bluuebunny/crossref_metadata_2025 huggingface dataset:
RANDOM WAVE SIGNAL GENERATION BY MINICOMPUTER
Authors: Funke Ed. R.
Published: June 2019

The computer programmed implementation of a pseudorandom noise generator based on the use of a binary feedback shift register and an associated digital filter is described. Descriptive details are given for the compensation of the filter for the various dynamic transfer functions in the system. The random signal generator has been programmed both for a dedicated computer (NOVA 1200 with 4K core) which can carry up to 50 different spectra in core at any one time and for the EAI 64 0 with 16K core and disc storage which was used to investigate the spectral and statistical properties of the generated wave. JONSWAP spectra with 0.6 and 1.0 Herz centre frequencies were generated and observed at locations from 5 to 40 meters from the wave maker using a hydraulically operated machine in a partial piston and partial hinged flap mode m 0.9 meter of water. Measurements indicate that JONSWAP spectra can be closely matched in the flume. The 1.0 Herz spectrum is less stable as a function of distance, all spectra indicate a significant decrease of the spectral peak as a function of distance from the wave maker and the ratio of ^xaax/^av ls ln general larger than that observed by Wiegel and Kukk.
MODEL TESTS WITH DIRECTLY REPRODUCED NATURE WAVE TRAINS
Authors: Gravesen Helge , Fredericksen Ebbe , Kirkegaard Jens
Published: June 2019

Hydraulic model tests are still recognized as the best and in many cases the only tool, indeed, for investigations of design criteria for harbours concerning a) the effect of wave disturbance on moored ships in harbour basins and at offshore terminals, b) stability of structures and wave forces on structures. Model tests with waves have until recently usually been made with regular waves varying the wave height, wave period, wave direction for each test run. An important improvement in the model technique has been the development of irregular wave generators, capable of generating waves directly from nature wave records. The following aspects are presented below 1) A discussion on the methodology of wave model tests. 2) A method for direct reproduction of nature wave records. 3) A method for determining the incoming wave heights in a short wave flume with a reflecting structure and reflection from the wave generator paddle.
CRITICAL TRAVEL DISTANCE OF WAVES IN SHALLOW WATER
Authors: Siefert Winfried
Published: June 2019

A new criterion for shallow water wave analysis is evaluated from prototype data off the German coast on the reef and wadden sea areas south of the outer Elbe river. Correlations of mean wave heights H with mean wave peri- - H ods T, and wave height distribution factors C. /-, = -l/3 t-^ respectively show that the mean periods and both complete height and period distributions of waves in shallow water can be expressed as functions of mean height and topography. So the mean wave height H proves to be the characteristic parameter for the description of the complete shallow water wave climate. The upper envelop of the values H = f (meteorology, topography) is defined as the case of fully developed sea, which leads to the function of the highest mean wave heights Hmax.
MASS TRANSPORT IN GRAVITY WAVES ON A SLOPING BOTTOM
Authors: Bijker E.W. , Kalkwijk J.P. Th. , Pieters T.
Published: June 2019

In the present investigation the influence of bottom slope on mass transport by progressive waves was investigated, both theoretically and experimentally. Theoretical considerations based on linear wave theory show the greatest influence of the slope on the bottom drift velocities for relatively long waves and steep slopes. The numerical values, however, remain rather small (influence less than 20%). In addition, the experiments show that the bottom drift velocities are more determined by the local parameters than by the magnitude of the bottom slope m the cases examined. Considering the net bottom velocities, the discrepancy between the horizontal bottom theory (Longuet- Higgms) and experimental results is considerable. Taking into account the first harmonic of the local wave form and the small slope effect for relatively small depths in horizontal bottom theory does show, however, the same tendency as the experimental results.
ON WAVE DEFORMATION AFTER BREAKING
Authors: Sawaragi Toru , Iwata Koichiro
Published: June 2019

Waves will dissipate their energy rapidly after breaking. In this paper, the three factors , (i) formation of a horizontal roller,(11) bottom friction, and (in) turbulence with air entrainment, which will contribute to the energy dissipation, are dealt with experimentally and theoretically The horizontal roller formed by a plunging breaker is approximated as a Rankme-type vortex by experiments, and it is calculated that 15$-30%of wave energy is dissipated due to the formation of horizontal roller alone from a breaking point to a point of the roller disappearance. A bottom shear stress due to a breaker is measured by the shear meter deviced by the authors and it is clarified that the energy dissipation due to bottom friction is a little Mam part of the energy dissipation is taken to be caused by the turbulence with air entrainment. It is indicated that an incident monocromatic wave is transformed into a higher frequency wave due to the turbulence. Furthermore, a new basic equation for breaking waves with a turbulence term expressed by a Reynolds stress is presented The theoretical curves computed numerically have a consistent agreement with the experimental results.
STORM SURGE EFFECTS AT LEIXOES
Authors: Morais C. Campos , Abecasis F.
Published: June 2019

In this paper, the effects of a storm surge that happened on the 16th-17th January 1973 in the harbour of Leixoes are analysed and described. These effects were of two types: - As the storm surge coincided with a spring tide and rough seas, severe damages occurred in the outer breakwater, mainly in its head. - Associated to the storm surge range phenomena happened in the nS 2 dock; these movements, acting on a ship berthed in a nodal zone, caused several breakings in the ropes and damages in harbour structures. The characteristics of the storm surge and of the waves are analysed. Their effects on the breakwater are described. By comparing the periods of long waves observed in the tide records with the resonance periods of the inner docks it was possible to conclude that the intensity of the range phenomena observed was due to a half wave length resonance. Having in mind the affinities with the phenomena referred to above, the effects of range action in an oil terminal and new damages in the outer breakwater, that occurred in January and February 1974 respectively, are also briefly examined.
VELOCITIES UNDER PERIODIC AND RANDOM WAVES
Authors: Lee Allen , Greated Clive A. , Durrani Tariq S.
Published: June 2019

Using the linear approximation for predicting velocities under periodic water waves, relationships are established between the velocity spectrum and the surface elevation spectrum for three-dimensional waves. The two dimensional forms of these relationships are used for comparison with velocity and elevation spectra measured in a laboratory wave tank. The predicted distortion of the spectrum shape can be observed in the experimental results. Velocity measurements were recorded using a laser velocimeter employing a rotating diffraction grating for shifting the optical frequencies. This allows measurement without sign ambiguity. The random waves were generated using a servodriven paddle with a filtered white noise input.
INTERNAL VELOCITIES IB THE UPRUSH AND BACKWASH ZONE
Authors: Kemp Patrick H. , Plinston David T.
Published: June 2019

In an earlier paper the authors reported the results of both field and hydraulic model investigations into the reaction of beaches to the action of waves of low phase difference. These waves are those whose time of uprush on the beach is equal to or less than 0.7 T, where T is the wave period. The present paper summarises the study of the internal velocity field under similar conditions. By making certain simplifying assumptions based on observations of the profile of the wave during uprush and backwash, the surging wave is open to quantitative description. For very low phase differences the uprush is approximately the reverse of the backwash, but to a different time scale. However, as the phase difference approaches the limit for the surging condition, the uprush starts and may remain in the form of a bore.
COMPUTER AID FOR OPTIMUM DESIGN OF TSUNAMI WAVES
Authors: Iwasaki Toshio
Published: June 2019

The tsunami process of their generation and propagation to the near-coast offshore region is discussed. Purpose is to give optimum configurations of tsunami waves of large magnitude, which can be used as boundary conditions for the analysis of the dynamic process near the shore or around structures in coastal zone. They are obtained by numerical computations along the southern coast of the Hokkaido and the Sanriku Coast for various tsunami sources set on the continental shelf facing to the Japan Submarine Trench. Dispersive nature of the tsunamis seems to make the problem very complicated. However statistical results thus obtained can be accepted for the base of design of structures.
FEASIBILITY OF COASTAL MORPHOLOGICAL MODELS
Authors: Nielsen Evald
Published: June 2019

The paper deals with the initial ideas and concepts for development of a morphological model for a Delta coast, having particularly the Nile Delta in mind. The paper concentrates on the offshore zone, in which sediment is assumed primarily to be transported in suspension and during periods of sufficient agitation by the combined action of waves and ocean currents. In the Nile Delta great offshore changes take place due to the deprivation of the shelf area of Nile sediments by the closure of the Aswan High Dam, and serious nearshore long-range changes are expected to result from the changes to the offshore morphology. The modeling aids in establishing the mechanisms of the Delta shore, but the primary goal of the model is reliable prediction of future coastal changes. Fundamentally, the modeling is based on verification of the model - by trial and error - against known states of the model domain. Part A of the paper deals with the general concepts, while especially the entrainment of sediments is treated in Part B of the paper, yielding practical formulas for determining the threshold values for sediment entrainment by unidirectional flow and by wave action.
COMPUTER EVALUATION OF LITTORAL TRANSPORT
Authors: Mogel Theodor R. , Street Robert L.
Published: June 2019

Hindcast deepwater wave statistics and bottom hydrographic data are combined with a water-wave refraction analysis to estimate the littoral transport in a beach zone. The effects of hindcast data station location, of wave ray density in the breaker zone, of changes in the bottom-fitting surface in the depth calculation of the refraction analysis, and of methods of smoothing the contribution of individual rays to the littoral transport computation are explored.
SAND TRANSPORT AND COASTAL STABILITY, LANCASHIRE, U.K.
Authors: Parker William Reginald
Published: June 2019

The stability of an alluvial coast depends upon the local sediment budget. Along the shore, changes from erosion to accretion may reflect changing sediment fluxes, sediment residence times and patterns of sediment movement. Processes influencing these parameters, such as mud sedimentation or migration of intertidal channels will, through their influence on beach gradients and sediment transport patterns, affect the processes and rates of coastal dune erosion and the safety of the dune protected hinterland. A qualitative description of some of the various processes and phenomena linking foreshore and dune stability with sediment circulation and coastal evolution is presented.
THEORY ON FORMATION OF RIP-CURRENT AND CUSPIDAL COAST
Authors: Hino Mikio
Published: June 2019

The hydrodynamic instability theory is developed on the formation of rip-current and cuspidal coast. The most preferred wave length is shown to be about four times the distance from the shore to the breaker zone. Typical patterns of flow field and bottom configurations are represented. Finally, the theory is compared with field observations.
EQUILIBRIUM PROFILES OF COARSE MATERIAL UNDER WAVE ATTACK
Authors: Van Hijum E.
Published: June 2019

In order to obtain design criteria for artificial gravel beaches, a research programme was drawn up to study the behaviour of gravel beaches under wave attack. The present paper gives the main results of the first step in this programme, viz. the determination of the dimensions, form and way of formation of an equilibrium profile under regular, perpendicular wave attack. One of the conclusions is that gravel with a D0(,
LAB PROFILE AND REFLECTION CHANGES FOR H /L =0.02
Authors: Chesnutt Charles B. , Galvin Cyril J.
Published: June 2019

Reflection coefficients and profile changes were measured during four lengthy experiments in two relatively long, narrow wave tanks. Each tank had a periodic wave generator at one end and a 0.2 mm movable sand bed at the other end. Generator period (1.90 sec), water depth (2.33 ft), nominal wave height before reflection (0.36 ft), and initial sand slope (1:10) were constant In the four experiments. Measured reflection coefficients (K = H /H.) ranged from 0.05 to 0.30, with the typical time variation of K related to profile changes as follows: K increased by a factor of 3 to 4 within the first minutes while a steep foreshore was built on the undeformed profile; K fluctuated and dropped to a lower value as the inshore widened; K increased as the offshore steepened. Large variations in K near the end of the experiments appeared to result from minor profile changes. The apparently similar experiments showed very different rates of profile development, implying control by other variables such as water temperature or tank geometry. "Equilibrium" in these experiments was never reached, even after as many as 375 hours of wave action.
FORMATION OF DUNES BY TIDAL FLOWS
Authors: Yalin M.S. , Price W.A.
Published: June 2019

Schematical relations for the size of dunes and for the duration of their development are derived assuming that the large scale formations on the surface of a movable bed are due to the largest eddies of turbulence. The considerations are confined to the simplest case of a two-dimensional flow and to the cohesionless granular material. The relations for tidal dunes are obtained by generalising the relations for unidirectional flow dunes, Special cases and the validity regions of the forms presented are discussed; suggestions for future measurements and model tests are included.
NEW METHOD FOR THE REDUCTION OF SOUNDINGS IN THE TIDAL AREA OF THE GERMAN BIGHT AND IN TIDAL FLATS, WITH THE OUTER ELBE SERVING AS EXAMPLE
Authors: Gerken Bernhard
Published: June 2019

The topographic survey by sounding the water bottom is becoming an ever increasing part of the work of engineers and scientists on the German Horth Sea coast. In order to fulfil the various tasks in the estuariers of tidal rivers in the foreshore areas, charts are needed with depth data of the greatest possible accuracy. The problem now is this: There exists a big accuracy gap between, on the one hand, the values obtained by the levelling method or by means of the water line method, often applied in the tidelands, yielding accuracies from 1/4 to 1 dm and, on the other hand, the soundings carried out from vessels in the adjacent sea area. According to the investigations into the accuracy of nearshore hydrographic surveying, a tenfold of inaccuracy - compared with the above given values - must be assumed. Scientific studies of the natural processes in the foreshore area (the major programme of the German Sesearch Society (DFG) "Sandbewegung im Deutschen Kustenraum" / The shift of sand in the German coastal area / may be cited here as an example) do not yield a reliable picture so long as the accuracy standard of tideland surveys is not approximately reached. Moreover, the Offices of the Federal Republic of Germany and of her coastal provinces that have been entrusted with sea surveying, each use their own methods which have often evolved differently in the course of history. So, additional difficulties by frequent overlappings of surveyed areas are inevitable.
GIANT AND MEGA RIPPLES IN THE GERMAN BIGHT AND STUDIES OF THEIR MIGRATION IN A TESTING AREA
Authors: Pasenau Horst , Ulrich Johannes
Published: June 2019

In a lot of regions the bottom of the North Sea is covered with large ripple fields, especially in the estuaries and in the tidal channels. A great number of echo sounding profiles (29.500 n.m.) were evaluated to determine the boundaries of these areas and to describe the dimension of patterns. Special investigations of the hydrographic situation, the distribution of deposits and the migration of ripples under the influence of tidal currents only, were carried out in a testing area in the Lister Tief on 11 cruises since 1971.
EXPERIENCE WITH MOVABLE BED TIDAL MODELS
Authors: Giese E. , Harten H. , Vollmers H.
Published: June 2019

A particular problem, of those arising in the economic development of estuary regions, concerns the maintenance and enlargement of navigation channels. The sediment transport plays an important role in connection with this problem. .Though the hydrodynamical processes are today, with the help of mathematical procedures, fairly exactly grasped, there is still insufficient knowledge about the related transport processes, the formation of ripples and dunes and of longterm periodical morphological changes. Nevertheless, the engineer wants information about sediment transport for his planning. A well-known aid is the movable bed hydraulic model, which has been technically developed to simulate the natural fluid-sediment interaction. Such models are not yet standard in hydraulic research institutes and. furthermore, they are not easy to handle. This is probably due to a lack of suitable similarity criteria for insuring valid experimental results. However, there exist recently developed somewhat compromised similarity relationships, which can be used for distorted movable bed tidal models. The experience gained with the movable bed. model Elbe I at the Bundesanstalt fur Wasserbau (BAW) in Hamburg provides an incentive for investigating special cases in other large tidal models of the German North-Sea coast. These models are presented in Fig. 1.
BARRIER BEACHES AND SEDIMENT TRANSPORT IN THE SOUTHERN GULF OF ST. LAWRENCE
Authors: Owens E.H.
Published: June 2019

Barrier islands and barrier beaches have developed across structurally controlled estuaries and embayments in the southern Gulf of St. Lawrence. The supply of sediments to the littoral zone and the subsequent accumulation of barrier deposits is a result of the reworking, transportation and longshore dispersal of sediments which are moved landward by tidal and wave-induced currents from the adjacent shallow sea floor. The size and stability of the barriers is controlled by the shoreline orientation.
STABILITY AND BEARING CAPACITY OF BOTTOM SEDIMENTS by R.J.
Authors: Mitchell R.J. , Hull J.A.
Published: June 2019

The results of model testing show that the strength and stability of bottom sediments can be substantially reduced by the cyclic loading pulses induced by wave action. The minimum soil strength is approximately equal to the remoulded vane strength and the depth of wave remoulding appears to be mainly a function of the wave characteristics. The phenomenon of wave remoulding should be considered in the design of offshore foundations as reductions in bearing capacity and lateral shearing resistance can develop as a result of the action of storm waves. Where bottom sediments are sloping such that the static factor of safety against slope failure is less than the soil sensitivity, severe storm conditions may lead to submarine landsliding. Wave induced submarine landsliding has been reproduced in model tests and the results are correlated with current analytical approaches to this problem.
MORPHOLOGICAL CHANGES IN A FINE SAND TIDAL ESTUARY AFTER MEASURES OF RIVER IMPROVEMENT
Authors: Hovers G.
Published: June 2019

Artificial shipping channels in fine sand tidal estuaries are difficult to maintain. The attempt to stabilize the river beds and thus the fairway in the upper reaches of the Outer Weser by means of systems of river structures has been a success. The further deepening of the fairway necessitated the artificial narrowing of the river bed. The successes of improvement achieved over a prolonged period have up to now been satisfactory. Some explanations concerning the effects of the river structures on the morphology are given in the present report. In the improved river bed a continuous shifting of sediments is taking place, which is mainly due to the incessant action of the tidal currents. It is inevitable in this process that sand is drifted into the deep excavated channel. If one has a good knowledge of the natural shifting processes, it is possible nowadays, by using suitable Hopper suction dredgers, to employ to a certain extent methods of dynamic river engineering by means of the proper artificial shifting of the excavated soil within the cross sections of the river. The capability of improvement of tidal rivers and their estuaries is of great importance for the sea ports that are situated on them. This is particularly true in a time when the dimensions of sea-going ships are still increasing and the countries are confronted with the problem of permanently having to improve the approaches to their sea ports, if they want to participate in overseas trade also in the future. The reason why the improvement of fine sand tidal estuaries is so difficult and so expensive, depending on the local hydrographical and morphological conditions, is that the sediments are continually shifted on account of the tidal currents which are constantly changing in place and time and varying in their force as well as on account of the motion of the sea and the wash of the waves. This renders the improvement, the maintenance, and the marking of artificial fairways for ocean shipping rather difficult.
COMPATIBILITY OF BORROW MATERIAL FOR BEACH FILLS
Authors: Dean R.G.
Published: June 2019

A simple method is presented for estimating the relative compatibility of borrow material being considered for beach fill purposes. The method defines the "compatible" fraction of the material as that coarser portion with the same mean diameter (in "phi" measure) as the native material on the beach. A single graph is presented which allows determination of the number of units of borrow material required to obtain one unit of compatible material. Use of this method requires that the size distributions be reasonably represented by the "lognormal" relationship and also requires knowledge of the means of the native and borrow materials and the standard deviation of the borrow material (all in phi measure). This method overcomes shortcomings of the Krumbein-James method published in 1965. Several examples are presented illustrating the application of the method presented in this paper.
THE LARGE-HEIGHT RESPONSE OF TWO WAVE RECORDERS
Authors: Draper L. , Humphery J.D. , Pitt E.G.
Published: June 2019

Two commonly used deep-water wave recorders which depend on acceleration measurement were calibrated on a Hi metre diameter vertical wheel, and also on much smaller laboratory test rigs, over a range of wave periods likely to be encountered at sea. The results showed that the instruments behaved according to expectations. In addition, spectra from two instruments of the same types which were deployed within one mile of each other were compared and shown to be similar.
BEACH DEVELOPMENT BETWEEN HEADLAKD BREAKWATERS
Authors: Chew S.Y. , Wong P.P. , Chin K.K.
Published: June 2019

Breakwaters in a series can be employed to protect sedimentary coasts. They are used to protect newly reclaimed land along the southeast coast of Singapore; they act as headlands between which sand beaches are formed. The development of these beaches takes place under conditions of low energy waves, a predominant wave direction from the southeast and an east-west littoral drift. The characteristics and development of three beaches over a one-year period are presented. Surveys of the reclaimed land show various beach types between the headland breakwaters. A relationship exists between berm orientation and headland breakwater orientation. Beach stability is tentatively indicated by the formation of a wide berm.
FIELD AND MODEL STUDY ON THE PROTECTION OF RECREATIONAL BEACH AGAINST WAVE ACTION
Authors: Tanaka Norio
Published: June 2019

The heightening of a sea wall is often proposed for the purpose of decreasing the amount of wave-overtopping. In a recreation beach, however, the heightening of sea wall is undesirable from the view-point of environmental preservation and beach utilization. In this paper, instead of it, a proposal is made of the sea wall with a wide frontal step as well as the widening of beach by artificial nourishment. The frontal step is not only effective to decrease the amount of wave-overtopping, but also serves as a promenade for visitors. The widening of beach is known to serve to decrease wave-overtopping as well as to increase the utility for recreation. However, the protection of the nourished beach itself becomes sometimes a difficult problem. In this paper, the hydraulic characteristics of a wide frontal step and the effect of several protective measures for the nourished beach are described on the basis of model and field tests conducted for the improvement of Suma Beach. Suma Beach is a recreational beach situated west of Kobe Port as shown in Fig. 1. The shore-line is about 2 km long and runs from east to west (Fig.11). The beach profile, as shown in Fig.2, has the narrow backshore at about 3 m above L.W.L. and a small step at about 1.5 m below L.W.L. The beach slope is 1/10 in the foreshore, 1/25-1/30 between 2 and 5 m below L.W.L and 1/60-1/80 in the offshore beyond about 6 m below L.W.L. The waves are predominant from the direction of SSW so that the beach materials tend to move eastward along the shore.
A REFRACTION GROYNE BUILT BY SAND
Authors: Fuhbuter Alfred
Published: June 2019

The interaction between a normal groyne and waves mostly is by diffraction, i.e. the structure of the groyne, especially the width, is very small in comparison to the wave length. But when a groyne is built with lateral slopes comparable with normal beach slopes, also refraction processes occur and surf zones are created nearly parallel to the center line of the groyne. It can be shown that, for all directions of wave approach, the longshore currents always are directed shoreward. So, when such a groyne is built by sand, due to the erosion of the groyne an artificial sand spit is formed and a beach nourishment at the adjacent areas of the shore can be expected. Furthermore, sand originating from the normal littoral drift can be caught by such a structure as it happens in case of normal groynes. In a field experiment at the shore of the city of Westerland on the island Sylt/Germany, with 680,000 m of sand such an artificial sand groyne was built in 1972. One year later, this sand masses were grown up to nearly 1,050,000 m . After a sequence of five heavy storm surges in November and December 1973, still 770,000 m could be detected before the shore in 1974. The evaluation of the experiment is continued; the aim of it is find out whether repeated beach nourishment is more economic than protective works. For this reason the knowledge of the "half decay time" of a beach nourishment is necessary.
PERFORMANCE OF A JETTY-WEIR INLET IMPROVEMENT PLAN
Authors: Purpura J.A. , Beechley B.C. , Baskette C.W. , Roberge J.C.
Published: June 2019

Comprehensive monitoring has been carried out since 1970 to determine the performance and effects of a navigation and inlet stabilization project at Ponce de Leon Inlet, Florida. The improvement plan at the tidal inlet included construction of two jetties, a weir sand by-pass system, and dredging of a navigable channel (Figure 1). An evaluation was made of the general current patterns, the relative refracted wave energy distribution, and the volumetric beach and hydrographic fluctuations associated with the inlet. An analysis of this data was used to interpret the dramatic and unexpected changes which have resulted along the adjacent coastline and within the inlet after the completion of the inlet improvements.
PERFORMANCE ASSESSMENT OF SELF-DREDGING HARBOUR ENTRANCES
Authors: Carmichael J.W. , MacInnis I.
Published: June 2019

This provides further information and assessment of the three harbour entrance wave traps at Dingwall, Inverness and Pleasant Bay located in Canada. These were constructed to reduce the amount of maintenance dredging required in the entrance channels. Wave climate data and littoral material analysis are presented. Observations on the performance of each structure are given and conclusions drawn as to restrictions and constraints on applicability.
FIELD AND MODEL STUDIES FOR VISAKHAPATNAM HARBOR
Authors: Ince Simon , Jamieson W.W.
Published: June 2019

Model studies and analysis of oceanographic and littoral drift data were undertaken to advise Howe India (Private) Ltd. on littoral drift, siltation and shore erosion problems to be encountered during and after the construction of Visakhapatnam Outer Harbor Project. Distorted fixed-bed and movable-bed models with a horizontal scale of 1:300 and a vertical scale of 1:80 were calibrated to reproduce the integrated net effect of an average southwest and northeast monsoon season. Experiments were conducted to assess and predict seasonal changes resulting from the construction of the system of breakwaters under normal and extreme conditions. Recommendations were made concerning breakwater and sand trap location, shore protection, dredging and disposal of dredged material.
HYDRAULICS OF TIDAL INLETS ON SANDY COASTS
Authors: Mayor-Mora Ramiro
Published: June 2019

A series of laboratory experiments was carried out on an idealized ocean inlet- bay system subjected to reversing flows caused by tidal and surface wave actions. The testing was done in a rectangular basin simulating a "bay" or "lagoon" and separated from an "ocean" basin by a sand barrier across which inlet pilot channels of varying cross sections and lengths were cut prior to starting each run; the ocean side of the barrier formed a 1:30 flat beach throughout the tests. Disturbances in the ocean were created by tide and wave generators. Their effects in the bay and inlet channel were measured by water level and current velocity recording units. Experimental measurements are presented here in normalized form in order to determine the relationships governing the hydraulic behaviour of a tidal inlet. These results are also compared to those obtained from a numerical approximation (the lumped parameter approach), all as functions of a proposed coefficient that includes the ocean-inlet-bay system characteristics. The experimental findings are further compared to available field data. Investigation of the effects of surface waves, controlling jetties, and fresh water inflow into the bay on the dimensionless parameters are also explored.
A TRANSMISSION LINE WAVE HEIGHT TRANSDUCER
Authors: Zwarts C.M.G.
Published: June 2019

A simple but accurate wave transducer has been developed for the measurement of waves and tidal levels on inland and coastal waters. It consists of a tunnel diode oscillator, using a transmission line to sense the water-level. The output voltage consists of a square wave, with a period linearly proportional to the water-level. In addition an analog output signal is provided. The quasi-static accuracy of the instrument is equal to or less than 0.2%.
HYDRAULIC CONSTANTS OF TIDAL ENTRANCES
Authors: O'Brien M.P. , Clark R.R.
Published: June 2019

Data contained in the Tide Tables, Current Tables and navigation charts of National Ocean Survey pertaining to tidal entrances along the coasts of the continental United States are analyzed to obtain flow coefficients defined by a simple hydraulic equation. The evaluation of the published data indicates that the data are sufficiently accurate and representative, despite some unexplained anomalies, to permit determination of the approximate discharge coefficients and, more importantly, to identify categories of flow regimes of inlets. A few conclusions are: 1. The Keulegan approach and similar analyses of inlet hydraulics provide a useful qualitative framework for ordering data but they apply quantitatively only to small inlets and lagoons with simple inlet channel geometry. 2. The lag of slack water in the entrance channel after HW and LW is a powerful tool in the analysis of the hydraulic regime. It is easily measured in the field and should become an identifying characteristic of each entrance. 3. The resistance coefficient F represents the overall impedance and exit losses, reflections from the lagoon shore, fresh water discharge and the configuration of the channel between the inner and outer bars. It may be determined from measurements of lag and maximum velocity at the throat and the range of ocean tide.
EVALUATION OF OVERALL ENTRANCE STABILITY OF TIDAL ENTRANCES
Authors: Bruun P. , Gerritsen F. , Bhakta N.P.
Published: June 2019

This paper is written in continuation of earlier published material (2, 4, 5) dealing with stability of tidal inlets on littoral drift shores. The experience available at that time was responsible for the introduction of two parameters: .vmean max/ defined as the mean max. velocity in the gorge at spring tide and the K/M-tot ratio (tidal prism at spring tide divided by material transport to the entrance from the adjoining shores) as the most pertinent parameters for description of overall stability. A more detailed justification for this choice is given in this paper, based on computation of the relative sediment transport at various tidal phases. Examples of earlier date (4) and twelve new examples from India are given.
CHANNEL STABILITY IN TIDAL INLETS: A CASE STUDY
Authors: Byrne Robert J. , DeAlteris Joseph T. , Bullock Paul A.
Published: June 2019

Wachapreague Inlet, a downdrift offset inlet in the barrier island complex of the mid-Atlantic U.S. coast was studied during the period 1971-1973. Elements of the study included: (1) the inlet morphometric history (120 years), (2) assessment of surficial and sub-bottom sediments within the inlet complex, (3) response of the channel cross-sectional area to short-term variations in wave activity and tidal volumes, and (4) the distribution of tidal flows within the channel. It is concluded that: (1) a qualitative correlation exists between short-term channel cross-sectional area change and the ratio of ebb tidal power to wave power. It is inferred that the important element is the direct wave activity on the ebb-tidal delta; (2) duration differences in rising and falling phases of the tide (flood longer than ebb) lead to an ebb dominence in bedload capacity at the inlet with the result that this inlet has a natural flushing ability; (3) there is pronounced sand circulation within the inlet complex via a sediment flow loop which is driven by wave refraction and lateral inflow on the updrift side. The sand volumes thus delivered annually to the inlet channel from the ebb delta appears to far exceed the estimated littoral drift. The local sand circulation should, therefore, be considered in engineering design for inlet control structures.
SCOUR UNDER A VERTICALLY OSCILLATING LEG
Authors: Silvester Richard
Published: June 2019

Mishaps with jack-up oil rigs could be caused by scour beneath their legs as they oscillate vertically, either on site or when being shifted to or from site. This action was replicated in the laboratory by moving cylindrical feet to and from a sandy bed at frequencies appropriate to the scale of the model. By retaining equal Reynolds numbers for the sand grains, whose size was commensurate with prototype material, the period of oscillation had to vary with the leg diameter. By adopting a suitable size scale, a range of periods was determined from knowledge of resonant motions of rigs in relatively deep water. Erosion was recorded which appeared sufficient to cause mal-distribution of load in the structure. Even when oscillations occurred in a leg penetrating the bed, no support was available due to liquifaction of the soil. The two pilot studies herein described indicate the need for a comprehensive research program on the subject, due to the large investments in jeopardy.
EXPERIMENTAL INVESTIGATION OF TURBULENCE NEAR CYLINDERS
Authors: Carstens Torkild , Kjeldsen Soren Peter , Gjorsvik Ola
Published: June 2019

Model tests with locally generated turbulence near horizontal and vertical cylinders are reported. Turbulence is measured with newly developed ultra-sonic probes, and spectral density functions and auto-correlation functions are given. Tests are carried out in uniform currents, in sinusoidal waves, and in combinations of current and waves. Results are given for a viscous laminar boundary layer corresponding to a very fine sediment, and for a turbulent boundary layer corresponding to a hydraulically rough bottom. In Norway recent scour research, initiated by the North Sea oil operations, has been guided in three directions: 1) Scour around big gravity structures 2) Distribution of pore pressures in the ground under wave loads. 3) Local scour near unburied pipelines.
STABILITY OF DOLOS SLOPES
Authors: Brorsen Michael , Burcharth H.F. , Larsen Torben
Published: June 2019

The stability of dolos armour blocks against wave attack has been investigated in wave model studies. Simple definitions to describe the block movements are introduced and the following results are discussed: 1. The stability of dolos slopes against regular waves and the influence of the slope. 2. The stability of dolos slopes against irregular waves that are not Rayleigh distributed. 3. Comparison between the stability of dolos, natural stones and cubes. 4. The influence of the surface roughness of the dolos model blocks. 5. The applicability of Hudson's formula.
CONSECUTIVE HIGH WAVES IN COASTAL WATERS
Authors: Siefert Winfried
Published: June 2019

The problem of statistics of numbers of consecutive high waves has not yet been treated in detail. Some numerical results (Goda, 1970) and evaluations of prototype data in water depths of 100 m (Rye, 1975) and 40 m (Wilson and Baird, 1973) respectively were published. Data from measurements in nearshore coastal waters, with unbroken, breaking and broken waves, obtained in the Elbe estuary, are treated in this paper.
CHANGES IN INLET OFFSET DUE TO STABILIZATION
Authors: Hubbard Dennis K.
Published: June 2019

Available evidence indicates southward littoral transport through the Mem'mack Embayment. In apparent contradiction, the beach on the southern (Plum Island) side of the inlet has built seaward of the updrift beach. This phenomenon is related to a balance between storm and fair weather conditions. Wave observations under a variety of surf conditions show that during storms, sand is transported southward along the face of the nearshore bar fronting Plum Island. During calm periods sand is moved northward along the beach until it is trapped by the southern jetty and removed from the then active tidal current transfer system. Using discharge data and wave measurements from the Merrimack Inlet area, Bruun's bypassing coefficient (r = Qis/Qmax. where Qis is the longshore transport rate in M-fyyr and Qmax is the maximum inlet discharge in M^/sec) was computed for storm and fair weather conditions. During storms, the bar bypassing observed in the field was clearly indicated. During calmer periods tidal current transfer was predicted. This relationship is considered only an approximation as it does not consider many important physical parameters (grain size, nearshore slope, wave type, etc.).
TOPOGRAPHIC CHANGE RESULTING FROM CONSTRUCTION OF A HARBOR ON A SANDY BEACH: KASHIMA PORT
Authors: Tanaka Norio , Sato Shoji
Published: June 2019

This paper presents some general properties on topographic change on the shore and sea bed in the vicinity of ports and harbours constructed on the sandy beach, mainly with the case study of Kashima Port. Following three characteristics of the topographic change due to prolongation of breakwaters are discussed; that is, i ) The shoaling and the change of topography in the area surrounded by breakwaters and shoreline, ii ) Topographic change of artificial beach in the updrift beach of breakwater having the long oblique part, iii. ) Erosion and accretion of downdrift beach due to the prolongation of the oblique part of breakwater.
SAND CIRCULATION PATTERN AT PRICE INLET, SOUTH CAROLINA
Authors: FitzGerald Duncan M. , Nummedal Dag , Kana Timothy W.
Published: June 2019

A sand circulation pattern has been determined for Price Inlet, South Carolina, using wave refraction diagrams, littoral process measurements, bedform orientations and inlet hydraulic data. The dominant process acting on the ebb-tidal delta is wave swash which impedes the ebb-tidal currents and augments the flood-tidal currents. This produces a net landward transport of sand on the ebb-tidal delta as evidenced by the landward migrating swash bars. Bedform orientations and velocity measurements taken on the swash bars also support this conclusion. Countering the general landward transport direction is the ebb dominance of the main channel. This dominance can be explained by higher inlet efficiency at low water than at high water. Consequently, bay tide phase lag is larger at high than at low water resulting in a longer flood duration. This causes higher mean ebb-tidal currents and a consequent larger potential net ebb transport of sand. This inlet characteristic explains why little sand is transported inside the inlet, why the throat remains scoured and why sand entering the main channel is carried seaward.
BEACH HAVEN AND LITTLE EGG INLETS, A CASE STUDY
Authors: DeAlteris Joseph , McKinney Thomas , Roney James
Published: June 2019

A comprehensive investigation of coastal processes active within and in the vicinity of Beach Haven and Little Egg Inlets was completed as part of the Coastal Processes Investigation for the proposed Atlantic Generating Station. The suspected complex nature of this dual natural inlet system was documented and a process-response model is presented to relate the more significant physical forcing functions to observed morphologic and hydraulic changes. A rising sea level, a net littoral drift from the north and the sediment scouring power of the flow in the two main channels serving the tidal basins are the principal factors related to the geographic and hydraulic stability of the system. The results of the study can be used to evaluate the potential impact, if any, of the proposed Atlantic Generating Station on the adjacent coastal environment.
OFFSHORE SEDIMENTARY PROCESSES AND RESPONSES NEAR BEACH HAVEN-LITTLE EGG INLETS, NEW JERSEY
Authors: McKinney Thomas , DeAlteris Joseph , Chao Yung Y. , Stahl Lloyd , Roney James
Published: June 2019

The offshore region in the vicinity of the Beach Haven and Little Egg Inlets of New Jersey is the site of the proposed Atlantic Generating Station, a floating nuclear power plant to be constructed 2.8 n. mi. offshore by Public Service Electric and Gas Company (Figure 1A). In order to assess the impact of this proposed project on the region, a comprehensive study of the nearshore and offshore region was conducted. A complete synopsis of this study is available in PSESG (1976). This paper presents the results of the investigations into the sedimentary processes operative in the offshore region. The dynamics and coastal evolution of the nearshore region is summarized in DeAlteris et al, (1976; this conference). The proposed Atlantic Generating Station (AGS) is located offshore of the complex and transi.ent tidal inlet system of Beach Haven and Little Egg Inlets. These inlets are the major hydraulic connections between the Atlantic Ocean and the Great Bay and Little Egg Harbor estuaries. A large, roughly triangular ebb-tidal delta is present at the mouths of and between the two inlet channels. The major offshore bathymetric feature is a broad linear sand ridge, the Beach Haven Ridge, which trends northeast and reaches a maximum elevation of -28 feet (NLW) (Figure 1A). The AGS site is located on the landward flank of the ridge and partially in the adjacent trough in about 40 feet of water. Landward of the wide, northward-deepening trough, the ocean bottom slopes gently up towards the ebb-tidal delta of Beach Haven and Little Egg Inlets. The offshore zone adjacent to the proposed AGS is separated from an extensive tidal marsh lagoon system by a broken chain of barrier islands, from Long Beach Island on the north to Little Beach and Brigantine Islands on the south. The Beach Haven Ridge is one of a system of sand ridges which occur on the shelf surface. In recent years the origin of these features has been the subject of a number of studies. Duane et al, (1972) studied the sand shoals on the inner portions of the eastern continental shelf of the United States. Swift et al, (1973) review the question of the ridge and trough topography of the Middle Atlantic Bight. A detailed description of the geomorphic elements of the inner New Jersey continental shelf for this region is presented in PSESG (1975). Duane et_al, (1972) suggested that the shoreface- connected ridges originated in a shallow nearshore environment in response to the interaction of south-trending, shore-parallel, wind-driven currents and waves during winter storms. They suggest that as sea level rises, and the shoreface retreats, the shoals are abandoned and isolated as "relict" features on the shelf surface. This .concept was proposed i(n part by Moody (1964) from studies of the ridge system at Bethany Beach, Delaware.
BARRIER ISLAND DYNAMICS: OVERWASH PROCESSES AND SOLIAN TRANSPORT
Authors: Leatherman Stephen P.
Published: June 2019

The northern 5 miles of shoreline at Assateague Island, Maryland are presently being eroded. During storms, swash surges are able to overtop the most landward (storm) berm as overwash with deposition occurring on the barren flats. Where primary barrier dunes still exist, sediment-charged surges are funneled through breaches in the dune field for deposition of the entrained material on the washover fan. Sediment budget computations show that there has been a small net loss of material at each washover area, in spite of 7 discrete overwash events during a 26 month time interval. The predominant northwest winds effectively eroded the overwash material, transporting the majority of the sand back to the beach. This analysis indicates that there exists a balance between overwash and eolian processes with wind transport being slightly dominant.