thermal patterns than can be obtained with contact measurements. An 

 example of a water temperature observation network is shown in Figure 

 3-9. 



(9) Sedimentation . Only those data required for verification 

 of shoaling patterns in a fixed-bed model are discussed in this section. 

 Requirements for movable-bed models are discussed in Section VII. Many 

 model shoaling investigations are conducted in existing navigation channel 

 projects. In this case, available periodic hydrographic surveys of a 

 channel by the Corps of Engineers or other responsible agency will prob- 

 ably be sufficient for use in the model study. Channel surveys of several 

 representative years [at least two, but preferably three or more surveys) 

 should be analyzed to determine the distribution of shoaling throughout 

 the length of the channel. The channel should be subdivided into several 

 sections (usually longitudinal), and the volumes of shoaling between 

 dredging operations determined for each section for each year. This in- 

 formation is determined from the postdredging survey for 1 year and the 

 predredging survey for the following year. In this manner the average 

 percentile distribution of shoaling along the channel can be determined. 

 If shoaling tests are required over the entire width of the estuary, or 

 if no navigation channel exists, hydrographic surveys over a much broader 

 area are required. Again, surveys are required for a period of several 

 years, and should be of sufficient detail and accuracy to develop scour- 

 and-fill maps for the area to be studied. The only information required 

 of the nature of the sediments is the grain size or even a very qualita- 

 tive indication of whether the material consists of clays, silts, or sand. 



3. Model Construction . 



a. Construction Procedures . There are several basic methods of 

 estuary model construction. For example, the model can be constructed 

 of individual slabs, or it can be of essentially continuous construction. 

 The construction control points can be parallel templates (male or female), 

 templates which follow a given contour, or rods for which the top (or 

 bottom) elevations are set to the desired model elevation. Only the 

 general practice of WES will be discussed here. 



The model construction effort actually begins by laying out the hori- 

 zontal control grid on the maps from which the model will be built. Par- 

 allel gridlines should be established at 2- to 3-foot intervals along the 

 length of the model. In areas of low relief such as in broad, shallow 

 bays or offshore, grid intervals of 4 to 6 feet can be used. The grid- 

 lines should generally be laid out about normal to the main channel within 

 the estuary or normal to the shoreline in the offshore area. Although it 

 is convenient for all gridlines to be parallel or perpendicular to each 

 other, a rather irregular grid system should sometimes be developed. 



After the grid system has been developed, cross-sectional profiles 

 are determined for each grid and transferred to template material (typi- 

 cally hardboard; e.g., Masonite). Sheet metal templates corrode in salt- 

 water and should be avoided in estuary models. Typical templates are 

 shown in Figure 3-10. 



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