periods (Vellinga 1986, Dette and Uliczka 1987b, Uliczka and Dette 1987). 

 Irregular waves will most closely reproduce naturally occurring profile 

 change. Mimura , Otsuka , and Watanabe (1987) compared beach change produced in 

 a small laboratory wave tank by irregular waves and corresponding representa- 

 tive monochromatic waves. They found that macroscale patterns of profile 

 change, such as bar and berm development, were similar if representative 

 monochromatic waves were chosen as the mean wave height and period of the 

 irregular wave train. On the other hand, microscale features, such as 

 initiation of sand motion and ripple size, were best described by the signifi- 

 cant wave height. Properties compared included profile morphology, cross - 

 shore sand transport rate, and critical depth for sediment motion. 



166. Irregular waves introduce additional independent parameters 

 associated with the wave spectrum, whereas in monochromatic wave tests the 

 effects produced by the basic parameters of wave height and period can be 

 isolated and systematically investigated. Hughes and Chiu (1981) discuss 

 theoretical and practical problems associated with use of irregular waves in 

 movable bed modeling. At this first stage of quantification of prototype 

 beach change, it is probably most fruitful to examine the response of the 

 profile to elemental, monochromatic waves. 



167. Recently, two independent data sets on beach profile change have 

 become available from experiments performed using LWTs and monochromatic waves 

 (Kajima et al . 1983a, 1983b, Kraus and Larson 1988a). These experiments 

 involved combinations of waves, water levels, beach slopes, and sands of the 

 scale that exist in the field, but with the advantages of true two-dimension- 

 ality, control of the external (wave) force, and an optimized measurement 

 schedule. These data sets formed the core data for this study and are 

 described next. 



Laboratory and Field Data Sets 



Laboratory data 



168. Two data sets on beach profile change generated in experiment 

 programs using LWTs were employed. These independent data sets allowed 

 systematic examination of profile evolution through time for a wide range of 



46 



