Aeolian sand transport: Video analysis of streamer structure and dynamics

Abstract:

Aeolian sand transport moves downwind in semi-organized, elongated zones of particle concentrations that merge and bifurcate over space and time, often referred to as streamers or sand snakes. The spatio-temporal variability of streamers cause marked fluctuations in transport fluxes spatially, and are thought to be related to the interaction of large eddies from the upper boundary layer with the sediment surface. However, the nature of streamer interaction remains poorly understood. Here, we extend previous video processing techniques to quantify streamer structure and dynamics. We use video data collected during intense steady-state transport observed in the intertidal zone on a wet, dissipative beach 4 miles north of Corolla, North Carolina during the passage of Tropical Storm Nestor. We introduce an extended wavelet analysis to characterize the distribution of streamer length scales and how they evolve over time. This technique is used to measure the widths of both primary streamers as well as nested streamers that are often found to co-occur within primary streamers. The steady-state distribution of streamer widths for a given set of transport conditions is then related to metrics for streamer interaction using a population balance model that incorporates information about streamer collisions/merger events, streamer breakup, and streamer growth and decay rates. We show that this approach is a promising avenue to link streamer evolution through time to streamer morphology.