In a hilly region with purple soils, a study looked at how rainfall affects runoff and sediment wash-off. They found that when rain gets heavier, surface water and soil sediment increased. Steeper slopes led to more runoff and less underground water flow. Surface water disappeared quicker than underground flow. Sediment wash-off rose with heavier rainfall and steeper land. This research shows that rain intensity mostly controls how much soil gets carried away by water.