Journal of Arid Environments Journal of Arid Environments 71 (2007) 216–228 Willy-willies in the Australian landscape: Sediment transport characteristics A.M.C. Oke à , D. Dunkerley, N.J. Tapper School of Geography and Environmental Science, Monash University, Clayton, P.O. Box 11A, Monash University, Clayton, Victoria 3800, Australia Received 26 May 2006; received in revised form 5 December 2006; accepted 14 March 2007 Available online 17 May 2007 Abstract Willy-willies (dust devils) are local convective circulations that characteristically arise in arid and semiarid environments. They are visually defined by their entrainment and transport of surface debris but little is known of their sediment transport role in the landscape. This study conducted in semiarid north-west New South Wales, Australia, provides quantitative information on the sediment entrainment and transport characteristics of willy-willies. The particles being transported in the lower 160 cm of 20 willy-willies were sampled using a tape-based vertical profile sampler developed as part of this study. The analysis of the samples, using a visual-based digital analysis method, revealed that almost 18% of the particles counted were being transported within 10 cm of the soil surface. It was also discovered that over 80% of the particles overall were 63 mm or smaller in major axis diameter. The results from this analysis, considered with respect to the characteristics of the surface the willy- willy traversed during sampling, show that the sediment load carried in the willy-willies increases with decreasing vegetation cover. This relationship with vegetation combined with the preferential entrainment of silt sized particles could, over time, make willy-willies a potent mechanism for the local differentiation of surface textures. r 2007 Elsevier Ltd. All rights reserved. Keywords: Australia; Dust devil; Fowlers Gap; Vortices; Willy-willy ARTICLE IN PRESS www.elsevier.com/locate/jaridenv 0140-1963/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2007.03.014 à Corresponding author. Tel.: +61 3 9905 2918; fax: +61 3 9905 2948. E-mail addresses: Alison@environmentaljobs.com.au (A.M.C. Oke), David.Dunkerley@arts.monash.edu.au (D. Dunkerley), Nigel.Tapper@arts.monash.edu.au (N.J. Tapper).