When is surface runoff most likely to occur?

Surface runoff most likely occurs during heavy rainfall events due to the saturation of the soil and the inability of the ground to absorb more water. When intense rainfall happens, especially over a short period, the volume of water can exceed the infiltration capacity of the soil. As a result, the excess water flows over the surface instead of being absorbed into the ground. This increased surface runoff can lead to various consequences, including erosion, flooding, and the transportation of sediments and pollutants to bodies of water.

The other options do not contribute to conditions that favor surface runoff. Drought periods and arid regions typically have dry soil, which can absorb rainwater more effectively once rainfall does occur, reducing surface runoff. In wetlands, the saturated soil is already at capacity, but the continuous presence of water often leads to a different hydrological dynamic, such as slow-moving water rather than rapid surface runoff as seen during heavy rain events.