Morphological changes of coral gravel beach in the atoll islands

Abstract

 Coral gravel is one of the important resources in the atoll islands, however, maintenance plan is not prepared due to the lack of fundamental information on morphological change. This research focused on the coral gravel spit formed in the southern tip of the Fongafale island of Funafuti Atoll, Tuvalu, and measured changes of it by field investigation and satellite images. In addition, the potential of moving the gravel was considered by the Shields number evaluated from the monthly averaged wave field. The detected shape of coral gravel spit indicated that the tip of the spit changed actively. But the area of spit was stable. The calculated Shields number showed that the tip and ocean side coast has high transport potential of the coral gravel. However, the high transport potential was identified seasonally.