Erosional response of granular material in landscape models

Tectonics and erosion/sedimentation are the main processes responsible for shaping the earth surface. The link between these processes has strong influence on the evolution of landscapes. One of the tools we have for investigating coupled process models is analogue modeling. Here we contribute to the utility of this tool by presenting laboratory-scaled analogue models of erosion. We explore the erosional response of different materials to imposed boundary conditions, trying to find the composite material that best mimics the behaviour of the natural prototype. The models recreate conditions in which tectonic uplift is no longer active, but there is an imposed fixed slope. On this slope the erosion is triggered by precipitation and gravity, with the formation of channels in valleys and diffusion on hillslope that are function of the analogue material. Using Digital Elevation Models (DEMs) and laser-scan correlation technique, we show model evolution and measure sediment discharge rates. We propose three main components of our analogue material (silica powder, glass microbeads and PVC powder) and we investigate how different proportions of these components affect the model evolution and the development of landscapes. We find that silica powder is the main responsible for creating a realistic landscape in laboratory. Furthermore, we find that varying the concentration of silica powder between 40 wt.% and 50 wt.% (with glass microbeads and PVC powder in the range 35-40 wt.% and 15-20 wt.%, respectively) results in metrics and morphologies that are comparable with those from natural prototypes.