Isao Irie

REGULATION OF NEARSHORE CIRCULATION BY SUBMERGED BREAKWATER FOR SHORE PROTECTION

A study of alternatives including a shoreline evolution numerical modelization has been carried out in order to both diagnose the erosion problem at the beaches located between Cambrils Harbour and Pixerota delta (Tarragona, Spain) and select nourishment alternatives.

LANDWARD TRANSPORT OF SPRAY GENERATED FROM A WAVE ABSORBING SEA WALL

A study of alternatives including a shoreline evolution numerical modelization has been carried out in order to both diagnose the erosion problem at the beaches located between Cambrils Harbour and Pixerota delta (Tarragona, Spain) and select nourishment alternatives.

OPTIMUM SIZE OF DISTORTED RIPPLE TRAIN FOR THE CONTROL OF CROSS-SHORE SEDIMENT TRANSORT

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.

CONTROL OF CROSS-SHORE SEDIMENT TRANSPORT BY A DISTORTED RIPPLE MAT

A special reflecting wall 12 m long and 2.1 m high was built off the beach at Reggio Calabria, and 30 wave gauges were assembled before the wall and were connected to an electronic station on land. It was possible to observe the reflection of wind waves generated by a very stable wind over a fetch of 10 Km. The experiment aimed to verify the general closed solution for the wave group mechanics (Boccotti, 1988, 1989), for the special case of the wave reflection.Significant features on Wadden Sea wave climate are evaluated in respect of the state of the art. Main emphasis was laid on an analysis of the governing boundary conditions of local wave climate in island sheltered Wadden Sea areas with extensions being sufficient for local wind wave growth. Explanatory for significant wave heights a reliable parametrization of local wave climate has been evaluated by using generally available data of water level and wind measurements.

NUMERICAL SIMULATIONS OF MUD TRANSPORT BY A MULTI-LAYERED NESTED GRID MODEL

Tanah Lot Temple is situated in Tabanan Regency - Bali, on the coast of the Indonesian Ocean. Due to continuous wave attack, wind force, and weathering of the rock bank where the Temple stands, abrasion has occured which is more and more threatening the existence of the Temple. Considering that Tanah Lot Temple is a sacred place for the Hindu Balinese people and a place of high cultural value, and also an important tourism, steps to save the Temple are imperative. The Central as well as the Regional Authorities, and also the Bali nese community are very much interested in the effort to keep the Temple intact. Measures have been undertaken to protect both the seaside and land-side banks of the Temple rock bank. This paper only discusses counter measures of the sea —side bank of the Temple.

EVALUATION OF WATER QUALITIES OF SEA AREAS IN JAPAN USING A NEW WATER QUALITY INDEX

To evaluate the water quality of sea areas around Japan, a new water quality index was proposed using the data released by public organizations. First, to make the water quality index of sea areas, principal component analysis was applied for the data at 6008 observation points where the data of TN (total nitrogen), TP (total phosphorus) and COD (chemical oxygen demand) were gathered for four years from 1999 to 2002, and the first principal component was considered as the comprehensive index of water quality. Next, the water qualities of sea areas around Japan were compared by the water quality index. The evaluation shows that the water qualities are relatively bad in sea areas near the big cities and in large harbors. And it is found that the value of the water quality index in polluted sea areas with organic substances is less than -1. In addition, the water quality of the Hakata bay for 20 years (from 1983 to 2002) was shown by using the proposed index, and the change of the water quality due to various developments was investigated.

AN EXPERIMENTAL STUDY ON EFFECTS OF MOUND ON HYDRAULIC CHARACTERISTICS OF THE FLARING SHAPED SEAWALL

A Flaring Shaped Seawall (FSS), a new type of one, can drastically reduce a crest height and wave overtopping quantity in comparison with a conventional upright one. The FSS will usually be set on a mound from the point of a cost of manufacturing and construction. Thus, in this paper, effects of the mound on hydraulic characteristics of the FSS (a wave overtopping rate, a wave run-up height and a reflection coefficient) are clarified from experiments using a two-dimensional flume. Furthermore a method for the FSS on the mound is proposed, and it is shown that the method is adequate under the condition of experiments in this paper.

STUDY ON CHARACTERISTICS OF TRANSPORT OF SPRAY AND SOUND ENVIRONMENT BY NON-WAVE-OVERTOPPING TYPE SEA WALL

Authors have proposed a non-wave overtopping type seawall (Flaring Shaped Seawall) with deep circular cross section in order to facilitate a safe and excellent use of coastal space for various purposes. The seawall satisfies a non-wave overtopping condition with extremely lower crown height in comparison with conventional upright seawall. In this study, wind field near the seawall, water spray transported behind the seawall and sounds when waves running up were measured in the experiments, and compared with an upright seawall.

LONG PERIOD OSCILLATION OF FLUID VELOCITY BEHIND SUBMERGED BREAKWATER CAUSED BY ABSORBING WAVE GENERATOR

In the previous experiments on a submerged breakwater, a very long period of oscillation of fluid velocity at the bottom is observed behind the breakwater in a two-dimensional wave flume. The period of the oscillation is far larger than the period of seiche in the wave tank, and thus the oscillation may influence the estimation of the mean water level and steady flow velocity. To clarify the effect of this long period oscillation, we conducted two-dimensional wave tank experiments with a submerged breakwater and also with a constantly sloped beach for comparison. Water surface oscillation, horizontal fluid velocity at the bottom and the motion of the paddle of the wave generator were measured. The time variations of the mean water level, the steady flow velocity, the amplitudes of wave harmonics were calculated.

Reduction of Impulsive Breaking Wave Pressures by Wave Dissipating Works with Low Crest Elevation

Low crested wave dissipating works with low void content were considered in this study to reduce the impulsive breaking wave pressures acting on a non-wave overtopping type seawall. The wave transmission coefficient and wave pressure distribution were measured through two dimensional wave tank experiments. The numerical computation based on Greens Identity Formula was also applied to estimate the transmission coefficient. The wave transmission coefficient decreases linearly with decreasing of the void content. The maximum wave pressures also decrease linearly with decreasing of the void content, and the variations of the maximum wave pressures depending on the relative water depth become small.