How far into runoff does shallow concentrated flow typically begin?

Shallow concentrated flow typically begins within 150 feet of the onset of runoff due to the accumulation of water as it moves across a surface. This flow occurs when water that originates from precipitation or melting snow can no longer be absorbed by the soil and starts to gather in small channels or rills. As the volume of water increases, the flow transitions from being diffuse or sheet flow to becoming more concentrated, particularly after this distance is reached.

The 150-foot distance is significant as it reflects the typical behavior of water movement in response to land surface characteristics, such as slope, soil type, and vegetation. Understanding this distance is vital for managing erosion and stormwater runoff effectively, as it helps in predicting where concentrated flow may occur and where preventative measures might be necessary to minimize erosion and related issues.