Fig. 3. Observed threshold shear velocity u_*tw data vs. gravimetric water content w data for dune sand with particle-size range of (a) 100 to 200, (b) 50 to 500, (c) 200 to 500 µm, and (d) sand loam soil aggregates with particle-size range of 100 to 200 µm, (e) 200 to 300, and (f) 300 to 500 µm. Also plotted is Eq. [1] with A from Eq. [2] and A₃ = 3 x 10¹⁴ N^–1 m^–1. The oven-dry data are from Cornelis and Gabriels (2004).