The Three Kinds of Soil Erosion

Wind Erosion

• Wind erosion of soil incorporates the removal, transport and deposition of soil particles. Wind erosion is especially prevalent in areas with flat, bare terrain and sandy or poor soils. Wind erosion can move soil particles, depending upon the size of the particle by rolling or saltation or even farther through suspension. Rolling, or soil creep, generally accounts for the lowest percentage of soil movement and encompasses the rolling movement of sand-sized particles or larger aggregates on the soil surface. Typically, the majority of soil moved during a wind event moves by a process known as saltation. This type of movement involves a "bouncing" of mid-sized soil particles along the soil surface, which also knocks additional particles into motion. These grains of soil often accumulate on-site near ridges, in vegetation debris or next to structures. Suspension is the movement of fine soil particles like clay or organic matter into the air and over long distances. Although suspension does not necessarily account for a large portion of total wind erosion, this process transports valuable nutrients that impact soil quality.

Preventing Wind Erosion

• A general rule is that soil requires at least 30 percent ground cover to resist wind erosion. Maintain ground cover by observing environmentally friendly tillage practices or mulching and incorporating clay and planting field shelter belts: rows of trees or shrubs, generally along property lines or field edges, that serve to reduce wind velocity over open fields.

Water Erosion

• Water's eroding effect on soil can be subdivided into multiple types, or stages, beginning with splash erosion, the initial impact of raindrops hitting the soil, which can cause soil particles to detach or compact the soil. When water or rain is supplied to the soil faster than it can infiltrate, a more noticeable detachment and transport of particles may occur. Sheet erosion describes the fairly uniform removal of a thin layer of soil from the surface. Water flow eventually begins to concentrate in small rills, a process known as rill erosion. Larger concentrations of water create larger channels, or gullies. Gully erosion causes relatively large and permanent features.

Preventing Water Erosion

• Water erosion is affected by soil texture, structure aggregation and organic matter. Other influencing factors include the type of precipitation, slope and vegetative cover. There is more loss potential on steep slopes, which permit a greater water velocity. Surface vegetation can intercept rain drops and decrease their direct impact on the soil, as well as slow water flow across the soil surface and increase a more uniform deposition.

Mass Movement Erosion

• Mass movement describes soil erosion caused largely by gravity, and includes earthflow, landslips, avalanches and soil creep. This type of erosion is responsible for dramatic, though relatively infrequent soil movement events. Mass movements like landslides are often caused, in part, by over-saturation of soils, especially in areas with high clay content.

Preventing Mass Movement Erosion

• Mass movement, or gravitational erosion, often requires a combination of vegetation and engineering structures for effective prevention. Control measures may include dense vegetation above the susceptible area, surface and subsurface drains, soil pins or staples in combination with fabric that hold soil in place, retaining walls and slope grooming.