GIS AND FIELD-BASED DOCUMENTATION OF ARMORED ESTUARINE SHORELINES IN GEORGIA

Sea level rise is inundating coastal regions around the world, driving intertidal habitats onto uplands. This is not a concern in undeveloped areas, where the land/sea boundary is allowed to retreat naturally, preserving habitat, but armored shorelines block this retreat, endangering the persistence of intertidal habitats. In addition, areas of armored shoreline are likely to be further armored as sea levels rise, leading to further environmental degradation. GIS tools allow us to accurately map and attribute armored shoreline features, providing a means to delineate areas for ecological retreat and potential protection.

This study delineated armored shorelines in the six coastal counties of Georgia. Armored structures identified in the coastal environment included bulkheads, revetments, jetties and groins. These features were digitized in ARCGIS 9.3 from geo-referenced aerial orthophotographs. Each county was analyzed using color imagery with better than 1 sq m pixel resolution. Photographic observations were augmented with field observations in areas where imagery was not adequate to identify shoreline character. Each county was analyzed as a separate project, with shapefiles for armored shorelines, causeways and field inspections routes. Length of armored shoreline, broken out by type, and field inspection routes, were calculated from these data.

Because all land/water boundaries could not be inspected in photographs or by field inspection, the extent of armoring in this study is a minimum estimate. Within Georgia, 212 kilometers of shoreline is armored, with the most armoring found in Chatham County (109 kilometers). We examined the relationship between length of armored shoreline in each coastal county and basic demographic parameters (i.e., population, per capita income and county area) for the counties. Of these parameters, only population exhibited a significant relationship with armored shoreline length. We are currently quantifying the length of the extensive backbarrier shoreline to put length of armored shoreline into a regional context. The results of this study are being used by state and local governments for better management of the Georgia coast, including storm surge flood modeling and to plan for adaptation to climate change.