On the Sand Transport Rate by Wind on a Beach

Abstract

The sand transport rate due to wind action was investigated in the field and in the laboratory. For the field experiment, the sand volume blown off from a beach area enclosed by large traps in the form of trenches and the sand volume accumulated in one of the trenches were compared. It was concluded from this comparison that the empirical coefficient of the Kawamura formula for the sand transport rate averaged over a section normal to the shoreline should be approximately 2.3. In order to obtain data for wind conditions corresponding to high shear velocities, an experiment in a wind tunnel was carried out. This experiment showed that the Kawamura and Bagnold formulas were valid for well-sorted sand in the range of shear velocity between 60 to 300 cm/s. However, both formulas underestimated the transport rate for a sand widely distributed in grain diameter under high shear velocities. In order to predict the transport rate for the widely distributed sand, the Bagnold and Kawamura formulas were modified. A significant discrepancy was noted in the transport rate as determined in the laboratory and in the field. This difference is attributed to the fluctuations which are present in natural wind, but which do not appear in the typically steady wind generated in a wind tunnel.