refraction diagram, figure U, the deep-water height would be 2,3 feet* 



Waves of 20— second period are about 2,000 feet long in deep water and 

 it is consequently understandable that waves of this length and a height of 

 only 2 feet would not be observed at sea. It is also understandable why 

 waves of this height in deep water would not be noticeable at the shore 

 when their energy was further distributed lengthwise by refraction. 



The wave period was not measured but it was certainly greater than 20 

 seconds, the period used for the refraction diagram, A longer period would 

 not change the character of the refraction diagram but would have produced 

 slightly greater focusing by refraction and a greater ratio, H< /H . 



Thus, it appears probable that the larger breakers which damaged the 

 Long Beach breakwater during the interval April 20 to 24, 1930 were gener- 

 ated by a storm almost due south of Long Peach, in the area not covered by 

 available weather maps. 



LITTORAL DRIFT AT SANTA BARBARA 



The shoreline phenomena effective at Santa Barbara have been the subject 

 of extensive study and one can now speak more positively about them than was 

 possible when erosion first aopeard. Refraction diagrams played an important 

 part in providing a rational basis for reasoning about the causes of erosion 

 and the means of improvement. 



Ihen this study was started, there were almost as .many theories about 

 the cause of erosion as there were inhabitants of Santa Barbara County and 

 it was necessary to develop an explanation satisfactory not only to engi- 

 neers but to public officials as well. 



'"hen refraction diagrams were prepared, they corresponded so obviously 

 with what anyone observed from the end of the breakwater or from vantage 

 points along the shore that the remainder of the reasoning about the direc- 

 tion of the littoral drift ana the causes of erosion was generally accepted. 



Briefly, the littoral drift at Santa Barbara runs almost continuously 

 from west to east and the volume transported is estimated to be around 

 1,000 cubic yards per day past each point on the shoreline. The beach 

 consists of a relatively thin layer of sand overlying solid upland material 

 and erosion quickly denudes the shore of sand. In 1929 construction was 

 started on a breakwater at Santa Barbara harbor (3). Immediately, sand ac- 

 cumulated on the westerly side and erosion developed progressively eastward, 

 becoming markedly evident as much as 5 miles east of the breakwater about /+ 

 years later. As soon as the effect of this breakwater became evident, steps 

 were taken to discover its cause. 



The cause of the easterly littoral drift becomes evident when one examines 

 the exposure of the shoreline between Point Conception and Mugu Lagoon, and 

 the prevailing winds and waves. A line of islands, broken only by relatively 

 restricted channels, parallels the shore and about 20 miles seaward. Pre- 

 vailing winds and waves are from the west, only occasional periods of southerly 



