The processes of the action of wind and/or water on the soil surface as well as the processes of soil movement caused by wind and/or water are complex. In view of the great complexity of the phenomena involved in aerodynamics and hydraulics, they are not always described theoretically with sufficient accuracy, and the experimental approach is often more reliable. Processes of water erosion are often studied under rainfall simulation whereas wind erosion processes are investigated by means of wind tunnels. At the International Centre for Eremology (I.C.E.), Ghent University, Belgium, a wind tunnel is installed which not only enables to study wind and water erosion processes separately, but also to investigate the interaction and the combined effect of wind and water on soil movement. 1. Description of the I.C.E. wind tunnel The wind tunnel at the I.C.E. is a closed-circuit low-speed type made of sheet metal (see Fig. 1 and Plates 1 and 2). Air flow is generated by an axial fan, 1.5 m in diameter, with 16 adjustable blades (photo 1) driven by a 200 h.p. electric motor which is mounted in the fan nacelle. The wind speed is controlled by adjusting the pitch angle of the blades by means of a compressor. At the entrance of the working area, the minimum