The distribution of the hydrodynamic efforts under solid horizontal or scoured bed downstream of a roller bucket spillway can be represented by two typical distributions: type A and B for pressure and type I and II for pressure fluctuation. However, the scoured bed presents a pressure distribution that is closer to the equilibrium pressure compared with that of the horizontal bed and a much lower pressure fluctuation distribution. This could be due to the bed scour in the vicinity of the bucket that carries an effective value for the height of the bucket lip, which decreases the suction effect, and the fact that the eroded shape of the bed corresponds with reduced pressure efforts, which translates into weaker turbulence and therefore a more stable flow. These results show the advantage of a scoured bed that could be more secure when the bucket lip height of the roller bucket spillway is well chosen.Key words: hydrodynamic efforts, pressure, pressure fluctuation, hydraulic energy dissipation, roller bucket.
