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Effective countermeasure has been concerned with the issue of wind-blown sand from nourished beach to hinterland in Niigata West Coast. Although it has been confirmed that the countermeasure using number of fences is effectively worked so far, it is expected to reduce the number of fences for the cost reduction. In this study a trench trap which has been usually used as measuring method of wind-blown sand was excavated with the size of D=1m, W=5m and L=20m on the beach in February, 2008 to check the effectiveness as the countermeasure of wind-blown sand. Through the 5 times observation surveys, it was found that the trench trap itself was effectively functioned to prevent wind-blown sand, however, the most part of trench trap was filled with the wind-blown sand when strong winter wind would continue to blow for about one week.

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Effective countermeasure is required for the issue of wind-blown sand generated from nourished beach to hinterland in Niigata West Coast. Double-row sand fences on a parallel with coast and wing fences having with the fence height of 2m have installed in 2005. The comparison was made with past observation results after conducting site observations in the winter season (November, 2006 through February, 2007) in this study. As the result, the volume of wind-blown sand reaching to hinterland was decreased to around 1/10,000 to 1/100,000 comparing with the volume without fences and it has been confirmed that the countermeasure by double-row sand fences and wing fences are extremely effective. The cheaper countermeasure by reducing the number of fences is to be studied.

Masuda port is located in both sides of the mouth of Takatsu River, the access channel of which passes behind a river-mouth bar. This study intends to develop a tool for examination of countermeasures against channel infilling which is very linked with deformation of river-mouth bar. First, the relation between the sand bar deformation and channel infilling has been examined for the river mouth area of Takatsu River through analysis of aerial photos, current and wave data, bathymetric survey data, and so on. As the results, two dominant processes of flushing sand bar due to flood and reformation of sand bar by waves are confirmed. Also, numerical simulations for the two dominant processes have been conducted and the reproducibility of the model has been examined.

In an open-channel flow, a turbulent structure is affected by the presence of a free surface, and therefore, its characteristics are quite different from those of duct flow near the free surface. Many researchers have suggested that the turbulence redistribution changes complicately near the free surface. In this study, turbulence measurements were three-dimensionally conducted in open-channel flows by using two sets of twocomponent fiber-optic LDA. Some comparisons of the experimental LDA data with a direct numerical simulation (DNS) were conducted. Then, the peculiar characteristics in open-channel flows were clarified in detail.

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