Answer;
rapids and waterfalls.
Explanation;
A V-shaped valley is a narrow valley that has a profile suggesting the form of the letter "V," characterized by steeply sloping sides. It results from a stream eroding downward, a process referred to as downcutting.
V-shaped valleys form in mountains or other highland areas where streams are in their beginning or "youthful" stage and are flowing rapidly down steep slopes.
The most prominent features of a narrow V-shaped valley where the stream profile drops quickly are rapids and waterfalls