A comparison of measured catchment sediment yields with measured and predicted hillslope erosion rates in Europe

This study aims to understand better the relationship between measured soil loss rates due to sheet and rill erosion (SL), predicted SL rates and measured catchment sediment yields (SY) in Europe. Analyses were based on a recently established database of measured annual SY for 1794 catchments, a database of 777 annual SL rates measured on runoff plots and two recent maps of predicted sheet and rill erosion rates in Europe (i.e. one based on empirical extrapolations of measured SL data and one based on the PESERA model). To identify regional trends, all data were grouped into eight climatic zones. Measured SL rates are generally a factor of five to ten times larger than predicted SL rates and are strongly biased towards erosion-prone situations in terms of land use. Also measured SY are generally higher than predicted SL rates, especially in the Mediterranean and Alpine regions where SY is generally ten times higher than predicted SL rates. This illustrates the importance of other erosion processes contributing to SY. Regional differences in the importance of these processes and their implications are discussed. This study confirms previous findings indicating the relatively low sheet and rill erosion rates compared to SY in the Mediterranean region and illustrates the importance of other erosion processes contributing to SY in most regions of Europe. This indicates that hillslope erosion rates cannot be used directly to estimate SY, and consequently soil conservation programmes should focus more on the dominant erosion processes in each catchment.