The characteristics about aeolian ripple migration and shear velocity on the sand surface

Authors: Pei Zhang*, , Douglas Sherman, The University of Alabama, Bailiang Li, Xi'an Jiaotong-Liverpool University, Jean Ellis, University of South Carolina, Eugene Farrell, National University of Ireland Galway
Topics: Coastal and Marine, Coastal and Marine
Keywords: ripple migration rate, shear velocity, sediment transport
Session Type: Paper
Day: 4/6/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Stones Throw 1 - Granite, Marriott, Lobby Level
Presentation File: No File Uploaded

Aeolian sediment transport is one of the most important dynamic landscape processes shaping the surfaces of Earth and extraterrestrial bodies. The development and migration of ripples is a first-order response to wind and represent a basic interaction between saltation and wind systems. This paper concerns the characteristics of ripple wavelength, height, migration rate, and the sediment transport represented by the bedform movement. Despite their fundamental importance, the behavior of aeolian ripples in natural environments remains seldom studied and poorly understood. Here, we present field data to assess ripple response to changing shear velocity.
This field work was executed in October 2008, near the village of Jericoacoara, Brazil. We measured ripple migration rate and wavelength (using two pins and two cameras); ripple height (manually measured); wind speeds to derive shear velocity estimates (using ultrasonic anemometers); sand transport rate (using mesh traps); and obtained sand samples for grain size analysis. We tested ten different time intervals to characterize an optimal ripple relaxation period. The results indicated that eight minutes interval provided the best interval for establishing a statistical relationship between ripple behaviors and shear velocity. Based on the optimal time interval, the adjustment of ripple wavelength did not show a clear association with shear velocity. The height of equilibrium ripples also varied minimally. The regression analysis showed that shear velocity explains, statistically, 43% of the variability in ripple migration rates. Sand transported by ripple migration represented about 5.2% of the total sediment transport.

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