The effect of unsteady winds on sediment transport on the stoss slope of a transverse 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 min duration. Increases in the sediment transport rate towards the dune crest are associated with a small degree of flow acceleration. The increase in wind speed is sufficient, however, to greatly increase values of the intermittency index (gamma), so that the duration of saltation is extended in crestal regions of the dune. The pattern of sediment transport on the stoss slope and, therefore, the locus of areas of erosion and deposition change with the regional wind speed. Erosion of the crest occurs during wind speed events just above transport threshold, whereas periods of higher magnitude winds result in deposition of sand upwind of the crest, thereby increasing dune height. Although short-term temporal and spatial relations between sand transport and wind speed on the stoss slope are well understood, it is not clear how these relations affect dune morphology over longer periods of time.