The determination of coastal sensitivity indices for Cocos and Columbus bays, Trinidad using GIS multi-criteria analysis.

A Coastal Sensitivity Index (CSI) map is a critical input for deriving coastal management plans. Development of these maps has typically been challenging since many of the datasets required are non-existent or unavailable. This study focused on determining CSIs for Cocos and Columbus Bays on the island of Trinidad.
Historically, both bays have experienced severe erosion, which have led to the construction of high-priced
coastal protection structures. Ten (10) erosion-inducing physical variables for each bay were categorized into two groups; one containing five (5) structural variables and the other consisting of five (5) process variables. Using a multi-criteria analysis approach, these variables were incorporated into a geographic information system (GIS) for the determination of the CSIs. All variables were ranked using published ranking criteria based on a scale of 1 - 5 (5 being the most sensitive). Two additional variables, storm surge and coastal protection structures, not traditionally used in sensitivity studies, were also included. Variables were manipulated using the geo-processing and spatial analyst tools in ArcGIS 10.4.1 to calculate the indices and generate the final CSI maps. CSI values were validated against field and desktop studies. Final CSI maps revealed that sensitivities for both study sites were predominantly high and very high. Erosion, sea level rise and increasing storm intensity and frequency are ever escalating threats to the coast. The initial results of this study and these growing threats further justify the need to include CSIs in coastal management plans. Hard engineering coastal protective structures usually require significant financial investment and the establishment of coastal setback distances can be a preferred shoreline management tool.