Spatial evaluation of extreme wave deposits at Boca Olivia, Bonaire

A field mapping survey was conducted in early November, 2006, on the east coast of Bonaire, Netherlands Antilles, to help assess the potential risk of extreme wave events such as tsunamis and hurricanes in the Caribbean. The purpose of the survey was to determine the extent, spatial distribution, and origin of a sedimentary deposit occurring along the shoreline near Boca Olivia that ranges in size from sand to boulder. The deposit, which rests on an older Pleistocene reef platform now 4 to 7 m above present sea level, is presumed to have been formed by one or multiple extreme wave events over time. Approximately 600 boulders were measured in the deposit and georeferenced using GPS and high-resolution aerial photographs collected using a specially designed kite and digital camera system. In addition, topographic profile transects and geologic field observations were recorded. Boulders were mapped over nearly 5 km of coastline with most measurements concentrated along roughly 500 m in the Boca Olivia area. Boulders were observed up to 250 m inland from the shoreline and ranged in volume from 0.01 m3 to 74 m3. Approximately 80% of the boulders measured were smaller than 1.0 m3. The extent and spatial distribution of the deposit is being investigated to determine what type of extreme wave event or combination of events formed and modified the deposit over time. Mapping and analyzing spatial distributions of sedimentary deposits formed by past extreme wave events will help develop a greater understanding of the potential tsunami risk for the Caribbean and other parts of the world.