Energy dissipation in presence of block ramps with enlarged stilling basin

The hydraulic jump downstream of river training structures, such as check dams, spillways or block ramps, causes high energy dissipation. Inside the stilling basin a scour process generally takes place. If opportunely controlled, the threedimensional scour hole which occurs in the enlarged basin can be considered as a natural pool representing an eco-friendly solution to sustain both biodiversity and assure fish passages. The paper aims to evaluate the effect of each hydraulic and geometric parameter on the energy dissipation which occurs in an enlarged basin downstream of a block ramp in presence of a mobile bed. The experimental investigations were conducted in different flow and geometric conditions. Different ramp slopes, channel enlargements and channel bed materials were tested. The energy dissipation process was analyzed and compared with the case of fixed stilling basin bed. The results show considerable differences between the two bed configurations in terms of energy dissipation.