Morphometric study of a virgin prairie area and adjacent cultivated farm land reveals no statistical difference in the slopes of the two areas. However, analysis by use of an elevation-percent area curve provides evidence that the landscape has been lowered about 0.132 feet in the last 100 years. Calculations of erosion rates using this curve are of the same order of magnitude as erosion rates calculated from sediment yield data. The erosion rates of individual basins are inversely proportional

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... to the stream gradients in the basins. This observation is in accord with the equilibrium theory of drainage basin development and suggests that the erosion resistance of the glacial till varies between first order basins.