Masaaki Ikeno

EXPERIMENTAL STUDY ON SEDIMENT TRANSPORT IN SURF AND SWASH ZONES USING LARGE WAVE FLUME

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.

Improvement of Collision Force Formula for Woody Debris by Airborne and Hydraulic Experiments

The relationship between the collision direction angle and the collision force of woody debris and its behavior is investigated through large-scale bore flow and airborne experiments. In the case of the airborne experiments oblique collision angle being larger than 20°, the oblique collision force is reduced by up to half of the longitudinal collision force. In the case of the bore flow experiments initial arrangement along the transverse direction, the wood-log moved with a rotation along the channel floor. Collision forces in the bore flow experiment indicated the trend less than that in the airborne experiment. The effects of water cushioning between the wood-log and vertical wall, and the surrounding water caught by the rotation of debris were considered. Major collision force formulas for collisions in the long axis direction of woody debris are verified through comparison of this study and recent experiments. By considering the reduction in collision energy by the rotational motion of debris after oblique collisions, their collision force formulas are improved to estimate the oblique collision force. The improved formulas can reproduce the reduction of significantly oblique collision forces compared with longitudinal collision forces by the above experiments. The effect of the collision angles uncertainty on the estimation of the collision force was investigated as a case study on a probabilistic evaluation of the collision force.

WAVE DIRECTION MEASUREMENT USING MARINE X BAND RADAR

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.

INVESTIGATION OF EFFECTS OF SILTATION SUPPLY FROM A SEA CLIFF ON SAND DEPOSITION INSIDE A HARBOR BY FIELD OBSERVATION AND NUMERICAL SIMULATION

In this study, firstly, the field observation was executed on wave, current and concentration of silty sand in the sea area around the harbor of the Haramachi-thermal power plant site of Tohoku Electric Power Company and in front of the Nitta River and the sea cliff, which are surmised as silt sources. The actual situation of erosion of the sea cliff due to waves is investigated by using the aerial laser beam survey. The physical mechanism of migration of silty sand into the harbor and the supply mount of silty sand are estimated from the field observation results. The facilities of the Tohoku Electric Power Company have stood on the land behind the above sea cliff. So, prevention of the sea cliff from more erosion should be focus for the above facilities. Secondly, the beach deformation numerical model was modified in order to consider supply of siltation from the sea cliff. Finally, using the modified numerical model, effects of siltation supply from the sea cliff on accretion amount and seabed change around the harbor are investigated during a year.

PLANE DESIGN OF "SPAC"; COUNTERMEASURE AGAINST SEABED SCOUR DUE TO SUBMERGED DISCHARGE AND LARGE WAVES

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.