Abstract: Thresholds of sediment motion are integral to bedload transport estimates, which inform calculations of aquatic habitat, reservoir sedimentation, channel form and stability, and landscape evolution. Despite often being assumed constant, the critical Shields stress (stress needed to cause sediment motion) can vary by an order of magnitude between different gravel-bedded streams and even within the same river over time. This noise in critical Shields stresses obscures the actual mechanics of grain motion, including the spatial and temporal variation of key processes and variables that affect particle mobility. Using a broad combination of laboratory experiments, field measurements, numerical modeling, and mechanistic theory, we quantify and predict the key controls on particle motion. We highlight the influence of flow turbulence and granular dynamics and the potential interactions between these processes in controlling particle transport. Our results demonstrate that much of the noise in critical Shields stresses can be explained by including these grain-scale mechanics in reach-scale estimates of sediment motion.
Biography: Elowyn Yager is a professor in the Department of Civil and Environmental Engineering and the Center for Ecohydraulics Research at the University of Idaho. Elowyn obtained her B.S. and Ph.D. in geology at SUNY Buffalo and the University of California at Berkeley, respectively. Elowyn’s research is focused on understanding the mechanics of geomorphic processes from the grain to the landscape scale including sediment and nutrient transport, post-fire hillslope erosion, bedrock erosion, and interactions between physical and ecological processes. She has received several awards for her research, teaching, and outreach, including a National Science Foundation Career award and a Fulbright Fellowship.
Lecture begins at 11 a.m. U.S. Eastern time (New York) and will be followed by a question and answer session. Registration is required prior to the free event.