What is the term for the movement of water and materials on the surface of the soil?

The term "runoff" refers specifically to the movement of water over the surface of the soil after precipitation or melting has occurred. It plays a crucial role in the hydrological cycle, as it represents the portion of water that does not infiltrate into the ground. Instead, this water flows across the land, transporting various materials such as sediments, nutrients, and pollutants. Understanding runoff is essential for managing soil health, water quality, and erosion control.

In contrast, percolation refers to the downward movement of water through soil layers, drainage typically describes the process by which water is removed from an area, and infiltration involves water traveling into the soil from the surface. Thus, while these terms all relate to the movement of water in the environment, runoff is specifically focused on surface movement, making it the correct term in this context.