Physical models have a long history and have been refined to a sound 

 predictive technique. On the other hand, comprehensive mathematical 

 models have only been introduced recently, but the modeling techniques 

 are expected to continue to be rapidly developed and used for tidal 

 modeling. Physical model techniques should also be continually improved, 

 refined, and reduced in cost to provide some of the answers to tidal 

 problems that cannot now be obtained in any other way (Simmons, Harrison, 

 and Huval, 1971). 



d. Predictive Capabilities . Physical hydraulic models have long 

 been successfully used to predict the response of estuaries to alterations 

 such as dredging, landfills, constricting works, and flow alterations. 

 Model predictions of tidal elevations and phases, current velocities, 

 circulation patterns, and salinity intrusion are considered highly re- 

 liable; however, little attention has been given to a careful comparison 

 of model predictions and prototype conditions after the proposed modifi- 

 cations to the system have been made. Other phenomena, such as pollutant 

 and sediment transport, which are considered to be reproduced only quali- 

 tatively in physical models, have similarly suffered from a lack of study 

 to determine the relative merits of modeling them. 



There are several reasons for the lack of comparison between model 

 prediction and prototype behavior, which is termed post construct ion veri- 

 fication or model confirmation. First, resources are seldom available 

 to follow up on a project if it is functioning satisfactorily. Other 

 problems usually demand attention and money that might be applied to 

 followup studies. Second, many projects are changed before construction 

 due to considerations that are not pertinent to the model study; thus, 

 detailed comparisons are not possible unless costly additional model 

 tests are conducted. Finally, if model results show a project to be 

 infeasible, it is not constructed; consequently, comparison is not possi- 

 ble. The limited number of confirmation investigations on Corps of Engi- 

 neers model study predictions includes hydraulic characteristics of the 

 St. Johns River (Fortson, 1970), and shoaling characteristics of the 

 Alameda Naval Air Station (U.S. Army Engineer Waterways Experiment Sta- 

 tion, 1950), and in the Delaware River (U.S. Army Engineer Waterways 

 Experiment Station, 1947). 



The increasing environmental awareness in recent years has resulted in 

 a demand for more detailed model predictions of many estuarine phenomena. 

 Recognizing the need for postconstruction verification of model studies 

 to provide more reliable results, the Office, Chief of Engineers (OCE) , 

 authorized WES in 1971 to begin a series of confirmation studies. The 

 primary objective of these studies was to define the degree of accuracy 

 to which the results of tests conducted in physical hydraulic models pre- 

 dict the changes induced by modifications to estuarine systems. A second- 

 ary objective was to improve modeling techniques such that the value of 

 physical model studies may be increased. 



The first study in this series evaluated the predictions made in the 

 Delaware River model for the effects of a navigation channel enlargement 

 project between Philadelphia and Trenton (Letter and McAnally, 1975). 



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