Abstract
Detached breakwaters have been used as coastal protection structures. In the sandy beach, group of breakwaters that have the openings are constructed. According to the analysis of the bottom sounding, it is known that tombolo will formed behind detached breakwaters. And local scour will occur in an opening or offshore after detached breakwate s construction. It is difficult to estimate the amount of sand trapping effect because the shoreline data is few. Thus the purpose of this study is to research the relationship shoreline profile and detached breakwaters profiles. As a result of this research, with the increase of length of dike, the shoreline advances. The top of tombolo is ifluenced by many parameters that are not only the wave direction but also other factors. With the increase of the ratio of the average opening width, the recession of the shoreline decreases.
