What key factor determines the volume of runoff in a watershed?

The volume of runoff in a watershed is significantly influenced by the area and surface characteristics of the land. This includes various factors such as soil type, land use, and the nature of the surface through which water flows. For instance, impervious surfaces like asphalt and concrete lead to increased runoff because they do not allow water to infiltrate into the ground. Conversely, vegetated areas with permeable soil can absorb more water, reducing runoff.

Terrain features like slope also play a role, but they are part of the broader surface characteristics. The overall land area of the watershed contributes to how much precipitation is captured and what portion becomes runoff. Thus, the combined evaluation of both the area and its surface properties gives a comprehensive understanding of potential runoff volumes during rainfall events. This multifaceted approach is vital for effective stormwater management and erosion control strategies.