Erosion By Overland Flow
Between valley’s at the top of interfluves water runs across the landscape in flat sheets known as overland flow. As rain drops begin falling in a rain storm they are first absorbed by the landscape. As the ground becomes saturated, the drops begin moving across the landscape above the surface. As this happens, small amounts of dust and dirt are carried with the water. This is known as splash erosion. As more and more water falls, the sheet of moving water becomes larger and larger.
Eventually the water forms rills. Rills are small channels of water running across the surface of the landscape. The creation of rills happens much more quickly in areas where there is little vegetation. Plant roots help to hold dirt and rocks in place, retarding the formation of rills.
Eventually, many rills come together, forming larger gullies. Gullies can get quite large, and help to feed large amounts of water into streams and rivers.