Scour protection downstream of block ramps

Block ramps or rock chutes are structures used in many river restoration projects. Generally, in such structures, a scour that must be controlled is present at the toe of the ramp. Aim of the paper is to analyse the scour that occurs downstream of the ramp and to indicate the protection works needed in order to avoid structural problems. Experimental tests have been carried out at the Hydraulic Lab. of the University of Pisa. Two different channels have been used for a total of about 300 tests. The ramp slope was varied between 1V:4H to 1V:12H while different materials have been used for both the ramp and the downstream base material. The protection has been realized by means of sills with different characteristics (i.e. continuous, permeable, or made by rocks). The advantages of a rock sill protection is evident in the sense of reducing the maximum scour depth.