Kimberly Hill’s research focus is on the behavior of particle and particle-fluid flows, including environmental applications such as sediment transport, associated stream restoration issues, and debris flow with its related hazards.  Her group uses a combination of carefully controlled physical experiments and computational models to develop a physics-based understanding of a wide range of phenomenology where both interparticle interactions and fluid-particle interactions play important roles in the system dynamics.  Hill’s group collaborates with scientists who have expertise in earth-surface processes, fish habitats, and ecological systems to fully explore the interdependence of the behavior of particle-fluid systems and their fully interactive surrounding landscape and ecosystem.

Current specific research projects fall under four categories.  First, the group investigates particle-scale and system-scale dynamics that lead to dramatic examples of pattern formation associated with spontaneous sorting or segregation.  Examples in nature include gravel patches in stream beds and fingering in pyroclastic and debris flows.  Next, the group also investigates how the transport of particles and other properties of a particle mixture are influenced by the local and global particle size distribution.  Examples in streambeds include the destabilizing effects of fines over a gravel bed.  Hill’s group also studies the nature of fluid-particle interactions and how they influence particle transport.  In gravel-bed rivers, they are interested in turbulence statistics under steady and unsteady conditions and the specifics as to how they influence bedload transport. In debris flows, they are interested in the mechanics of buoyancy effects, lubrication, and viscous drag and how they influence system flow behaviors and bedrock erosion for predicting landscape evolution and associated hazards.  Finally, the group investigates the manner in which biota affect sediment transport and how the nature of sediment transport affects certain aspects of fish and wildlife habitat, including the influence of plants on sediment transport and bed evolution and certain details on how fine infiltration affects fish habitat.