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Slide 55 of 77
Notes:
bore
inrush of water that advances upstream with a wavelike front, caused by the progress of incoming tide from a wide-mouthed bay into
its narrower portion. The tidal movement tends to be retarded by friction as it reaches the shallower water and meets the river current; it
therefore piles up and forms a low wall of water that moves upstream with considerable force and velocity as the tide continues to rise.
In the mouth of the Amazon River a tidal bore known locally as the pororoca occurs every spring tide. It has a wall of water from 5 to
15 ft (1.5 –4.6 m) high and advances at a speed of from 10 to 15 mi (16 –24 km) per hr. The highest recorded bore (15 ft/4.6 m) is
found in the Ch'ien-tang River near Hangchow, China. Bores are found also in the Bay of Fundy, in Solway Firth, in the Severn,
