The effect of unsteady winds on sediment transport on the stoss slope of atransverse dune, Silver Peak, NV, USA

Rapid (10 s) measurements of sediment transport and wind speed on the stoss slope of a transverse dune indicate that the majority of sand transported is associated with fluctuations in wind speed with a periodicity of 5-20 mi n duration. Increases in the sediment transport rate towards the dune crest are associated with a small degree of flow acceleration. The increase in w ind speed is sufficient, however, to greatly increase values of the intermi ttency index (gamma), so that the duration of saltation is extended in cres tal regions of the dune. The pattern of sediment transport on the stoss slo pe and, therefore, the locus of areas of erosion and deposition change with the regional wind speed. Erosion of the crest occurs during wind speed eve nts just above transport threshold, whereas periods of higher magnitude win ds result in deposition of sand upwind of the crest, thereby increasing dun e height. Although short-term temporal and spatial relations between sand t ransport and wind speed on the stoss slope are well understood, it is not c lear how these relations affect dune morphology over longer periods of time .