thumb|Rapids of Kern River, [[California, USA.]] Rapids are sections of a river where the river bed has a relatively steep gradient, causing an increase in water velocity and turbulence. Flow, gradient, constriction, and obstacles are four factors that are needed for a rapid to be created.
Rapids are sections of a river where the riverbed slopes steeply, which causes the water to flow faster and become turbulent. They form when certain conditions exist together—including water flow, a steep gradient, a narrowing of the river channel, and obstacles in the water—making rapids important features that significantly affect how rivers behave.
AI-generated from the Wikipedia summary — may contain errors.
thumb|Rapids of Kern River, [[California, USA.]] Rapids are sections of a river where the river bed has a relatively steep gradient, causing an increase in water velocity and turbulence. Flow, gradient, constriction, and obstacles are four factors that are needed for a rapid to be created.
== Physical factors == Rapids are hydrological features between a run (a smoothly flowing part of a stream) and a cascade. Rapids are characterized by the river becoming shallower with some rocks exposed above the flow surface. As flowing water splashes over and around the rocks, air bubbles become mixed in with it and portions of the surface acquire a white color, forming what is called "whitewater". Rapids occur where the bed material is highly resistant to the erosive power of the stream in comparison with the bed downstream of the rapids. Very young streams flowing across solid rock may be rapids for much of their length. Rapids cause water aeration of the stream or river, resulting in better water quality.
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