Interrill Erosion on Desert Hillslopes, Southern Arizona
Athol Abrahams Principal Investigator
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Soil erosion on both natural and cultivated slopes is a serious problem in the United States and throughout the world. Effective solutions to water-induced erosion are impeded by the absence of basic microlevel understandings of the relationship between precipitation and erosion processes. In particular, we lack sound mathematical models that will predict soil erosion resulting from water flowing across surfaces in broad sheets (interrill erosion), an important form of erosion in many regions, especially in arid and semi-arid areas. Existing models do not take into account loose sediment that has accumulated on ground surfaces prior to rainfall (detachment storage), and the omit processes of flow erosion. This research will refine models of interrill erosion by including and comparing those variables. Professor Abrahams and his students will apply simulated rainfall to matched pairs of experimental plots at the U.S. Department of Agriculture's Walnut Gulch Experimental Watershed in Arizona. One plot will be covered with a screen that will dissipate raindrop impact; the other will receive the full impact of the simulated raindrops. Thus the second plot will be subject to erosion from both raindrop impact and flow erosion, while the first will experience only flow erosion. The measurements that will be taken on the paired plots will make it possible to model variations in relative rates of flow and in raindrop erosion, to calibrate the interrill erosion model and thereby develop predictive equations, and to compare the characteristics of sediments eroded by flowing water and by raindrop impact. This project will yield basic insights into a major geomorphologic process with important implications for soil conservation programs domestically and abroad.