Erosional response of granular material in landscape models

Tectonics and erosion-sedimentation are the main processes responsible for shaping the Earth's surface. The link between these processes has a strong influence on the evolution of landscapes. One of the tools we have for investigating coupled process models is analog modeling. Here we contribute to the utility of this tool by presenting laboratory-scaled analog 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 behavior 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 The models recreate conditions in which tectonic uplift is no longer active, but there is an imposed fixed slope.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 functions of the analog material. Using digital elevation models (DEMs) and a laser scan correlation technique, we show model evolution and measure sediment discharge rates. We propose three main components of our analog material (silica powder, glass microbeads and PVC powder; PVC: polyvinyl chloride), and we investigate how different proportions of these components affect the model evolution and the development of landscapes. We find that silica powder is mainly responsible for creating a realistic landscape in the 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 wt %-40 wt % and 15 wt %-20 wt %, respectively) results in metrics and morphologies that are comparable with those from natural prototypes.