Collaborative Research: Incorporating hillslope transport into laboratory landscape experiments

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Hilly and mountainous terrain has a remarkable tendency to organize itself into repeating ridges and valleys. The spacing of these landform sequences, which sets the density of drainage networks and the height of mountains, depends on the competition between advective sediment transport in channels and diffusive sediment transport on hillslopes. Despite promising results from numerical models, it is unclear how climate and tectonics modulates the relative effectiveness of hillslope and channel processes in determining landscape dissection. To test controls on these fundamental landscape properties, this research will incorporate diffusive hillslope transport into an existing laboratory model for actively eroding landscapes. Our physical experiments will generate reproducible hillslope transport via sediment incorporation in needle ice on the landscape surface while channels will evolve through precipitation from sprinklers. Because the experiments will be able to isolate and manipulate rates of hillslope and channel processes, we will document landform development under a wide range of climatic and tectonic scenarios. Furthermore, as the first physical experiment to explicitly incorporate hillslope processes, this research will track the dynamics of landform adjustment, such as ridge migration and drainage capture, in a system with relevance to much of the Earth?s surface.Previous numerical and experimental studies of climate controls on landscape evolution generally focus on how precipitation drives channel discharge and valley incision. However, climate also modulates sediment production and transport on hillslopes through changes in periglacial processes and vegetation, profoundly affecting the topographic organization of landscapes. Results from our experimental landscape will inform efforts to decode past climate signals in topography as well as predict the effect of future climate change on landscape evolution. Physical experiments are a powerful tool for outreach and science recruitment because of their ability to reduce complex, million-year-scale processes in a real-time and highly accessible fashion. The funds will also provide for the construction of an experimental landscape apparatus designed explicitly for teaching and outreach. In addition to supporting the education of a PhD student, this grant includes research experience for students from local community colleges and provides for the development of a landscape evolution seminar for undergraduates.