Kench, Paul S., Nichol, Scott L., McLean, Roger F., Smithers, Scott G., and Brander, Robert W. (2007) Impact of the Sumatran tsunami on the geomorphology and sediments of reef islands: South Maalhosmadulu Atoll, Maldives. Atoll Research Bulletin, 544. pp. 105-134.

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Abstract

Mid-ocean atoll islands are perceived as fragile landforms being physically susceptible to climate change, sea level rise and extreme events such as hurricanes and tsunami. The Sumatran tsunami of 26 December 2004 generated waves that reached reef islands in the Maldives 2,500 km away, that were up to 2.5 m high. Here we present observations of the affects of the tsunami, based on pre- and post-tsunami topographic and planform surveys of 13 uninhabited islands in South Maalhosmadulu atoll, central Maldives. In contrast to the devastation along the continental coasts subjected to the tsunami, and also to the infrastructure on inhabited resort, village, capital and utility islands in the Maldives, our surveys show there was no extreme island erosion or significant change in vegetated island area (generally <5%). Instead, the tsunami accentuated predictable seasonal (monsoonal) oscillations in shoreline change promoting localised retreat of exposed island scarps, commonly by up to 6 m; deposition of cuspate spits to leeward; and, vertical island building through overwash deposition, up to 0.3 m thick, of sand and coral clasts covering a maximum 17% of island area. The main erosional and depositional signatures associated with the tsunami were scarping and gullying, and sand sheets and spits respectively. It is believed that these signatures will be ephemeral and not permanent features of the Maldivian islandscape.

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