What characterizes sheet flow?

Sheet flow is characterized by the movement of water across the surface of the ground in a thin, uniform layer without the presence of a defined channel. This phenomenon typically occurs in response to precipitation, where water flows over relatively flat or gently sloped land, spreading out over the surface rather than concentrating in one area.

The description emphasizes that sheet flow is usually associated with upland areas, meaning it can happen in landscapes that do not have established stream beds or channels, leading to surface runoff. This can contribute to soil erosion, as the thin layer of flowing water can transport loose sediment from one area to another.

The other options are not accurate representations of sheet flow. For example, flow through large river systems refers to channelized flow, while heavy rainfall may influence the occurrence of sheet flow but is not a defining characteristic. Similarly, flow restricted to areas with high vegetation does not capture the essence of sheet flow, which can occur in both vegetated and bare soil areas, provided the conditions are suitable for surface water movement.