The effect of a hedge on the flow of air

Experiments are described in which the horizontal wind speed at three heights up to 2 m is measured at various distances up and down wind from a dense hedge 1·68 m high on occasions with wind directions approximately normal to the hedge. The results show that the hedge begins to exert an influence on the wind speed at 2 m at a distance equivalent to approximately 15 hedge heights upwind, and that downwind its influence extends to a distance approximately equivalent to 60 hedge heights. At the two lower heights of wind‐speed measurement the range over which the hedge has an effect is smaller. Diagrams are constructed to show the decrease in wind speed at the various heights within the distance range mentioned above.