Scour downstream of eco-friendly in-stream structures

Eco-friendly in-stream grade-control structures [i.e. Cross-Vane, J-Hook vane, W-weir, Log vane, Block Ramps, etc.] represent a valid system both to control bed sediment transport and to create suitable habitat for fish species. They have the advantage to minimize their impact and at the same time they do not require frequent human intervention, such as dredging. Nevertheless, the free surface flow causes scour hole and dune downstream of them, contributing to change river morphology. In technical literature, there are several criteria to design them, but they are not complete and require a further development. Thus, this thesis aims to experimentally analyze the erosive process downstream of Cross-Vane, J-Hook vane and W-weir, in order to highlight the parameters affecting the phenomenon and furnish tools for a correct design. In particular, scour morphology and dunes formations have been investigated. Experimental data were analyzed and empirical relationships were derived to predict the main lengths of the scour hole and dune. The proposed equations can be useful for practical applications.