Design Factors - Wind

Design Factors - Wind

A major  factor to take into account when designing effective systems in Thunder bay is wind.

The effect of winter wind, and wind blown snow, can be observed everywhere from the amount of snow you have to clear from the driveway, to the power lines that get severed during a winter storm by falling trees.

As the air cools, it becomes denser. This means that a 20 Kph wind on a balmy 30°C August day contains considerably less energy than a 20 Kph wind on a freezing -30°C February one.

In this climate, there is an enhanced opportunity to create micro climates in the landscape because of the wide temperature variance between seasons.

A shelter belt of trees doesn't just slow the wind down, it actually generates heat because the wind is slowed down through friction.

A shelter belt in the winter will therefore enable the survival of plants and trees that are marginally hardy in this zone 3 environment. Couple shelter belts with berms, and you start to get into creating small pockets of zone 4 and 5 growing areas.

Looking at wind direction statistics for Welcome Island, it becomes clear that the predominant wind there is from the West to North West:

Local effects due to the topography of your area are important, and so wind directions need to be monitored and recorded for your individual site.

How about Summer?

 It's clear that we have a different seasonal effect in play, with Southerly winds predominating.

This means that a wind break installed to counteract the winter WNW wind, will not create a significant heating effect in the summer time for this specific location.

An East - West wind break would be useful for increasing summer temperatures for growing annual crops, while a North East - South West wind break would be useful for protecting perennials and fruit trees.

A wind break in Thunder Bay designed to counter the desiccating effects of the winter wind will also accumulate snow drift on the windward side. As wind carries other things (like dust), the windward side of the shelter will accumulate nutrients as well.

This would be an ideal location to place a swale, so that when the spring melt comes, all this water and nutrients are absorbed into the landscape where they can be put to good use.

Of course, wind breaks don't have to run in straight lines, nor should they.