Rapid

A rapid is a section of a river where the river bed has a relatively steep gradient causing an increase in water velocity and turbulence. A rapid is a hydrological feature between a run (a smoothly flowing part of a stream) and a cascade. A rapid is characterised by the river becoming shallower and having 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 colour, 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.

Famous quotes containing the word rapid:

“The idealism of Berkeley is only a crude statement of the idealism of Jesus, and that again is a crude statement of the fact that all nature is the rapid efflux of goodness executing and organizing itself.”
—Ralph Waldo Emerson (1803–1882)

“In clear weather the laziest may look across the Bay as far as Plymouth at a glance, or over the Atlantic as far as human vision reaches, merely raising his eyelids; or if he is too lazy to look after all, he can hardly help hearing the ceaseless dash and roar of the breakers. The restless ocean may at any moment cast up a whale or a wrecked vessel at your feet. All the reporters in the world, the most rapid stenographers, could not report the news it brings.”
—Henry David Thoreau (1817–1862)

“More rapid than eagles his coursers they came,
And he whistled, and shouted, and called them by name:
“Now, Dasher! now, Dancer! now, Prancer and Vixen!
On, Comet! on, Cupid! on, Donder and Blitzen!
To the top of the porch! to the top of the wall!
Now dash away! dash away! dash away all!””
—Clement Clarke Moore (1779–1863)