Slope recession in the Onefour Badlands, Alberta, Canada: an initial appraisal of contrasted moisture regimes

Abstract

The initial 2 years (1975–1977) of a 10 year program of slope process measurement in the Onefour Badlands of Alberta, Canada, has encompassed two highly contrasted moisture regimes with measurable differences to process–response mechanisms. The Onefour Badlands are one of several distinctive and recurring dryland erosional landform elements which together are responsible for large sediment yields in Southeastern Alberta. Somewhat unique among temperate semiarid lands, the study area undergoes limited snowmelt runoff effects during the spring months which, together with typical temperate semiarid runoff processes, produces an extensive contemporary pedimented (glacis) surface.With a 48 year average precipitation of 32 cm, the 46 cm in the first year caused an average scarp retreat of 8.6 mm but with little erosion of the glacis surfaces. During the second drier year (20 cm), the scarps retreated only an average 3.7 mm. There was, however, active sheet erosion of the glacis surfaces during the second year which amounted to an average 7.0 mm. Observations of debris accumulation, runoff mechanisms, and measured profile changes suggest that glacis surfaces operate as transport slopes during wet years when there is significantly increased scarp erosion. During drier years when there appears to be much less scarp erosion, the glacis surfaces become a sediment source.