Predictive model of beach changes around a groin due to longshore sand transport is developed by applying the contour line change model. In the case that a groin does not connect to the solid structure such as seawall and beach erosion is permitted at its landward end, littoral drift can pass through the landward end of the groin, while carrying a large amount of sand. This greatly decreases the shore protection effect of the groin. This phenomenon is modeled numerically. On July 26, 1997, storm waves attacked the Chigasaki coast and during this typhoon, the phenomenon as mentioned above occurred. Results of numerical simulation explain this situation qualitatively.

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Beach changes triggered by the construction of detached breakwaters near the end of a pocket beach were investigated at the Tojo coast in Kamogawa City in Chiba Prefecture. This beach has an around 3.9km long stretch and is facing the Pacific Ocean. Shoreline changes were read from the aerial photographs and field observation was carried out. Sand accumulated behind detached breakwaters thanks to their wave dissipation effect. Simultaneously this caused beach erosion in the other area and countermeasures were needed to protect facilities. The cause is due to the lack of thinking on overall balance of sandy beach in a closed system of littoral drift. It is concluded that construction of offshore breakwaters in a pocket beach should be carefully done because of the impact to the surrounding coast.

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Beach changes of the southwestern part of the Suruga coast located in Suruga Bay were investigated through the comparison of aerial photographs, historical photographs showing the damaging process of coastal dike in 1972 and photographs taken in the field observation on April 24, 1999. On this coast, southwestward longshore sand transport dominated before the construction of the breakwaters of Yoshida Port. After its completion, the shoreline northeast of the breakwater approached stable condition. In this area, coastal dike was destroyed by wave action in 1972 and new coastal dike was built landward of the original position. Due to this activity, present shoreline became stable with seasonal variations. On the southwest side of the harbor, beach was eroded by longshore sand transport and measures by detached breakwaters were taken. This further induces beach erosion and steepening of the foreshore at further southwest coast.

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Shoreline changes around Misawa fishing harbor facing the Pacific Ocean in Aomori Prefecture were analyzed through the comparison of aerial photographs taken between 1966 and 1997. On this coast, northward longshore sand transport dominates and construction of harbor breakwaters caused beach erosion on the north side and accretion on the south side of the harbor due to the obstruction of continuous sand movement. Since sand source disappeared on further south coast, sand bypassing from south to north coast of the harbor became impossible. Instead, sand recycle from inside the harbor to the south coast is required with suitable facilities to form a stable beach.

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The social mechanism of rapid disappearance of natural sandy beach caused by lack of adjustment between protection of coastal forest and shore protection is investigated through the case study on the Niigata coast facing the Sea of Japan. This coast has been eroded for a long time because of decrease in sand supply from the Shinano River, which is the main supply source to this coast, and subsidence of the ground level due to the excess pumping-up of natural gas. Until now, most severe erosion expanded west of Shinkawa fishing harbor. Coastal forest extends along this coastline and in order to protect this coastal forest, seawall has been constructed without sufficient understanding of causes and mechanisms of shoreline recession, and this brings a monotonous extension of artificial coastline covered with seawall. In order to change this situation, the overall cooperation between the works of shore and coastal forest protections is needed as well as the comprehensive consideration of stabilization of all the Niigata coast.

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The Northern Sea Route (NSR) is the shortest sea-lane linking between Europe and Japan. The NSR represents an up tp 40% saving of distance from Northern Europe to Northeast Asia compared to southerly sea routes via the Suez Canal. Russian federation opens the NSR to foreign flagships. To use the NSR safely and commercially, many legal, technical and environmental issues have to be resolved. INSROP (International Northern Sea Route Program) had been implemented as a 6-year international research program designed to create an extensive knowledge base about the shipping lane along the coast of the NSR. The NSR shall keep its advantages in costs against other alternative transportation means including railways or routes through the Suez Canal. INSROP Phase II are assigned tasks to perform a ship transit simulation in order to answer concerns about the cost benefit and associated risks in case of utilizing the NSR commercially. This paper addresses the outline of the simulation study after briefly introducing navigation knowledge on the NSR.

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