in reaches that experience none in the prototype. Dredge-disposal prac- 

 tices are normally not reproduced in the model. If there is a return of 

 material to the channel from the disposal area, this source of material 

 may not be reproduced in the model shoaling tests. 



If prototype data are not available for a detailed shoaling verifica- 

 tion, any model shoaling tests are of a highly qualitative, rather than 

 quantitative, nature. The relative shoaling tendencies of the various 

 plans tested can be compared but shoaling rates cannot be predicted. In 

 this case, the only verification possible is the intuitive judgment of 

 the model operator as to whether or not the model shoaling pattern looks 

 reasonable. The development of more than one shoaling test technique may 

 be necessary to simulate the effects of various possible primary sediment 

 sources. 



f . Dye Dispersion . Verification of dye dispersion is normally not 

 accomplished because field dye-dispersion data are usually not available. 

 However, the data were available in suitable form at the proper time for 

 use in the San Diego Bay model. Because the prototype injection rate was 

 very low, direct scaling of the dye release in the model was not possible. 

 However, it was necessary to properly scale the density of the prototype 

 dye release (1:1) and to make the release at the correct location and at 

 the scaled times. A satisfactory verification was achieved (see Fig. 

 3-40). 



g. Heat Dispersion . Verification of heat dispersion has never been 

 accomplished at WES for a particular project investigation. This is 

 usually because no heated discharge exists at the time the model study 

 is conducted. To determine the validity of far-field thermal dispersion 

 tests in a distorted-scale model, a heat-dispersion verification was con- 

 ducted for three existing powerplants in the Delaware Estuary (Trawle, 

 1976). Figure 3-41 shows comparisons of model and prototype thermal 

 plumes at the Eddystone powerplant, which is located in the intermediate 

 salinity zone of the estuary. The results demonstrated that this model 

 (scales 1:100 vertically and 1:1,000 horizontally) can be used effec- 

 tively for trend predictions of far- field thermal plume characteristics. 



5. Utilization of Scale Models . 



a. Problems Susceptible to Model Analysis . Hydraulic models are 

 highly valuable tools in investigations of physical (as opposed to bio- 

 logical) phenomena in estuaries. A wide range of phenomena can be repro- 

 duced or simulated in hydraulic models, and a wide range of problems or 

 projects are susceptible to model investigations. However, there are 

 definite limitations to the capabilities of hydraulic models. The capa- 

 bilities and limitations of fixed-bed models are discussed below. 



The various phenomena which can be reproduced or simulated in hydrau- 

 lic models include tides, tidal currents, density currents, littoral 

 currents^ currents generated by riverflows, salinity, mass dispersion, 

 heat dispersion, shoaling, hurricane surges, tsunami surges, and the 



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