An investigation of the destructive potential of falling tree branches striking a target was conduct at Tree Biomechanics week 2013.  The force of impact on a rigid target will be presented and considered as a worst-case scenario.   Considerable work has been done in the industry  to develop condition assessment methods and hazard mitigation techniques.  In contrast, quantitative information available for use in determining consequences of tree failures is limited. A review of the literature revealed little in the way of studies quantifying the energy, momentum transfer, or impact forces associated with tree and branch failures.  

Target strikes were simulated in a series of branch drop tests from a fixed height onto a rigid target.  Data that describe the branch, its velocity, and acceleration of both the branch and target were recorded.  Eighteen branch specimens in full leaf from two different tree species were dropped on a fixed target.  As many as six replications were completed with each specimen.  A subset of these replications was conducted with branches that had been stripped of leaves.  Branch velocity was determined by interpretation of high speed video.  Target acceleration and branch deceleration due to impact were recorded directly.  These data, and the mass of the branch, were used to calculate the potential energy, kinetic energy, momentum transfer, and force of impact on the target.