prototype alternatives to assure that the final solution is the most 

 desirable (U.S. Army Engineer Waterways Experiment Station, 1969). 



Most problem areas concerned with tidal modeling techniques are 

 listed in Table 3-1. Environmental considerations are inherent in most 

 of these problem areas and are of primary consideration in predicting 

 construction effects. Some problems are quite amenable to modeling; 

 others are not (U.S. Army Engineer Waterways Experiment Station, 1969). 

 Sedimentation problems are a general class which has resisted accurate 

 quantitative solution by hydraulic modeling, although modeling techniques 

 provide highly useful qualitative information. 



Tidal modeling techniques are generally classified as: hydraulic 

 (also referred to as physical or scale) modeling and mathematical model- 

 ing. Hydraulic modeling is performed by designing, constructing, verify- 

 ing (adjusting or proving), and testing a scale model of the prototype 

 situation. Mathematical modeling requires developing, constructing, 

 verifying, and testing a set of mathematical or logical expressions for 

 a solution (usually on a high-speed digital computer) which yields the 

 desired parameters. Other modeling techniques such as electronic analogs 

 and hybrid computers are also used on certain problems; however, hydrau- 

 lic and mathematical modeling are the most widely used tidal modeling 

 techniques (U.S. Army Engineer Waterways Experiment Station, 1969). In 

 this report, only hydraulic modeling will be discussed. 



All models of estuaries have one common characteristic; i.e., the 

 models cannot be a completely accurate simulation of all of the complex 

 phenomena inherent in tidal waterways. To approximate complete model- 

 prototype similarity, a hydraulic model of an estuary should reproduce 

 the geometry and boundary roughness of the prototype and be able to 

 simulate the following (individually and collectively) as they vary 

 with tidal cycle time at all points in the system: 



(a) Water surface elevations; 



(b) current velocities and directions; 



(c) salinities; 



(d) physical characteristics of sediments; 



(e) transportation, deposition, and scour of sediments; 



(f) parameters reflecting water quality, such as dissolved 

 oxygen, temperature, viscosity, diffusion of introduced pollu- 

 tants, etc. ; 



(g) freshwater and saltwater discharges into the estuary, 

 and the turbulent intermixing within the water mass; and 



(h) effects of winds on setup, waves, local water currents, 

 mixing, diffusion, etc. 



Simulation of all of these estuarine phenomena is unnecessary to 

 solve every problem. In model studies of certain problems, some of the 



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