Principles and Practice of Engineering (PE) Civil: Water Resources and Environmental (WRE) 2025 – 400 Free Practice Questions to Pass the Exam

The time of concentration refers to the time it takes for water to travel from the furthest point in a watershed to a specific point of interest, typically a point where the runoff is measured. A change that increases the time of concentration typically results in increased vegetation and more natural land cover, which enhances water infiltration and delays runoff.

Transitioning from bare soil to woodlands is likely to increase the time of concentration. Woodlands have deeper root systems and a denser canopy, contributing to greater water absorption and slower surface runoff. The tree cover also provides a natural barrier that slows down precipitation, allowing more time for water to infiltrate into the soil rather than running off directly. This process effectively prolongs the time of concentration compared to areas with less vegetation, such as bare soil.

In contrast, other options generally result in reduced time of concentration. For example, urban development leads to increased impervious surfaces, thus causing quicker runoff and shorter times of concentration, while agricultural land often involves tillage practices that can cause quicker stormwater runoff compared to woodlands. Therefore, the transformation to woodlands enhances retention and infiltration of water, leading to an increase in the time of concentration.