Measurements of Wave Reduction Due to Artificial Reef With Varying Width on an Atoll

The Spratly Islands consist of many islands, banks and shoals and especially coral reefs. Since 1980s, manmade structures have been increasingly constructed, thus resulting in unexpected negative effects on these shoals and reefs. Reef balls would be a feasible measure to create a favorable environment for restoring corals and sea creatures and to reduce waves attacking any cay of the atoll platforms. Therefore, the article explores how a field of Reef Balls affect the propagation process of and reduce the height of wave on an atoll. Using a 2D physical wave flume, we conducted 75 test scenarios, which combine three crest freeboards, five widths of the Reef Ball field and five deep-water waves. The experimental results reveal that the width and freeboard mainly govern the wave reduction. The wave reduction efficiency tends to be dependent upon the relative field width. Furthermore, the Reef Balls field performs most effectively with a width ranging from 1/5 to 3/5 of the shallow water wavelength (on the atoll platform).