As the river flows, it deposits all of the stuff it carries. Large items like rocks get deposited first. Soil is deposited last. Over time the soil that a river deposits can build up and create new land areas. End of the Road River deltas are land areas that are formed at the mouth or end of a river as the minerals and soil the river carries are deposited.
Deltas are very rich in nutrients.
Some of the best farmland on Earth is found in river deltas. Although river water makes up only about 0.2 percent of all the fresh water on Earth, they play a very important role. Rivers are like roads. They carry water, organisms, and important gases and nutrients to many areas. They also help drain rainwater and provide habitats for many species of plants and animals.