Trees and wind

The effects of strong winds on trees is a much-researched topic. International conferences have been conducted on the issue.

Trees bend and sway in strong winds to dissipate energy and help them withstand the onslaught without failing. Young trees that are exposed to persistent one-direction winds develop stronger root systems to resist wind loads.

The Bureau of Meteorology states, “The predominant wind stream over Victoria is of general westerly origin, although it may arrive over the State from the northwest or from the southwest. There are wide variations from this general description, however, and many northerlies or southerlies are experienced. Furthermore, the hot northerlies which bring heatwave conditions from the interior are well known, whilst in winter and spring exceptionally cold weather may accompany a southerly wind stream.”

The recent strong easterly wind Gippsland experienced was caused by the combination of a low-pressure system off the southern NSW coast and a slow-moving high-pressure system south of Tasmania. Winds travel clockwise around lows and anticlockwise around highs.

As a result of the developing pressure system, the BoM published forecasts of strong easterly winds for much of Victoria for several days in a row.

Some easterly gusts were quite strong and placed trees in this district under conditions they are not acclimatised to.

Street trees or stand-alone trees, without the protection of other nearby trees, are more exposed to wind loads. Urban trees will often have root zones that are restricted by building foundations, roads and footpaths, etc. Urban trees will often be exposed to environmental stresses that cause them to exhibit ‘old age’ characteristics years before their wild-growing relatives. Urban and stand-alone trees may not have the support of a root system entwined with other nearby trees.

Urban and stand-alone trees are often more susceptible to failure by windthrow. Trees compromised by decay or previous damage are at higher risk of wind damage.

Climate change is intensifying the strength and frequency of strong wind events by increasing atmospheric heat and moisture, leading to more violent thunderstorms, faster-intensifying cyclones, and stronger gusts.