some low, and of varying length o In the deeper water the longer waves 

 travel the faster and overtake and move through the shorter waves o Thus 

 the picture is generally confused and descriptions of the state of the 

 sea usually describe only the dominant waves present whereas a complete 

 description would involve a breakdown into all the types of waves 

 presento 



Another feature of wave action on beaches is angularity of approach, 

 !Ihe waves in deep water may approach a beach at almost any angle from 

 the perpendicularo However, as they move into shallow water they, are 

 refracted in such a way that they tend to adjust their crests parallel 

 to the bottom contours » Thus, a wave approaching in deep water at say 

 4,5° may have an angularity of some 5 degrees or so hy the time it fi- 

 nally breaks on the beach o However, even this slight residual angular- 

 ity has the effect generally of setting up a littoral current along 

 shore in the direction of the angularity o !Ihis littoral current in 

 turn, frequently becomes a dominant feature* in beach erosion and accre- 

 tion o 



itefore leaving the subject of waves, mention should be made of the 

 contrasting action of storm waves and swells on the beaches o Generally 

 speaking, the swells ^ those waves with high L/H ratios j, tend to move 

 sand from offshore and deposit it on the beach above mean tide level© 

 On the other hand, waves resulting from local storms tend to tear the 

 beach down by removing sand from above the mean tide line and placing 

 it in the form of submerged bars offshore <> These two statements are 

 somewhat generalized! other factors such as beach slope and sand size 

 enter the picture at times in such a way as to upset this generalized 

 relatione 



* * * 

 Extract from a lecture by Joseph Mo Caldwell at the Engineer School 



12 



