Title: Connecting granular dynamics to landscape patterns

Author (Invited): Douglas Jerolmack, University of Pennsylvania

Abstract:

The landscape on which we live is principally granular, and has been shaped over eons by transport of sediment by water and wind. Sand ripples, desert dunes, barrier islands, river channels and deltas are patterns that have evolved through complex feedbacks among fluid flow, sediment transport and erosion and deposition. Predicting the dynamics of the sediment-fluid interface is difficult because these problems involve both turbulent fluid flows and heterogeneous sediment - and the boundary conditions are often unknown. Traditionally, research in these problems has focused on fluid dynamics; however, many aspects of environmental sediment transport appear - at least qualitatively - to be similar to dry granular flows. Here I discuss recent progress in landscape problems at several scales, highlighting the importance of granularity: anomalous diffusion of pebbles moving in a stream; coarsening dynamics in the growth of river dunes, and channel network formation on river deltas. I will show how laboratory experiments and simplified analytical models, that neglect many of the complications of natural systems, nonetheless quantitatively capture the evolution of "natural" landscape patterns. I will highlight the importance of stick-slip dynamics, hysteresis, disorder, and aging/memory; and will outline opportunities for advancing our understanding of geophysical transport by incorporating insights from granular physics