Session B6: Hydraulic Research on Fish Passage Design at Lock & Weir Sites

Abstract: Both European and Belgian legislations aim at restoring and enhancing the ecological strength of the water systems. Besides improvement of water quality and protection through legislation, restoration of free fish migration on the rivers and main waterways. To solve the problem of the disruption of longitudinal habitat connectivity by manmade obstacles such as locks and weirs, fish passages are constructed. In close cooperation with the Institute for Nature and Forest Research (INBO) of the Flemish Government (hydraulic) research on fish passage design at weir-lock sites on Flemish rivers has been done since 1995 at Flanders Hydraulic Research (FHR). The research is done via scale model tests, field measurements and literature study. To determine the effectivity of a fish passage both passability and attractiveness are assessed. The passability requires limitations to the maximum velocity and minimal depth along the fish passage. The attractiveness is defined as the extent to which fish can find the entrance of the fish passage. To obtain maximum attractiveness an attraction flow at the passage entrance is applied. The presentation gives an overview of the FHR research. Regarding the passability current results and research questions relating both nature like fish passages as bypass channels and more technical solutions as V-shaped fish ladders and vertical slot passages are addressed. Also previous research on swimming and leaping capacities that has been done with living fish is presented. In recent years several scale model tests have been done regarding the attractiveness of fish passages downstream of weirs applying a perpendicular attraction flow. Current research focusses on the comparison of perpendicular with parallel attraction flows and on sharp bends in Vshaped fish ladders