Parts OF A River By: L.Ruelas High water level going down to low and emptying into a larger body of water Flood Plain A flood plain is the flat, wide area of land along a river. HeadWAters A tributary stream of a river close to or forming part of its source Source a source is where the water begins at. Mouth This is where the river is once it's in the larger body of water. Delta An are formed from sediments in the mouth. Down River A down river is between headwaters and a floodplain. Tribrutary A side stream that go's into a larger river. Divide Mountains or valley ranges that separate a river. Great Basin A watershed where the water does not flow to the ocean.