Runoff is the process by which water moves across the land surface and eventually flows into rivers, lakes, and oceans. This occurs when precipitation, such as rain or snowmelt, exceeds the amount of water that can be absorbed by the soil. Factors like soil type, vegetation, and land slope can influence how much water becomes runoff. Runoff plays a crucial role in the water cycle, helping to transport nutrients and sediments. However, excessive runoff can lead to problems like soil erosion and water pollution, as it can carry contaminants from urban areas or agricultural fields into nearby water bodies, affecting ecosystems and human health.