Calculation of Slope Terrain Movement Rate from Tree Trunk Deformation

Karel Vojtasik

Movement of terrain on slopes, unless intense, as in the case of landslides, is practically imperceptible and the deformed trunks of trees growing on slopes are detectors of these movements. The deformation of a tree trunk may therefore be considered as a continuous record of terrain movement for the period of tree vegetation life. The cause of trunk deformation is a slight change in the inclination of the terrain on slope that accompanies terrain movement, and to which the tree trunk adapts during its time growth development. Submitted article presents a proposal for a method that, based on the time dependence of the development of the curvature of a tree trunk, allows a calculation of the path length and rate of the slope terrain movement for either the whole or a particular time period respectively. The calculation of the path length of the terrain movement assumes that the horizontal position of the center of gravity of the tree trunk remains unchanged in time and space, and the horizontal component of the terrain movement path is given by the horizontal distance of the center of gravity of the tree trunk from the heel of the trunk. The rate of movement is calculated from the terrain movement path length and age of the tree, which is determined from the diameter of the trunk. The position of the trunk's center of gravity is calculated from the digitized shape of the trunk according to the principles of solid body mechanics.