Entrainment of fine sand particles from rough surfaces at high wind speeds
Wind tunnel experiments were conducted to characterize the effects of immobile surface roughness elements 
on entrainment of loose soil at wind speeds up to 113 m/s. Soil beds consisting of a dry loose desert soil (50% finer-byweight 
diameter, 
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50 180 ¥im) were laid out on the tunneli¯s 7.32-m long floor (0.457-m width) and measurements of 
velocity profiles (dusty gas pressure probe) and time-dependent soil loss (vertical slot collector) were obtained. Four types 
of non-erodible simulated surface roughness were tested including ridges, clods, stubble and random gravel aggregate 
(natural mountain pebble; 
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50 42 mm). Roughness heights were varied up to 50.8 mm in elevation. Measured soil 
losses were always less than flat, dry, loose results and decreased with rough surface elevation consistent with low-speed 
data. For ordered roughness textures (ridges/clods/stubble), ridges were found to be the most effective in reducing soil 
loss and clods the least. Ridge soil loss data scale favorably with ridge elevation as normalized by ridge separation. The 
normalized elevation for the onset of minimum soil-loss-rate for the ridge data (10% of flat soil value) was approximately 
0.12. As exposure time for the gravel-seeded soil beds increased, soil loss was progressively reduced illustrating the 
effects of surface armoring (i.e., shielding of fines by non-erodible elements). Correlation of this decay process with 
scaled time based on free stream velocity to the 3/2i¯s power was favorable.