How does impervious surface area affect stormwater runoff?

Impervious surfaces, such as concrete, asphalt, and rooftops, play a significant role in stormwater management due to their impact on runoff. When precipitation falls on these surfaces, water cannot infiltrate into the ground as it would on permeable surfaces like grass or soil. Instead, it flows over the surface, leading to an increase in both the volume and velocity of runoff.

This increased runoff can overwhelm drainage systems and lead to flooding. Moreover, as water flows over impervious surfaces, it picks up pollutants such as oils, heavy metals, and debris, ultimately leading to higher pollutant loads in nearby water bodies. This scenario emphasizes the importance of managing impervious surfaces in urban planning and stormwater management practices to mitigate the negative environmental impacts associated with increased runoff.

In contrast, choices related to decreased runoff or no significant effect overlook the crucial role that impervious surfaces play in altering natural hydrology. Additionally, stating that impervious surfaces only affect runoff during heavy rainfall ignores the cumulative effects of smaller rain events as well, which can also contribute to runoff problems. Therefore, understanding the role of impervious surfaces is essential for effective stormwater management.