Abstract
Understanding the formation mechanisms of coral cays is essential especially for beach protections of tropical islands. This study aims to clarify the conditions required for formations of coral cays through a laboratory experiment. Through the experiment, we found: (i) waves penetrating toward the coral layers significantly enhance the accumulation of coral gravels around the swash zone; (ii) flooding tide plays an important role in formation of coral cays and also in development of shallow area on which the coral cay is developed; (iii) a coral cay is developed only when the amount of gravels provided during the period of flood tide exceeds the total amount of gravels required for formation of the coral cay; (iv) the amount of gravels required for formation of the coral cay depends on the required height of the cay and thus it is important to develop a shallow area since the it lowers the required height of the coral cay.
