Storm Wind Loads On Trees
University Outreach Publication
Trees must withstand wind to survive. Wind and gravity both impact trees in storms, but the dominant load is from wind. Storm winds push on tree crowns and stems causing root plates to rock. The result of storm winds are forces twisting and bending tree parts causing either the part to fail or the supporting soil to fail. Trees sense structural stress and attempts to minimize failures through reactive growth. Trees modify their structure over time as they are challenged by wind. Trees are biologically designed to sustain average wind loads. What are the loads applied by storms to trees?
A tree has a large sail area (leaves and twigs) held upright high into the air by a tapered mast (stem). The stem is woven onto a thick horizontal mat of large structural roots at the stem base which forms a root plate. Rapidly tapering roots grow away from the stem base to provide the tree with an absorbing surface. The center of gravity (effective weight center) of a tree is usually somewhere in the middle of the stem above the root plate. Gravity is pulling down on the tree all over but has a total effect focused at the center of gravity. Wind is pushing the tree around its center of gravity.
SFNR07-3
K.D. Coder
February 2007
Warnell School of Forest and Natural Resources, University of Georgia
Athens, GA (US)
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SFNR07-3
Mechanics (tree), Risk Assessment and Hazard, Storms, Storms (hurricane), Storms (ice), Storms (tornado)
National, International
Beauford, Beaufort, Coder Index of Tree Crown Reconfiguration, Coder Scale of Tree Wind Damage, Coder Storm Intensity Zone Map, Fujita, Hurricane Scale, Meaden, Saffir-Simpson, Storm Intensity Scale, Storm damage, Storm winds, Storms, T-Scale, Tornado Scale, Tree Crown Reconfiguration Index, Wind, Wind Scale, Wind damage, Wind force, Wind loading, Wind pressure
