Abstract
Trees are, though they are playing important roles for soil conservation, often triggering land-slides and mud avalanches, if they fall down due to strong winds. Relatively small number of research papers are available regarding with the magnitudes of wind forces acting on trees and wind hydrodynamical drag coefficients. Mayhead proposed an evaluation system of this problem. This paper presents the recent advancements on this problem including wind tunnel tests carried out by Johnson and others, and field tests by Shi-igai and Maruyama.
