Scarp retreat, slope stability, and the evolution of piedmont assemblages

The behaviour of escarpments in various structural and topographic settings determines style and rate of landscape development and of the piedmont landform assemblage. Where there is little or no overland flow and no basal sapping or erosion, slope recession is slow. The upper slope becomes rounded. The bluff is worn backwards and upwards by basal sapping and is eventually eliminated. The faceted slope is converted to a graded sigmoidal form. Detritus accumulates at the base of the slope. Convex upward bedrock slopes evolve. Where the slope is worn back as a result either of basal erosion or overland flow or strong sapping of the bluff, the cliff recedes and its height and inclination are maintained. Reduction of catchment causes retardation of retreat, and scarp-foot weathering assumes greater importance. A characteristic assemblage of forms is developed by the subsequent etching of the scarp-foot zone. Capped piedmont residuals fronting scarps are related to mass movements on the hillslopes above. Dip slopes are fronted by similar assemblages but are locationally stable. Slope behaviour in space and time is relevant both to the question of models of landscape evolution and to the problems posed by very old palaeosurfaces. © 2000 Taylor & Francis Group, LLC