Date of Award
Doctor of Philosophy (PhD)
Measurements in a small drainage basin in the Little Missouri Badlands of western North Dakota indicate an average rate of hillslope lowering by slopewash of 0.41 inch per year on the west-facing hillslopes underlain by the Sentinel Butte Formation, 0.14 inch per year on the southwest-facing hillslopes underlain by the Tongue River Formation, and 0.11 inch per year on the northeast-facing hillslopes underlain by the Tongue River Formation. Soil creep occurs mainly on the Tongue River Formation and is mostly restricted to the northeast-facing hillslopes where the average rate of soil creep parallel to the hillslope surface is 0.23 inch per year in the upper 2.5 inches of surficial sediment. Erosion perpendicular to the face of seepage steps is 0.29 inch per year.
The Sentinel Butte Formation has a lower rate of infiltration and percolation, which results in a higher rate of surface runoff than on the Tongue River Formation. This in part causes the higher rates of lowering of the hillslope by slopewash on the Sentinel Butte Formation than on the Tongue River Formation.
The lowering of the hillslopes by slopewash contributes 99.9 percent of the 43,000 cubic feet of sediment per year from the hillslopes in the study areas. Comparison of the hillslope sediment yield with the rates of valley-bottom deposition from June to July 1969 indicates that approximately 62 percent of the hillslope sediment left the drainage basin.
Tinker, John R. Jr., "Rates of hillslope lowering in the Badlands of North Dakota" (1970). Theses and Dissertations. 299.