(4) Type and size distribution o£ prototype bottom material. 



(5) Size and capabilities o£ model test facilities. 



(6) Model test materials either available or readily 

 procured. 



(7) Accuracy to which model test results are desired. 



(8) Funds available to conduct the study. 



(9) Time available to conduct the study. 



(10) Qualified personnel available for assignment to the 

 study. 



The above items are not necessarily compatible; i.e., funds or time 

 available to conduct the study may not be commensurate with the desired 

 accuracy of the experimental results. However, after full consideration 

 of the above items, a set of wave-flume experiments is recommended before 

 final selection of the scale-model laws. These tests would be two- 

 dimensional beach profile tests where it would be attempted to reproduce 

 the dominant existing beach characteristics (relative to onshore-offshore 

 transport) using several different scaling relations and beach materials. 

 After a particular set of scale-model laws (and consequently linear scales 

 and bottom material) is selected, it is recommended that the same law be 

 applied using a larger model (and consequently a different model material) 

 and that wave-flume tests be conducted to ensure reproducibility of re- 

 sults and establish confidence in the selected scaling relations (at least 

 for onshore-offshore transport). 



At this point in the investigation, a set of scaling relations has 

 been tentatively selected and the recommended prototype data have been 

 obtained (to the best possible extent) . A bottom material and tentative 

 model scales (for the three-dimensional, movable-bed model) have also 

 been selected. Before proceeding further, one more step in assuring the 

 accuracy of model results is necessary. An average bottom profile should 

 be used to construct a test section of straight parallel bottom contours. 

 Tests should be conducted with waves at an angle to this test section and 

 measurements made of the longshore transport and the evolution of the 

 model bottom topography. Model test results should then be compared 

 with either those predicted or those measured during the prototype data 

 acquisition phase of the study. After confirmation of the longshore 

 transport, the investigator is ready to proceed to the model operation 

 phase of the study and in particular to model verification. 



4. Model Operation . 



a. Verification of the Model. The first and most important step 

 in conducting a quantitative, movable-bed scale-model investigation of 

 coastal erosion or coastal sediment transport is model verification. 



292 



