Showing papers on "Breakwater published in 1974"
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TL;DR: In this paper, it is shown by an idealised laboratory experiment that such currents could be produced by an alongshore gradient of breaker height with wave crests parallel to the beach.
30 citations
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29 Jan 1974
TL;DR: In this paper, the authors have proposed and tried to apply the detached breakwater system as a measure against beach erosion for the last 8 years, which is for the purpose of developing the sand deposition behind the breakwater.
Abstract: Beach erosion is one of the serious problem in Japan. As a countermeasure against beach erosion, many preventive works, such as sea walls and groins, have been constructed during the past 20 or more years. However, as the result of field investigations, it has become clear that sea walls and groins are not always effective on beach erosion prevention, and inversely, in some cases, they accelerate the beach erosion. Based on the above cognition, the author has proposed and tried to apply the detached breakwater system as a measure against beach erosion for the last 8 years. This is for the purpose of developing the sand deposition behind the breakwater. Therefore several experimental works of the detached breakwater system were carried out under the guidance of the present author, and most of these tests were successful. The design method of this system was composed by the author on the basis of the result of field investigations, which have been conducted for more than 8 years. The numerous construction works of detached breakwaters have been carried out in accordance with the design method proposed in this paper, and the effectiveness of detached breakwaters has been proved on the several coasts in Japan where severe beach erosion occurs.
25 citations
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29 Oct 1974
TL;DR: In this article, a floating breakwater or wave tripper supported by pontoons or floats is disclosed, which is used for moderating waves and for creating a generally calm surface on the water behind the breakwater.
Abstract: A floating breakwater or wave tripper supported by pontoons or floats is disclosed. The breakwater is useable for moderating waves and for creating a generally calm surface on the water behind the breakwater. Since the device is carried by floats or pontoons, it is portable and may be moved and positioned as desired. The pontoons or floats which support the breakwater are so shaped that the device cuts through waves striking it instead of floating over them, and is therefore more effective in reducing the height of incident waves than are prior devices which float on the surface of the wave. Suitable anchors are provided to secure the device in a desired location and a plurality of wavebreakers may be joined together to form a portable breakwater of generally any desired length.
21 citations
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01 Sep 1974
TL;DR: In this article, a semi-empirical theory of nearshore currents due to breaking waves in the presence of a shore-connected breakwater or an offshore breakwater is presented.
Abstract: : This study provides a semiempirical theory of nearshore currents due to breaking waves in the presence of a shore-connected breakwater or an offshore breakwater. The effects of diffraction are studied in addition to refraction by shoaling waters. The concept of radiation stresses applied to uniform longshore current and rip currents forms the starting point of the theory. Many empirical relations included in this study with regard to the surf zone are similar to, and extrapolations of, the ones used in related works. Ignoring convective inertia and lateral turbulent diffusion, the governing equations are solved numerically by the method of finite differences. Sample results for stream functions and mean sea levels are plotted for various beach profiles or incidence angles. For the offshore breakwater, the predicted current pattern is consistent with available laboratory observations and the known tendency of tombolo formation; for the shore-connected breakwater. the computed flow pattern exhibits cells in both downwave and upwave regions. Directly relevant observations have not been found but part of the predicted features has some indirect experimental support. More experimental and theoretical work is suggested.
13 citations
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TL;DR: In this paper, an extension of the author's method of solution for two-dimensional permeable breakwater by the method of continuation of velocity potentials for two different fluid regions into three-dimensional problems by means of Green functions is presented.
12 citations
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29 Jan 1974TL;DR: In this paper, the characteristics and development of three beaches over a one-year period are presented, and a relationship exists between berm orientation and headland breakwater orientation, indicating the formation of a wide berm.
Abstract: 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.
10 citations
01 Jun 1974
TL;DR: In this article, a 1:100-scale undistorted hydraulic model of Port Orford, Oregon, and sufficient offshore area to permit generation of the required test waves was used to develop and test several plans of improvement proposed to eliminate harbor shoaling without adversely affecting wave heights at the existing pier.
Abstract: : A 1:100-scale undistorted hydraulic model of Port Orford, Oregon, and sufficient offshore area to permit generation of the required test waves was used to develop and test several plans of improvement proposed to eliminate harbor shoaling without adversely affecting wave heights at the existing pier. Improvement plans consisted of (a) removal of portions of the existing breakwater, (b) realignment or lengthening of the existing breakwater, and (c) construction of new breakwater structures in the vicinity of Fort Point and Battle Rock. A 54-ft-long wave machine, electrical wave height measuring and recording apparatus, and coal and nylon tracer materials were used in the model. Tests were conducted with prebreakwater and existing breakwater conditions, and the results were compared to determine the causes and sources of harbor shoaling. Improvement plans were then tested and compared with existing prototype conditions. Of the plans tested, the optimum configuration appears to be that designated as plan 11F. (Author)
8 citations
01 Jan 1974
6 citations
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01 Jan 1974TL;DR: In this article, a 3D model investigation of the Atlantic Generating Station is presented, which consists of two nuclear power plants mounted on floating platforms and protected against wave action by an encircling breakwater.
Abstract: A description is presented of a three-dimensional model investigation to evaluate a design for the Atlantic Generating Station, which consists of two nuclear power plants mounted on floating platforms and protected against wave action by an encircling breakwater. The primary study objectives are to evaluate: platform motions, mooring strut forces, breakwater stability, platform hull pressures, wave field, near-field thermal effects and effects of a tanker collision on the breakwater. The investigation consists of a small scale (1:196) model and a large scale (1:64) model. Comprehensive results of platform heave, pitch and roll determination are available for the small scale model over the expected range of wind-generated wave periods. These results indicate the most critical design conditions in terms of: wave direction, period, and height. Of particular interest is the relative absence of strong resonant peaks in the normalized responses for heave, pitch and roll.
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TL;DR: In this paper, a crenellated breakwater is proposed for coastal engineering in Japan, and the authors present a detailed survey of the breakwater construction process and its operation.
Abstract: (1974). On a Crenellated Breakwater. Coastal Engineering in Japan: Vol. 17, No. 1, pp. 93-116.
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29 Jan 1974TL;DR: In this article, model studies and analysis of oceanographic and littoral drift data were undertaken to advise Howe India (Private) Ltd. on drift, siltation and shore erosion problems to be encountered during and after the construction of Visakhapatnam Outer Harbor Project.
Abstract: 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.