Studio teorico-sperimentale sull'influenza del diametro dei contenitori nelle misure di erosione da impatto

The knowledge of impact erosion process constitutes an interesting theme research for its implications in many studies such as the seal formation, which results in a rapid drop in the infiltration rate, or the analysis of vegetation cover efficiency on rainfall erosivity. To determine impact erosion two different experimental techniques can be used: receiving or ejecting splash cups. Both experimental techniques, as well as theoretical approaches, showed a dependence of impact soil erosion to the splash cup diameter. In this paper, after a brief review of the main impact soil erosion models, a theoretical model is presented. The model is based on the assumption that the mass of soil eroded deposits out of the ejecting splash cup along a circumference, which centre is the raindrop impact point and which radius is a predefined equivalent mean jump length. Accounting for main physical parameters influencing impact erosion process, a hyperbolic relationship between sediment yield and splash cup diameter is derived. By using a rainfall simulator, for one clay loam soil, for different ejecting splash cup diameters, experimental runs have been carried out. Experimental results proved the theoretical hyperbolic relationship between the sediment yield and the splash cup diameter. A comparison between measured impact sediment yields and those derived by the theoretical model showed an overestimation of the latter probably due to i) the adopted simplified hypothesis and to ii) to the uneasy evaluation of physical parameters which the model depends on. Finally, a relationship between a calibration factor, accounting for the parameters uneasy to evaluate, and the rainfall intensity has been derived. Satisfying calibration results suggest further applications on soil with different textural and structural characteristics also exposed to natural rainfall events.