On the use of lightweight materials in small-scale mobile bed physical models

In this paper an evaluation of the morphodynamic response of different relatively common lightweight materials in small-scale physical models is presented. Results must serve to provide an overview of the various aspects likely to sensibly influence on sediments morphological response in small-scale tests and to determine the possible suitability of the low-density particles investigated for coastal modelling. Different granular materials, covering densities between 1150 kg/m3 and 2650 kg/m3 and median diameters from 0.07 mm to 1.5 mm have been selected to reproduce the experiments carried out in 1987 in the Groβen Wellen Kanal (Hannover, Germany). Tests have been performed at the Technical University of Bari (Bari, Italy) at scale 1:100 and at the Technical University of Catalonia (Barcelona, Spain) at scales ranging from 1:15 to 1:50, using irregular wave conditions and geometries based on Froude scaling. An analysis of the erosion and deposition volumes, the shoreline evolution and the beach profile slope has been done. Results show different mobility rates and beach profile morphodynamics depending on particles intrinsic characteristics, demonstrating that for lightweight materials not only settling velocity is paramount to determine particles suitability and morphodynamic response. Finally, a comparison between the morphological evolutions of the models and the prototype moving along the beach profile cross-section is presented.