sorting and water content. Debris flows are highly viscous and are therefore able to transport large rock blocks (> 1m) on their surface. Their erosive power is several orders of magnitude greater than water floods and hypoconcentrated flows. Following Hungr et al. (2001) “debris flood is a very rapid, surging flow of water, heavily charged with debris, in a steep channel�. Many debris flows become diluted with water downstream to become debris floods. It is regarded as a mass transport phenomenon distinct from landslides and simulating what have been described as hypoconcentrated flows or sediment slurries which can easily move on gentle slopes (Costa, 1984; Hungr et al., 2001). Sources of sediments include storm-induced landslides, loose sediments on slopes derived from old slope failures and sediments in the water courses related to previous sediment-water floods. The mobilization potential of these sediments is high and, in many cases, it is the deposition of sediments rather than water that leads to disasters in river basins. Post-disaster damage assessment surveys carried out by the author in the parish of Portland in Jamaica in the wake of rainfall associated with tropical storms Michelle in 2001 and Lilli and Isidore in 2002 revealed many such cases. For example, in the Bybrook area of Portland parish and Bull Bay in St. Andrew it was noted that many of the culverts and bridges failed to function as debris flow chutes as they were small and designed to accommodate water floods. Tsunami hazard: Following the catastrophic Boxing Day 2004, Indian Ocean Tsunami, the scientific community has documented evidence in support of giant wave events throughout the Caribbean including the ABC1 islands, the Bahamas, Cayman Islands, Jamaica, southern and central Antillean island arc (for example, Lander et al., 2002; Ahmad et al., 2005; Grindlay et al., 2005; Scheffers et al., 2005; Robinson et al., 2006). These studies have highlighted the potential for devastating tsunamis in the Caribbean. Previously known Caribbean tsunami events include Jamaica (1692, 1780); Hispaniola and Virgin Islands (1842), and Dominican Republic (1946). According to Grindlay et al. (2005), “with increased populations, especially in the coastal area, some 35.5 million people are now at risk should another strong tsunami hit the northern Caribbean (Fig. I.3). An Intra Americas Sea Tsunami Warning Project has been approved by the Intergovernmental Oceanographic Commission and US Geological Survey.
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Aruba, Bonaire, and Curacao
R.Ahmad
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