I would say the waterfall and the rapids are the most prominent features of a narrow V - Shaped valley where the stream profile drops rapidly.
cuts mainly side to side
gravel sized particles
Stream erode their channels by abrasion, grinding, and by dissolving soluble material.
Lowering the land.
The main channel of a stream divides into several smaller creeks. Occasionally, deposition causes the main channel of a stream to divide into several smaller channels called distributaries.
..decreasing from top to bot..