CGRG Bibliography of Canadian Geomorphology
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Author : Davidson-Arnott, R.G.D.; Bauer, B.O.; and Walker, I.J.
Date : 2008.
Title : Instantaneous aeolian sediment transport rate on beaches: measurement, prediction, and influence of surface moisture.
Publication : Joint Annual Meeting of the Canadian Geophysical Union and the Canadian Geomorphology Research Group. May 11-14, Banff, Alberta.
Issue :
Page(s) :
Abstract
While high frequency (~1Hz) measurements of aeolian sediment transport have been made using a variety of laser devices in wind tunnel research for over 30 years it is only in the last 15 years that measurements at this frequency have been made in the field and the number of published studies is small. Measurements have been made with a variety of instruments ranging from sensors that measure the impact of saltating grains on sensitive microphones and on piezo-electric crystals, or balance traps which continuously weigh sediment tapped by a vertical or horizontal trap. None of these instruments provides a reliable estimate of instantaneous sand transport and no single instrument has emerged as a "standard". Published studies show that aeolian transport on beaches is typically intermittent, especially where the beach surface is moist, and transport rates respond rapidly to fluctuating wind speeds (gustiness). While wind tunnel studies suggest an upper limit of about 2% gravimetric moisture content for entrainment of sand, field studies show transport with surface moisture of 5% or greater. Stout (1997) proposed the Time Fraction Equivalence method to define the threshold wind speed for conditions of intermittent transport in the field but it has been shown that there are a number of problems with this approach, most notably the dependence on the sensitivity of the instrument used to detect sand transport. Evaluation of instantaneous sand transport rates against some measure of horizontal wind speed from co-located sensors typically produces correlations that are either not significant or have very low R2 values. This poor correspondence may be due in part to inadequacies of the sensors used to measure transport and to fundamental differences in the probability distribution functions of wind speed compared to sand transport rates as mean wind speed increases. Field tests of a new sensor which counts the number of particles breaking a laser beam suggest that this may provide an improvement over sensors that have been deployed in earlier studies.
Bibliography of Canadian Geomorphology