American Institute of Certified Planners (AICP) Practice Exam

Which type of area typically generates the most storm water runoff?

1. Undeveloped areas

2. Commercial areas

3. Multiple family residential

4. Single family residential

The correct answer is: Commercial areas

Commercial areas typically generate the most stormwater runoff due to their extensive impervious surfaces, such as roofs, parking lots, and roads. These surfaces prevent rainwater from being absorbed into the ground, leading to increased runoff. The high density of development, along with larger areas of concrete and asphalt, means that more water flows directly into drainage systems without being filtered or absorbed by soil. In contrast, undeveloped areas tend to have vegetation and natural ground, which can absorb rainwater, thereby reducing runoff. Multiple family residential and single-family residential areas usually have somewhat permeable surfaces with yards, gardens, and landscaping that can mitigate runoff compared to commercial developments. Thus, commercial areas stand out as the category with the greatest potential for generating significant stormwater runoff.