BEACH PROFILE CHANGE MEASURED IN THE 

 TANK FOR LARGE WAVES, 1956-1957 AND 1962 



PART I: INTRODUCTION 



Background 



1 . Engineering activities in the coastal zone may alter the pattern of 

 sediment transport and bathymetry in the vicinity of the site, and expected 

 changes in the profile must be estimated as part of the design process. For 

 example, quantitative prediction of changes in the beach profile induced by 

 wave action is required for designing structures, beach fill, and berms and 

 dunes that will serve as shore protection against storms. Accurate data are 

 the foundation upon which a quantitative understanding of beach profile change 

 must be built. 



2. To obtain the most useful data in the laboratory, experiments should 

 be performed at a sufficiently large scale to reproduce the physical processes 

 that are responsible for profile change on field beaches. There are limita- 

 tions to laboratory experiments, even those of prototype scale. These include 

 potential residual scale effects, artificial wave reflection, absence of very 

 long wave motions, artificial vertical water circulation, and seich, as well 

 as absence of alongshore sediment movement if tanks are used. However, the 

 capability to measure the response of the profile under controlled conditions 

 of the laboratory and with systematic changes in sand grain size, wave charac- 

 teristics, and water depth allows isolation of the underlying physical pro- 

 cesses far more easily and much less expensively than can be done in field 

 experiments. In this sense, complete elimination of longshore effects in tank 

 studies may be viewed as a benefit. 



3. During 1955-1983, the Beach Erosion Board (BEB) and its successor 

 organization, the Coastal Engineering Research Center (CERC), operated a large 

 wave tank called the "Tank for Large Waves" or the "Large Wave Tank" (LWT). 

 Two series of movable-bed model experiments on beach profile change were 

 conducted in the LWT. The series were mainly distinguished by the grain size 

 of the bed material. Nine major cases, called "tests" in the original work, 

 were run with each of two sand sizes (0.22 mm and 0.40 mm median diameter) 

 with essentially the same water depth and "offshore" wave conditions. Cases 



