Young Brunette Girl Shows Off On Rocks With A Mountain Stream Nearby

The point on a stream's profile where a sudden change in stream gradient occurs.
• Waterfall or cascade
The fall of water where the stream goes over a sudden drop called a nickpoint; some nickpoints are formed by erosion when water flows over an especially resistant stratum, followed by one less so. The stream expends kinetic energy in "trying" to eliminate the nickpoint.