Evaluation of r‐factors as exemplified by the Alsace region (France)

Abstract

Even within temperate climatic zones such as Central Europe, soil erosion contributes mainly to soil degradation. Soil erosion models offer the possibility to estimate the influence of various parameters on the soil erosion process and allow for estimating the effects of management practices on soil erosion. One input parameter of the widely used Universal Soil Loss Equation (USLE) is the R‐Factor, which describes the influence of rainfall and runoff on soil erosion. This study elaborated R‐Factor values for three Alsace meteorological stations. The availability of long recording periods for two of the three stations offered the possibility to compare the accuracy of R‐Factor calculations based on different lengths of evaluation periods. Depending on the investigated station, between 30 and 40 years of observation would be necessary for receiving an R‐Factor with the highest possible accuracy. However, after 15 to 20 years of observation, the mean R‐Factor values can be regarded as sufficiently indicative. R‐Factors and annual respective summer precipitation amounts for the Alsace region compare well with values for the directly bordering Baden‐Württemberg. Therefore the two datasets were combined into two new equations of the form Y = 0.098 × RY (Y = R‐Factor [N/h], RY = annual precipitation [mm]). Y = 0.223 × RS (Y = R‐Factor [N/h], RS = summer precipitation [mm]) These preliminary equations allow to estimate R‐Factor values with higher precision than the two original datasets alone. Yet, a good database for their development is still lacking.