GEOLOGICAL MAPPING OF THE COASTAL ZONE: CRITICAL INFORMATION FOR MANAGEMENT OF COASTAL RESOURCES

The earth science community is being asked to predict the vulnerability of the shoreline to erosion, and the response of coastal areas to future sea-level rise. Unfortunately, sediment response to oceanographic and geologic processes in the coastal environment, although critical to understanding the evolution of a shoreline, is poorly understood. Coastal environments differ widely, and processes and controls vary in importance both spatially and temporally. In addition, coastlines with limited sand supplies are significantly influenced by the geologic framework of older stratigraphic units that occur beneath and seaward of the coastal zone. This antecedent geology can determine the morphology of the shoreface-inner shelf and strongly influence modern beach behavior.

A better understanding of sediment dynamics in coastal areas can be attained by high-resolution mapping of surface sediment distribution and subsurface stratigraphy on a regional basis. Systematic mapping of coastal areas is being conducted by the US Geological Survey using high-resolution sidescan-sonar, chirp subbottom profiling, swath-bathymetry, coring, video/photography, beach profiling/monitoring, and laser altimetry technology. Resulting digital maps are used to investigate the role that geologic framework and physiography play in the dynamics of coastal evolution, and to help identify sand resources suitable for beach nourishment. These maps provide a framework for ongoing and future studies designed to address and potentially predict the dynamics of sediment transport in the coastal zone. In addition, the maps form the baseline for studies that focus on the geologic framework of biologic habitats and prediction of coastal vulnerability.