bluuebunny/crossref_metadata_2025 huggingface dataset:
DESIGN CONSIDERATIONS FOR THE SAND ISLAND AND BARBERS POINT OUTFALLS
Authors: Koh Robert C.Y. , Brooks Norman H. , Vuillemot Floyd Louis
Published: June 2019

The design and construction of a major ocean outfall and diffuser system for disposal of wastewater effluents is a complex process involving an interplay of requirements originating from various disciplines. These include, among others, considerations of physical oceanography, mixing and dispersion, treatment processes, regulatory requirements, marine geology, economics and construction. The recently completed Sand Island Outfall and the newly designed Barbers Point Outfall are both on the southern coast of the island of Oahu, Hawaii, and are designed for treated sewage effluents from the densely populated portion of the City and County of Honolulu. In this paper, some design considerations of these outfalls will be examined. The emphasis in this paper is on the hydrodynamics, although other design aspects are also discussed briefly. The design of a large submarine outfall must consider two basic objectives. First, the design must assure the physical integrity of the structure when subjected to the sometimes violent environment. Second, the mixing, dispersion and transport of the effluent must be such that environmental degradation is acceptably small and that water quality requirements are met. In addition, the design process also includes considerations of economics, overall system compatibility, and construction. The Sand Island Outfall was constructed in 1975-1976 while construction of the Barbers Point Outfall began in 1976. The cost of the Sand Island outfall was 13.7 million.
TIDAL RESPONSE OF TWO-LAYER FLOW AT A RIVER MOUTH
Authors: Yoshida Shizuo , Kashiwamura Masakazu
Published: June 2019

This paper describes various features of tidal effects on the behavior of a salt wedge and on the mechanism of mixing between the salt water and the fresh water in the vicinity of a river mouth. The studies have been performed through experiments, field observations and theoretical considerations. The condition upon which the fresh water begins to show an intermittent flow-pattern owing to an increase of the tidal action, and the criterion of a transition of the mixing type from negligible into intense, were obtained, with two dimensionless parameters X and 6. The former parameter X is given by A = A0/U0T0, in which T0 is the tidal period, A0 is the tidal amplitude of the sea level, and U0 is the temporal mean velocity of the fresh water at the river mouth. The latter parameter 9 is the so-called Keulegan number. Besides, it came evident that a tidal motion of the salt wedge couldn't be understood without a consideration of the internal wave inside the mouth, which were induced by the tide, in addition to a direct effect of the tide.
EVALUATION OF AIR-SEA INTERFACE HEAT FLUX
Authors: Street Robert L. , Miller A. Woodruff
Published: June 2019

A theoretical analysis, laboratory experiments, and the routine availability of infrared remote sensors for boat, airplane or satellite use are combined to provide a simple method for evaluating the total heat flux through the air-water interface under nighttime field conditions in which the water surface is rough; all indications are that the technique can be extended to other conditions as well. To evaluate this flux all that is required is the local windspeed, the water surface temperature, a subsurface temperature, and the character of the sea surface. Conversely, the theory can also be applied to predict temperature differences across the interface if the heat transfer can be otherwise established.
STATE ESTIMATION OF ESTUARINE CIRCULATION AND WATER QUALITY BY NUMERICAL SIMULATION AND OBSERVATION
Authors: Leendertse J.J. , Liu S.K.
Published: June 2019

This paper describes a hindcast of post-rainstorm coliform bacteria distributions in Jamaica Bay made by use of a water-quality simulation model of that bay and models of the surrounding drainage basins on the basis of tide, wind, and rainfall data. That hindcast is then compared with coliform estimates obtained by field sampling. Although the investigators did not have access to the results of the field sampling until the hindcast was completed, the estimates obtained by simulation agree well with the estimates from field data. It is concluded that the models used here are capable of making predictions for engineering assessments.
WIND-DRIVEN CIRCULATION OF SAGINAW BAY
Authors: Saylor James H. , Danek Larry J.
Published: June 2019

A combination of Lagrangian measurements and fixed current meter moorings were used during the summer of 1974 and the winter of 1974-75 to determine the circulation patterns of Saginaw Bay. Because the bay is shallow, the water responds rapidly to wind changes. Distinct circulation patterns were determined for southwest and northeast winds. These directions parallel the major axis of the bay and were the prevailing wind directions during the study. A typical exchange rate between the inner , _. and outer bay during moderate winds aligned with the bay axis is 3700 m s '~s If sustained, this flushing rate would completely exchange the water of the inner bay in about 26.5 days. However, winds perpendicular to the axis of the bay cause little water to be exchanged and the residence time of water in the bay is much longer. Comparison of measured currents with the results of an indpendently-developed numerical model for the bay indicates there is good agreement between the observations and the simulation of the circulation in the shallow inner bay. Agreement is poor in the deeper outer bay, where specification of proper boundary conditions at the open mouth of the bay is important for meaningful model simulations. Ice cover during winter shields the water surface from wind stress. Currents are sluggish and driven almost entirely from interactions with the lakescale circulation of Lake Huron.
ENERGY DISSIPATION IN TIDAL ESTUARIES
Authors: Partenscky Hans-Werner , Barg Gunther
Published: June 2019

In this study, the method for damped co-oscillating tides is used to evaluate damping and energy dissipation characteristics for various estuaries of different geometry and depth. Of special interest are the damping and energy dissipation characteristics of the German tidal rivers such as Elbe, Weser and Ems in comparison with North-American tidal estuaries, since the former are characterized by deep navigation channels and relatively flat wadden areas at their lateral boundaries. Harleman and Ippen have applied a mathematical model for co-oscillating tides to the Bay of Fundy and the Delaware estuary. This model gives information about the damping behaviour and energy distribution in the tidal estuaries. Both of the above mentioned estuaries represent special cases since the geometric form of the Bay of Fundy allows it to be approximately represented as a rectangular canal of constant width and depth, whereas for the Delaware Estuary one can assume a constant depth of water. Partenscky has applied an extended form of this model to the St. Lawrence Estuary. The method of co-oscillating tides has now also been used in a mathematical model for the German tidal rivers such as Elbe, Weser and Ems. This method takes into account the influence of geometry and depth on the tidal motion and also the damping of the tidal wave due to friction and partial reflection. Data from gauges situated along the estuaries are needed as initial input for the calculation of the damping coefficient and the phase change. The wave amplitude and the time of highwater must be known from these stations.
ALGORITHM FOR VERTICAL DIFFUSION
Authors: Kjeldsen Soren Peter
Published: June 2019

A mathematical method and a computer algorithm is developed for the case of one-dimensional vertical mixing for an estuary with rather small advection. In the case under consideration varies the diffusion coefficients both with time and depth, and the case is therefore closer to actual estuaries than earlier computing methods that applies constant coefficients. Model experiments with a small grid oscilliating with high frequencies in two fluids with different densities were performed to test the algorithm. Reynolds number for turbulence was near 1.6-101'. The results showed that the ratio between the stabilizing Brunt-Vaisala frequency and the agitating cyclic frequency was a governing parameter for the system, and dimensionless. diffusion coefficients could be expressed as a function of this parameter.
MODEL VERIFICATION FOR TIDAL CONSTITUENTS
Authors: Whalin R.W. , Perry F.C. , Durham D.L.
Published: June 2019

Installation and operation of an automated model data acquisition and control system have made it possible to make a quantum advance in the accuracy and time required for verification of tidal inlet (or estuary) hydraulic models. The flexible sampling rate (usually about 200 samples per model tidal cycle for each gage) and digital recording of these data make them ideal for harmonic analysis and comparison with prototype data defining the coefficients and phase for each tidal constituent at various key locations within the tidal lagoon and at an open-ocean station removed from the immediate influence of the tidal inlet. The concept used is to force the model with the M2 tidal constituent with the amplitude being correct at the ocean tide gage. A harmonic analysis is performed at all other gage locations corresponding to the prototype measurements, and the amplitude and phase (relative to the ocean tide gage) are calculated and compared with the prototype data. Investigation of the relative phases between various gages quickly shows those areas where either more or less model roughness is required. It is reasonable to expect to be able to have all phases for the M2 constituent verified within 1 degree. Tidal elevations can almost always be expected to be verified to within a maximum deviation of ;+0.1 ft in both tidal height and mean tide level. Upon verification of the M2 constituent, which practically insures that the proper channel roughness is obtained, a progressive tide can be constructed; and it should be attempted to perform a verification for a 14.765-day (synoptic period for M2 and S2 components) progressive tide at east coast locations using the prototype measurements of tidal velocities for the final verification data. Should additional roughness be necessary, it will almost always be on the mud flats or marsh areas. Computations are made to illustrate the energy transfer from the M2 constituent to higher order harmonics as the wave propagates from the ocean to the back of the estuary, and it is shown that this energy transfer is, at worst, the same order of magnitude in both the model and prototype.
CHURCHILL RIVER SALT-WATER TIDAL MODEL
Authors: Pratte Bruce D.
Published: June 2019

The Port of Churchill is located just inside the mouth of the Churchill River, on the western shore of Hudson Bay (Fig. 1, Photo 1). Each shipping season, about 25 x 106 bushels of grain are shipped to Europe and Britain. The Port opens just after mid-July when Hudson Strait and Bay become relatively clear of ice. However, it is forced to close 3 months later by ice forming upstream in the rapids, sweeping down as slush ice at ebb tide, jamming between the ships and the dock and breaking mooring lines. Since the route to Europe is shorter and therefore the laidin cost of the grain slightly less than from other Canadian ports, there is a demand to extend the operating season at Churchill. A feasibility study and field survey in 1965 by Dick (Refs. 1, 2) showed that the Port could remain open about 2 weeks longer than the present October 23 closing if the slush ice could be kept out of the harbour. To this end, the National Harbours Board in 1974 commissioned the Hydraulics Laboratory of the National Research Council of Canada to do an hydraulic model study of the harbour and estuary.
ANALYSIS OF TIME CONDITIONS FOR HYBRID TIDAL MODELS
Authors: Holz Klaus-Peter
Published: June 2019

Hybrid models for the investigation of tidal waves in rivers and estuaries are a combination of mathematical and hydraulic models, which are coupled under real-time conditions. The coupling procedure cannot be performed without some time delay which mainly depends on the time needed for the computation of the mathematical model and for the control operations on the instrumentation. An analysis of their influence on the accuracy of a hybrid model is given and experimental results from a feasibility study are presented.
COASTAL PROBLEMS IN SRI LANKA
Authors: Gerritsen Frans , Amarasinghe Suma R.
Published: June 2019

As an island state with about 900 miles of coastline, Sri Lanka is endowed with a large natural resource: its 720 miles of sandy beaches. The coastal zone is under stress by a burgeoning population, living in the coastal belt, and a variety of other demands with conflicting interests. Due to natural causes and interference of men, erosion is a serious problem in the densely populated southwest part of the island. This paper describes the principal characteristics of the coastal environment and discusses the nature of some of the basic problems. In the recommendations, emphasis is placed on the setting up of an organizational structure to study the problems, both in the field and in the laboratory, with respect to the management aspects in the coastal zone.
STUDY OF AN ARTIFICIAL ISLAND
Authors: Lepetit J.P. , Moreau S.
Published: June 2019

The location of large surface industrial zones along sea shores often competes with other coastal activities, such as recreational pursuits, fishing, nature reserves, etc. The construction of an artificial island in the sea, near the shore, is a solution to which it will perhaps be necessary to have recourse in the fairly near future. The design of such a project poses many problems particularly in respect of its impact on the environment. We present here the results of a study which examines this aspect. The problems are as follows : - influence of the island on the local wave climate, or swell, and consequent shoreline changes, - influence of the island on tidal currents and resulting evolution of the sandy sea bed, - dispersion of industrial effluents. The effect of the island on swell and on shore stability and the calculation of pollutant dispersion are approached by the use of mathematical models ; the effect of the island on tidal currents is analysed on a reduced scale physical model.
WAVE HEIGHT DISTRIBUTION OF WIND WAVES OVER LONG WAVES
Authors: Ou Shan-Hwei , Tang Frederick L.W.
Published: June 2019

Influence of long wave on the wave height distribution of wind waves was studied through the laboratory experiment. Experiments were conducted in a wind-wave tank where the wind waves were generated by a wind blower and the long waves were developed by an oscillating pendulum type wave generator. The wave height distribution of the wind waves over long wave is slightly different from the Rayleigh distribution in the small steepness of long wave. The ratios between the average of highest l/n-th waves vary with the steepness of long waves. The magnitude and the location of the spectral peak of wind waves are altered. The amount of the attenuation of wind wave energy is larger than the results of Mitsuyasu (1966).
PHYSICAL ASPECTS OF WAVE-INDUCED NEARSHORE CURRENT SYSTEM
Authors: Mizuguchi Masaru , Horikawa Kiyoshi
Published: June 2019

Since a theoretical approach on rip currents was made by Bowen (1969), our understandings on that system have progressed steadily. It will be considered that the dynamics of current system are governed by the following equations which indicate the balance among the gradients of radiation stress and of mean water level, and the friction force induced by the current velocity.
NEARSHORE CURRENT ON A GENTLY SLOPING BEACH
Authors: Sasaki Tamio , Horikawa Kiyoshi , Hotta Shintaro
Published: June 2019

The authors developed a new field observation system called STEREOBACS by which simultaneous measurements of a spacial distribution on waves and currents in the nearshore environment can be obtained. This system was applyed on Ajigaura Beach, Japan, and several analyzed results are presented. Also field observations of infragravity low mode edge waves to support the Infragravity Domain Hypothesis on nearshore currents concerning a gently sloping beach [Sasaki(1974,1975), Sasaki and Horikawa (1975)] are introduced.
LATERAL AND BOTTOM FORCES ON LONGSHORE CURRENTS
Authors: Huntley David A.
Published: June 2019

A two-component electromagnetic flowmeter has been used on a natural beach of slope 0.01 to measure mean longshore currents and the horizontal fluctuating velocities in the frequency range 0-1 Hz. The measurements extend up to 120 m offshore and span about one third of a wide surf-zone. The cross product of the fluctuating horizontal velocities, assumed to contain the combined effects of radiation and Reynold's stresses, is plotted as a function of distance from the shoreline. The on/offshore gradient of the cross-product is then equated with a bottom friction term either in the form used by Bowen (1969a) or in a form similar to that used by Longuet-Higgins (1970). The apparent values of bottom friction coefficient obtained in this way are at least a factor of two smaller than expected for Reynolds numbers and bottom roughness appropriate to the beach. Attempts to separate the radiation stress and the Reynold's stress contributions to the total stress term using cospectra fail to show distinguishable Reynold's stress contributions. Although this may be construed as being consistent with Battjes' (1975) beach slope dependent form for horizontal eddy viscosity rather than Longuet-Higgins' (1970) form, it is argued that, in fact, the significant horizontal turbulence was not measured at all but was confined to a surface layer above the flowmeter. This leads to the hypothesis that lateral friction, as a surface boundary layer, and the bottom friction act on a less turbulent central layer, and that the small measured friction coefficient in the present experiment is the result of the combined effects of these layers.
TIME DEPENDENT FLUCTUATIONS IN LONGSHORE CURRENTS
Authors: Meadows Guy A.
Published: June 2019

During constant sea state conditions, longshore current velocities were monitored continuously for fifteen minute periods separated by fifteen minute periods separated by fifteen minute intervals. Three ducted impellor flowmeters were placed at equally spaced vertical positions through the water column. Sequential measurements were made with similar vertical current meter arrays at different locations across the surf zone. Simultaneous measurements of wave height, period and celerity were made at stations placed at equal intervals from the outer surf zone to the beach. The fifteen minute continuous records were subjected to spectral analysis. This analysis showed that the major power associated with fluctuations in the longshore current velocity field occurs in two major frequency bands. A significant spectral peak was coincident with the breaker period of the incident wave field, 4.2 seconds and, another dominant signature occurred at 78.8 seconds. Attenuation with depth of both the steady and fluctuating components of the longshore current flow field was relatively small. The maximum observed velocities for each station and each vertical current meter position varied from 90 to 150 percent above the observed mean longshore current velocity. However, at each station, variation of the means with depth was not appreciable and thus supports the results from time and space averaged theories of vertical uniformity in longshore currents, away from the boundary layer. Results from the field investigation of Wood and Meadows (1975) indicated that the steady state components are dominated by the fluctuating portions of the flow field. Therefore, time averaging of conservation equations in longshore current theory is a physically inappropriate procedure. In order to evaluate the magnitude of the unsteady components, a close examination of surf zone dynamics was made. The most obvious contribution to unsteadiness in longshore currents arises from the longshore component of the maximum horizontal particle velocity. However, the magnitude of observed current fluctuations is too large to be completely accounted for by this component. Spectral peaks at longer periods appear to be related to modes of edge wave phenomena. The long period spectral signature of 78.8 seconds is in direct agreement with the calculated period for a zero mode edge wave in shallow water.
TERRESTRIAL PHOTOGRAMMETRIC MEASUREMENTS OF BREAKING WAVES AND LONGSHORE CURRENTS IN THE NEARSHORE ZONE
Authors: Maresca Joseph W. , Seibel Erwin
Published: June 2019

We conducted a study to determine the feasibility of shore-based, oblique photographic monitoring of breaking waves, water levels, and currents within the surf zone. The purpose of this paper is to describe a new method of oblique single-image and stereoscopic-image analysis, the potential errors, and the types of measurements that can be made in the surf zone. Examples of application are presented to demonstrate the technique. Sophisticated photographic equipment is not required to collect, analyze, and interpret the data. The analysis and error discussions are directed toward the problems encountered using common equipment. Vertical images from aircraft, helicopters, and balloons have been used in the past to study shoreline changes, directional ocean-wave spectra,8 and longshore currents.3 Oblique images taken from the bridge of a ship have been successfully used to measure whitecap coverage under different wind speeds.4 Terrestrial oblique images have been used to study longshore currents,5 ice-ridge formation and breakup,6'7 and beach changes .8 Oblique images, taken with a 35-mm single-lens reflex camera from an elevated point such as a bluff, are particularly suitable for the measurement of breaking waves, water level, beach run-up, and current in the surf zone under storm conditions. In contrast to other techniques of monitoring the surf zone, the photographic technique described in this paper is simple to install, reliable, accurate, and inexpensive. It can be used in all weather conditions, and the analysis of the images is simple. Both stereoscopic and single oblique images can be analyzed, depending on the specific needs and existing environmental conditions. Since the scale of an oblique photograph changes with increasing distance from the camera, the technique is limited in range to about 250 m for a cliff approximately 8 m above the mean water level. Accuracies to within 1% in the horizontal plane and better than 10% in the vertical plane are achievable at this distance.
DATA COLLECTION AKD ANALYSIS FOR COASTAL PROJECTS
Authors: Loewy E. , Witthaus K.G. , Summers L. , Maddrell R.J.
Published: June 2019

Modern design concepts for coastal engineering" works make increasingly, heavy demands in respect of the number of variables to be investigated, of the accuracy of the field measurements and of subsequent methods of analysis. In general the larger the projects the greater the demand for accurate site data but frequently, whatever the field data requirement might be, environmental conditions impose severe limitations upon the quality and quantity of the obtainable information. Before field measurements commenced on the two projects reported in this paper (see Figures 1 and 2) careful consideration was given to the relation between the probable status of the data, the level of statistical analysis to be applied and the constraints the results might impose upon research objectives or upon projected works. Such appraisal was specially relevant since the projects drew upon results from both physical and mathematical models and, in one case, involved assessments of extreme sea conditions related to nuclear safety. This approach provided sufficient flexibility to adjust the method or extent of data collection to take advantage of optimum conditions in the field and changing requirements for input to models and designs. The time and energy expended in obtaining data of the correct order of confidence was justified by its direct applicability to alternative designs in the face of rapidly inflating construction costs. It was considered essential that the planning and control of data collection be co-ordinated by the design engineer for relating individual items to the project as a whole. It was found equally important that the hydrograpnic surveyors and oceanographers, familiar with the physical aspects involved, understood how their results were to be applied and hence appreciated the necessity of achieving appropriate tolerances for different parts of the work.
CURRENT DEPTH REFRACTION USING FINITE ELEMENTS
Authors: Skovgaard Ove , Jonsson Ivar G.
Published: June 2019

A computational model is presented for the steady state prediction of currents, waves, and sea surface elevations in a coastal region outside the surf zone. Irrotational flow of surface gravity waves on large-scale steady currents over a gently sloping sea bed is considered. A second order Stokian approach is used, and all dynamic quantities are integrated over depth and averaged over time, in that order. The flow equations and the boundary conditions are presented. A method is developed for the solution of the non-linear steady model by introducing a sequence of two-level calculations, viz. a 'wave level' and a 'current level'. The variables are split on the two levels. The wave field is found, using that the flux of wave action is constant between adjacent wave rays. The current field and the mean sea surface elevation are determined using a Galerkin finite element method. The current field is approximated by triangular elements with linear interpolation functions, and the mean sea surface elevation is approximated by a triangular element with quadratic (parabolic) interpolation functions. A quasi-twodimensional test solution is tabulated.
WAVE RUN-UP IN FIELD MEASUREMENTS WITH NEWLY DEVELOPED INSTRUMENT
Authors: Erchinger Heie F.
Published: June 2019

The height of dikes and other coastal structures can only be calculated after determination of the wave run-up. Several formulas for the calculation of wave run-up are developed after model tests as a rule. But the influences of scale effects and natural wind conditions are practically unknown. To clear these questions further investigations and especially field measurements should be carried out. By measuring the markerline of floating trash on the slope of the seadikes the maximum wave run-up could be found out after four storm surges in 1967 and 1973- In two graphs it will be shown that on the tidal flats the run-up depends on the waterdepth. The run-up was higher than it could be expected after model tests of 1954. With a newly developed special echo sounder the run-up could be measured in January 1976. The waves and the run-up could be registrated synchronously during two severe storm surges. As shown in Fig. 9 it was found a logarithmic distribution of the wave height, wave period and the higher part of the wave run-up. The found wave run-up is considerably higher than estimated before. The measured 98 % run-up is found about twice the computed value. That is an interesting and important result of the first synchronous recording of wave run-up on sea dikes.
MACH-REFLECTION AS A DIFFRACTION PROBLEM
Authors: Berger Udo , Kohlhase Soren
Published: June 2019

As under oblique wave approach water waves are reflected by a vertical wall, a wave branching effect (stem) develops normal to the reflecting wall. The waves progressing along the wall will steep up. The wave heights increase up to more than twice the incident wave height. The £jtudy has pointed out that this effect, which is usually called MACH-REFLECTION, is not to be taken as an analogy to gas dynamics, but should be interpreted as a diffraction problem.
RESONANT REFRACTION BY ROUND ISLANDS
Authors: Meyer Richard E.
Published: June 2019

Wave trapping by refraction can give rise to resonance of a kind unfamiliar in oceanography. Trapping over realistic seabed topographies is incomplete, but conversely, possesses a mechanism for direct, harmonic excitation from the open sea that is unknown in classical resonance. These phenomena have been studied for the simplest example of an axisymmetric island of typical shape with small seabed slope. Asymptotic analysis has led to simple formulae for resonant frequencies, energy leakage rates and resonant response coefficients. Resonances of extraordinarily large but narrow response have been found.
REGIONAL NETWORK FOR COASTAL ENGINEERING DATA
Authors: Seymour Richard J. , Sessions Meredith H.
Published: June 2019

The California Department of Navigation and Ocean Development (DNOD), responsible for shoreline protection within the state, was particularly aware of the lack of coastal wave statistics to support their beach erosion program. As a direct result of the 1974 ASCE-sponsored New Orleans Conference on Ocean Wave Measurement and Analysis, discussion was initiated within DNOD and then with the Scripps Institution of Oceanography (SIO) at La Jolla, on the feasibility o"f establishing a regional wave monitoring network for California. The initial specification presented by DNOD was for a 200-station network reporting directional wave spectra twice daily for a period of ten years. SIO ocean engineering personnel responded with a system concept employing low-cost pressure transducers hardwired to shore with a dialup telephone data gathering link to a central station. The initial cost estimates appeared attractive when compared with Corps of Engineers experience as reported in Peacock (1974). As a result, a small program was funded in February 1975 at Scripps to demonstrate critical hardware items through the breadboard stage. With the successful completion of this work, additional funds were allocated by DNOD as matching funds for a California Sea Grant Project. Th_e first station in the network began operation on 3 December 1975 at Imperial Beach, California. A second station was added at Ocean Beach (San Diego) on 27 March 1976, a third at SIO (La Jolla) on 18 May 1976 and the fourth at Oceanside, California on 2 June 1976. The locations of these initial stations are shown in Figure 1. Considerable effort has been directed during the past 10 years toward the development of numerical models to predict deep-water wave conditions from meteorological data. Reasonable results have been obtained and sufficient accuracy achieved to allow routing of both commercial and military ship traffic.
CURRENTS IN TIDAL FLATS DURING STORM SURGES
Authors: Gohren Harald
Published: June 2019

Wind action in the viewpoint of coastal engineering is mainly a topic for discussions or investigations of waves, breakers, storm surges, sand transport on beaches and so on. Offshore currents, generated by wind shear stress concern more the scientific field of oceanographers. But in shallow coastal water wind induced drift currents indeed may be important for coastal engineering problems, as sediment transport, sewage spreading, salinity and so on. For example, along the German North Sea Coast (Fig. 1) we have a rim of extended tidal flats, built up by sand and mud and covered only by a water layer of 1 to 2 m at high tide. At low tide sands and mud flats fall dry. Fig. 2, an aerial view, gives an impression of a typical tidal flat, the "Neuwerker Watt" at the south side of the Elbe Estuary. The distance between main land and the sea side border of the flat is here about 20 km. A lot of investigations have been carried out here - initiated by a harbour planning task - giving some interesting results about currents in the tidal flat area during strong winds and storm surges. For the current measurements a recording current meter (Fig. 3) has been used, fixed at a tripod aluminum frame in 40 cm above bottom. The propeller meter starts at velocities of 5 cm/s. Tests in a flume proved that orbital currents give no disturbance if unidirectional currents of a certain magnitude are superimposed.
WAVE MEASUREMENTS IN OPEN OCEAN
Authors: Chen Davidson T. , Yaplee Benjamin S. , Hammond Donald L. , Bey Paul
Published: June 2019

The ability to measure the wave spectra in the open ocean from a moving vessel has met with varying degrees of success. Each sensor to date has suffered in its performance due to environmental conditions or due to its physical placement aboard the vessel for measuring the unperturbed sea. This paper will discuss the utilization of a microwave sensor on a moving vessel for measuring the open ocean wave spectra. Employing microwaves, some of the limitations of other sensors are not experienced. Tucker [1] developed the Tuckermeter for measuring the wave spectra from a moving ship by sensing changes in water pressure due to surface wave conditions. The Tuckermeter is placed below the water line and thus requires calibration for each wave frequency, ship speed, and depth. Since the sensor operates on pressure, it performs as a low pass filter and will not sense the higher frequencies. A microwave shipboard wave height radar sensor for measuring the ocean wave spectra was developed by the Naval Research Laboratory (NRL) and was installed on the S.S. McLean in February 1975 and its performance, design, and analysis of data for one data run will be discussed.
CALCULATIONS OF WAVES FORMED FROM SURFACE CAVITIES
Authors: Mader Charles L.
Published: June 2019

The wave motion resulting from cavities in the ocean surface was investigated using both the long wave, shallow water model and the incompressible Navier-Stokes equations. The fluid flow resulting from the calculated collapse of the cavities is significantly different for the two models. The experimentally observed flow resulting from explosively formed cavities is in better agreement with the flow calculated using the incompressible Navier-Stokes model. The resulting wave motions decay rapidly to deep water waves. Large cavities located under the surface of the ocean will be more likely to result in Tsunami waves than cavities on the surface. This is contrary to what has been suggested by the upper critical depth phenomenon.
PREDICTIVE EQUATIONS REGARDING COASTAL TRANSPORTS
Authors: Swart D.H.
Published: June 2019

Morphological changes are the result of gradients in longshore and onshore-offshore sediment transport. The coastal engineer is continually faced with engineering problems in which a quantitative knowledge of these morphological changes is required. For this purpose predictive equations have been developed for both longshore and onshore-offshore sediment transport, which are being used in practical applications. In this paper a few of these predictive techniques, as well as one of their typical applications, viz. to a beachfill problem, will be discussed.
SAND TRANSPORT BY WAVES
Authors: Bijker E.W. , Van Hijum E. , Vellinga P.
Published: June 2019

Sand transport parallel to the direction of wave propagation by waves of arbitrary form over a rippled bed has been investigated in a flume, at the Laboratory of Fluid Mechanics of the Dept. of Civ. Eng. of the Delft Univ. of Techn. The transport has been measured by means of a special procedure which does not disturb the process. The measured sand transport is related to the measured wave form parameters. The results indicate that the direction of net sand transport depends upon the form of the waves.
LONGSHORE TRANSPORT AT A TOTAL LITTORAL BARRIER
Authors: Bruno Richard O. , Gable Christopher G.
Published: June 2019

Analysis of longshore transport at a littoral barrier is presented. Channel Islands Harbor, California was selected as the study site because its offshore breakwater and jetties form a unique complete littoral barrier. Through repetitive surveys an accurate determination of longshore material transport in one direction was made. Measured transport rates ranged from 160,000 to 1,284,000 cubic meters per year. Utilizing visual observations of surf parameters, estimates of longshore wave thrust were computed. The range of wave thrust was 145 to 1,988 Newtons per meter. Comparison of the relation of wave thrust and longshore sediment transport is made. This study indicates that in an environment of high transport, nearly twice as much transport is predicted tinder corresponding wave thrust as that of the data summarized in the Coastal Engineering Research Center's Shore Protection Manual.
RIP-CURRENT AND COASTAL TOPOGRAPHY
Authors: Hino Mikio
Published: June 2019

At the 1974 Conference on Coastal Engineering (Copenhagen), the -writer proposed a new theory on the mechanism of generation of ripcurrent and cuspidal coast that the alongshore homogeneous structure of wave field and movable sedimental bottom (that is two-dimensional wave setup and bottom topography) is unstable to a small perturbation, the motive force of instability being the radiation stresses caused by incident wave. In this paper, based on the response concept and the mathematics already presented at the previous conference some improvements in solving the fundamental equations are attempted, since the direct solution of the full system of basic equations did not necessarily result in the sufficient conclusion. The response of water-wave system to an infinitesimal perturbation in bottom boundary is quick enough compared with that of sediment system to a change occurring in water-wave system. Consequently, the water system is treated as quasi-stationary. By solving the equation of mass conservation of sediment transport under the prescribed boundary conditions, the preferred wavelength of rip-current as well as the profiles of velocity distribution and the bottom perturbation have been determined as an eigenvalue problem.
A SAND BYPASSING SYSTEM USING A JET PUMP
Authors: McNair E.C.
Published: June 2019

All harbors and tidal inlets that are located in coastal areas have one characteristic in common-the need to bypass littoral materials that collect nearby. If natural harbors and tidal inlets are left unattended, bypassing will often occur naturally, but in the process, the harbor or inlet is usually rendered unfit for commercial or navigation purposes. Quite often, the inattention results in the total closure of the inlet. Therefore, at almost all harbor entrances and controlled tidal inlets, the natural bypassing must be augmented by secondary, usually mechanical, means. The customary technique for bypassing sand and maintaining harbors and inlets is the use of floating dredge equipment. This equipment is rugged, reliable, has been proved over and over, and appears to be irreplacable for many applications and locations. However, there are many locations and situations for which this floating equipment is not suitable and may, in fact, be detrimental or prohibitively costly. Waves of even moderate height, moderateto- high tidal excursion and currents, draft limitations, limited maneuvering area, and interference with normal navigation operations are examples of conditions which decrease the desirability and application of floating dredge equipment. Small volumes of material to be bypassed are an economic liability for the floating plant since mobilization and demobilization costs contribute extraordinarily to the unit cost for bypassing work.
SAND-BYPASS AND SHORE EROSION, BRIDGMAN, MICHIGAN
Authors: Johnson C.N. , Hiipakka L.W.
Published: June 2019

The objectives of this paper are two-fold: a. Demonstrate by means of a well-documented full-scale case history in the Great Lakes that beach nourishment can mitigate shore damage due to a littoral barrier; b. Detail a methodology for analysis of the effectiveness of mitigation measures which lead to conclusions on the needed frequency of nearshore soundings as a tool for monitoring. In 1970 a temporary harbor was installed by private interests along the southeastern Lake Michigan shoreline near Bridgman, Michigan, (Figure 1). The harbor was necessary to protect floating plant involved in building a large privately-owned electric generating facility. The harbor was constructed of steel sheet pile and extended lakeward about 125 meters from the water's-edge to a depth about 3 meters below low water datum (LWD)2. Net littoral transport is about 75,000 cubic meters per year southward. The updrift and downdrift lakebed and bluff materials consist of sand. To ensure that this littoral barrier would not have an adverse effect on adjacent properties it was necessary for the Corps of Engineers to impose stringent requirements for issuance of a Federal permit for the installation. Bypass of at least 75,000 cubic meters per year of sand was required to mitigate potential erosion of downdrift beaches due to interruption of littoral transport. The permit also required intensive monitoring of the shoreline to ensure that any adverse effects of the harbor would be promptly detected and remedied. The monitoring consisted of: a. Monthly 1:3000 scale aerial photographs of the shoreline sixteen kilometers north (updrift) to sixteen kilometers south (downdrift) ro\-fF tthheo htla'i rVtbt-lof\rv>. b. Monumenting and thrice-yearly measurement of backshore-nearshore profiles spaced 150 meters apart, for a distance of 2450 meters north and 2450 meters south of the harbor, extending about 900 meters lakeward to about -8 meters LWD (Figure 2). The nearshore soundings were made by acoustic sounder every 30 meters along each profile. The survey boat was located along the profile by triangulation. Backshore profiles were provided by photogrammetric mapping.
DESIGN AND BEHAVIOUR OF SANDTRAPS IN REGIONS OP HIGH LITTORAL DRIFT
Authors: Sarena P.C. , Vaidyaraman P.P. , Srinivasan R.
Published: June 2019

Siltation in harbours and their approach channels is one of the major problems connected with the development of harbours. The economics of harbours are directly related to their annual maintenance dredging, and as such a proper assessment of the quantity of siltation and provision of adequate measures for the maintenance of depths would form an important part of planning the development programmes. Siltation could occur due to various reasons viz. deposition of littoral drift which is interrupted by the approach channel, deposition of sediments brought into suspension by wave action (including during storm/cyclone) Whenever the alongshore drift is large, wave action obviously is quite substantial which renders the maintenance of depths during this period by dredging difficult. In such cases it would be necessary to make adequate provision to ensure that the depths are not deteriorated to any substantial extent by the movement of the drift. One of the common means for achieving this is the provision of sandtraps on the updrlft side of the approach channel which would 'store' the drift material temporarily and from where the material could be dredged at convenience. The design of the sandtrap would be governed by a number of factors such as the extent over which a major part of the drift takes place, quantity of material transported, size distribution of sediments, velocity of currents, mode of dredging etc. Waves of moderate to high intensity occurs along the eastern coast of India from south and south west direction during south west monsoon period from May to September and from North Easterly direction during North East monsoon beginning from November. In view of this climate the direction of drift along the shore changes with Mason. The quantities of drift during these periods are also different owing to the magnitudeand periods of wave action which differs between the two seasons. The net drift along this coast varies from 0»60 million m3 at Madras on the south which increases progressively to 1,00 million m3 at Paradip further North (Fig, 1),
HEADLAND DEFENSE OF COASTS
Authors: Silvester Richard
Published: June 2019

Crenulate shaped bays are ubiquitous and constitute the largest proportion of coastline length. The characteristics of stable bays (i.e., no littoral drift) are known, so that realistic encroachment limits can be defined. Allowances for long term changes in direction of persistent swell and annual attack from multidirectional storm waves may have to be made. The exposure of a rock outcrop during an erosive sequence will create a new fixed point on the coast and hence a new bayed system. An existing non-stable bay can be prevented from indenting to its equilibrium shape by the construction of one or more fixed points around its periphery. Research should be conducted to minimise the cost of headlands which might start off as offshore breakwaters, even mobile units.
GROIN LENGTH AND THE GENERATION OF EDGE WAVES
Authors: Gaughan Michael K. , Komar Paul D.
Published: June 2019

A series of wave basin experiments were undertaken to better understand the selection of groin spacings and lengths. Rather than obtaining edge waves with the same period as the normal incident waves, subharmonic edge waves were produced with a period twice that of the incoming waves and a wave length equal to the groin spacing. Rip currents were therefore not formed by the interactions of the synchronous edge waves and normal waves as proposed by Bowen and Inman (1969). Rips were present in the wave basin but their origin is uncertain and they were never strong enough to cause beach erosion. The generation of strong subharmonic edge waves conforms with the work of Guza and Davis (1974) and Guza and Inman (1975). The subharmonic edge waves interacted with the incoming waves to give an alternating sequence of surging and collapsing breakers along the beach. Their effects on the swash were sufficient to erode the beach in some places and cause deposition in other places. Thus major rearrangements of the sand were produced between the groins, but significant erosion did not occur as had been anticipated when the study began. By progressively decreasing the length of the submerged portions of the groins, it was found that the strength (amplitude) of the edge waves decreases. A critical submerged groin length was determined whereby the normally incident wave field could not generate resonant subharmonic edge waves of mode zero with a wavelength equal to the groin spacing. The ratio of this critical length to the spacing of the groins was found in the experiments to be approximately 0.15 to 0.20, and did not vary with the steepness of the normal incident waves.
LABORATORY INVESTIGATION OF SHORE EROSION PROCESSES
Authors: Brater E.F. , Ponce-Campos David
Published: June 2019

The laboratory investigation was undertaken as part of a shore protection demonstration program sponsored by the Michigan Department of Natural Resources. Subsequently funding was also provided by the Sea Grant Program. The laboratory work is being done in the Lake Hydraulics Laboratory, a facility of the Department of Civil Engineering of the University of Michigan. The field demonstration program consists of 19 field installations at locations on Lakes Michigan, Huron and Superior. The laboratory program was planned to supplement information from the field installations by testing over a wider range of variables and to test procedures not included in the field program. This program has also proven to be useful in the demonstration of shore erosion processes to groups concerned with shore problems. Although erosion rates determined in a model cannot be converted quantitatively to nature it was reasoned that if natural shore erosion processes could be simulated and if repeatable erosion rates could be produced in the model the results could help to evaluate the relative effectiveness of many protective methods. The advantages of using a model are the much lower cost compared with field installations, the control over such variables as wave height and water level and the speed with which results can be obtained.