Abstract
Coral cays formation mechanism has various field surveys, experiment, and numerical simulations. The characteristic feature was made clear gradually. In these researches, sufficient amount of coral gravel are transported and can make island under certain condition (wave height, wave period, water level). However, the condition in the real coral reef does not necessarily correspond to the experiment condition. In this research, we studied the form of offshore structure which can advance formation of coral cays by movable bed experiment. We got the some results that permeable structure is more effective than impermeable structure, that the form of structure can change the efficiency of sedimentation and sea-bottom slope under the condition that permeable structure's height was under water level, and that the structure which has tetrapod (like a coastal structure) was efficient. In addition, we conducted numerical simulation about wave and change of seabed topography, and the results corresponded to experiment data with considerable accuracy.
