The channel -deepening project between Philadelphia and Trenton caused 

 significant, but not large, changes in the hydrodynamic and salinity reg- 

 imen of the estuary. The magnitude of the changes induced was much larger 

 than the fluctuations due to the imperfect repeatability of the model, but 

 not great enough to strain the initial calibration of the model. There- 

 fore, the deepening project constituted a valid test of the capability of 

 the model to predict the changes in the estuarine system caused by projects 

 of that scale. 



The original verification was considered very good, and this study 

 concluded that the accuracy of the model predictions was as good as the 

 original verification. Tidal phenomena, current velocities, and the 

 salinity regimen of the estuary have been predicted by the model with 

 accuracy for the postconstruction conditions. 



The results of this study show not only the validity of the Delaware 

 River model predictions but also the necessity of interpreting the results 

 in general terms rather than for specific point values. The model is very 

 accurate for predicting changes and general trends for the estuary, but a 

 particular value at a particular time and place should not be considered 

 completely quantitative in all cases. Physical hydraulic models used 

 with proper caution to avoid too literal an interpretation of the results, 

 are of significant value as a decisionmaking tool. 



Several additional confirmation studies presently underway or planned 

 will consider a variety of projects, estuarine phenomena, types of estu- 

 aries, and model scales. 



6. Examples of Model Studies Conducted . 



a. Navigation Channel Shoaling — Columbia River Estuary . 



(1) Project . South jetty rehabilitation, improvement of entrance 

 channel by construction of a new jetty, and enlargement of existing navi- 

 gation channel. 



(2) References , Herrmann and Simmons (1966); Herrmann (1968, 

 1971, 1974). 



( 3) Laboratory . WES . 



(4) Test Period . South jetty (August 1963 to January 1964); 

 Wauna-Lower Westport Bar (August 1964 to October 1965); jetty B (January 

 to May 1967). 



(5) Problems . The authorized length of the south jetty (Fig. 

 3-42) is about 6,6 miles with a top elevation of +24 feet mean lower low 

 water (MLLW) . In 1941, a terminal block was constructed 3,900 feet shore- 

 ward of the outer end of the structure; by 1960, the jetty needed exten- 

 sive rehabilitation shoreward of the terminal block. The entrance channel 

 dimensions are 48 feet deep and 0.5 mile wide over a distance of about 



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