Akira Ozaki

Bio: Akira Ozaki is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

On the effect of an offshore breakwater on the maintenance of a harbor constructed on a sandy beach

Abstract: In this paper the author describes an experimental attempt to prevent the rapid blocking of a harbor entrance caused by littoral drift in the summer period. This work was conducted at "Seppu", a fishing harbor constructed on a sandy beach in Hokkaido, Japan. This investigation was originally sponsored by the Harbor Section of the Hokkaido Prefectural Office One of the top priority objectives, at that time, was to determine the efficiency of two jetties constructed on the updrift side for the purpose of countering the sand drift. Detailed observations including preliminary model experiments, were made from 1961 to I963 on the general aspects (ie condition and phenomena) of the coast in question. Meteorological data were also compiled together with investigations as set forth by the government. Based on the above, the author finally suggested the utilization of natural forces ie waves, offshore currents etc, by constructing an offshore breakwater to curb the blockage of the harbor mouth. This idea was shown to be adequate at least qualitatively by model experiment with the exception of the troublesome time scale problem. These findings, however, have not been adopted as yet for actual improvement of the harbor at present.

Onshore-offshore transport and beach profile change

Abstract: In this paper a model is presented to describe onshore-offshore sand transport in the surf zone. The model is based on the physical consideration that when the net transport attains a state of equilibrium, the power expended through gravitational force in suspending sand grains is balanced by that due to the uplifting force arising from the turbulence generated by breaking waves. Two important parameters controlling sand transport are the dimensionless fall-time parameter and bottom slope.

Stabalizing beaches downcoast of harbor extensions

Abstract: In geomorphological terms, the sandy shoreline of a bay downcoast of a harbor may be stable or in static equilibrium, or could be in dynamic condition, if sediment is still being supplied from upcoast or from downcoast to form a salient predicted by a static bay shape equation. Should commercial expansion demand a larger port, the general solution is to run a breakwater from the headland or existing structure. This has the potential to create a new static equilibrium beach, often with accretion in the lee which is at the expense of beach erosion downcoast. It is strongly recommended that geomorphic approach be incorporated to stabilize downcoast beaches early in the planning stage of a harbor, or as remedial measures. By creating bay beaches in static equilibrium, the potential beach erosion downcoast of a harbor will be kept to a minimum or may be prevented completely.

Scale-Model Relationship of Beach Profile

Abstract: This paper presents a scale-model relationship for the similarity between large and small scale-models in two-dimensional equilibrium beach profiles. Taking large scale-models using large scale equipment as prototypes, the experimental scale of a medium-sized model was gradually varied keeping the grain size ratio of model to prototype constant. A similarity-comparison between large and small scale beach profiles is made by considering the degree of experimental errors. Judgement results are graphically shown, and a scale-model relationship is proposed. It is found that the scale-model relationship proposed agrees with the ones derived from the empirical formulae expressing the properties of beach profiles. Additionally, the applicability of this scale-model relationship to the reproduction test of natural beaches is examined.

Geomorphic approach for mitigating impact of harbor construction on sandy beaches

Abstract: Some harbors constructed on sandy shore have interrupted littoral drift, resulting in updrift beach accretion, siltation in navigation channel, or downdrift erosion. Conventional harbor design proc...

On the similitude in two-dimensional beach change

Abstract: The purpose of this paper is to present a scale-model relationship for similarity between full-scale and scale models of two-dimensional equilibrium beach profiles. A similarity comparison between full-scale and small-scale model is made by considering the degree of experimental error. The similitude obtained is graphically shown, and the scale-model relationship is also formulated. It is found that the small-scale relationship agrees with the ones derived from shoreline change, critical water depth of sediment movement, and beach profile.