Abstract
The aspect of avalanche injury of forest trees is similar to that of wind damage. Regarding the avalanche as a kind of fluid composed of snow-air mixture, the force of avalanche exerting on a standing tree is computed by the same way as the case of wind pressure. From the view-point of forest damage, surface avalanches keeping the velocities of 30 m/s and over or ground avalanches of 15 m/s and over are estimated to be equivalent to the stormwinds blowing at the velocities of over 40 m/s.
