Running water causes erosion through friction. Additionally, running water can carry dust, silt or sand particles, which may also work to erode a given surface. Typically, water erodes surfaces in one of four ways.
The most common type of water-induced erosion is called “sheet erosion." When water causes sheet erosion, a thin layer of substrate is removed. Sheet erosion is most common following flood events or the changing of the tides.
Rill erosion occurs when small streams of water pour down a hillside. This type of erosion takes the form of small, thin ditches that resemble a river and its tributaries. Greater erosion occurs at the bottom of hills with rills, because the water carries dirt with it, which causes the bottom of the hill to be eroded by both the water and the free sediment.
Gully erosion is caused by running water; it typically occurs as a result of the digging of a river channel. Gullies are usually so large that they do not disintegrate quickly. Erosion can also be caused by the splashing of water. Called “splash erosion”, water droplets cause the soil to fly up into the air. Sometimes, grains of sand are thrown three feet or more.