HILLSLOPE EVOLUTION EXPERIMENT INITIATED BY CIVIL WAR ERA EARTHWORK CONSTRUCTION

Civil War earthworks near Charleston, South Carolina provide the opportunity to observe the rate and pattern of hillslope evolution over a 140-year period. Little did the Confederate defenders of Charleston know that their fortifications would later be used as a model for hillslope degradation. It is difficult to accurately estimate the rate and pattern of changes in hillslope morphology when neither the age nor original form of the hillslope is unknown. The construction dates of many Charleston area earthworks are known, however. In addition, their original morphology is known both from the fact that most of the earthworks were constructed according to specific military engineering guidelines as taught at West Point, and also from the detailed mapping and profiling of the Charleston defenses done by Union General Q. A. Gillmore at the close of the war.

The present morphology of these earthworks has been extensively surveyed and compared with the Gillmore survey. Results from the comparitive study reveal rates and patterns of hillslope evolution in keeping with transport-limited slope conditions. Subtleties in the original slope have been reduced or eliminated. Increased rounding of the crest and base, and slope angle reduction, is observed. These findings suggest that diffusion-like processes dominate the degradation of these earthworks.