Secondary forest use practices such as removal of the forest floor for the purpose of bedding in stables (litter raking, lopping), and forest grazing not only interfered with the nutrient balance of the forest, but also influenced their rainfall-runoff reaction, possibly until today. To quantify this hydrological impact, within the HILUC (Hydrological Impact of Historical Land Use and Climate) project a hydrological modelling approach is used to reconstruct surface runoff patterns in small Alpine catchments in the time periods around1850, 1960 and 2020. Therefore, an expert-system is developed, based on the ‘Code of Practice for the Assessment of Surface Runoff Coefficients’ of Markart et al. (2004, 2011), data from the BFW rain-simulation experiment database, especially of experiments at about 100 forest sites in the Eastern Alps, data from literature and expert assessments in the field. With regard to historical land use, ‘translation keys’ have been developed for the textual description of land use practices. Land use data for the period around 1850 has been stored in archives in the form of forest descriptions and corresponding maps. The period around 1960 is characterised by the first availability of aerial photographs and local inventory data. The current situation of land use and the corresponding surface runoff disposition is essential as a basis for reconstructing the past, which is why a detailed mapping of the catchment areas in terms of relief, soil and vegetation was carried out in the field using PSINOT, the comprehensive surface runoff coefficient map for North Tyrol, as a reference. The resulting surface runoff coefficient maps taking into account the historical land use for the respective time steps are used as input parameters for rainfall-runoff modelling with the conceptual model ZEMOKOST in order to quantify the impact of the historical land use practices.