Possible model laws prepared by Noda (1972) are presented in Table 

 5-1; several of the possible scale-model laws are derived from various 

 combinations of seven derived similitude conditions. 



The table shows several uncertainties. Noda includes a column for 

 assumed conditions to clear up any discrepancies resulting from uncertain- 

 ties in the basic seven conditions of similitude. An interesting column 

 in Table 5-1 is for n . = n^ = n^ = 1 which gives the scale-model rela- 

 tions when a prototype material is used. Noda uses this table to guide 

 his experimental testing program where he first concludes that condition 

 four is the proper one and then proceeds to derive a completely empirical 

 model law based on similitude of equilibrium beach profiles in the breaker 

 zone. Several proposed model laws are shown in Table 5-2. A considerable 

 number of uncertainties obviously exist relative to the proper similitude 

 laws for movable-bed models. The inherent basic problems are discussed 

 further in Section V,6. 



3. Model Design . 



a. Prototype Data Required . An important step in conducting a 

 movable-bed scale model of coastal sediment transport is to obtain the 

 essential prototype data, and to assure that the data quality is suffi- 

 cient for use as a basis of model verification. Data of the quantity 

 and quality considered necessary for exact model verification have never 

 been obtained; however, the acquisition and analysis of such data and the 

 lise of the data for model verification are within the present state-of- 

 the-art. Collection of the following prototype data is considered 

 essential: 



(1) A detailed sediment-size distribution over the entire 

 area of interest (both offshore, beyond the breaking zone for 

 the largest waves considered important, and alongshore). 



(2) A computational estimate of yearly and monthly net 

 longshore transport. V.'ave statistics should be used to per- 

 form this computation along with refraction, shoaling, and 

 breaking criteria. The selection of a suitable formula for the 

 longshore velocity must be largely subjective at the present 

 time, and the use of two or three formulas may be warranted to 

 obtain the best possible selection. These computations serve 

 to (a) illustrate which part of the wave climate is responsible 

 for the majority of the longshore transport (even if the accuracy 

 of the total computation is incorrect, the relative contribution 

 of each component of the wave climate should be approximately 

 correct); (b) indicate the months during which the majority of 

 sediment is transported; (c) indicate the relative importance of 

 the long wave climate (which may be more important on the west 

 coast than the east and gulf coasts) ; (d) allow an appreciation 

 of the large quantities of material that can be transported in 

 each direction even though the net transport may be quite small; 

 and (e) indicate the relative importance of major storms and 



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