WAVE REFRACTION AT LONG BEACH 

 AND SANTA BARBARA, CALIFORNIA 



The following paper was first published in limited 

 issue as Technical Report HE-116-246, Fluid Mechanics 

 Laboratory, University of California „ It is re- 

 produced here to bring the utilization of wave 

 refraction analyses and wave forecasting principles 

 in shoreline improvement investigations to the at- 

 tention of coastal engineers and others interested 

 in the action of waves and surf . The paper was 

 prepared by Dean Mo P. O'Brien, University of 

 California in May 194-7. 



Wave refraction analyses are rapidly approaching the status of a stand- 

 ard component of shoreline investigations (1)„ Results obtained from these 

 analyses are frequently of only a qualitative character but even so, they 

 provide a rational basis for planning shore protection and improvement. 

 This report presents two examples of wave refraction problems prepared in 

 1936 which illustrated the way in which this technique may be used to supple- 

 ment and explain fragmentary observations. 



HEAVY SWELLS AT LONG BEACH 



During the period April 20 to 2Z., IP 30, large breakers damaged the outer 

 portion of the Long Beach harbor breakwater (see figure 1). Damage to break- 

 waters by heavy wave action is not noteworthy but the circumstances at Long 

 Beach were unusual because it was only at and near the end of the breakwater 

 that large breakers were observed There was only a light wind and the sea 

 offshore was calm. At the gambling ships anchored in deep water, no unusual 

 wave action was observed. At the San Pedro breakwater, only a few miles 

 away there were no breakers and along the shore downcoast from the Long Beach 

 breakwater, life guards noticed no wave action of unusual intensity. The 

 swells broke against the breakwater and dislodged stones ranging in weight 

 from A- to 20 tons. In the Long Peach channel, just off the end of the break- 

 water, the swells peaked up but apparently did not break. Several small 

 craft are reported to have "surf- boarded" in through the channel, 



These circumstances indicate that, during this period, waves must have 

 approached this shoreline from such direction, and with such period, that 

 they were focused on the end of the Long Beach breakwater . but were elsewhere 

 of negligible size. The wave period was not measured but from the statements 

 of eyewitnesses, it is believed to have been between 20 and 30 seconds. 



In 1930, the Los Angeles-Long Peach outer breakwater had not been con- 

 structed and the Long Beach harbor breakwater was exposed to ocean swells 

 over limited sectors from south and west 'figure 2). In order to locate 

 the possible sources of waves during this interval, the Northern Hemisphere 



