Larinier-brush fishway: Passage for multiple fish specie

Inthis study, Larinier bottom baffle and brush fishways were arranged in par allel to provide different migration corridors for multiple fish species. The flow characteristics of a Larinier-brush composite fish pass were investigated experimentally in a 2 m wide rect angular flume which has a bed slope of 4% for discharges ranging between 0.3-0.55 m3/s. The water surface elevation was measured by an ultrasonic displacement meter which was mounted above the flow and scanned downward the flow free-surface. An acoustic Doppler velocimeter was used to measure the three-dimensional instantaneous velocity fields for a flow rate of 0.4 m3/s. In all experiments, quasi-uniform flow conditions were observed. The hydraulic test results reveal that the Larinier-brush fish pass fulfills the requirements of an efficient fish passage by providing different velocity corridors and horizontal momentum exchange for several fish species. The flow characteristics start with an intensely turbulent flow above the baffles and change continuously to a less turbulent flow pattern in the brush part. In the baffle part, the flow field is characterized by symmetrical macro-scale vortices with a streamwise axis. The flow velocity has higher values in the centre of the baffle unit and the velocity decelerated between the baffles. On the other hand, the brush part with a gravel bed and low-velocity zone suggests hydrodynamically favorable conditions for small-bodied fish and macroinvertebrates. Also, the flow fields were compared between Larinier-brush and vertical slot-brush fishways for the same discharge. Moreover, the details of a pilot fishway project with a bed slope of 5% in Sandford on the River Thames in the UK is given.