A third generation erosion model: The combination of probabilistic and deterministic components

A combination of the classical deterministic mechanics of soil erosion and stochastic description of controlling erosion factors (driving and resistance forces) gives significant advantages and leads to the development of a new (the third) generation of erosion models. In contrast to existing models, the STOSEM model allows determination of the relationship between the rate of erosion and controlling factors inside the model theoretically, by a solution of the governing deterministic equations with stochastic initial and boundary conditions. It is possible to calculate the mean erosion rate explicitly from the probability density functions (PDFs) of flow velocity, soil aggregate size, cohesion, integrity and other basic controlling factors. Variability of the PDFs of controlling factors through time and space due to the changes in flow regimen and/or soil composition produces differences in the structure of relationship between the mean erosion rate and controlling factors, as well as in resulting mean rate of erosion. The model is still far from application due to the lack of specific experimental data for validation. Nevertheless, its theoretical basement, transparency and flexibility show new direction in soil erosion science.