G. Oliveto - DIFA, Università della Basilicata, Potenza, Italy
A. Rossi - DIFA, Università della Basilicata, Potenza, Italy
W.H. Hager - VAW, ETH-Zentrum, Zurich, Switzerland

This paper aims at analysing the local scour processes at piers founded on piles. Experiments were conducted at DIFA in two rectangular channels. All tests were run under steady flow conditions and clear-water scour regime. Several scenarios involving different distances from the initial bed level to the top of the pier footing were analysed. Based on the experimental data collected, the effects of the foundation on the temporal scour evolution are highlighted. All the results are given in terms of equivalent pier or pile diameters, as synthetic parameters of the whole geometry of the composite pier structure. Thus, a straightforward design procedure is provided. A previously established scour equation for the temporal progress of scour at uniformly shaped piers was assumed as framework for this analysis.