cannot be recorded at a point. It is believed that clapotis groupings and 

 flats mil average out to a uniform organization of the various systems com- 

 posing the state of the sea. 



That TJ-ave systems do conform more closely to classical theory than one 

 might expect has important implications. Wave refraction theory, which is 

 based on a single system of waves of specific direction and period^ is in 

 no way vreakened by the knowledge that usually more than one system is present, 

 but instead the use of the theory is strengthened inasmuch as the various 

 systems can be analyzed separately and their net effects evaluated; a step 

 beyond present refraction procedures. This will require a reversal of 

 present processes; and to the betterment of the practice, refraction diagrams 

 may be drawn from the known inshore conditions seaward, rather than from the 

 computed or assumed offshore conditions to sometimes doubtful inshore results. 



Tte development of refraction theory during the last decade is probably 

 the greatest contribution that has been rriade to coastal oigineering, yet 

 little use has been made of refraction diagrams on the east coast of the 

 United States, primarily because the wide continental shelf -with its many 

 irregular submarine features produces such complicated ray paths that they 

 go beyond present refraction procedures. Furthermore, the magnitude of 

 some of the diagrams is such that gross errors are introduced even over a 

 fairly uniform bottom. For example, to bring in a long-period diagram 

 from due east to the Long Island and Northern New Jersey coasts it is 

 necessary to go some four-hundred miles offshore to the eastern edge of 

 Georges Bank, and even though the bottom were regular, the errors over this 

 distance would be considerable. Add to this the fact that the bottom 

 topography is most complex, causing the orthogonals to cross and sometimes 

 recross, any computations for values at the shore would be most unj^ielia:Mlfi% •' 



In view of the foregoing it is sufficient to say that present refraction 

 procedures are inadequate, and that attention should be given to the develop- 

 ment of more feasible methods of studying nearshore conditions. To that end, 

 the aerial photographs in the files of the Beach Erosion Board were studied 

 in detail, and as a result, the method of separating the i-vave ^sterns and 

 determining their direction ■was developed. If accurate determination of 

 direction alone can be accomplished, (since indications are that even the 

 eye is unreliable in many cases) substantial progress will have been made, 

 but to be able to separate the various systems of waves that are present 

 and determine the directions and at least some of the other properties of 

 each, opens up a mde range of study for both the scientist and the coastal 

 engineer. 



There is a wide conception that waves in deeper water are not long 

 crested, uniformly spaced, but are instead a series of short crests which 

 somehow miraculously unite in shalloTir water to form the breakers usually 

 observed. After examination of many aerial photographs this concept is 

 questioned. It is true that due to interferences of other wave trains 

 the single crests show breaks at the Instant of film exposure, such breaks 



