relatively low cost (about 20 to 60 percent o£ the cost of a conplete 

 model) o£ each of these models can lead to a desirable approach for 

 specific information. 



The uses of specific types of physical hydraulic models for inlet 

 studies are summarized below. 



a. Fixed- Bed, Undistorted-Scale, Sectional Model . This model may 

 be used for investigations when little or no hydrographic information is 

 available from the prototype. Although effective use of this model re- 

 quires that bed forms and general inlet configurations be assumed before 

 initiation of studies, the effects of these forms on the resulting hydrau- 

 lics of the inlet can be obtained with a relatively high degree of confi- 

 dence. Specifically, the fixed-bed, undistorted-scale, sectional model 

 can be used to define the hydraulic characteristics of a proposed new in- 

 let where prototype information cannot be obtained. The results from the 

 model can then be used in a distorted-scale model to define the effects 

 of the inlet on the ocean-inlet-bay system. The model can also be used 

 to investigate the interaction of tidal flow and wind waves which may 

 affect bed movement, flow through the inlet, and navigation conditions 



in the inlet. 



b. Fixed-Bed, Undistorted-Scale, Complete Model . This model will 

 provide the most accurate results on hydraulic conditions in the inlet- 

 bay system; however, the costs are extremely high. Studies in this type 

 of model for an inlet-bay complex have never been conducted at WES, since 

 no study to date has sufficiently justified the high costs compared to 

 costs for obtaining results by other models or other means; therefore, 

 only estimates on the improvement of accuracy of results can be made. 



c. Fixed-Bed, Distorted-Scale, Sectional Model . If a problem con- 

 cerns the evaluation of effects of changes to an inlet on the inlet hydrau- 

 lics or shoaling, this model can be effective. The major disadvantage is 

 that the model does not provide specific information on the interaction 

 with the bay; therefore, estimates of conditions at the boundaries of the 

 model must be made. 



d. Fixed-Bed, Distorted-Scale, Complete Model . This is the model 

 most commonly used to investigate general hydraulic conditions in an 

 inlet -bay system. The model can provide reasonably accurate data without 

 excessive costs. The major limitations to the model are that for inlet 



or bay conditions where both wave refraction and diffraction are important, 

 extreme care must be taken in selection of the model scales as true simil- 

 itude for both wave refraction and diffraction cannot be achieved. 



e. Movable-Bed, Distorted-Scale, Sectional Model . This model has 

 the potential of being the most effective type of model to investigate 

 shoaling and scouring trends within the inlet. Because of the methods 

 required to conduct movable-bed studies, the capability to control the 

 flow at both the bay and ocean ends of the inlet enhances the operation 

 of the model (discussed later in this section). 



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