These are the four factors: the first factor is the amount of rain an area receives, the second factor is vegetation, the third factor is the type of soil, the fourth factor is the shape of land, and the final factor is how people use the land. Soil characteristics, plants and animals, and slope angle are the natural factors that affect the percentage of runoff. Human changes are the artificial factors that affect runoff. All these factors affect and/or determine the percentage of runoff caused by precipitation on various kinds of properties.