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GIS-based Flood Susceptibility and Risk Mapping Trinidad Using Weight Factor Modeling

Flooding is a major concern in Small Island Developing States (SIDS), particularly the Caribbean region due the tropical climate. Flood susceptibility and risk mapping has proven to be a critical tool in modern natural hazard analysis. It provides geospatial representations of hazard susceptibility and risk, which has become vital in land use management and planning. This paper reports on the use of model builder application within ArcGIS 9.3 to develop a flood susceptibility and risk map of the island of Trinidad utilizing traditional inundation factors to determine flood susceptibility and then combined with population and building density to determine flood risk. Results indicated that rainfall was the most influential inundation factor followed by slope, elevation and drainage density, with the most susceptible areas being low lying coastal regions. Cross validation utilizing intersect analysis and field verification revealed 91% and 100% accuracy. Quantitative analysis of risk showed that 23% of the country's landmass can be considered to be at high risk with concentrations in the urban and suburban centres of the country. Utilization of the information provided can inform future planning and management strategies and consequently mitigate potential threats associated with flooding. The methodology also allows for uncomplicated replication and application in other Caribbean islands, where data limitation may prevent use of more complex models.

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