Aeolian transport over a wet, sandy beach

Authors: Christy Swann*, Naval Research Laboratory, Dylan Lee, National Academy of Sciences, Sarah Trimble, National Academy of Sciences, Charles Key, Naval Research Laboratory
Topics: Coastal and Marine, Geomorphology, Physical Geography
Keywords: coastal, geomorphology, aeolian, sediment transport, wind
Session Type: Virtual Paper
Day: 4/9/2021
Start / End Time: 8:00 AM / 9:15 AM
Room: Virtual 45
Presentation File: Download



Quantifying aeolian transport within the intertidal zone is critical to understanding feedbacks between aeolian and nearshore processes in coastal environments. Here, we report a field study of saturated transport over a wet bed in the intertidal zone. Alignment of predominate winds and beach orientation provided a nearly unlimited fetch. Mean grain size of bed samples were 0.18 mm and moisture content ranged from 16 to 17%. Velocity profiles were measured with a vertical array of 5 cup anemometers deployed between 7 and 93 cm above the bed. Sustained wind velocities were 9.5 m/s at 93 cm above the bed with gusts reaching 13.5 m/s. Five saltation traps captured particles in transport from the bed to a height of 15 cm. Here, we observe transport below the fluid threshold for motion. Observed fluxes are in good agreement with models using field-calibrated coefficients. However, vertical flux profiles show a higher concentration of flux closer to the bed (81 to 89% below 5 cm) than those measured over dry beds. Power and exponential decay functions were fit to 3 dry bed, flux profile datasets and our wet bed dataset. Over a wet bed, the exponential decay function best fit flux profiles with larger coefficients and smaller
estimates than those fit to dry bed profiles. Our results suggest transport mechanics over wet beds are fundamentally different from those over dry beds. However, more research is needed to discern the mechanics driving deviations in flux profiles over wet beds in field environments.

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