DISTAL EROSION AND DEPOSITION OF THE 2004 TSUNAMI IN THE MALDIVE ISLANDS

Observations on seven islands in Central Eastern South Malé Atoll (Maldives Island Chain, western Central Indian Ocean) documented a substantial flooding and erosion event that occurred in conjunction with the South Asian Tsunami of 26 December 2004. Islands located closest to the eastern atoll barrier reef are the most damaged and those in the lagoon have undergone lessor or minor damage. Structures on the eastern side of any given island have been more damaged than those on the western side. Erosion is most pronounced on the eastern and southern portions of the islands although erosion due to flooding and flooding drain back is present on the western sides of the islands nearest the reef. Damage to jetties and docks (on the west side of the islands) has also been observed. The maximum inundation measured was in excess of 3 meters and the minimum on the marginally flooded islands visited was about one meter (measured relative to low tide). An inundation event coming from the west was reported on three of the islands visited and appears to be associated with wave ‘wrap-around' from deep water channels cutting through the main barrier reef. Survivors commonly reported that the flooding they experienced was up to a meter more than the flood lines left on the buildings. The primary geological feature associated with the tsunami in these small island settings was erosion. Only locally, were any depositional units present: rubble armoring on the seaward coastlines, and local sand sheets and patches of carbonate sand in areas sheltered from strong current activity.