PART III: DATA EMPLOYED IN THIS STUDY 

 Data Acquisition Approaches 



160. Three approaches can be used to obtain data for studying beach 

 profile change and the underlying physical processes; laboratory experiments 

 using small wave tanks, field measurements, and experiments employing large 

 wave tanks. For reference, a small wave tank is considered to generate wave 

 heights on the order of 0.1 m, whereas wave heights on the order of 1 m can be 

 generated in large wave tanks. 



Small-scale laboratory approach 



161. Numerous laboratory studies of beach profile change have been 

 performed with small wave tanks (for example, Waters 1939, Bagnold 1940, 

 Keulegan 1945, 1948, Nayak 1970, Rector 1954, Scott 1954, Watts 1954, Watts 

 and Dearduff 1954, McKee and Sterrett 1961, Iwagaki and Noda 1963, Sunamura 

 1975, Sunamura and Horikawa 1975, Hughes and Chiu 1981, van Hijum and 

 Pilarczyk 1982, Shibayama 1984). Such experiments have proven valuable for 

 identifying potential parameters controlling beach change and qualitatively 

 describing profile features. However, as demonstrated in a landmark paper by 

 Saville (1957), in which profile change generated in small and large wave 

 tanks was compared, a large scale effect is introduced through the magnitude 

 of the wave height. Other independent variables may also produce a scaling 

 distortion, and generally applicable scaling laws for interpreting results of 

 small-scale movable bed models of beach change have yet to be determined 

 (Hughes 1983, 1984, Sayao 1984, Vellinga 1984). Thus, data sets from labora- 

 tory experiments performed with small-scale facilities are of limited value 

 for establishing quantitative understanding of profile change in nature. 



Field approach 



162. Field data sets useful for quantitative study of beach profile 

 change are extremely rare because of the required high resolution in time and 

 space of morphology and associated wave climate and water level. Because of 

 the great spatial and temporal variability of waves and the three-dimensional 

 character of nearshore bathymetry in the field, it is difficult to extract 

 conclusive cause and effect relationships between waves and profile change 



44 



