bluuebunny/crossref_metadata_2025 huggingface dataset:
PROTOTYPE TESTING OF DOLOSSE TO DESTRUCTION
Authors: Terao T. , Terauchi K. , Ushida S. , Shiraishi N. , Kobayashi K. , Gahara H.
Published: June 2019

The Dolos, a type of armor unit, has been used widely for breakwater and shore protection works in the world. However, it has been reported that the armor layers of several breakwaters have been damaged by wave action, and it is probable that the breakage of Dolos has been the cause of that failure. In this paper, static and dynamic tests using Dolosse units are described. 4t reinforced units and 4t, 0.4t and 0.04t unreinforced units were used. In these tests, concrete surface and reinforcing bar stress of Dolos, and impact load were measured. The results of these tests were as follows: (1) From the both tests i.e. the static load test and the drop test, stress was greatest in the corner between the chamfer and the stem. Cracks occurred at this point. (2) In the static load test, comparing the results of both units with reinforced and unreinforced chamfer, it became clear that the reinforcement of the chamfer could reduce the magnitude of the stress concentration. (3) In the drop test, the drop height which made cracks was almost constantly independent of the weights of the units. And it could be considered that there was little influence of increasing the concrete strength as to the breakage of Dolos.
THE MONITORING OF RUBBLE MOUND BREAKWATER STABILITY USING A PHOTOGRAPHIC SURVEY METHOD
Authors: Kluger J.W.J.
Published: June 2019

A method of surveying the above-water slope of breakwaters by means of photography has been developed at the National Research Institute for Oceanology. The method is simple and inexpensive and yet capable of detecting movement or displacement of a single armour unit on a breakwater. This poster paper describes the method and presents some examples of its application in the field.
DISSIPATION OF WAVE ENERGY IN A SEAWATER OUTFALL CHANNEL
Authors: Witthaus K.G. , Retief G. de F. , Prestedge G.K. , Huskins L.R.
Published: June 2019

This paper describes the investigation of means of reducing wave action reaching the shoreward end of a power station cooling water outfall channel without resulting in significant head loss to the outflowing water. A variety of conceptual methods of reducing wave action in the outfall channel was examined. A physical model of the outfall was constructed. It was found that a rubble mound wave energy dissipator located in the outfall channel dramatically reduced wave action at the discharge seal pit.
THE ESTUARIES OF NATAL: A METHOD OF CLASSIFICATION
Authors: Perry J.E.
Published: June 2019

This poster paper describes a .hydrological/hydraulic classification of the estuaries of Natal, based upon aerial photography. The modus operandi is outlined and although the study is in its early stages, some key factors (natural and man-made) are indicated together with the method by which they are quantified.
YACHT HARBOURS IN THE UNITED KINGDOM
Authors: Mettam J.D. , Mornement P.C. , Berry J.G.
Published: June 2019

The authors describe the introduction and development of commercial yacht harbours in the United Kingdom. In the case of the south and west coasts where there is a high mean spring tidal range of up to 8 metres, this has resulted in the provision of enclosed basins, provided with either some form of gate or sill to retain the water. These are described, with typical examples. Recent developments in the design of sector gates are reviewed.
LOCAL WIND FORCING AND SMALL SCALE UPWELLING
Authors: Bain Cairns A.R.
Published: June 2019

This study characterizes some wind stress effects on a coastal site which is a focus of small scale upwelling having a scale of the order of 10 km. Two time scales are considered. Firstly the seasonal character of wind stress with the associated sea temperature fluctuations is described. Secondly individual wind events of a few days duration are characterized by extent and rate of upwelling and offshore displacement of the thermocline front. Data on the thermocline displacement is fitted to Csanady's model of coastal upwelling, which leads to the prediction of upwelling parameters for given wind events.
MULTIPURPOSE GATE OPERATION
Authors: Mizumura Kazumasa
Published: June 2019

Predictions of time-varying salinity under arbitrary gate operations are presented of a tidal lake and its inlet. Particular regard is given to the modeling of salinity and gate operations and the applying the Markov process with Kalman filtering. In contrast to previous papers that predict only water levels the present paper also estimates salinity downstream the gate and of the tidal lake, simultaneously. It is postulated that present water level and salinity are expressed by the explicit linear functions of water levels, salinity, and gate operations at the other and the same positions in the past step. Using physically plausible estimate for these parameters in the functions the results of the predictions are in good agreement with observation.
THE COASTAL WIND FIELD OF THE SOUTHERN CAPE
Authors: Hunter Ian Tyrrell
Published: June 2019

The coastal region of the South Cape is presented as a typical semideveloped coastal zone with a limited environmental dataset. The author places himself in the position of a coastal engineer requiring wind data for design purposes. The various sources of wind measurement are discussed. Time series are presented depicting responses at different sites to the same large-scale synoptic situation. Spatial variations, both across the coastal boundary and in the offshore region are emphasized. These variations are brought to the attention of those engineers who may have to extrapolate wind conditions to their site of interest.
TIDAL AND INERTIAL CURRENTS AROUND SOUTH AFRICA
Authors: Schumann E.H. , Perrins L.A.
Published: June 2019

Limited information is available on currents in the semi-diurnal and diurnal frequency bands for the coastal ocean areas around Southern Africa. However, recently mooring data have become available from sites on the east, south and west coasts, and this paper analyses these results in an attempt to assess the importance of tidal and inertial currents. It is clear that on the narrow shelf on the east coast the Agulhas Current dominates the energy spectrum, and tidal currents should be relatively unimportant at such sites. In the south on the Agulhas Bank the Current is still important, but comparable energy resides in inertial and tidal fluctuations. Modal analysis indicates the tides are primarily barotropic, with the inertial fluctuations mainly baroclinic. In the absence of a major current on the west coast, most of the current variance occurs in the tidal and inertial bands; a complex vertical structure is also found. It is therefore clear that there are regions where such currents cannot be ignored.
MOORED SHIP RESPONSE IN IRREGULAR WAVES
Authors: Mansard E.P.D. , Pratte B.D.
Published: June 2019

The traditional concept of representing a "random" sea state by just a variance spectral density has been found to be insufficient for modelling the slow drift oscillations of large moored ships. This paper illustrates, through experimental investigations, the importance of including wave grouping as an additional design parameter. A special technique called SIWEH, developed by the Hydraulics Laboratory of the National Research Council Canada, for the generation of realistic wave climates which include wave grouping, is presented. However, when generating the grouped sea state, one also has to properly create the group-bound long wave components. The effect of proper compensation for the spurious free wave components is illustrated by the test results on the moored vessel response.
MEASUREMENT TECHNIQUES FOR MOORED SHIP DYNAMICS
Authors: Moes J. , Holroyd S.G.
Published: June 2019

Problems arise during adverse sea conditions with ships moored to the ore loading jetty at Saldanha Bay. Under certain wave conditions moored ships undergo large motions which cause breakage of mooring lines. In order to obtain a quantitative insight into the problem an extensive measurement system was installed at Saldanha Bay. This system comprises instrumentation for the measurement of short and long waves, currents and wind, mooring line and fender forces and the motions of the moored ships. Preliminary results show that during storm conditions long waves with periods between 50 and 150 s occur at the jetty. These periods fall within the same range as the observed natural periods of horizontal oscillation of the moored ships.
SOME PROPERTIES OF SWELL IN THE SOUTHERN OCEAN
Authors: Hinwood John B. , Blackman Deane R. , Lleonart Geoffrey T.
Published: June 2019

Records of pressure from a bottom-resident instrument deployed near the western margin of Bass Strait have been analysed. Discrete wind-sea and swell spectra have been identified and have been related to meteorological events. The spectra fit a finite-depth form of the Wallops spectrum.
ON THE RELATION BETWEEN CHANGES IN INTEGRAL QUANTITIES OF SHOALING WAVES AND BREAKING INCEPTION
Authors: Yasuda Takeshi , Goto Shintaro , Ysuchiya Yoshito
Published: June 2019

This paper describes a mechanism of breaking waves over sloping bottoms in terms of changes in integral quantities of the waves. Systematic computations are made of wave profiles of shoaling waves up to the numerical unstable points by using the K-dV equation with variable coefficients and internal properties such as horizontal and vertical water particle velocities by a stream function method satisfying the conservation laws of mass and energy. Applicability of the numerical results is examined and a relation between numerical unstable points and actual breaker points is found. Characteristics of the integral quantities of shoaling waves are investigated in relation to the existence of the extremum of the energy of the shoaling waves and their breaking inception.
STUDY OF HURRICANE WAVES AROUND THE TAIWAN COAST
Authors: Hou Ho-Shong , Kuo S.C. , Tseng R.S.
Published: June 2019

The objective of this research is to study the prediction method of hurricane waves around this island, especially in the Taiwan Strait. The paper describes the prediction of hurricane waves used by Bretchneider's (1976) Method and finds out the predicted waves are different from measured waves, therefore the Bretchneider predicted model is modified by the authors and then the modified model is applied to predict waves again. It is found out that predicted waves match well with the measured waves. The results of the modified Bretchneider model are compared with those of the Ijima tracing method and find out the former is better than the latter. The second part is to apply the modified model to predict the extreme value of wave heights and compute the worse hurricane wave condition of the surrounding sea area around island, within recent score year (1959-1978). The calculated sites are Chu-Wei, Nan-Liaw, Ta-Shih, Cheng-Kung, Pu-Tai, Tung-Kang, Nan-Wan as shown in Fig.1 and Shiau Liu- Chieu totally 8 stations. Then use the Gumbel Distribution TYPE 1 to predict the extreme wave height of each returned period.
A COMPUTER MODEL FOR THE REFRACTION OF NON-LINEAR WAVES
Authors: Crowley J.B. , Fleming C.A. , Cooper C.K.
Published: June 2019

A non-linear wave refraction model was developed which allows for the combined refraction and shoaling of Vocoidal waves over an arbitrary sea bed. The effects of bed friction and percolation are also catered for. The method is based on the cirular arc technique which is widely used for linear wave refraction. The method was extensively tested against Vocoidal wave refraction results obtained previously for a plane beach. A comparison of Vocoidal and linear wave refraction over an arbitrary sea bed indicated that Vocoidal waves refract less than linear theory, thereby yielding higher wave heights and angles of incidence at the breaker line. This result is in line with results of non-linear refraction over parallel bed contours quoted for other non-linear wave theories in literature. Further work is required before caustics can be adequately treated. Future research should include wave spectrum transfer and the re-evaluation of empirical relationships in use in the shallow water region and which will use this new higher-order refraction technique.
RESONANCE IN SOUTH AFRICAN HARBOURS
Authors: Botes W.A.M. , Russell K.S. , Huizinga P.
Published: June 2019

The geographic situation of Southern Africa, and the associated climate of the South Atlantic Ocean, cause the harbours on the west and south coasts of South Africa to be subjected to resonance or range action caused by longperiod 50 s to 300 s waves. Since the construction of Duncan Dock in Table Bay in 1940, Table Bay harbour has become a classical example of resonance. Range action in the harbour has been studied extensively in the past and extensive physical model studies were undertaken to optimise the layout of the Schoeman Dock, construction of which was completed in 1976. In 1976 South African Railways and Harbours (now South African Transport Services) commissioned the Coastal Engineering and Hydraulics Division of the National Research Institute for Oceanology to optimise plans for future extensions to Table Bay harbour. As a preliminary study, the advantages and disadvantages of all existing methods of simulating resonance were reviewed. For this investigation it was decided to adapt an existing "finite difference" numerical model developed by Leendertse (1967). Prototype long-wave data were gathered in Table Bay and at a later stage at the cooling water intake basin of the Koeberg Nuclear Power Station. These data were used to calibrate the numerical model and an attempt was made to find a correlation between long waves and short wind waves in order to determine the frequency of occurrence of long waves. A method was also developed to incorporate a range of frequencies in one model-run instead of single wave input conditions. This resulted in a considerable reduction of expense and time.
NUMERICAL MODEL STUDY OF TEMPERATURE DISTRIBUTIONS IN A HARBOUR
Authors: Falconer Roger A.
Published: June 2019

The paper gives details of a study to predict numerically the background temperature rise in Poole Harbour and Holes Bay, in Dorset, England, caused by the siting of either a 700MW or a 350MW power station. The numerical model is based on the numerical integration of the flow equations which simulate the water movements of tides and upon numerical integration of the advective-diffusion equation representing the movement of heat. The results of the study predominantly suggest that the temperature field is proportional to the station capacity, with the maximum and mean temperatures across the basin for the 700MW station capacity being almost exactly double the corresponding values predicted for the 350MW station capacity. Observations from the velocity fields and tidal prism ratios both tend to suggest that Poole Harbour and Holes Bay have poor flushing characteristics, which confirm the relatively high temperature predictions in that only a relatively small volumetric percentage of the heated water is flushed out of the basin during each flood tide.
ENGINEERING APPROACH TO NONLINEAR WAVE SHOALING
Authors: Walker James , Headland John
Published: June 2019

Determination of a design wave height at a coastal structure requires calculation of a shoaling coefficient or determination of the maximum probable breaking wave height at the point of interest. In shallow water over a sloping bottom, low steepness waves are not accurately predicted by linear shoaling coefficients. Empirical breaking indices are inconsistent with both linear and nonlinear wave theories. Nevertheless, the coastal engineer must select a design wave in order to responsibly design the structure. A graphical procedure is presented herein to relate the equivalent deepwater wave to a breaking wave as it transitions into shoaling water. The procedure provides the coastal engineer with a more consistent understanding of the shoaling process. The results furthermore identify regions of relative depth and steepness where discrepancies arise when using linear shoaling coefficients that may significantly alter engineering design and laboratory studies.
A NEW TWO DIMENSIONAL TIDAL MODELLING SYSTEM
Authors: Benque J.P. , Chenin M.I. , Hauguel A. , Schwartz S.
Published: June 2019

A new method for numerical simulation of tidal currents is presented. Based on a technique involving the splitting of operators, it allows an accurate calculation of momentum advection, and wave propagation for large Courant numbers. It also provides a satisfactory treatment of tidal flat uncovering and flooding, and permits the use of a curvilinear computational grid. The generation method for such grids is presented here, followed by an engineering application on cartesian grid.
A THREE-DIMENSIONAL MODEL OF BERING AND CHUKCHI SEA
Authors: Liu Shiao-Kung , Leendertse Jan J.
Published: June 2019

A part of the continental shelf area of the Bering and Chukchi Sea are now being opened up for oil exploration. For engineering and ecological risk analyses, extensive field data collection efforts are being carried out by various United States agencies and petroleum corporations to understand the hydrodynamic behavior of this vast offshore area. In addition, modeling studies are being made for which a three-dimensional model of the area, outlined in Fig. 1, has been developed. This model is dynamically coupled to a two-dimensional stochastic weather model. This weather model contains a Markov synoptic component and a storm track component. The parameters of this model are derived from a 20-year data base. This paper presents a description of the three-dimensional model and the results of a series of simulations using the model to compute tidal propagation and circulations induced by tides and wind. The results of a simulation of a moving storm through the eastern Bering Sea are also presented.
A NEW APPROACH TO TRANSIENT WAVE GENERATION
Authors: Mansard E.P.D. , Funke E.R.
Published: June 2019

An analytical model of an "episodic" wave as a function of time is given. The linear dispersion theory is applied to the transient to hindcast the wave train at a wave board which is a specified distance up-wave from a test site. First order wave board theory and linear system theory is used to convert the wave train at the wave board into a control signal. Conversion of the time discrete control signal into a smooth analog voltage signal by means of a real time digital program is described. Examples of numerical simulations and physical measurements are given.
THE CONTROL OF WAVE ASYMMETRIES IN RANDOM WAVES
Authors: Funke E.R. , Mansard E.P.D.
Published: June 2019

The concept of wave asymmetry is reviewed and a prototype wave record is analysed. A three stage non-linear transformation, together with a Fourier transform substitution technique, is described. The method is tested by numerical simulation using statistical analysis procedures. Physical realizations are compared graphically.
THREE-DIMENSIONAL MARINE MODELS FOR IMPACT STUDIES
Authors: Nihoul Jacques C.J. , Ronday Francois C.
Published: June 2019

A three-dimensional non-linear hydrodynamic model is developed for the determination of the mesoscale (tides, storm surges, ...) and macroscale (residuals, gyre, ...) circulations in the North Sea. The model consists of a hierarchy of submodels of different grid sizes, with interactive coupling at boundaries. The model is used to study the impact of coastal engineering projects along the Belgian coast and in the Scheldt estuary.
WAVE RUN-UP AT SEA DIKES UNDER OBLIQUE WAVE APPROACH
Authors: Tautenhain E. , Kohlhase S. , Partenscky H.W.
Published: June 2019

Besides wave impact forces, erosion of the inner side of a sea dike is a serious cause of destruction. Therefore, wave run-up and overtopping effects have to be considered with respect to the safety of a dike. Strong relations were found between both these influences (TAUTENHAIN et.al., 1980, 1981, 1982), based on experiments in a wave flume and using an energy conservation concept. However, under natural conditions, an oblique wave approach has to be considered. This paper deals with the influence of wave direction on wave runup on a smooth dike slope in order to provide a basis for calculating the overtopping rates for both regular and irregular waves.
WATERWAVES CALCULATION BY NAVIER-STOKES EQUATIONS
Authors: Daubert O. , Hauguel A. , Cahouet J.
Published: June 2019

N.S.L. program is a finite-difference code for two dimensionnal flows with a free surface in a vertical plane. Basic equations are Navier-Stokes Equations with a simple simulation of turbulent effects by an eddy viscosity coefficient related to the mixing length and the mean velocity gradient. Theses equations are solved in a variable domain in time. The main features of the numerical method are presented. Some comparisons with theoretical solutions give a good validation of the code both in linear and non linear cases. Other examples of application are given.
INTEGRAL PROPERTIES FOR VOCOIDAL THEORY AND APPLICATIONS
Authors: Bleach G.P.
Published: June 2019

A comparison is made between two reference frames that can each be used to define "still water" for finite amplitude waves on water of finite depth. The reference frame characterized by zero mass flux due to the waves is used to find some exact relations between the wave integral properties. The averaged Lagranian (wave action) approach and the energy/momentum approach to the interaction of finite amplitude waves with slowly-varying currents are also derived in this reference frame. Results in many cases are simpler than those in the more commonly chosen reference frame characterized by zero mean horizontal velocity under the waves. An application of the integral properties is made to Vocoidal wave theory, which is defined in the zero mass flux frame. It is shown that the rotation present in the orbital velocity field of Vocoidal waves is not always negligible.
FIELD STUDY ON ON SHORE-OFFSHORE SEDIMENT TRANSPORT
Authors: Hattori Masataro
Published: June 2019

The mechanism of onshore-offshore sediment transport and the process of beach profile evolution were studied through field investigations performed at Oarai Beach, Japan. The principal data set consists of twenty-four profile surveys taken at hourly intervals on each of two parallel lines spaced 10 m apart and of length 150 m. The lines extended from the backshore of the beach to a point on the sea bottom at a depth where no sand movement occurred. Simultaneous measurements of the waves and wave-induced currents were also made; the essential requirement of two-dimensionality was found to hold during the experiment. The profiles were used to calculate the net sediment transport rate on-offshore, and for an empirical eigenfunction analysis. A negative correlation was found between the transport direction (and resultant bottom change) and the mean sea level change. The sediment transport rate in the foreshore region was found to be proportional to the wave power, whereas outside the surf zone and near the breaker position it was proportional to the tractive force.
LONGSHORE TRANSPORT DETERMINED BY AN EFFICIENT TRAP
Authors: Dean R.G. , Berek E.P. , Gable C.G. , Seymour R.J.
Published: June 2019

The Nearshore Sediment Transport Study (NSTS), sponsored by the National Sea Grant Office included a field component to quantify the total longshore sediment transport relationship. This component was conducted at Santa Barbara, California and encompassed a period of eighteen months during which ten surveys were conducted. To date, eight of these surveys have been analyzed, yielding seven intersurvey periods. A total of 288,600 m3 of net sediment transport was documented by these eight surveys. The wave characteristics are based on one of two Sxy gages located in a water depth of 7 m. The most widely used correlation constant, K, in the relationship I = KP, is 0.77. The values found from the data were 0.93 and 1.23 for linear and log best-fit values, respectively. The corresponding values of K4 relating I and S are 2.60 and 2.63 m/s, respectively.
CHANGES IN THE COASTAL MORPHOLOGY OF VRACHATI, GREECE
Authors: Moutzouris C.I. , Rogan A.J.
Published: June 2019

The coastal morphology of Vrachati, which lays on the southeastern coast of the Corinthiakos Gulf, has considerably changed since the construction of two successive coastal structures. The present paper describes these changes and attempts to estimate the rate of longshore drifting sediment load. The description of the changes and the estimation of the rate are based on observations of aerial photographs of the area and on extensive bottom sediment sampling.
BREACH/INLET INTERACTION AT MORICHES INLET
Authors: Schmeltz E.J. , Sorensen R.M. , McCarthy M.J. , Nerseslan G.
Published: June 2019

Moriches Inlet is located on the south shore of Long Island, New York, approximately 45 miles (72 kilometers) west of Montauk Point and 80 miles (130 kilometers) east of New York City. The inlet forms the primary outlet through the barrier island between Moriches Bay and the Atlantic Ocean. The inlet is protected and stabilized by two stone jetties approximately 800 feet (245 meters) apart . During 3anuary, 1980, a severe northeast storm resulted in the breaching of the barrier island immediately to the east of the existing Moriches Inlet. By the fall of 1980, the breach had expanded to nominally 2900 feet (885 meters) in width with a maximum depth of around 10 feet (3 meters) and the U.S. Army Corps of Engineers was requested to affect its closure. The method adopted by the Corps consisted of the placement of beach fill in the opening to develop a cross-section with a center line elevation of +13.25 feet (4 meters) MLW and side slopes of 1V:25H. Initiated in October 1980, the closure operation was succesfully completed in February, 1981. The formation of a significant breach immediately adjacent to the existing inlet and the artificial closure of the opening afforded a unique opportunity to study the dynamics of a tidal inlet under the influence of relatively rapid changes in tidal prism and cross sectional area. The purpose of this paper is to present the results of a field measurement program and subsequent analyses of the dynamics of the inlet/breach system. The analyses were based on data obtained before, during and after closure of the breach.
HARBOUR SEDIMENTATION - COMPARISON WITH MODEL
Authors: Pratte B.D. , Willis D.H. , Ploeg J.
Published: June 2019

A mobile-bed model study of Pointe Sapin Harbour, in the Gulf of St. Lawrence, resulted in construction of a detached breakwater and sand trap to prevent harbour entrance infilling. The sand trap is filling in at a faster rate than predicted from the model. This is partly due to incomplete modelling of the wave climate; partly to incorrect modelling of distribution of alongshore sand transport; and partly to a complex sand supply at the site. Nevertheless, the sand trap solution is performing well.
MODELLING OF SEA-BED EVOLUTION UNDER WAVES ACTION
Authors: Coeffe Y. , Pechon Ph.
Published: June 2019

This paper presents a numerical model computing sea-bed evolution due to longshore current s, which has been developed at the Laboratoire National d'Hydraulique. This model has been applied to a schematic semi-circular bay. The computation of sand sea-bed modifications reveals two main tendencies ; a marked accretion in the "up-stream" zone of the bay and a marked erosion in the "down-stream" zone of the bay, as far as longshore currents are concerned.
SUSPENDED SEDIMENT DISCHARGE ON A NON-TIDAL COAST
Authors: Coakley J.P. , Skafel M.G.
Published: June 2019

A field study was conducted on a non-tidal sand beach to measure the relationship between wave energy and the longshore transport of suspended sediment. The range of suspended sediment concentrations was similar to that reported elsewhere. The relation between longshore transport and longshore energy flux derived from this data set is about half that amount predicted by such widely quoted sources as Komar and Inman (1970).
FIELD INVESTIGATION OF BEACH PROFILE CHANGES AND THE ANALYSIS USING EMPIRICAL EIGENFUNCTIONS
Authors: Hashimoto Hiroshi , Uda Takaaki
Published: June 2019

In order to investigate the response of beach profiles to incident waves, computations by the empirical eigenfunction analysis proposed by Winant et al. are performed. The analysis of the data obtained at Ajigaura Beach over three years from 1976 to 1979 indicates that beach profile changes due to longshore and onshore-offshore sediment transport are separable by the empirical eigenfunction method. The beach profile changes due to longshore sediment transport has a time lag of 12 weeks with respect to the change of wave direction at Ajigaura Beach. It was found theoretically that this time lag was due to the sand waves propagating in the longshore direction. Regarding as onshore-offshore sand transport, the second eigenfunction is associated with the beach changes due to onshore-offshore sand transport caused by the change of wave height.
DESCRIPTION OF BEACH CHANGES USING AN EMPIRICAL PREDICTIVE MODEL OF BEACH PROFILE CHANGES
Authors: Uda Takaaki , Hashimoto Hiroshi
Published: June 2019

In order to analyze beach profile changes due to longshore and onshore-offshore sand transport, here is proposed a new model named the "empirical predictive model of beach profile change", which is an application of the empirical eigenfunction method. The analysis of the profile data obtained at the Misawa fishery port in Ogawarako Coast over five years from 1973 to 1977 indicates that profile changes due to longshore transport and to onshore-offshore transport can be separated. The model is shown to be effective in the analysis of profile changes near coastal structures.
MODELING ON-OFFSHORE SEDIMENT TRANSPORT IN THE SURFZONE
Authors: Bailard James A.
Published: June 2019

An energetics-based surfzone sediment transport model was evaluated in its ability to predict on-offshore sediment movements using current meter and beach volume measurements from the Nearshore Sediment Transport Study at Torrey Pines Beach, California. The magnitude of pertinent wave velocity moments were also evaluated from the same data set. These moments were found to be adequately represented by linear functions of the significant wave height. Because of the apparent noise in the beach volume measurements and the limited duration of the current meter records, the results of the model evaluation were inconclusive. However, a simplified version of the model, when coupled with estimated wave velocity moments, was found to mimic observed on-offshore sediment movements as a function of significant wave height.
NATURAL BAR-BYPASSING OF SAND AT A TIDAL INLET
Authors: Sexton Walter J. , Hayes Miles O.
Published: June 2019

Captain Sam's Inlet, a shallow unstable inlet, periodically migrates up to three kilometers (km) alongshore over a 30- to 40-year period. As the inlet migrates, sediment accumulates at the seaward terminus of the tidal inlet to form a wave-modified ebb-tidal delta that trends downdrift. Continued sediment accumulation on the tidal-delta shoal and subsequent lengthening of the tidal channel in a downdrift direction results in an unstable channel configuration. The ebb delta is eventually breached on its updrift side, releasing a sediment package for inlet bypassing. The sediment-bypassing process was initiated at Captain Sam's Inlet after the final landfall of Hurricane DAVID in September 1979. Initially, the newly formed updrift hurricane channel scoured 1.1 m, migrated updrift, and became the predominant tidal channel at the inlet with eventual abandonment of the prehurricane, main ebb channel. These two channels outlined a portion of the ebb-tidal delta that was freed for bypassing. The initial sediment volume contained in the bypassing shoal, above the -0.6 m (-2 ft) MSL contour, was 47,000m3. The sediment volume of the bypassing shoal did not change significantly until final attachment to Seabrook Island. This channel dominance and the wave-induced migration of the bypassing sediment package aided the bypassing of sand at the inlet. Immediately after filling of the prehurricane, main ebb channel on the delta, the downdrift beaches began accreting. The accretion continued throughout the bypassing process. The tidal prism and cross-sectional area reflected little change during the bypass, showing evidence of the system's overall stability.
SHOALING WITH BYPASSING FOR CHANNELS AT TIDAL INLETS
Authors: Galvin Cyril
Published: June 2019

A channel dredged at the mouth of a tidal inlet is subject to rapid shoaling because of longshore transport, but this shoaling is slower than would be computed from simple trapping of all the moving littoral drift. The reduction in shoaling rate is due to the bypassing of littoral drift which occurs simultaneously with shoaling. This report presents a systematic method for computing the rate of shoaling in channels subject to shoaling with bypassing. The method also permits estimates of the effect of the dredged channel on the downdrift beaches.
DREDGING TO MINIMIZE WAVE PENETRATION INTO A HARBOUR
Authors: Riedel H.P. , Byrne A.P.
Published: June 2019

Wave protection within a new harbour development has been achieved by shaped dredging in place of long breakwaters. The dredging shape was initially established through wave refraction calculations and then confirmed and optimized in a physical three dimensional model. The cost of additional dredging for the specified shape was A$100,000 compared to estimated breakwater costs of A$l,000,000.
THE NILE LITTORAL CELL AND MAN'S IMPACT ON THE COASTAL ZONE OF THE SOUTHEASTERN MEDITERRANEAN
Authors: Inman Douglas L. , Jenkins Scott A.
Published: June 2019

Man's intervention with coastal processes takes many forms. However, the most serious large scale, long term coastal erosion results from the interception by dams of rivers supplying sediment to the coast. This loss of sediment may have catastrophic effects along coasts where streams discharge directly into coastal waters. The Nile littoral cell is an impressive example of the effect of dams on coastal erosion. The Nile littoral cell is located in the southeastern Mediterranean Sea and extends 700 km from Alexandria, Egypt in the south to Akko, Israel in the north. The sediment load from the Nile River was deposited along the submerged portion of the delta, where it was sorted and transported to the east by the prevailing waves and by currents of the counterclockwise east Mediterranean gyre that commonly flows at about 50 cm sec over the delta. Prior to 1964, the turbid plume of the flood waters of the Nile River could be traced along the Mediterranean coast for over 700 km to the shores of Lebanon. Fine silt and clay sized material were carried easterly and into deeper water, while sand is carried easterly along the shelf and shore as far as Haifa Bay. Until 1964, the major sediment source of the littoral cell was the Nile River. Construction of the High Aswan Dam, which began filling in 1964, has resulted in a near absence of Nile River flow into the Mediterranean and a corresponding complete loss of the Nile River as a source of nutrients to coastal waters, and as an active sediment source for the delta and the coastline of the Nile littoral cell. As a result, the Nile Delta is now subject to severe erosion in a number of localities.
GRADING EFFECTS IN CONCENTRATION MEASUREMENTS
Authors: Van de Graaff J. , Roelvink J.A.
Published: June 2019

In analysing measured sediment concentration distributions the effect of the non-uniformity of the bottom material is frequently not taken fully into account. Examples of calculations are given to clarify the grading effect on the parameters that determine the concentration distribution
LABORATORY REPRODUCTION OF SEABED SCOUR IN FRONT OF BREAKWATERS
Authors: Irie Isao , Nadaoka Kazuo
Published: June 2019

Mechanism of scour in front of breakwaters by standing waves in two and three dimensions has been studied theoretically and experimentally to clarify the experimental conditions by which the prototype behavior could be best reproduced in laboratory. The phenomenal reproduction of scour in laboratory is satisfactory if some conditions on the characteristics of waves and bed materials are fulfilled. This enables experimental approach to find out the optimum protection methods against scour in front of breakwaters.
SEDIMENTATION IN DREDGED CHANNELS AND BASINS. PREDICTION OF SHOALING RATES
Authors: Vicente C.M. , Uva L.P.
Published: June 2019

A method is presented for predicting shoaling in dredged chan nels and basins where deposition of finer sediment fractions carried in suspension by tidal currents occurs. The method is based on the analysis of hydrographic surveys of different dates, which show the hydrographic evolution of dredged areas located in the site or in its vicinity. It can also be applied to experimental dredged pits. Results obtained from the analysis of surveys are worked out by using mathematical expressions deduced from a simplified hypothesis, empirically based. Parameters are determined which can be used to predict shoaling either when new dredgings are made or when previously dredged sites are deepened.
BEACH FORESHORE RESPONSE TO LONG-PERIOD WAVES
Authors: Howd P.A. , Holman R.A.
Published: June 2019

A field experiment has been carried out to test the hypothesis that infragravity and lower frequency waves influence patterns of erosion and deposition on the beach foreshore. The data show coherent fluctuations in the foreshore sediment level which can be related to low frequency wave motions. The fluctuations have heights of up to 6 cm with typical time scales of 8 to 10 minute periods. They can be characterized in two ways: by the progression of the fluctuation up the foreshore slope (landward), and by the decrease in the root-mean-square (RMS) height of the fluctuations as they progress landward. Analysis of runup time series obtained by time-lapse photography concurrent with the sediment level measurements reveals long-period waves of undetermined origin which are positively correlated with the sediment level fluctuations. This strongly suggests that the waves are responsible for forcing the sediment level fluctuations.
CROSS-SHORE TRANSPORT OF BIMODAL SANDS
Authors: Richmond Bruce M. , Sallenger Asbury H.
Published: June 2019

Foreshore sediment level and sediment size were monitored as part of an extensive nearshore processes experiment - DUCK 82. Changes in foreshore texture were compared with computed values of onshore transported material based on current measurements from the surf zone and sediment transport theory (Bagnold, 1963, 1966). Preliminary results indicate reasonable agreement between predicted size of sediment transported onshore and beach texture changes. It is also demonstrated that coarse sediment may move onshore while finer material may simultaneously move offshore.
PERMEABLE GROYNES: EXPERIMENTS AND PRACTICE IN THE NETHERLANDS
Authors: Bakker W.T. , Hulsbergen C.H. , Roelse P. , De Smit C. , Svasek J.N.
Published: June 2019

This paper reports on model experiments and up to 20 years of practice in nature with a permeable groyne system, consisting of single or double permeable rows of wooden piles perpendicular to the beach, without bottom protection. This system costs only 10 to 25% of the impermeable stone groynes which have for centuries been used in the Netherlands. Model experiments confirm that wave-induced currents in the protected areas are reduced to 65%, and tidal currents even to 50%, depending on the pile screen configuration. Prototype measurements could not lead to straightforward conclusions with statistical significance: the effect of the pile screens on beach evolution is partly merged into natural fluctuations and trends. Wooden pile screens do not prevent the shoreward motion of tidal channels, which can cause washing out of piles. Furthermore, constructional failures, which in the future can be avoided, at some places resulted in negative experience. It is concluded that permeable pile screens deserve serious consideration as a first flexible and cheap phase in combating coastal erosion. Its application however should be based on a thorough analysis of the local coastal current climate.
MECHANISM OF BEACH PROFILE DEFORMATION DUE TO ON-OFFSHORE SAND DRIFT
Authors: Pae Wi-Gwang , Iwagaki Yuichi
Published: June 2019

In the present study, two-dimensional laboratory experiments were performed to investigate the sediment transport due to waves on a fixed sloping beach. Polystyrene particles and glass balls were used as tracers to determine the mass transport velocity near the bottom and the net transport velocity of sediment moving on an impermeable slope. Relationships between the mass transport velocity of water and the net sediment transport velocity are investigated experimentally. The mechanism of two-dimensional beach deformation from an initial uniform slope toward an equilibrium profile due to bed-load movement is discussed on the basis of spatial distributions of the net sediment transport velocity. In addition, some results of experiments using a movable bed are presented to confirm the validity of a beach deformation model derived from the discussion of the tracer experiments.
UPDATE: THE NATIONAL FLOOD INSURANCE PROGRAM AND THE COAST
Authors: Fry William G. , Rhodes Perry A.
Published: June 2019

This report will update the coastal zone practitioner on the National Flood Insurance Program (NFIP) as it affects the implementation of manmade changes along the coastline. It is our intent to place in proper perspective this fast-changing and often difficult to interpret national program. Readers will achieve an overall understanding of the NFIP on the coast, and will be in a position to apply the program's requirements in their efforts. We will begin with a history of the application of the NFIP to the coastal zone. The history of the problems encountered will lead into current regulations, methodologies, and the changes the Federal Emergency Management Agency plans for the future.
A THEORETICAL AND EXPERIMENTAL STUDY OF UNDERTOW
Authors: Hansen J. Buhr , Svendsen I.A.
Published: June 2019

It is well known that on a three-dimensional beach large volumes of water carried shorewards by the breakers feed longshore currents, which eventually escape back through the breaker line, often as rip currents. In a steady two-dimensional situation, however, the mass flux represented by (among other things) the surface roller in the breakers returns as a seaward current close to the bottom. This current is called the undertow. In this paper theoretical results for the undertow are compared with the results of recent laboratory experiments.
ACCURATE MODELLING OP TWO-DIMENSIONAL MASS TRANSPORT
Authors: Bode Lance , Sobey Rodney J.
Published: June 2019

Any numerical solution of the convective transport equation in an Eulerian framework will exhibit inherent numerical dispersion and solution oscillations. The magnitude of such numerical errors is often so severe as to destroy the value of many computed solutions. A successful and economical algorithm for the convective transport equation in one spatial dimension has been published recently by one of the authors (RJS), in which an exact solution is achieved by means of a moving coordinate system. The present study describes the extension of this work to the more important and challenging two-dimensional case.
STABILITY OF ARMOR UNITS IN FLOW THROUGH A LAYER
Authors: Thompson Alex C. , Burcharth Hans F.
Published: June 2019

As part of a program to study the hydraulics of wave attack on rubble mound breakwaters tests were made on model armour units in a steady flow through a layer laid on a slope. The flow angle has little effect on stability for dolosse or rock layers. The head drop at failure across each type of layer is similar but the dolosse layer is more permeable and fails as a whole. There was no viscous scale effect. These results and earlier tests in oscillating flow suggest a 'reservoir' effect is important in the stability in steep waves.
REEF TYPE BREAKWATERS
Authors: Ahrens John P.
Published: June 2019

Reef type breakwaters refers to a low-crested rubble mound breakwater without the traditional multilayer cross section. This type of breakwater is little more than a homogenous pile of stones with individual stone weights sufficient to resist wave attack. In recent years a number of low-crested breakwaters has been built or considered for use at a variety of locations. Most of these structures are intended to protect a beach or reduce the cost of beach maintenance. Other applications include protecting the water intakes for power plants, the entrance channel for small boat harbors, and providing an alternative to revetment for stabilizing an eroding shore line. In situations where only partial attenuation of the waves on the leeside of the structure is required, or possibly even advantageous, a low-crested rubble mound breakwater is a logical selection. Since the cost of a rubble mound increases rapidly with the height of the crest, the economic advantage of a low-crested structure over a traditional breakwater that is infrequently overtopped is obvious. Because the reef type breakwater represents the ultimate in design simplicity it could be the optimum structure for many situations. Unfortunately, the performance of lowcrested rubble mound structures, and particularly a reef type breakwater, is not well documented or understood.
REEF RUNWAY WAVE PROTECTIVE STRUCTURE, HONOLULU INTERNATIONAL AIRPORT, OAHU, HAWAII, STABILITY PERFORMANCE EVALUATION
Authors: Chun Robert S. , Noda Edward K. , Tamaye Elaine E.
Published: June 2019

An inspection survey of the Reef Runway Wave Protective Structure at the Honolulu International Airport was accomplished in 1982 to access the performance of the dolos and rock armored structure to date. The inspection showed the structure to be performing adequately considering that the design wave conditions were experienced.
MARINE ROUGHENED CYLINDER WAVE FORCE COEFFICIENTS
Authors: Nath John H.
Published: June 2019

Steel cylinders were submerged on a platform in the South Pass region of the Gulf of Mexico for one year to accumulate biofouling for later laboratory testing to determine wave force transfer coefficients. They were positioned at -55, -140, and -190 feet below the still water surface. Laboratory tests comprised steady tow up to Reynolds number cd 7x10^, and periodic waves up to Reynolds number of 1.6x10 and Keulegan-Carpenter number up to 25. The force transfer coefficients for the -55 cylinder were about equal to those for a sand roughened cylinder with relative cylinder roughness, e/D, of .03, where e is the height of the equivalent sand roughness size and D is the smooth cylinder diameter. The drag coefficient for very high Keulegan-Carpenter number, or steady tow, is about 1.0 if the effective cylinder diameter is taken into account, for the rougher cylinders.