Technical Abstract: Friction velocity and aerodynamic roughness are characteristics of the soil-plant-atmosphere interface which affect wind erosion. Although exchange of momentum at the interface can be altered by land management practices, no attempts have been made to quantify the effect of tillage on friction velocity and aerodynamic roughness within the Columbia Plateau region of the Pacific Northwest United States. Wind velocity profiles above adjacent field plots (>2 ha) subject to conventional or undercutter tillage during the summer fallow phase of a winter wheat – summer fallow rotation were measured to determine friction velocity and aerodynamic roughness of tillage treatments during high wind events in 2005 and 2006. Wheat stubble plots were either disked (conventional) or undercut with wide sweeps (undercutter) in spring and then periodically rodweeded prior to sowing winter wheat in late summer. Friction velocity ranged from 0.31 to 0.56 m/s for conventional tillage and from 0.33 to 0.58 m/s for undercutter tillage while aerodynamic roughness ranged from 0.001 to 0.012 m for conventional tillage and from 0.001 to 0.021 m for undercutter tillage across 50 high wind events observed over two years. Friction velocity and aerodynamic roughness during high wind events were respectively 10 and 75% greater for undercutter tillage than for conventional tillage. Vertical dust flux estimated from friction velocity and threshold friction velocity for high wind events prior to sowing was null for undercutter tillage and was 0.5 and 4.5 µg/m2/s for conventional tillage in subsequent years. Undercutter tillage, therefore, appears to be an effective management practice to roughen the surface and suppress dust emissions from agricultural land subject to summer fallow within the Columbia Plateau.