Sediment transport by dry ravel

[1] Dry ravel is a general term that describes the rolling, bouncing, and sliding of individual particles down a slope and is a dominant hillslope sediment transport process in steep arid and semiarid landscapes. During fires, particles can be mobilized by the collapse of sediment wedges that have accumulated behind vegetation. On a daily basis, particles may be mobilized by bioturbation and by small landslides. Experiments on a dry ravel flume indicate that a basic expression of the momentum equation predicts the distance traveled by particles propelled down a rough surface. This equation is further elaborated to produce a nonlinear slope-dependent transport equation for dry ravel that represents the rate at which sediment crosses a contour width of slope. Sediment traps installed on two hillslope transects near Santa Barbara, California, measured the flux from dry ravel initiated by bioturbation, and the data support the form of the equation. Additionally, a physical model, based on the infinite slope stability analysis, is proposed for the initiation of dry ravel by landsliding. The analytical result from this model is supported by experiments and field data reported by others.