Scheffers, A.

Situated just north of the Venezuelan coast around 12° to 13° N, the Netherlands Antilles are normally well outside the hurricane belt. Nevertheless, some of these powerful storms sent waves and swell of significant size to these islands, strong enough for impacts on the coastal geomorphology. Hurricane Ivan of September 2004, with Saffir–Simpson category 5 and around 250 km/h sustained winds less than 150 km north of Bonaire, was the most recent and one of the strongest of these events in history. Waves along the rocky eastern coastline reached heights of >12 m. Our observations during the days of Hurricane Ivan on Bonaire Island include impacts on exposed and sheltered shorelines, transformation of beaches and cliffs, sediment movement on higher terraces, as well as boulder transport. The latter is important to distinguish storm wave-induced boulder movement from boulder movement by tsunami, which have affected Bonaire several times during the Younger Holocene.

Tsunami are one of the major natural hazards in the Caribbean. The historical record lists 88 tsunami, from local events to teletsunami, in the time period from 1489 to 1998. This study focuses on the spatial distribution and geomorphologic evidence related to coarse littoral sediment and boulder deposition by tsunami events of Holocene age in the Southern Caribbean. At a worldwide scale, these debris deposits represent the most extensive and impressive records of Holocene paleo-tsunami so far studied. Hitherto, the Leeward Lesser Antilles, consisting of the islands of Aruba, Curaçao and Bonaire, were not known to have had tsunami affecting their coastlines. The possible contribution of tsunami to configuring coastlines (e.g. the questions of embayment development, the coastal environment changes, and the absence of Holocene fringing reefs along the windward coasts) is discussed.