Spatial organisation of catchments – assessment and usage for impartial sub-basin ascertainment and classification

Abstract. A hydrological model should represent the hydrological most relevant catchment characteristics. These are heterogeneously distributed within a watershed but often interrelated and subject of a certain spatial organisation. In order to reproduce the natural rainfall-runoff response the reduction of variance of catchment properties as well as the incorporation of the spatial organisation of the catchment is desirable. In this study the method of the characteristic structure is introduced to detect and visualize the spatial organisation of catchments, based on stream flow length rearrangement of any catchment feature of interest. Moreover, the method is implemented in an algorithm for automated sub-basin ascertainment, which includes the definition of zones within the newly defined sub-basins. The algorithm is applied on two parameters characterising topography and soil of four mid-European watersheds. Results indicate a wide range of applicability for the method and the algorithm. As a limitation of the application for the algorithm the presence of small scale soil enclosures that do not follow the geomorphologic structure of the catchment could be identified. Finally, results of subdivisions based on soil and topography were intersected to gain insight into catchment organisation. Based on this analysis four types of physiographical types could be established.