Alternately, the researcher can abandon the idea of reproducing the dominant physical processes and 

 instead attempt to maintain similitude of important observed engineering characteristics such as beach 

 profile shape or longshore transport rates (Hudson et al. 1979). 



7. Regardless of the approach taken to develop scaling relationships for movable-bed models, the 

 nearly unanimous opinion among researchers is that it is important to verify the scaling laws by 

 reproducing prototype-scale events. Preferably, the scale model should be validated using field data, but 

 often this is not practical, and large-scale laboratory results must suffice. Only after validation can 

 credence be given to the model results, and then only for situations which seem to be governed by the same 

 processes that were assumed dominant in the validation. That is to say, for example, a movable-bed model 

 validated for surf zone sediment response is not necessarily valid for application outside the surf zone 

 because diflFerent mechanisms may be governing the transport of sediment. This leads to the axiom that 

 scale laws should be derived with a main requirement of invariability of the scale for the material transport 

 over the entire area of the model concerned (Bijker 1967). Under such constraints, situations where 

 sediment is transported by significantly diff'erent mechanisms in different regions usually cannot be 

 modeled simultaneously except at the prototype scale. 



8. In spite of the problems associated with the use of movable-bed physical models, researchers must 

 strive to improve their capabilities with these engineering tools. Dean (1985) summarizes the role of 

 physical models by stating that they will continue to be important engineering tools for several decades 

 because: 



a. They do not require mathematical quantification and representation of the physical 

 processes as do numerical models. 



b. They can adequately deal with complex geometries. 



c. They offer advantages in measurement and visualization of the processes when dealing with 

 small-scale versions of the system. 



9. Bijker (1967) stated that ". . .a (physical) model can act as a means to guide the considerations of 

 the engineer in charge of the design of the project" ; but he also cautions, in reference to movable-bed 

 models, ". . . the model is a rather dangerous tool in the hands of a not very cautious and conscientious 

 investigator." 



Objectives and Purpose of Study 



10. The objectives of the study were to determine suitable scaling relationships appropriate for 

 modeling turbulent wave-induced scour phenomena in small-scale movable-bed physical models, to validate 



10 



