Influence of geological setting of islands and significance of reefs for tsunami wave impact on the Atoll Islands, Maldives

This paper discusses the influence of the geological setting of islands and reefs in the Maldives on the impact of the 26 December 2004 Indian Ocean Tsunami. Geological and geomorphological data (including orientation, location, size, ellipticity, reef-island distance, proportion of reef area to island area) were collected for completely flooded and <25% flooded islands. The results show that although the different parameters may interact to reduce or magnify the impact, the reef-island distance is the most important factor. The critical minimum distance between the reef and the island shoreline required for the wave to set up is estimated as 89 m on the eastern and 140 m on the western sides of the island, respectively. Circular islands with short reef-island distance and small percent of reef area seem to be safer in the context of tsunami. The result of this study can be applied to identify islands that are naturally protected/resilient against natural disasters such as tsunami and those where the hazard is greatest.