Investigation of solids loss and erosion process on compost blankets used for soil erosion control under concentrated flow conditions
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Although a variety of composts have been effective in reducing soil erosion from the impact of rainfall, the response of compost to concentrated flow and compost failure due to erosion, were largely unexplored. This dissertation examined the solids loss and the process of rill erosion on compost blankets subjected to concentrated flow under both laboratory and field conditions. Some erosion of yard waste compost in the laboratory was minimally similar enough to follow the shear stress equation used to describe soil erosion. Nevertheless, an additional equation was necessary to describe all the compost erosion processes observed. For the first time, this investigation made systematic observations of the formation of micro-dams in compost that are often observed ad hoc during rill erosion and failure of some compost applications. Micro-dams formed and truncated rill formation in erosion control compost in both the laboratory and field, and in yard waste compost on field plots, hampering estimation of shear stresses. Thus, the semi-empirical shear stress equation could not describe all compost erosion over the wide range of test conditions. This investigation derived an empirical equation based on laboratory erosion and tested the regression with field observations. The resulting regression equation better represented compost erosion both in the laboratory and in the field compared to the shear stress equation for soil erosion. The use of the Buckingham PI Theorem to derive dimensionless groups of parameters for the regression ensures that future observations can more easily generalize the empirical equation derived by this study.