Abstract: Field observation and theoretical analysis of wind velocity on windward slope of a isolated barchan dune indicated that velocity profile is non logarithmic; shear velocity and sand transport increase from foot of slope to the top as a whole though change correspondently with increase or decrease of the slope gradient. Changes of sand transport along windward slope lead to the variation of the intensity of erosion and deposition, to say concretly, erosion is more intense than deposition where slope gradient increases and deposition is greater than erosion at other locations. On the whole slope sand transport and net erosin is the greatest at the crest. Morphologically, net erosion at the foot and the crest results in forward movement of the dune, locations of erosion where slope degree increases and locations of deposition where slope gradient decreases will gradually become concave and convex respectively which inversely have a strong influence on surface flow. Therefore, correlationship among shear velocity, sand transport, intensity of erosion and morphology of windward slope plays a very important role in the evolution of barchan dune. Grain size analysis also indicates that grain size characteristics are mainly influenced by intensity of erosion or deposition and morphology of windward slope.

Key words: barchan dune, shear velocity, sand transport, intensity of erosion, slope morphology