Drag coefficients and crown area estimation of red maple

Abstract

During storms, shade trees may fall as a result of excessive drag; anticipating such events has obvious benefits. We measured the drag of red maples (Acer rubrum L.) up to 5 m tall in winds up to 20 m/s. Drag correlated with tree mass, height and crown frontal area as previously shown in conifers and small deciduous trees tested in wind tunnels. Drag coefficients, based on still-air frontal areas, decreased, whereas drag-induced bending moments increased as wind speed increased. Drag predictions based on approximating canopies as simple shapes like triangles and rectangles did not accurately reflect measured drag, although manipulating drag coefficients can allow drag predictions based on simple shapes.