Runoff occurs when water from precipitation or melting snow is not absorbed into the soil and instead flows over the land's surface. This phenomenon is primarily influenced by the saturation of the ground and the steepness of the slope. When the ground is saturated, it means that the soil is already full of water and can no longer absorb additional moisture. As a result, any extra water will flow away, particularly if the slope is steep, where gravitational force can aid the movement of water downhill, contributing to runoff.
The combination of saturated conditions and steep slopes facilitates the quick transport of water, leading to significant surface runoff. This runoff can eventually collect in streams, rivers, and other bodies of water. Understanding this process is crucial for managing water resources, addressing erosion, and predicting flooding events.