the beginning of a stream or river where runoff has cut a channel

a deep, steep-walled gorge carved in rock by a stream or glacier

all of the land drained by a river and its tributaries

a stream that flows into a larger stream or river

the course along which water moves

a flat plain created by sediment dropped at the river's mouth

a flat area next to a stream and made up of loose sediment, such as silt.

the point at which water from a river or stream empties into another body of water, such as a large stream, lake, or ocean