Which practices are used to control soil erosion and protect waterways?

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Controlling soil erosion and protecting waterways relies on keeping the soil in place and reducing both water and wind-driven loss at the surface. Contour farming follows the land’s natural elevation lines, so plowing and planting run along the slope rather than up and down it. This slows runoff, increases infiltration, and reduces the amount of soil that can be washed into streams. Terracing takes steep slopes and transforms them into a series of level steps; these reduce runoff speed dramatically and create stable surfaces that minimize soil loss and sediment flow to waterways. Cover crops occupy the field when the main crop isn’t growing, providing ground cover that shields soil from raindrop impact, adds organic matter, improves soil structure, and lowers erosion and nutrient runoff. Windbreaks—the rows of trees or shrubs planted to slow wind—cut wind speed at the soil surface, decreasing wind erosion and helping keep soil in place, which also helps limit sediment reaching waterways.

Why the other choices don’t fit: removing protective cover through clear-cutting and bare field tillage leaves soil exposed to rain and wind, greatly increasing erosion and sediment problems. Excessive irrigation without soil cover can create runoff and dilute or wash away soil and nutrients, but the lack of cover is the main issue. Overgrazing on steep slopes removes vegetation that protects the soil, making erosion and sediment delivery to streams much more likely.