PATTERNS OF HILLSLOPE EVOLUTION OBSERVED ON CIVIL WAR EARTHWORKS NEAR CHARLESTON, SOUTH CAROLINA

Civil War earthwork fortifications around Charleston, SC provide a means for high-resolution study of morphologic changes in hillslopes with time because the ages and initial morphologies of these features are tightly constrained. Estimates of time and initial morphology are useful in permitting accurate determination of rates and patterns of hillslope degradation. Constraint of these variables allows study of other slope process factors such as slope material, vegetation, and climate.

Further assessment/analysis of hillslope evolution is possible through the updated computer program SLOPEAGE (available for free download from http://www.uc.edu/geology/faculty/nash.html). Current slope profile measurements and initial (constructed) morphology parameters are entered into the program for analysis. The program then produces a variety of graphic and data output including slope aging (model), best fit slope for given initial slope boundaries, and mass balance (crest removal vs. base accumulation).

Observed erosion patterns are typical of transport-limited slopes and appear to be representative of diffusion-like slope processes. Pattern characteristics include rounding of edges, build-up of slope base, reduction of slope crest, and decrease in slope angle. The fit between the computer-generated SLOPEAGE model and the current slope morphology of many of the slopes measured is very good.