Mechanical Reaction of Vegetation Canopies to Wind Flow

In this study, an index is proposed to characterize physical properties of tree species. This will allow the application of a single momentum (or energy) equation to determine overall reaction of variety of tree species in a community. The index is derived based on the resonance frequency of the first mode of vibration of trees and a fundamental relationship for the homogeneous beams. The derived indexes for four species of coniferous trees were used in a mathematical model to estimate the drag and energy coefficients as representatives for tree reaction to wind flow and were able to account for the differences due to the leaf density, shape and rigidity of the tree species.