Overfall


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Overfall

 

a type of turbulence at sea in which wave motions and eddy currents are combined on the surface. The movement of water particles in overfalls is similar to the motion of such particles on the surface of boiling water. Overfalls result from a sharp change in the velocity of a current, particularly, a tidal current, when the current emerges from a narrow place or from behind a cape; they also may arise when two streams meet. The waves associated with overfalls are high amd may reach 4 m in some regions, for example, in the Arctic Ocean near bays or inlets fed by large rivers; such waves are dangerous for small craft.

References in periodicals archive ?
It was a relief to boat and skipper when, tide rips and overfall astern, they settled to the more comfortable rhythm of the open Pacific.
Chutes are designed to carry flow down steep slopes through a concrete-lined channel rather than by dropping the water in a free overfall.
70 fell five miles northwest of the Blankeney Overfalls bell buoy, along with Strasser, von Lossnitzer and 20 crewmen.
In nature, air bubble entrainment into water takes place at spillways of weirs, at river overfalls, in mountain streams and in breaking waves on the ocean surface.
This violent stretch of water, with its chaotic overfalls, sea surges and big whirlpools, is seen as one of the best tidal resources on earth.
Metaphorically reflecting in "Watch" on his three decades of marriage, he considers "Chartered years of bell-shaped lead-lines, / Riptides, overfalls, height and shallow, / So much unfathomed.
In the vicinity of Singapore the tidal streams can attain rates of some 6 knots with associated eddies and overfalls.
In an 18ft Drascombe lugger, the overfalls off the Great Orme and the Gower seemed a bit larger in proportion and our landfall at Rhyl harbour in the dark, I shall never forget