Which of the following is NOT a process of overland erosion?

Stream erosion is not classified as a process of overland erosion because it specifically refers to the erosion that occurs within established stream channels. This type of erosion involves the transport of sediment by flowing water in rivers and streams, primarily due to the flow dynamics within these confined channels.

In contrast, overland erosion pertains to the movement of soil and sediment across surfaces, primarily due to rainfall and surface runoff, where water flows across the land before entering any defined channel. Processes such as sheet erosion, gully erosion, and rill erosion all involve the direct detachment and transport of soil particles across the surface. Sheet erosion happens in thin layers over a broad area, rill erosion occurs in small, concentrated channels, and gully erosion refers to deeper and wider channels formed by cumulative runoff.

Thus, stream erosion operates in a different setting, focusing on an existing watercourse rather than the initial surface movements associated with overland flow.