Items (1) to (6) provide data needed to design and construct the 

 model and select the test waves and Stillwater level conditions. Items 

 (7) and (8) provide information for analyzing the test data to obtain 

 the best harbor-basin arrangement and the most efficient breakwater plan 

 for reducing wave action conditions within the harbor to tolerable levels 

 for the types and sizes of vessels that will moor in the harbor basins. 

 The ideal harbor for the movement of moored vessels is a harbor where 

 the geometry and depths are such that the water masses in individual 

 basins within the harbor are not tuning to any of the incident wave 

 periods, and where moored vessels are not excited to resonant oscilla- 

 tions by the incident waves. Waves in nature are complex and contain 

 different wave periods in the same train. The size, shape, and depths 

 of harbor basins are also determined primarily by the type and size of 

 vessels that frequent the harbor. Thus, all resonant phenomena cannot 

 be excluded by avoiding the harbor-basin dimensions that are critical 

 to incident wave periods. Likewise, it is not possible to exclude from 

 the harbor all vessels that are of a size that, with the normal mooring- 

 line assembly, are excited to abnormal oscillations by the forcing func- 

 tion of the incident waves. Some relief can be obtained by variations 

 in the elasticity, size, and tautness of lines, but the necessity of 

 allowing for changes in tide level makes it difficult without sophisti- 

 cated mooring tension apparatus. 



The short -period wave data needed for harbor wave action models are 

 similar to those required for stability models of coastal structures 

 (see Sec. VI). The significant deepwater wave heights and periods 

 (Hyg and Ty^, respectively) from the different directions of approach 

 are usually selected for use in testing, and these deepwater waves are 

 projected into the positions of the wave generator by existing wave re- 

 fraction techniques. However, for complicated inshore bathymetry, wave 

 refraction and shoaling effects become more complex, and there is a need 

 for a more reliable method of selecting shallow-water test-wave dimen- 

 sions and directions for both stability and harbor wave action model 

 studies. The heights of intermediate- and long-period waves that cause 

 objectionable surge oscillations of moored ships are relatively small, 

 even in harbor basins that are excited by resonant wave periods. Thus, 

 it is difficult and usually impractical, to obtain model input data for 

 such waves in areas other than those within the harbor basins or imme- 

 diately outside the breakwaters. Measurable wave heights are generally 

 easier to obtain in the antinodal areas where the vertical motion of the 

 water is maximiim; however, this may pose a problem for any but the most 

 simple geometry in mooring areas. If the mooring area is in the form of 

 a slip where the adjacent docks are impervious to the flow of water, a 

 simple two-dimensional oscillation of the standing wave system occurs, 

 and a wave gage in the shoreward end of the slip is in an antinodal area 

 and near enough to the ships docked in the slip so that there should be 

 good correlation between the recorded heights and periods of the waves 

 and the surge amplitude of the ships. When the mooring basin geometry 

 is more open and complex in plan form, the positions of the nodal and 

 antinodal areas are item functions of the wave period, and the selection 

 of satisfactory gage locations becomes difficult. Considerable help in 



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