Mapping erosion risk for cultivated soil in France

Surface runoff and soil erosion are major threats to sustainable agriculture and mapping regional erosion risk is increasingly needed by national and international environment agencies. Because erosion results from the interaction of several parameters which vary in space and time, no simple model can take into account all relevant factors, particularly in cultivated areas where human influences are predominant. The aim of this work is to develop a methodology based on present knowledge and available data for the evaluation of erosion risk at national scale. The various erosion factors have been graded for different geographical situations and erosion mechanisms have been expressed with the help of expert decision. The various erosion types observed in France had been previously classified. Soil crustability is considered as a key factor in runoff and erosion risk on cultivated soils. A geographical database has been created for French territory, and a model of erosion risk has been developed within a Geographical Information System (GIS). The model uses expert rules to combine data on land use (CORINE Land Cover database), soil crustability and soil erodibility (determined by pedotransfer rules from the French soil database), relief (Digital Elevation Model from the National Geographic Institute) and meteorological data from Meteo-France at the scale of 250 x 250 m pixels. Results are spatially aggregated using various administrative or environmental units. The main areas affected by erosion risk are the north, west and east of the Paris basin with intensive agriculture on crusting soils, the Rhone valley and southwest of France where vineyard or spring crops cover large areas. Other areas like Britany, the south of the Massif Central or the Mediterranean area are moderately affected. Areas with a permanent cover of woodland or grassland show a low erosion risk. (C) 2001 Elsevier Science B.V. All rights reserved.