1.1 Geomorphic Properties

The coastal plain is an expansive geomorphic region of the Southeastern USA that extends from southern New Jersey along the Atlantic coast through the coast of the Gulf of Mexico to South Texas. It comprises nearly 2/3 of the land area of South Carolina (Fig. 1); most of which is either in agriculture or forestry. The coastal plain was initially deposited during a series of sea level rises and recessions; it has been subject to depositional and erosional forces moving and relocating sediments from the Pliocene Epoch (1.8-5 million years ago, [91]) to today. Below Pliocene age sediments are geologic strata consisting of beds of multicolored sands, intermixed with gravel and clay beds laid down during the Tertiary Epoch from 5 to 38 million years ago [91].

Terraces and scarps commonly occur across the coastal plain that are reflective of glacioeustatic changes in ocean level, deposition of sediments, and river dissec­tion during the last 5 million years [30]. The terraces are gently eastward-sloping on the surface, which are bounded by seaward-facing scarps [25] . These scarps are a

few meters in height and demark a time when sea levels were higher. Some of the scarps are definitive on the landscape [32] and are used to divide the area into phys­iographic divisions consisting of (1) lower, (2) middle, and (3) upper coastal plain, based on topography, sediments, elevations above mean sea level, and soils [30]. Their elevations range from sea level to about 150 m.