Hydraulic modeling of nature-oriented fishways and fluvial structures

Great efforts are currently being made to fulfill the requirements of the EU Water Framework Directive concerning the restoration of aquatic fauna passages in rivers. In Germany, fishways of a nature-oriented design are increasingly built. The hydraulic patterns of such fishways must be analyzed to ensure they fulfil the required ecological criteria. Therefore, high-resolution 2D and 3D numerical simulations of nature-oriented fishways were performed within the framework of a research project at the Karlsruhe Institute of Technology (KIT). The construction of the model geometry has proved to be a major challenge. Terrestrial Laser Scanning (TLS) was applied for geodata acquisition. This technique enables collection of data from very complex topographical structures. Research activities at the KIT dealt with the post processing of detailed TLS data and their application as a basis for high-resolution hydraulic modeling. Hydraulic simulations were performed for two case-scenarios: A nature-oriented slide and a rock cascade pass. Simulation results were interpreted with regard to ecological questions. A new classification scheme of 3D flow patterns was developed, which served as a basis for ethohydraulic assessment.