Physical and numerical modelling of infiltration and runoff in unsaturated exposed soil using a rainfall simulator

Context Tropical soils have complex hydromechanical behaviour compared to ordinary soils and are often found in regions with well-defined wet and dry seasons. The analysis of the interaction between the soil and the atmosphere comprises understanding of multiple phenomena, such as infiltration and runoff. Unfortunately, the dynamics of soil–atmosphere interaction are commonly modelled at the watershed scale, using average parameters that do not allow an in depth understanding of the soil–water phenomena involved. Aims This paper presents an investigation of the soil–atmosphere interaction at the local scale, using numerical and physical modelling of the infiltration and runoff of an exposed tropical soil in a laboratory rainfall simulator. Methods The effect of rainfall with two different intensities of 86.0 and 200.0 mm h−1 was used to physically and numerically evaluate infiltration parameters, runoff, volumetric water content, and degree of saturation at five locations in the soil specimen. Key results Calibration of the numerical model showed a maximum root-mean-square error of 0.17. In addition, the modelling exercises indicated the need for an equilibrium time of 48 h for the sample studied under the imposed conditions. Conclusions Results of numerical simulation showed that the representation of the physical model by the numerical model was satisfactory and promising. Thus, the numerical model showed applicability for validating the boundary conditions of physical tests using rainfall simulators.