The correct answer is - False.
The surface runoff, in its natural form, is not a pollution source by any means. When there's heavy rains, once the soil is saturated with water, the water stars to move on its surface, downhill, thus making short-lasting streams of rain water coming down towards the lower parts.
The surface runoff is a big factor in the soil erosion, deposition of sediments, but also causing floods that are very dangerous, especially because they happen in a very short space of time.
