Antigua & Barbuda - St. Kitts & Nevis - Inland Flooding Hazard Map - OAS

Inland Flood Hazard Assessments have been completed under PGDM for Antigua, Barbuda, St. Kitts and Nevis. Both Technical and Summary reports on these hazard assessment are available by country. Individual inland flood hazard maps have been produced for each island.

This report describes the approach to mapping the natural hazard of inland floods on Antigua and Barbuda. It first presents a summary of the main cause of flooding on the islands. This is due not only to extreme rainfall, which provides the potential water for inundation, but also depends on the condition of the watersheds at the time of the event. The detrimental effects of flooding are then presented, which on the islands are mainly health hazards in terms of drowning and the contraction of diseases, and damage to economic systems including public infrastructure and private property. The data needs and adequacy for flood quantification are then discussed. For its quantification three sets of data are required, and they include rainfall data for characterizing the rainfall with potential to cause floods, the physical properties of the watershed which determine the volume and time-distribution of runoff onto low-lying areas, and the geometric features of the drainage channel which may or may not have sufficient capacity to accommodate the runoff from the watersheds. The two approaches used for flood mapping are described, followed by the presentation of the methodology implemented for producing the maps. A general summary of the findings for each island concludes this report. Among other things, it suggests what are necessary to improve the accuracy of the maps, which given the limited data, must be regarded as only preliminary maps.