Barrier Islands

Barrier islands were delineated in the Gulf using an imagery service database of natural color imagery from years 2001 to 2011, provided by the Microsoft Corporation through Esri basemaps in ArcGIS (Microsoft Corporation, 2011). Due to the varied coastal geomorphologic conditions of barrier islands, several simple rules were followed in digitizing: islands must be separated from the mainland by natural waterways, excluding capes and spits; an island must be fronted by the Gulf and not by marshes or mangroves; only the primary island was included in the delineation, excluding landward-side small islands not directly adjacent to the open Gulf; and islands must be sedimentary in recent origin, excluding islands developed from exposed reef tracts or hard substrate separated by the mainland due to erosion.