LandSoil: A model for analysing the impact of erosion on agricultural landscape evolution

The purpose of this research was to develop a model for the analysis of agricultural landscape evolution at a fine spatial resolution scale (1–10m) and a medium-term temporal scale (10–100years). The model (LandSoil: landscape design for soil conservation under Land use and climate change) works at a catchment scale and it is based on the STREAM soil erosion model. It is spatially distributed, event-based, and considers interrill, rill and tillage erosion as the main processes acting in soil redistribution. The specificities of the model include the use of a detailed representation of the agricultural landscape through parameters such as soil surface properties, hydrologic pathways and considering a climate component based directly on rainfall events. In this paper, we present the characteristics of the model and its application to a Mediterranean study area. The model was subjected to a calibration/validation procedure at two different spatial scales (field and catchment) with a medium-term data series of runoff and sediment concentration measurements. A number of medium-term field and catchment simulations were carried out, allowing us to observe landscape evolution under recent and actual agricultural practices and to formulate hypotheses based on changes related to different agricultural patterns and soil uses. Modelling at a field scale using rill, interrill and tillage erosion simulations on reconstructed prior topographic surfaces showed a relationship between observed and simulated topography with a prediction error<15% and a correlation coefficient (r) of 0.605. A catchment scale analysis of a degraded scenario, maximising hillslope runoff with the removal of all the grass strips between fields, indicated a global increase of the soil erosion rate (+29%), with spatial variability depending on the specific soil use type.