Modelling water and tillage erosion using spatially distributed models

Soil erosion models are valuable tools for understanding sedimentary records. In this paper, the potential use of a topography-based model (WaTEM) for simulating long-term soil erosion and its effect of soil properties is discussed. Long-term (derived from profile truncation) and medium-term (derived from Cs-137 measurements) erosion patterns are compared with simulated patterns of water and tillage erosion. Results showed that WaTEM is able to describe to reproduce the observed spatial pattern of long-term water erosion reasonably well. However, the Cs-137 data indicated that a major change in erosion and sedimentation patterns has occurred over the last decades: the dominance of water erosion over a time scale of several thousands of years explains the spatial pattern of soil truncation. On the other hand, the Cs-137 data indicate that the present-day pattern of soil erosion is dominated by tillage. WaTEM is also used to assess the effect of changes in landscape structure on soil erosion. It was shown that, when shifting focus from the field to the catchment scale, the way we represent space in distributed models affects the model performance at least as dramatically as the physical description of the process. Finally, a model application whereby WaTEM is linked with a mass-balance model, showed that simulating the effects of soil erosion on the redistribution of soil properties is an important issue when trying to link surface processes and sedimentary records.