Hydraulic Resistance in Rock-Ramp Fish Passes for Various Shapes of Macroroughness

The objective of this study was to improve the design criteria of rock-ramp fish passes by better describing the physics of frictional phenomena such as the impact of the deformation of the free surface or the bed shear stress due to the presence of obstacles. Experiments on square-shaped obstacles were performed in a scale model. A new analysis of the old and current measurements allowed us to specify the calibration coefficient of the drag and bottom friction forces. For a given water depth, the flow rate accuracy was about 10% by using only three parameters per shape. Thus, a more precise comparison of the flows according to the shape of the obstacles could be carried out. This plays an important role for the specification of projects of equipment of river dams. The theoretical advantages of each shape were highlighted, such as the significant reduction of the maximum velocity for the configuration with square obstacles.