HEIGHT 



121 



a common spectacle off many coasts, but spouting takes place off 

 beaches only when breakers come together. Surf of this sort is not 

 of immediate concern as regards landing operations in any case, be- 

 cause no one in his senses would attempt to come in through the break- 

 ers under the conditions of wind and weather and of coast, under 

 which it develops. 



In general, the height of the breakers depends on the height and 

 steepness of the waves offshore, as shown in table 32. The steeper the 

 waves in deep water, the less will be their proportionate increase in 

 height before breaking. The average relationship is shown in table 

 33, but it must be noted that observations may vary by 25 percent. 

 Moreover, very steep waves may break while the height is still less 

 than the original height. 



Table 32. — The approximate heights at breaking (boldface) and the ranges of depths 

 at which breaking occurs (italic) for waves of different dimensions. It is assumed 

 that the waves break where the depth is from 1.3 to 2 times the wave height at that 

 instant. The heights at breaking are based on studies made at the Scripps Institu- 

 tion of Oceanography and the Woods Hole Oceanographic Institution 



Table 33. — Ratio of breaker height to offshore height for waves of different degrees of 



steepness in deep water 



Waves that are 6 to 8 feet high out at sea — a common height in 

 moderate weather — are only of about this same height when they 

 break on the shore, if their ratio of length to height offshore is small. 

 Storm waves, say 15 to 20 feet high offshore, are likely to cause a surf 

 at least 18 to 22 feet high, if their crests are parallel to the coast, though 



