The greater the percentage of fine sand, silt or clay in soil the greater the risk of erosion. Generally the greater the slope the greater the risk that erosion will occur. Slope length is also a factor, for example, when slope lengths are greater than 100 m the risk of soil erosion is higher. Generally the greater the amount of soil surface covered by vegetation, the less the risk of soil erosion. Permanent grass cover has a low risk, while temporary cover crops or straw mulch have a moderate risk.
Bare soil has the highest risk.
Most runoff occurs as a result of severe rainfall events. It may be necessary to reduce the velocity of the flow and contain the flow in a retention structure or ditch. A properly designed ditch or grassed waterway will contain and control the flow. This water can be diverted to fields or watercourses if it remains uncontaminated. If the runoff is contaminated the water should be contained.