and overturning moment exerted on the cylinder. These expressions for the force and moment, which are presented in non-dimensional form are shown to be universal functions of a unique variable. Graphs are provided so that very few computations are required to determine the uplift force and overturning moment exerted on a cylinder. A comparison with various approximate theories reveals the present theory to be the only one which gives reliable results in general. The amplitude and phase angle of the oscillating wave-induced pressure along the cylinder base are determined numerically. Results for the pressure amplitude are presented as non-dimensional ratios to the amplitude of the pressure that would prevail if no cylinder were disturbing the wave field. Expressions for the exit gradient around the cylinder base are also determined. Contours of the ratio of the exit gradient to the one that would prevail in the absence of a cylinder are presented. Laboratory measurements of uplift pressure amplitudes on a circular cylinder show good agreement with theoretical calculations.
METHOD OF ANALYSIS OF RANDOM WAVE EXPERIMENTS WITH REFLECTING COASTAL STRUCTURES
Authors: Gaillard Pierre , Gauthier Michel , Holly Forrest
Published: June 2019

A method of evaluation of the incident and reflected wave spectra in laboratory experiments or field investigations, based on the analysis of wave records obtained with a three-gauge array, is presented. Results of a laboratory investigation with a rubble-mound breakwater and with a special type of sea-wall (ARC system) are given to illustrate the applications of the method.
HAVE IMPACT PRESSURES ON COMPOSITE BREAKWATERS
Authors: Mogridge G.R. , Jamieson W.W.
Published: June 2019

Wave impact pressures and forces on composite breakwaters have been measured in the laboratory. A solid wall breakwater and a perforated breakwater were instrumented with small pressure transducers in a study designed to estimate the relative effectiveness of perforated breakwaters in reducing impact loads caused by breaking waves. Experimental results of maximum pressures and forces measured on the breakwater walls are presented as cumulative probability distributions. It is concluded that the perforated breakwater experiences significantly lower breaking wave loads although local impact pressures may be as high as those measured on the solid wall breakwater. Further studies are required on the perforated breakwater and alternative designs to determine the most suitable caisson type for the reduction of wave impact forces.
CONSTRUCTION AND MODEL INVESTIGATION OF STORMWATER OUTFALL
Authors: Heathcate K.A. , Brittan G.W.
Published: June 2019

Posford Pavry Sinclair and Knight were commissioned in 1976 to design a new stormwater outfall off one of Sydney's surfing beaches. The location of the outfall was dictated by a previous outfall which had been built in the dry when the beach line was much further seaward but which had been destroyed by wave action when the beach line retreated to the 1976 position (a distance of approximately 50 metres (Figure 1)).
FULL SCALE NEAR SURFACE WATER PARTICLE VELOCITIES AND PRESSURES ACTING ON AN INCLINED TUBULAR MEMBER
Authors: Busching Fritz , Martini Eckehard
Published: June 2019

A field investigation programme on simultaneous wave force and water particle velocity measurements is decribed with reference to an inclined tubular member subjected to offshore wave kinematics. First measurements at supercritical Reynolds numbers indicate strong irregularities in successively taken pressure distributions on the circumference of the test section as well as in the velocity vectors. The influence of superimposed tidal currents is obvious.
ENERGY TRANSMISSION OVER BREAK WATER - A DESIGN CRITERION?
Authors: Bade P. , Kaldenhoff H.
Published: June 2019

The wave transmission from seaside to lee of break waters depends on structural parameters as well as on the initial wave climate. Transmission coefficients for special boundary: conditions are known, but information about wave parameters are often not available or they cover often only special cases. Again a case study, undertaken for the break water at the proposed deep water harbour at Scharhoern/Neuwerk, Germany, documented this lack. The results of the case study using conservative wave parameters did not answer the important questions of energy transmission sufficiently, thus we investigated the characteristics of the initial and transmitted wave spectra. A special case was treated initially and subsequently more general situations were examined. These tests were carried out using a physical model of a length scale of 1:10 under conditions described by Froude's law.
THE DESIGN CONCEPT OF DUAL BREAKWATERS AND ITS APPLICATION TO TOWNSVILLE, AUSTRALIA
Authors: Bremner W. , Foster D.N. , Miller C.A. , Wallace B.C.
Published: June 2019

In Central and North Queensland the coastline is protected by the Great Barrier Reef over a length of some 1900km from Gladstone in the south to the tip of Cape York (Fig. 1). The fetch distance from the reef to the coastline is very variable from about 15km to 140km. Hence the coastal areas north of Gladstone have moderate to low wave climates except during abnormal weather events such as cyclones or long time interval bands of strong winds. In these events larger storm waves of significant wave heights of 10m may be superimposed, in the case of cyclones, on storm surges several metres in height. The design of breakwaters and shoreline structures for protection against all except cyclonic and strong wind band effects requires, in the main, readily available sizes of armour rock and relatively low crest elevations. To offer similar protection against cyclonic weather events often requires the use of artificial armour units of concrete and a substantial increase in crest heights. The resulting increase in costs makes many of the small projects uneconomic. In this paper the concept of using an offshore breakwater which is designed to fail under extreme wave conditions to protect an inner breakwater or revetment is examined and the results applied to Townsville Harbour where cost savings of the order of 40 percent were achieved over a conventional design.
A DETACHED BREAKWATER SYSTEM FOR BEACH PROTECTION
Authors: Walker James R. , Clark Denton , Pope Joan
Published: June 2019

Three segmented, detached breakwaters were constructed In the fall of 1977 at Lakeview Park, Ohio, on Lake Erie, to protect a beachfill to be used for recreation and shore protection. This paper documents the design procedures which established the configuration of the breakwaters and the beachfill, and determined the need for a terminal groin. The beachfill has been monitored by aerial photography and bathymetric profiling. During the second year, a storm of near design intensity generated severe waves concurrently with high Lake levels and eroded the updrift beach; however, the initial beach configuration was partially restored by natural processes during the following summer season. The project has functioned well, with very little loss of sand from the system and without adverse impacts on the downdrift coast.
PROBABILISTIC DESIGN OF SEA DEFENCES
Authors: Bakker W.T. , Vrijling J.K.
Published: June 2019

Designs of dikes and dunes according to current Dutch guidelines, based on a deterministic approach, are not consistent with probabilistic philosophy. This statement is amplified in the present paper as a pilot investigation; a rough outline for a probabilistic method of dune and dike computation is given. Numerical comparison of probabilistic and deterministic methods is hampered due to the fact that the results according to the deterministic approach depend on engineering instinct in the choice of boundary conditions and because the probabilistic approach is not as yet operational. Illustrative computations show differences of a factor 1000 in failure probability, starting from dimensioning according to the same standards, following deterministic guidelines.