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The forecast for wind or snowstorms can give rise to anxiety for many farmers. How do you best prepare for these events? The tips below can assist you in reducing the chance of sustaining damage to your investment. As the elders say, “An ounce of prevention is worth a pound of cure.”
The wind is best prepared for by anchoring, bracing, breaks, orientation, and sealing. In anticipation of a forecasted wind event, loose items should be secured or stowed. Additionally, all hardware and rope or strapping should be inspected to ensure tightness and serviceability.
Anchoring. The most desirable anchoring for tunnels in sustained high wind contexts is either cement or ground anchors. Ideally, ground posts should be anchored on the corners and every other bow. The bows which are not anchored should be driven at least two feet deep. Traditional caterpillar tunnels with rebar should be secured using ground anchors in high wind contexts (see Fig. 1).
Bracing. Appropriate bracing for high wind includes wind or end wall bracing at each corner and a solid ridge purlin (see Fig. 2a and 2b). Wind bracing and purlin prevents racking of the tunnel from end to end. A lower profile tunnel is better in high winds. The lower profile is one advantage of caterpillar tunnels.
Breaks. Sustained high winds are the greatest danger to your tunnel. This does not negate the potential risk associated with gusting winds. One way to mitigate both types is by installing windbreaks if natural ones like trees are not present (see Fig. 3). Windbreaks can slow down the wind and offer a protected distance zone ten times its height.
Orientation. Understanding the wind pattern of your farm is important when choosing the orientation of your tunnel. Prevailing winds can be an indicator of how the tunnel should be positioned. However, wind can be unpredictable and orientation rendered useless. The ideal orientation is with the narrow end facing the prevailing wind. This makes the best use of anchoring and bracing while presenting a smaller profile for the wind to catch.
Sealing. Once you are in an actual wind event all openings should be closed. The side curtains should be dropped and secured with sandbags. If doors have been installed on the ends they should be closed and latched. If the ends are left open for summer ventilation a windbreak should be installed.
References
Fortier, J.-M. (2014). The market gardener: A successful grower's handbook for small-scale organic farming. New Society Publishers.
Sparks, B. (2016, February 17). Tips to help reduce wind and snow damage at your greenhouse. Retrieved October 17, 2019, from https://www.greenhousegrower.com/technology/tips-to-help-reduce-wind-and-snow-damage-at-your-greenhouse/.
