Energy Dissipation on Block Ramps

Block ramps are structures often used in river restoration projects. They generally ensure a stable streambed and produce high energy dissipation. This paper shows the results of an experimental investigation conducted at the Hydraulic Laboratory of the Univ. of Pisa, Pisa, Italy on ramps of different slopes characterized by different bed materials. Experiments have been carried out in three different rectangular channels, where block ramps with a slope varying between 1V:4H and 1V:12H have been tested. The results have been compared with the ones obtained for a smooth ramp, which can be considered as a limit case in which the diameter of the bed material tends to zero. The amount of energy loss of such structures is essentially a function of the relative submergence, the slope, and the ratio between the critical water depth and the length of the ramp. Viscous effects and air entertainment can be considered negligible in the experimental range. Tests were carried out to find the case of nonsubmerged ramp conditions.