Variables in Soil Erosion

Type of Soil

• The physical and chemical characteristics of soil affect its resistance to erosion. Soils with high levels of organic matter and strong structures resist erosion more than soils that contain a high proportion of very fine silt particles. Soils though which water can rapidly flow have a high infiltration rate and erode slower than those on which the water pools on the surface. Agricultural practices of tilling and cropping sometimes lower the soil's levels of organic matter, causing poor soil structure. In addition, these practices may compact the soil and form a crust through which water cannot easily flow. Wind erosion also affects soils with very fine particles, lifting the small particles into the air and blowing the larger particles along the ground.

Moisture

• Rainfall and runoff are two variables in the process of soil erosion by water. The force by which the raindrops hit the soil, especially during high-intensity storms, can break down the soil's structure and remove the soil. Light soils that contain fine sand and silt particles are particularly susceptible to this form of erosion. Runoff occurs when excess water on a slope cannot penetrate the soil and is trapped on the surface. The water flows down the slope, taking the top layer of soil with it. In hot climates, the soil becomes dry and even parched, releasing soil particles that can be eroded by the wind.

Vegetation

• The roots of vegetation hold soil together and strengthen its structure. Soil without vegetative covering is loose, has a weak structure and is without protection from the impact of rain. Vegetation also slows surface runoff and allows the excess water to infiltrate the soil beneath it. Plants that completely cover the soil are more effective at preventing erosion than those with only partial coverage. Plants that have long growing periods are more effective than those that leave the soil bare for a period of time, especially in the rainy season. Smooth, bare soils are also susceptible to wind erosion as they have no resistance to the wind blowing across them.

Topography

• The lay of the land is also a variable in soil erosion. Erosion of soil on steep slopes is through the runoff of water taking the soil with it. The steeper the slope, the faster the water moves, picking up more and more soil along the way. Long slopes also lose more soil in this way than short slopes. Planting large trees as windbreaks protects large expanses of soil, such as fields, from erosion by wind.