A fish pass is planned for Doesburg (Netherlands). The fish pass comprises a solid construction chan-nel. Within this channel, the water is guided by partition walls whose geometry was previously analysed by means of CFD simulations.

Extreme water level fluctuations (between flood (+ 8.84 m NAP [Normal Amsterdam Water Level] and low water (+ 5.00 m NAP)) have to be taken into account for the fish pass design. For this reason, an outlet flap (with a vertical rotation axis) has been arranged in the upper part of the fish pass. The outlet flap is used to control the flow through the fish pass and hence water damming within the fish pass.

The partition walls were designed as welded steel structures (stainless steel) in the project. The partition walls consist of fixed and movable components. As regards the movable components, the bolted con-nections were designed so that the channel cross-section may be adjusted by shifting the steel partition walls (in the longitudinal and transverse direction). This adjustment was taken account for in the CFD simulation and implemented by the construction company on site. The partition walls were mounted on a steel structure that was backfilled with stone rubble. This significantly enhances the passage of small animals (crabs, mussels, water fleas, etc.) living on the bottom in comparison to a reinforced concrete wall that is continued to the riverbed.

Notes on the photographs: In the course of the construction activities, galvanised steel components were used instead of the originally designed stainless steel components.

Scope of design:
- Partition walls and outlet flap
- Preparation of design drawings
- Preparation and handover of a 3D model of the partition walls
- Structural analysis of partition walls welded stainless steel fish pass structures
- Evaluation of CFD simulations for load calculation
- Calculation pursuant to DIN19704-1 and EC3
- Preparation of documents in English