OBSERVED HUMAN AND NATURAL CHANGES ON COASTAL LANDS AND SHORELINES

The physical changes, incurred since the last coastal lands and shorelines baseline, become a part of any new coastal geological map or update to an existing map. Geological mapping along the southern coast of South Carolina has identified both natural shoreline changes and areas of human alteration to the land surface. Identification of physical change is an automatic result of the mapping process. Both of these changes, when combined, can alter a substantial area of habitable, developable, natural resource rich lands, estuaries, and other wetlands. Using geological mapping, along with computer GIS input and adjustments, the areas of change can be identified. Twelve contiguous 7.5 minute USGS topographic quadrangle maps have been compiled; the geology mapped; and the alterations, since publication (anywhere from 1956 to 1972- depending on the specific quadrangle), by nature and man identified and quantified. GIS techniques to recognize baseline changes start with the original map as the baseline. Then, more recent data sets, such as hypsography, hydrology, and recent digital orthoquads, are superimposed on the previous baseline map, and the changes in shorelines and water features are noted. The geological information allows interpretation of the reasons for the natural changes (stream migration, shoreline loss/gain, dry land inundation) and identification of the changes from human alterations (residential construction, dredge/fill, golf course terrain sculpting, road construction, timber removal). Recording these physical changes now, and comparing them to the previous baseline, provide a new, more detailed baseline. The new baseline will allow better prediction of change. We need more data today on the physical changes so we can answer tomorrow's questions.