Working with wind

Wind is a pattern of nature. It’s an elemental force that shapes our landscapes and environments. If we observe its effect on the landscape our homes and gardens we can come to understand its force and plan. 

During early September we have experienced wind gusts up to 150 km an hour across Melbourne resulting in damage, and at one point more than 50,000 homes without power. Can we consider this an extreme weather effect?

Strong winds can break limbs of trees and branches, blow off blossoms of the future fruit, snap vegetables and dry plants out – creating big impacts on our food system.

According to the World Economic Forum, the severity and frequency of extreme weather events is expected to increase this century as the climate crisis persists.

Some winds are predictable, as they have been tracked providing valuable information to sailors, farmers and communities to navigate and plant by. 

Knowing the direction of our local winds helps us prepare. The prevailing winds in Melbourne come from the north (mainly), the west (westerlies) and south-west. 

As there has been a lot of clearing of trees north of Melbourne can we expect even stronger winds in the city as winds gain force moving across the bared landscape and building momentum?

Winds tend to fill in recesses as they blow material across the landscape; they create soil as well as move soil. Apart from moisture, the wind may carry heavy loads of dust, sand or ice, potentially causing particle blast and when they hit a barrier these things are dropped or settled out.

If a wind hits a solid structure it bounces over the top and creates a spiral (turbulence) on the other side. In our built environment, especially in the city, the winds get tunnelled between buildings, increasing velocity and, as buildings are solid barriers, winds are gusted stronger in the cities. 

To respond to this risk of severe wind events, it is important to both mitigate and adapt as promptly as possible. In the UK, developers and architects must ensure a safe and comfortable wind microclimate as a prerequisite on all new developments planned. 

In local planning, taking care to design outdoor spaces that are not overly windy ensures they are suitable for their intended use and can be fully enjoyed by their residents and the public.

Certain trees and shrub species are useful in their ability to slow, filter and divert the wind. Using trees and plants as windbreaks is one of the most effective ways to manage wind so that the elements in the built and planted environment are not threatened or degraded. Trees and plants spaced appropriately can disperse strong winds rather than blocking them entirely and so minimising the turbulent affect. 

Trees have learnt to adapt, as wind speeds increase, the trees leaves and branches deform so that the tree steadily reduces its exposed leaf area. At time of high winds, the trees’ normal priority of intercepting light, using water efficiently and heat management becomes secondary to their survival.

Trees put down heavy and non-rigid wide root mats. In their first year the tree bends and moves with the wind and learns which way the wind comes from so special wood cells are created to bear the tension and compression. This is demonstrated in forests where the trees on the edge of a forest are thick and sturdy. 

In our efforts to adapt and mitigate extreme winds we can look to tree and plant species from those climates where strong winds have been experienced for centuries indeed for millennia, such as alpine areas. 

However, until our current system of growth and exploitation pivots to the climate crises the priority will continue to be buildings over nature. •