Author(s): Jessica Klein; Mario Oertel
Keywords: Fish pass; Crossbar block ramp; Vertical slot pass; Numerical simulation
Abstract: Due to the European Water Framework Directive (EU-WFD, 2000) all water bodies have to be restored into“good”ecological conditions. To fulfil these requirements in order to hydro-morphological conditions the river’s patency may not be interrupted and may allow aquatic organisms to pass the river upstream. Therefore, technical fish passes are built to overcome large river bottom differences, which allow fish to migrate freely. Fish passes can be constructed in various ways. To overcome the height difference a number of stepped pools separated by walls are built, whereby the construction of the walls can vary. As a nature-like solution (rough channel) so called crossbar block ramps with small, shifted openings for the water discharge and fish passing can be constructed. Vertical slot passes represent a technical fish pass solution. Both variations can be found in practical applications. The present paper analyses two types of fish passes as a practical solution between the rivers Wakenitz and Trave in Lübeck, Germany, via numerical 3D CFD simulation. Both, Wakenitz and Trave, are anthropogenic modified since more than one century. Currently, the flow from Wakenitz to Trave conducts through a culvert system and patency is not given. Hence, a solution is necessary to guarantee a fish climb capability. Therefore, a 3D numerical CFD model of a crossbar block ramp and a vertical slot pass will be compared to analyse hydraulic boundary conditions and the possibilities for fish to pass. Indicators like water depths, flow velocities and flow structures are in the focus of interest.