What does the "runoff coefficient" represent in stormwater analysis?

The runoff coefficient is a critical concept in stormwater management, representing the fraction of rainfall that contributes to runoff in a particular area. It quantifies how much of the precipitation that falls onto a surface flows over that surface as runoff, rather than being absorbed into the ground or evaporated. This coefficient is influenced by various factors, including land use, surface materials, and vegetation cover.

In urbanized areas where impervious surfaces like roads and buildings are common, the runoff coefficient tends to be higher because these surfaces do not allow for water infiltration. Conversely, areas with more permeable surfaces, such as parks or other green spaces, generally have a lower runoff coefficient.

Understanding this coefficient is essential for accurately modeling stormwater runoff, designing effective stormwater management systems, and ultimately helping minimize flooding and water quality issues related to excess runoff. The other choices focus on different aspects of stormwater management but do not specifically capture the essence of the runoff coefficient's role in quantifying the relationship between rainfall and runoff.