Soil erosion models are essential tools for the successful implementation of effective and adapted soil conservation measures on agricultural land. Therefore, models are needed that predict sediment delivery and quality, give a good spatial representation of erosion and deposition and allow us to account for various soil conservation measures.Here, we evaluate how well a modified version of the spatially distributed multi-class sediment transport model (MCST) simulates the effectiveness of control measures for different event sizes. We use 8 year runoff and sediment delivery data from two small agricultural watersheds (0·7 and 3·7 ha) under optimized soil conservation. The modified MCST model successfully simulates surface runoff and sediment delivery from both watersheds; one of which was dominated by sheet and the other was partly affected by rill erosion. Moreover, first results of modelling enrichment of clay in sediment delivery are promising, showing the potential of MCST to model sediment enrichment and nutrient transport.In general, our results and those of an earlier modelling exercise in the Belgian Loess Belt indicate the potential of the MCST model to evaluate soil erosion and deposition under different agricultural land uses. As the model explicitly takes into account the dominant effects of soil-conservation agriculture, it should be successfully applicable for soil-conservation planning/evaluation in other environments.In order to improve the reliability, generality and accuracy of erosion prediction, more physical process-based erosion models have been developed within the last decades. The more recent ones are: the Water Erosion Prediction Project (WEPP, Flanagan and Nearing, 1995), the European Soil Erosion Model (EUROSEM, Morgan et al., 1998), the Kinematic Runoff and Erosion Model (KINEROS2, Smith et al., 1995) and the Limburg Soil Erosion Model (LISEM, De Roo et al., 1996a, 1996b. Due to the complexity and the spatial and temporal variation of erosion processes a large number of parameters have been integrated in these models. Hence, much attention was paid to the acquisition of input data (Jetten et al., 1996). Nevertheless, these models do not necessarily perform better than the lumped, empirical based models, mainly because input errors increase with model complexity (Jetten et al., 2003) and because of uncertainties in model structure and process representation (Parsons et al., 2004).In this context, reduced complexity modelling has received increasing attention during the past few years. This tendency can be found generally in the environmental sciences and is basically due to the fact that it is now realized that better predictions might be obtained using simpler model structures with a reduced parameter space rather than very complex model systems for which the necessary parameter values and input data are impossible to obtain (see, e.g., Brazier et al., 2000Brazier et al., , 2001. Examples of such models are the Sealing Transfer Runoff Erosion Agricultural Modification model (STREAM,...