Pan-European Soil Erosion Risk Assessment (PESERA)
The Pan-European Soil Erosion Risk Assessment model (PESERA) offers a methodology to assess regional risk of soil erosion by water. The model is intended as a regional diagnostic tool, replacing comparable existing methods, such as the Universal Soil Loss Equation (USLE), which are less suitable for European conditions and lack compatibility with higher resolution models.The PESERA model distinguishes between soil erodibility, the hydraulic properties of soil, and effects of land use and climatic changes. This offers the potential to explore the sensitivity of changing environments through scenario analysis.
PESERA offers an explicit theoretical response based on a simple and conservative erosion model, making use of land-use, topographic, soil and climatic data. Cell by cell hydrology and vegetation biomass are run to equilibrium. Runoff is estimated by integrating the incomplete gamma function which describes the distribution of daily rainfall. From the components, the model estimates water and sediment delivered to stream channels.
The PESERA model is based on a partition of daily precipitation into Hortonian and saturation overland flow, subsurface flow and evapo-transpiration. Hortonian overland flow, which is mainly responsible for soil erosion, is generated with respect to local soil and sub-surface moisture characteristics. Allowance is also made for snow accumulation and melting. The emphasis in the PESERA model is the prediction of hillslope erosion, and the delivery of erosion products to the base of each hillslope. Channel delivery processes and channel routing are explicitly not considered.
The PESERA model can be run on the 1km x 1km European data already compiled by the PESERA Project, or, alternatively, local data on climate, soils, land cover and topography. The climatic data are interpolated to 1 km spatial resolution from 50-km resolution grids of daily time series of rainfall, temperature and potential evapotranspiration, obtained from the MARS database at JRC-Ispra.
The European Soil Database has been used to provide a consistent level of soils data at 1km resolution across Europe. This database has been used to generate through pedo-transfer functions three data layers for the PESERA model: (1) soil erodibility, which converts runoff to erosion rates; (2) readily available soil water capacity, which provides the maximum storage capacity of the soil before runoff occurs under vegetative cover; (3) crustability, which sets the lower limit of storage capacity for a crusted soil in unvegetated areas.
Land use for PESERA was based on CORINE land cover at 250 m resolution for 1989, which provides a
suitable baseline for calculating soil erosion estimates for 1990, but will have changed in the meantime.
A 1-km resolution DEM has provided the topographic basis for work on PESERA, and for the erosion map. The critical parameter for the model is local relief, which has been estimated from the DEM as the standard deviation of elevation within a circle of 3 km diameter around each cell.
The model results have been validated at catchment level and compared with results of applying other erosion risk assessment methods across Europe at country and pan-European scale. Preliminary results suggest that, although the model can be applied at regional, national and European levels, low resolution and poor quality input data cause errors and uncertainties at more detailed scales.