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| Introduction |
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Length of protected zone Density affects the length of the protected zone both upwind and downwind of the windbreak. The length of the protected zone is measured in units of H, where H equals the height of the tallest row of trees. The influence of density of windspeed reduction can be seen in Table 2-1.
Table 2-1. Wind reductions on the downwind side of windbreaks with different densities, assuming an open-field windspeed of 20 mph (Adapted from Brandle and Finch 1991).
Low-density windbreaks (20-40%) reduce the windspeed only a small amount, and for a short distance downwind from the windbreak. Windspeed returns to 80% of its open-field value within 15H of the windbreak. At densities greater than 80%, windspeed drops substantially within 5H of the barrier. However, windspeed returns quickly to near open-field values. At intermediate densities, the drop in windspeed is not as great within 5H of the windbreak, but there is more protection farther downwind. This can also be seen graphically.
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Length of protected zone |
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