122 



Water 



Figure 109. Development of a breaker — curling over of crest followed by collapse. Height is about 1.5 meter. July 22, 

 1957, at Newport Beach. 



rents return seaward most of the water 

 trapped within the breaker zone by mass 

 transport, there may be no seaward return at 

 the bottom. In any event neither the high- 

 speed rip currents nor the slow bottom return 

 of water fits in any way the popular concept 

 of undertow capable of sucking a swimmer 

 down and drowning him. Perhaps the under- 

 tow myth is a result of faulty observation in 

 the breaker zone where a bather can be 

 bowled over by the crest of a wave which 

 strikes him head to foot, and then, by the 

 time he regains his feet, the longer slower 

 backwash between crests pulls his feet from 

 beneath him again. The combination of 

 landward push from head to foot and sea- 

 ward pull about the legs, even though not 

 simultaneous, may give the illusion of under- 

 tow, particularly to a frightened bather. In 

 fact, the stories in southern California news- 

 papers of drowning by undertow refer mostly 

 to victims carried beyond their depth by rip 

 currents. According to Captain J. F. Steven- 

 son, Chief Life Guard, Los Angeles County, 

 about 95 per cent of the 1500 annual rescues 

 made by county life guards are of bathers 



caught in rip currents. Since the currents 

 are strongest in the spring when waves are 

 highest (April 1 to June 15), about 75 per 

 cent of the rescues are made in this period. 



Figure 1 1 0. Superimposition of nearshore current system 

 on general coastal current. Shoreward mass transport of 

 water by waves is accelerated in breaker zone, longshore 

 current forms in surf zone, rip currents develop and 

 return most of water seaward through the zone of mass 

 transport by waves, and the head of the rip current is 

 moved parallel to shore by the coastal current. Adapted 

 from Shepard and Inman (195 IZ)). 



