What Causes Soil Erosion?

Soil erosion occurs when particles of soil are removed from an area by factors such as water and wind. It causes a loss of fertile topsoil, plus the eroded material pollutes streams, creeks, rivers, lakes and other water sources. Not only does it create sediment, but the process of erosion also carries oils, fertilizers, animal waste and other pollutants into the water. Being aware of what causes erosion can help you to minimize it in your yard.

According to the North Carolina State University Cooperative Extension, one of the main causes of soil erosion in and around human habitations is the disturbance of the vegetation. Plant roots serve to hold the soil in place, and when these are disturbed the soil is left vulnerable to erosion because the soil is no longer held in place, and it can wash or blow away. Plants may be uprooted during the construction of a home or other construction or during landscaping or gardening, when the soil is tilled or cleared to make way for something new.

Water is a major cause of erosion. The effects will vary depending on the amount of water and the condition of the soil. Sloped areas are particularly vulnerable to the effects of fast-flowing surface water that causes erosion.

Splash Erosion: When a water droplet hits soil that has no protection, the force of the droplet landing can break loose a small bit of the soil. If more water lands in an area than the soil can absorb, the water will begin to flow, carrying these tiny bits of soil with it.

Sheet Erosion: If enough water flows over an area it will remove the top layer, or sheet, of soil and wash it away.

Rill Erosion: The contours of the ground may shift the flowing water into small channels, something like tiny rivers. The water flows through these areas, cutting deeper into the soil and carrying away even more particles. This type of erosion is most evident on sloped areas and if not quickly controlled can turn into a gully.

Gully Erosion: This is rill erosion on a larger scale. The channels get deeper and wider, often taking away significant amounts of soil in the process.

Rain water can also hit unprotected soil, but instead of removing bits of soil they create a crust on the surface. The crust makes it difficult for the soil to absorb any water and it increases the runoff, which ultimately carries more soil away with it. This decreases the possibility of plants being able to grow through the hardened surface.

In some areas wind is responsible for erosion. Generally, winds blowing at a speed of 13 mph. or higher and at a height of a foot above the ground cause erosion to unprotected soils. If you live in a windy area and your yard doesn’t have windbreaks around it, you may be experiencing wind erosion. Wind transports soil in one of three ways:

Saltation: The wind lifts individual particles of soil and then drops them back down, where they hit other particles, dislodging them and making them available for the wind to lift and carry away. According to the Colorado State University Extension, this mechanism is responsible for up to 80 percent of all soil eroded by the wind.

Suspension: Some of the dislodged particles are small enough to stay in the air for long periods of time and can be seen as dust. These account for 20 percent or less of the movement of soil during the erosion process.

Surface Creep: Particles the size of a grain of sand begin moving during the saltation process and then they keep moving. They creep slowly over the surface of the soil, shifting from one place to the next. This process may account for as much as 25 percent of the total amount of soil moved by wind erosion.