Simulation of Windbreaks for Wind-Erosion Control in a Wind Tunnel W.M. Cornelis, D. Gabriels and T. Lauwaerts Introduction A "windbreak" is defined as any structure that reduces wind speed (Rosenberg, 1974) and is commonly associated with a natural vegetative barrier against wind. A windbreak can be a single element or a system of elements that through its presence in the airflow reduces the effect of wind speed not only at the system itself but also at a certain windward and leeward distance. The term "windscreen" refers to any artificial barrier, be it synthetic or mechanical, obstructing wind flow. The term "wind barrier" or "fence" can be used to indicate both windbreaks and windscreens. Wind barriers can control wind erosion by reducing the travel distance of wind across a field. The wind speed can be reduced by more than 50% at a leeward distance of 20 times barrier height H (Skidmore, 1986). The efficiency of a windbreak can be evaluated in terms of the ratio between the mean wind speed of the air current as obstructed by a wind barrier and the mean wind speed of the undisturbed air at a given height and distance windward or leeward from the windbreak. The objectives of this wind-tunnel study were the simulation and scaling of vegetative windbreaks (stem + canopy) and to evaluate their efficiency in reducing wind speed. Five single-row windbreaks, each with a different stem porosity and canopy porosity were tested. Also windbreaks consisting of different elements (2 and 3 rows) were scaled. Possible zones of deflation and deposition were determined from wind-speed measurements and compared with experimental wind-tunnel data of sand transport. Materials and Methods All experiments were conducted in the wind tunnel of the International Centre for Eremology, University of Ghent, Belgium (Gabriels et al., 1997) (see Figure 1) at a free stream wind speed of 6.3 m⋅s -1 . Wind speed was measured with 16-mm vane probes, at heights of 2, 5, 10 and 15 cm above the tunnel surface, and at distances of 660, 680, 690, 695, 700, 705, 710, 720, 740, 760, 800, 850, 900, 950 and 1000 cm from the test section entrance.