Impacts of category 5 tropical cyclone Fantala (April 2016) on Farquhar Atoll, Seychelles Islands, Indian Ocean

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This paper provides newinsights on the impacts of a category 5 tropical cyclone on Indian Ocean atoll reef islands.Using multi-date aerial imagery and field observations, the contribution of tropical cyclone Fantala to shorelineand island change, and to sediment production and transport,was assessed on Farquhar Atoll, Seychelles Islands.Results showthat the twolargest islands (N3km2) only suffered limited land loss (−1.19 to−8.35%)while smallislets lost 13.17 to 28.45% of their initial land area. Islands and islets exhibited contrasting responses dependingon their location, topography and vegetation type. Depending on islands, the retreat of the vegetation line occurredeither along all shorelines, or along ocean shoreline only. The structure (wooded vs. grassy) and origin(native vs. introduced) of the vegetation played a major role in island response. Five days after the cyclone,beach width and beach area were multiplied by 1.5 to 10, depending on the setting, and were interpreted asresulting from both sediment reworking and the supply of large amounts of fresh sediments by the reef outerslopes to the island system. Fourth months after the cyclone, extended sheets of loose sediments were still presenton the reef flat and in inter-islet channels and shallow lagoon waters, indicating continuing sediment transferto islands.