accretionary profiles with berm buildup. He found that the foreshore slope 

 was independent of the wave height and mainly a function of grain size. 

 However, the equilibrium height of the berm was linearly related to wave 

 height. The effect of a seawall on the beach profile was investigated by 

 allowing waves to reach the end of the tank. By varying the water level, a 

 tide was simulated; in other experiments, a varying wave height was employed. 



26. Evans (1940) studied bars and troughs (named balls and lows by 

 Evans) along the eastern shore of Lake Michigan and concluded these features 

 to be the result of plunging breakers. He regarded the bar and trough to form 

 a unit, with the trough always located shoreward of the bar. If the profile 

 slope was mild so that several break points appeared, a series of bars and 

 troughs would develop. Also, a change in wave conditions could result in a 

 change in bar shape and migration of the bar seaward or shoreward . A 

 decreasing water level would cause the innermost bar to migrate onshore and 

 take the form of a subaqueous dune , whereas an increase in water level would 

 allow a new bar system to develop inshore. The most seaward bars would then 

 become inactive. 



27. In support of amphibious landing operations during World War II, 

 Keulegan (1945) experimentally obtained simple relations for predicting the 

 depth-to-bar crest and the trough depth. He found the ratio between trough 

 and crest depths to be approximately constant and independent of wave steep- 

 ness. Important contributions to the basic understanding of the physics of 

 beach profile change were also made through further laboratory experiments by 

 Keulegan (1948). The objective of the study was to determine the shape and 

 characteristics of bars and the process through which they were molded by the 

 incident waves. He recognized the surf zone as being the most active area of 

 beach profile change and the breaking waves as the cause of bar formation. 

 The location of the maximum sand transport rate, measured by traps, was found 

 to be close to the break point, and the transport rate showed a good correla- 

 tion with the wave height envelope. Keulegan (1948) noted three distinct 

 regions along the profile where the transport properties were different from a 

 morphologic perspective. A gentler initial beach slope implied a longer time 

 before the equilibrium profile was attained for fixed wave conditions. For a 

 constant wave steepness, an increase in wave height moved the bar seaward. 



19 



