Rainfall induced soil seal (C) A dynamic model with kinetic energy instead of cumulative rainfall as independent variable

Abstract

This study presents a dynamic model of soil sealing, based on the extension of a previous model that considers the seal as a non-uniform layer, and the rainfall kinetic energy as the rain property dominating the sealing process. The model was applied in the case of two soils, sandy loam and loam, under saturated conditions, using an inverse procedure for its calibration. The validity of the theoretical model was examined for each soil by comparison to results of an infiltration test carried out under rainfall and flow boundary conditions different from those related to the data used for the model calibration. A very good agreement was found between the observed and the predicted infiltration curves in the case of sandy loam, but not as good in the case of loam soil. The error that may stem from using the cumulative rainfall instead of the rainfall kinetic energy, as the independent variable of the soil sealing model, was analyzed under various conditions. In cases where the rainfall kinetic energy per unit mass is a constant, independent of the rainfall intensity, the use of the cumulative rainfall is equivalent to the use of the rainfall kinetic energy. However, rainfall events often include long rainfall of low intensity and short time intervals of high rainfall intensity, with the kinetic energy per unit mass varying considerably during a single rainfall event. In such a case, the use of the cumulative rainfall as the model variable may lead to a considerable error. Applying the calibrated model for the sandy loam and characteristics of simulated and natural rainfall, the error associated with the use of the cumulative rainfall was found to lead to a large error in calculation of the infiltration rate during the sealing process.