A meandering river flowing through a floodplain is called a mature river. This picture shows the beginning of a meander pattern that this river formed when the green terraces in the picture were the floor of the floodplain. It has started cutting a V shaped valley again. A mature river carries a heavy load of sediment. When the flow of water slows, the sediment settles to the bottom.
Sand bars begin to appear.
The final stage in the life of a river is its joining with the sea. By now the river is traveling smoothly and carrying a lot of sand and clay. Merging with the sea slows the water flow even more, and the sediment drops out. This often leads to the formation of a delta, a broad, triangular river mouth with many sand bars and water channels. The delta becomes an estuary, an area with sheltered waters and a constant stream of nutrients from the land.