Section 4: Soil and Water Conservation Engineering
Soil and Water Erosion
Subtopic: Mechanics of soil erosion – wind and water erosion
Question Statement:
A windbreak of height 2.7 m protects a wheat field. Actual wind velocity (perpendicular, at 15 m height) = 9 m/s; minimum velocity to move the most erodible soil fraction = 9.6 m/s. Find the distance of full protection (m). (Rounded to 2 decimal places)
Official Answer Key:
48.65 to 50.49
Step-by-Step Solution & Explanation
Using the Woodruff–Zingg relationship for the distance of full protection, d = 17H×(Vt /(Va cosθ)), with θ = 0° (perpendicular wind): d = 17×2.7×(9.6/9) = 45.9×1.0667 = 48.96 m. (The factor ~17H reflects the empirically-established downwind distance over which a windbreak provides effective protection, scaled by how close the actual wind velocity is to the erosive threshold.)
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