Any errors or insufficiencies in prototype information will result in 

 inadequate and incorrect performance of the model. 



Prototype information required for a movable-bed model study includes 

 inlet geometry and sediment properties, bar configuration and sediment 

 properties, adjacent beach configuration and sediment properties, bay 

 geometry, wave measurements, littoral drift estimates, water surface 

 time histories, and concurrent tidal currents in the ocean, inlet, and 

 bay. Wind observations are also required to determine the resulting wind- 

 driven setup or setdown of the water surface. If evaporation or precipi- 

 tation appears to be important, or if freshwater inflows constitute a 

 significant part of the flow through the inlet, these should also be ob- 

 served. The occurrence of storms of low-return frequency should be noted 

 in the history of the inlet, since large volumes of sand can be displaced 

 during these activities. Hydrographic and wave observations should also 

 be made frequently enough to detect seasonal and yearly fluctuations. 



A longer data collection period is needed for a movable-bed study than 

 for a fixed-bed model. The period length also varies with the data type; 

 e.g., longer term wave data are needed than tide level and current data to 

 calibrate a movable-bed model. 



Prototype observations for several consecutive years before the model 

 study will allow an evaluation of both short- and long-term tendencies of 

 the inlet and the selection of a typical period on which to base the model 

 verification. A 3-year documentation period is probably the minimum length, 

 since major trends cannot usually be detected in shorter time periods. 



If these data are not available, a program to collect sufficient in- 

 formation may have to be initiated before beginning the model study. 

 Although such action at times may seem to unreasonably delay the model 

 study, experience has shown the impracticality of attempting model studies 

 without adequate prototype information. 



The construction of a movable-bed model is usually straightforward. 

 The charts containing the inlet hydrographic surveys are contoured, and 

 the contours are transferred to a network of templates. The templates 

 are suspended and the modeling material is carefully placed between them 

 so that the templates just touch the surface. The templates are removed 

 before the tests begin. 



c. Model Verification . The verification phase of the model study is 

 perhaps the most important. A we 11- accomplished verification will minimize 

 or eliminate the effects of small errors in construction, and will allow 

 the evaluation of the effects of poorly understood variables on the inlet 

 system during the testing phase. 



Verification requires the adjustment of model boundary conditions to 

 re-create or correct conditions that were altered in the scaling process. 

 Sedimentation verification is based on prototype observations and is 

 accomplished by selecting an appropriate model sediment and developing 



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