VMM (Flanders Environment Agency) Leuven Division installs triangular Bolina float at new river Dijle fish pass
In 2019, in the heart of Leuven city centre on the fourth Dijle branch, very close to the Stella Artois brewery, a new fish pass was put in place to make the existing shutter weir passable for migrating fish species.
The river Dijle passes through Leuven and breaks down into several anabranches in the city centre, which rejoin the main stem outside the city. These various anabranches are constantly littered with floating debris. In order to prevent the fish pass from being saturated with plastics and other floating litter, the inlet was fitted with a purpose-designed triangular floating construction.
The inlet of the fish pass is located in the left retaining wall just a few metres from the shutter weir and again at the top of the water surface with a depth of just 80 cm. A floating boom up against the retaining wall was not an option, as this would restrict the inflow for the fish. A boom placed entirely diagonally from bank to bank in turn proved impossible as this did not leave any way for the floating debris to be disposed of.
The only option was to custom-build a bespoke triangular floating debris construction based on our small PDB400 floats. This floating debris construction hangs up against the wall on 2 guidance piles, to the effect that the entire construction consistently follows the changing water level. As such, the V-shaped boom is seen to sink to its lowest point when the shutter weir is brought down in full once a day to flush the fourth Dijle branch, before it rises up again by itself when the water level rises back up after this flushing operation.